TypeScript, in layers, with a strict linter

The client was one main.js, one preload.js, three files in lib/ and one renderer
script. It is now a typed application whose imports point inward: domain (models,
ports, errors) knows nothing about Electron, Node or Python; application orchestrates
it through those ports; infrastructure holds the adapters — the Python CLI, HTTP, the
filesystem, Electron itself — and main, preload and renderer sit on top as hosts.

STRUCTURE.md is the map, and the deliverable as much as the code is: every layer, every
pattern in use (ports and adapters, repository vs gateway, service, DTO and mapper,
composition root, controller and router, single flight, observer streams, state store
with unidirectional flow, passive view, coded error hierarchy, frozen constant tables,
untrusted-data readers) and the naming rules — files, classes, and a verb vocabulary
for methods where find/require/read/list/apply/render/handle each state a contract.

Two properties fell out of the move, and they are why it was worth doing:

  - The catalog can be driven with no window and no Electron at all. The smoke test
    assembles the same services against the same ports in a plain Node process; it used
    to be a script that reimplemented the bridge.
  - The window never receives a filesystem path. A title crosses the bridge without
    one, and launching is asked for by name, resolved in the main process from the
    store's own state. Verified with a fake launcher: an unknown name answers false, a
    native title resolves to its menu entry, a hosted one to its catalog URL.

Types are mandatory, including where inference would manage: explicit return,
parameter and property types, strict plus noUncheckedIndexedAccess,
exactOptionalPropertyTypes, noImplicitOverride and noPropertyAccessFromIndexSignature,
typescript-eslint strictTypeChecked and stylisticTypeChecked, exhaustive switches, no
any, no non-null assertions, and no casts on foreign data — engine stdout and the
registry go through readers that turn unknown into typed values. naming-convention
enforces the patterns rather than trusting them.

Two rule conflicts had to be decided rather than papered over. typedef and
no-inferrable-types disagree about `fallback: string = ''`: the annotation wins, since a
signature states its types. erasableSyntaxOnly is off, because it forbids constructor
parameter properties, which are how dependencies are declared here.

The preload and the renderer are bundled by esbuild into one file each: a sandboxed
preload may not require its own modules, and a module script over file:// is blocked by
the page's own origin rules. tsc compiles the rest. The package ships build/** and
package.json — 111 entries, no sources, no toolchain.

New targets: build, typecheck, lint, lint-fix, and check — typecheck, lint, then both
test suites, cheapest failure first. Every script that runs the app builds first, so a
stale bundle cannot be tested.

Nothing about the window changed: same side menu, same categories, same switcher, same
two languages. make check is clean, both test suites pass with one store and with two,
the packaged 1.3.0 bundle drives the real store, and the window was photographed before
and after — the two are the same picture.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,2 +1,3 @@
 node_modules/
+build/
 dist/

Makefile

@@ -7,6 +7,7 @@
 #
 #   make            list the targets
 #   make setup      install the dependencies
+#   make check      typecheck, lint and both test suites
 #   make dist       package for this machine
 #   make release    package and publish to Gitea
 #
@@ -23,8 +24,8 @@ TAG ?= v$(VERSION)
 
 .DEFAULT_GOAL := help
 
-.PHONY: help setup node-check start smoke uitest test dist dist-mac dist-win dist-linux \
-        release publish clean distclean version
+.PHONY: help setup node-check build typecheck lint lint-fix check start smoke uitest test \
+        dist dist-mac dist-win dist-linux release publish clean distclean version
 
 help: ## List available targets
 	@echo "WarpEngine Store GUI $(VERSION) — usage: make <target>"
@@ -45,6 +46,22 @@ node-check: ## Check the Node version Electron's installer needs
 setup: node-check ## Install the dependencies
 	npm install
 
+build: ## Compile TypeScript and bundle the preload and the renderer
+	npm run build
+
+typecheck: ## Type-check everything, emitting nothing
+	npm run typecheck
+
+lint: ## Lint with the strict rule set
+	npm run lint
+
+lint-fix: ## Lint and fix what can be fixed automatically
+	npm run lint:fix
+
+# The order is deliberate: a type error explains a lint error, and both explain a
+# failing test, so the cheapest check that can fail runs first.
+check: typecheck lint test ## Type-check, lint, and run both test suites
+
 start: ## Run the app against whatever store is installed
 	npm start
 
@@ -75,8 +92,8 @@ publish: ## Upload the packages already in dist/ to the Gitea release
 # what this version produced.
 release: clean dist publish ## Package for this machine and publish it
 
-clean: ## Remove the built packages
-	rm -rf dist
+clean: ## Remove the compiled output and the built packages
+	rm -rf build dist
 
 distclean: clean ## Remove the packages and the dependencies
 	rm -rf node_modules
@@ -86,5 +103,7 @@ version: ## Show the versions involved
 	@printf "node       "; node --version 2>/dev/null || echo "missing"
 	@printf "npm        "; npm --version 2>/dev/null || echo "missing"
 	@printf "electron   "; node -p "require('./package.json').devDependencies.electron" 2>/dev/null || echo "missing"
+	@printf "typescript "; npx tsc --version 2>/dev/null || echo "missing"
+	@printf "eslint     "; npx eslint --version 2>/dev/null || echo "missing"
 	@printf "tea        "; tea --version 2>/dev/null | head -1 || echo "missing — devarea: make tea"
 	@printf "python3    "; python3 --version 2>/dev/null || echo "missing"

README.md

@@ -24,6 +24,9 @@ catalog it serves and where its configuration lives.
 - Nothing else at runtime. No Node, no package manager, no admin rights: the
   store installs under your own user account.
 
+To *develop* it you also need **Node 22 or newer** — see below — and nothing else: the
+toolchain (TypeScript, ESLint, esbuild, electron-builder) installs with `make setup`.
+
 ## Install
 
 Grab the package for your machine from the
@@ -145,19 +148,24 @@ names. `make` on its own lists everything.
 | Target | What it does |
 |---|---|
 | `make setup` | install the dependencies (checks the Node version first) |
+| `make build` | compile TypeScript, bundle the preload and the renderer |
+| `make typecheck` | type-check everything, emitting nothing |
+| `make lint` | the strict rule set (`lint-fix` fixes what it can) |
+| `make check` | **typecheck, lint and both test suites** — the gate |
 | `make start` | run the app against whatever store is installed |
-| `make smoke` | drive the store bridge with no window at all |
+| `make smoke` | drive the store with no window and no Electron at all |
 | `make uitest` | load the window once and report what rendered |
 | `SELFTEST_SHOT=shot.png npm run uitest` | the same, and the window photographs itself into that file |
-| `make test` | both checks |
+| `make test` | both test suites |
 | `make dist` | package for this machine (`dist-mac`, `dist-win`, `dist-linux` to pick) |
 | `make publish` | upload the packages already in `dist/` to the Gitea release |
 | `make release` | **package and publish in one go** |
-| `make clean` | remove the built packages (`distclean` also drops `node_modules`) |
+| `make clean` | remove `build/` and the packages (`distclean` also drops `node_modules`) |
 | `make version` | the versions involved, including whether `tea` is there |
 
 The npm scripts still work directly (`npm start`, `npm run dist:mac`) — the
-Makefile adds no logic of its own beyond the release step.
+Makefile adds no logic of its own beyond the release step. Every script that runs the
+app builds first, so there is no way to test a stale bundle.
 
 ### Publishing a release
 
@@ -174,6 +182,16 @@ Release notes come from `RELEASE_NOTES.md` when the file is present, otherwise t
 release gets a one-line note. The repository is read from `origin`, so a fork
 publishes to the fork.
 
+Each upload is retried up to three times, and the existing attachment is dropped
+before every attempt so a retry cannot leave two copies. A 100 MB upload does fail
+on its own: publishing 1.2.0 got *"invalid username, password or token"* on the
+second package while the first had just gone up with the same token, and the same
+command succeeded immediately afterwards.
+
+Package names contain a space — `WarpEngine Store-1.2.0-arm64.dmg` — so the list of
+files is passed one path per line rather than as one string; splitting it on
+whitespace is what broke the first attempt at publishing 1.1.0.
+
 It needs `tea` installed and logged in — the devarea repo has `make tea` for that.
 Overridable: `TAG`, `REPO`, `TEA_LOGIN`, `NOTES`, `DIST`.
 
@@ -200,33 +218,52 @@ SMOKE_HOME=/tmp/sandbox-root/ttg-desktop npm run smoke
 
 ### How it is put together
 
-| File | What it does |
+TypeScript, in layers, with the dependency rule pointing inward. **[STRUCTURE.md](STRUCTURE.md)
+is the map** — the layers, every pattern in use, and the naming rules. The short version:
+
+| Layer | What lives there |
 |---|---|
-| `main.js` | the window, the IPC, and the one-call-at-a-time guard |
-| `preload.js` | the entire surface the renderer gets — no Node reaches it |
-| `lib/store.js` | finds the store and Python, runs the CLI, parses its JSON |
-| `lib/bootstrap.js` | reads the registry, then downloads the engine, the core and a config |
-| `lib/i18n.js` | the two string tables |
-| `renderer/` | plain HTML, CSS and JS — no framework, no build step |
-| `Makefile` | the named sequences; no logic of its own beyond the release |
+| `src/shared/` | the IPC channel table, the bridge contract, the DTOs, the two message bundles |
+| `src/domain/` | models, ports and errors — no Electron, no Node, no Python |
+| `src/application/` | services and the domain → DTO mappers |
+| `src/infrastructure/` | the adapters: the Python CLI, HTTP, the filesystem, Electron itself |
+| `src/main/` | the window, the IPC controllers, the composition root, the self-test |
+| `src/preload/` | the bridge, bundled into one file — a sandboxed preload cannot require modules |
+| `src/renderer/` | the state store, the views and the renderer controllers |
+| `src/scripts/` | the smoke test: the same services with no window at all |
 | `scripts/release.sh` | creates the Gitea release and replaces its attachments |
 | `scripts/after-pack.js` | ad-hoc signs the macOS bundle during packaging |
+| `scripts/build-assets.mjs` | bundles the preload and the renderer, copies the page |
 
-`contextIsolation` is on, `nodeIntegration` off, `sandbox` on, and the page
-carries a CSP that allows only its own script and stylesheet plus images over
-HTTPS. Links open in the real browser; the window itself never navigates.
+Two properties are worth stating because they are what the layers buy:
 
-`lib/store.js` talks to the CLI through `--json`, which puts data on stdout and
-the human-readable log on stderr. That flag arrived with engine **1.1.0**, and the
-client checks: an older store is met with an offer to refresh it rather than a
-failed call.
+- **The catalog can be driven without a window.** `make smoke` assembles the same
+  services against the same ports with no Electron in the process at all.
+- **The window never receives a filesystem path.** A `GameDto` carries no paths; the
+  window asks to launch a title *by name* and the main process resolves what that means
+  from the store's own state.
 
-The bridge keeps an `ENGINES` list with one entry today. The RetroArch store has
-the same command shape, so a second entry is the whole change needed to drive it
-too — that is why the indirection is there.
+`contextIsolation` is on, `nodeIntegration` off, `sandbox` on, and the page carries a
+CSP that allows only its own script and stylesheet plus images over HTTPS. Links open
+in the real browser; the window itself never navigates.
+
+`PythonStoreCatalogGateway` is the only class that knows the store is a Python
+program. It talks to the CLI through `--json`, which puts data on stdout and the
+human-readable log on stderr. That flag arrived with engine **1.1.0**, and the client
+checks: an older store is met with an offer to refresh it rather than a failed call.
+
+`STORE_ENGINES` has one entry today. The RetroArch store has the same command shape,
+so a second entry is the whole change needed to drive it too — that is why the table is
+there.
 
 ## Verified, and not
 
+The 1.3.0 refactor was measured rather than trusted: `make check` is clean — no type
+errors, no lint findings, both test suites green — the window was photographed before
+and after and the two are the same picture, and the packaged 1.3.0 bundle was run from
+`dist/` and drove the real store. The published package contains `build/` and
+`package.json` and nothing else: 111 entries, no sources, no toolchain.
+
 Exercised on macOS (arm64), with the packaged app from the release rather than a
 dev run: the store is discovered, the catalog lists, a sync installs, the window
 renders the installed state, and `npm run uitest` passes with the grid rendered

RELEASE_NOTES.md

@@ -1,32 +1,42 @@
-# WarpEngine Store 1.2.0
+# WarpEngine Store 1.3.0
 
-**A side menu.** Everything that is not a title moved out of the bar into a menu on
-the left that folds away with `☰`: the stores on this machine, the two actions, the
-categories and the language. Open or closed is remembered between runs.
+**TypeScript, in layers.** The client was one `main.js`, one `preload.js`, three files
+in `lib/` and one renderer script. It is now a typed application with the dependency
+rule pointing inward: `domain` (models, ports, errors) knows nothing about Electron,
+Node or Python; `application` orchestrates it through those ports; `infrastructure`
+holds the adapters — the Python CLI, HTTP, the filesystem, Electron itself — and the
+hosts (`main`, `preload`, `renderer`) sit on top. **[STRUCTURE.md](STRUCTURE.md)** is
+the map: every layer, every pattern in use, and the naming rules, written to be read
+before adding anything.
 
-**Categories.** The grid narrows to *Installed*, *Updates* or *Not installed*, to a
-platform (`godot`, `tic80`, `love`, …), or to native/hosted titles — one at a time,
-each with its count. The axes are built from what the catalog actually contains, so
-nothing empty is listed, and a category that disappears under you falls back to
-*Everything* rather than leaving a blank grid.
+Nothing about the window changed. Same side menu, same categories, same switcher, same
+two languages — this release is the inside of the app.
 
-**Switching stores.** With more than one store installed, clicking another in the
-menu opens it: the grid, the categories and the folders follow, and the client
-reopens on the store last used. Two stores installed from the same catalog into
-different folders are told apart by their folder, since their id is identical.
+Two properties came out of the move, and both are worth having:
 
-While the store is working, the menu, the log drawer and the filters keep working —
-only what would start a second call is disabled.
+- **The catalog can be driven with no window and no Electron at all.** `make smoke`
+  assembles the same services against the same ports in a plain Node process. It was a
+  script that reimplemented the bridge before; now it is a second composition root.
+- **The window never receives a filesystem path.** A title crosses the bridge without
+  one, and launching is asked for *by name* — the main process resolves what that means
+  from the store's own state. Nothing in the renderer can be talked into opening a path.
 
-**The grid was broken, and now is not.** Its rows split the window's height evenly
-rather than following their content, so every card came out 94px tall: the box art
-collapsed to nothing and the action buttons were clipped away below the fold. The
-DOM was intact the whole time — ten cards, twenty buttons — which is why every
-automated count passed. Cards now carry a band of art of one height, with the
-title's first letter where the catalog has no image.
+**A strict linter, and types everywhere.** `strict` plus
+`noUncheckedIndexedAccess`, `exactOptionalPropertyTypes`, `noImplicitOverride`,
+`noPropertyAccessFromIndexSignature` and friends; typescript-eslint's
+`strictTypeChecked` and `stylisticTypeChecked` sets; explicit return types, parameter
+types and property types required even where inference would manage; exhaustive
+switches; no `any`, no `!`, no casts on foreign data — engine output and the registry
+go through readers that turn `unknown` into typed values. The naming patterns are
+enforced by `naming-convention` rather than trusted.
 
-Unchanged from 1.1.0: which stores exist is the site's answer (`GET /api/stores`),
-not something baked into this app, and `STORES_API` overrides that address.
+Two things the types now catch that a person used to: a translation with a missing key
+does not compile, and a channel the preload does not implement does not compile.
+
+**New make targets:** `make build`, `make typecheck`, `make lint`, `make lint-fix` and
+`make check` — the gate, which runs the type-check, the linter and both test suites in
+that order, cheapest failure first. Every script that runs the app builds first, so a
+stale bundle cannot be tested.
 
 ### Opening it on macOS
 
@@ -37,22 +47,17 @@ xattr -dr com.apple.quarantine "/Applications/WarpEngine Store.app"
 ```
 
 *Open Anyway* under **System Settings ▸ Privacy & Security** works as well.
-Nothing the store itself downloads is affected — Python fetches those, and Python
-does not set the quarantine flag.
 
 ### What is attached
 
-**macOS arm64 only**, the machine this was built and verified on. Windows and
-Linux packages need a build on those platforms (`make dist-win` / `dist-linux`).
+**macOS arm64 only**, the machine this was built and verified on. Windows and Linux
+packages need a build on those platforms (`make dist-win` / `make dist-linux`).
 
 ### Verified
 
-`SELFTEST_SHOT=shot.png npm run uitest` has the window photograph itself, which is
-how the collapsed rows were found and how the fix was confirmed — in English and in
-Hungarian, with the menu open and closed.
-
-`npm run uitest` loads the window and reports what rendered; with two stores in one
-root — a sandbox copy beside the real install — it now also clicks the store that
-is not open and checks that the bar, the grid and the categories follow. Both runs
-pass, and `npm run smoke` drives the same bridge with no window at all: ten titles,
-five native and five hosted, every installed one with something to launch.
+`make check` is clean: no type errors, no lint findings, the smoke test green against
+the real store and against a sandbox one, and the window test green with one store and
+with two — where it clicks the store that is not open and checks that the bar, the grid
+and the categories follow. The window was photographed before and after the refactor
+and the two are the same picture. The packaged app was run from the built bundle, not
+from a dev launch.

STRUCTURE.md

@@ -0,0 +1,289 @@
+# Structure
+
+This is the map of the client: which layer may know about which, what every kind of
+class is called, and which pattern is used where. It is written to be read before
+adding anything — the point of the layout is that a new feature has an obvious place.
+
+The application drives a program that **installs and deletes files**. That is why the
+rules below are strict rather than tasteful: an implicit `any` or a filesystem path
+that reaches the window is a safety question, not a style one.
+
+## The layers
+
+```
+shared      ← contracts and strings both sides need (no logic, no I/O)
+domain      ← models, ports, errors. Knows nothing about Electron, Node or Python
+application ← services and DTO mappers. Orchestrates the domain through its ports
+infrastructure ← adapters: the Python CLI, HTTP, the filesystem, Electron itself
+main        ← the Electron host: window, IPC controllers, composition root
+preload     ← the bridge, and only the bridge
+renderer    ← the window: state store, views, controllers
+```
+
+**The dependency rule: imports point inward.** `domain` imports nothing but `shared`.
+`application` imports `domain` and `shared`. `infrastructure` implements `domain`
+ports. `main`, `preload` and `renderer` are hosts: they may import inward, and nothing
+imports them. There is no barrel file and no `index.ts` re-export — every import names
+the module it needs, so a cycle is visible in the diff that creates it.
+
+Two consequences worth stating, because they are the reason the layout pays for
+itself:
+
+- **`domain` and `application` never import `electron`.** The smoke test assembles the
+  same services with no Electron at all (`src/scripts/SmokeTest.ts`), which is how the
+  catalog is exercised in a terminal.
+- **The renderer never receives a filesystem path it could act on.** `GameDto` has no
+  paths; a launch is asked for by name and resolved in the main process.
+
+## The tree
+
+```
+src/
+  shared/
+    contracts/
+      IpcChannels.ts          every channel name, frozen, in one table
+      BridgeApi.ts            the whole surface the window gets
+      dto/                    what crosses the bridge: plain, JSON-safe data
+    i18n/
+      EnglishMessages.ts      the key set, and the English bundle
+      HungarianMessages.ts    typed against those keys
+      MessageBundle.ts        MessageBundle, Locale, LOCALES
+      TranslationCatalog.ts   locale resolution and bundle lookup
+  domain/
+    models/                   Game, InstalledStore, RegistryStore, StorePaths, …
+    ports/                    the interfaces the application depends on
+    errors/                   DomainError and its subclasses, each with a code
+  application/
+    services/                 CatalogService, StoreSelectionService, …
+    mappers/                  domain → DTO
+  infrastructure/
+    process/                  Python: locating it, running it, reading its streams
+    repositories/             the port implementations
+    mappers/                  engine JSON → domain
+    http/                     HttpTextClient, HttpStatusError
+    json/                     JsonRecord: reading data that came from elsewhere
+    electron/                 ApplicationEnvironment and GameLauncher adapters
+  main/
+    main.ts                   the entry point: one line of work
+    ElectronApplication.ts    lifecycle, single instance, self-test mode
+    MainWindowFactory.ts      the window and its security settings
+    composition/              ServiceContainer: the composition root
+    ipc/                      IpcRouter, the controllers, the guard, argument readers
+    streams/                  WindowStreamBroadcaster: the three one-way streams
+    diagnostics/              SelfTestRunner
+  preload/
+    preload.ts                implements BridgeApi over ipcRenderer
+  renderer/
+    main.ts                   the entry point
+    RendererApplication.ts    wires views and controllers, owns the boot decision
+    BridgeAccess.ts           the typed window.storeApi
+    state/                    AppStore, CategoryFilter
+    views/                    one class per region of the window
+    controllers/              one class per group of actions
+    dom/                      Dom.ts: the DOM chores
+    index.html, style.css     copied into the build as-is
+  scripts/
+    SmokeTest.ts              the second composition root, with no window
+```
+
+## Patterns
+
+Every pattern in the codebase is listed here. If a change needs a pattern that is not
+on this list, it belongs on this list.
+
+### Ports and adapters
+
+`domain/ports/*` are interfaces; `infrastructure/*` implements them; the composition
+root is the only file that knows which implementation is in use. This is what makes
+the Python CLI, the registry HTTP call and Electron's `shell` replaceable — by a stub
+in a test, by a local endpoint in development, by a second engine later.
+
+### Repository and Gateway
+
+Both are ports; the distinction is what is behind them.
+
+- **Repository** — a store of records this application owns the shape of:
+  `InstalledStoreRepository`, `PreferencesRepository`, `StoreRegistryRepository`.
+- **Gateway** — another program or service with its own protocol:
+  `StoreCatalogGateway` (the engine).
+
+### Service
+
+`application/services/*` — one service per area of behaviour, no HTTP, no `fs`, no
+`child_process`. A service may depend on ports and on other services, never on a
+controller or a view.
+
+### DTO and Mapper
+
+Data crossing a boundary is a DTO, and a mapper converts. Two boundaries, two
+directions:
+
+- `infrastructure/mappers/Engine*Mapper` — engine JSON (snake_case) → domain model.
+  These are the only files that know the engine's field names.
+- `application/mappers/*DtoMapper` — domain model → DTO for the bridge. Decisions the
+  window must not make live here: the absolute box-art URL, whether a title can be
+  launched at all.
+
+### Composition root
+
+`main/composition/ServiceContainer.ts` for the application, `scripts/SmokeTest.ts` for
+the headless check. Wiring happens in exactly these two places. No service constructs
+its own adapter, and there is no service locator or global registry — dependencies
+arrive through constructors.
+
+### Controller and Router
+
+`main/ipc/*IpcController` register their channels on `IpcRouter` and translate a
+channel invocation into one service call. They validate their arguments
+(`IpcArguments.ts`) and map results through DTO mappers. The router normalises errors
+so a `DomainError` crosses as `CODE: message`.
+
+Renderer controllers (`renderer/controllers/*`) are the mirror image: a user action
+becomes one bridge call and one write to the state store.
+
+### Single flight
+
+`SingleFlightGuard` — one engine call at a time, because the store writes files and
+two writers would race. It reports its state, which is what lets the window disable
+exactly the controls that would start a second call and leave the filters and the log
+alive.
+
+### Observer streams
+
+Main pushes three one-way streams — log lines, progress events, busy state — through
+`WindowStreamBroadcaster`, which the engine sees as an `EngineProgressListener`. The
+renderer subscribes once, in `EngineStreamController`.
+
+### State store and unidirectional flow
+
+`renderer/state/AppStore.ts` holds the whole window state. Every mutator is named
+after what it changes and notifies afterwards; `RendererApplication` re-renders every
+view from the new state. Views never read each other and never hold state, so a
+listing can be thrown away and rebuilt.
+
+### Passive view
+
+`renderer/views/*` — a view takes its DOM nodes and callbacks in the constructor and
+has one `render(state)` method. It contains no decisions beyond presentation, and it
+never calls the bridge.
+
+### Error hierarchy with codes
+
+`DomainError` is abstract with a `code`; subclasses name a single failure
+(`PythonMissingError`, `StoreMissingError`, `EngineInvocationError`,
+`RegistryUnavailableError`, `BusyError`). The code is what crosses the bridge.
+
+### Frozen constant tables
+
+`IPC_CHANNELS`, `STORE_ENGINES`, the message bundles: `as const` tables with a derived
+type, so a typo is a compile error and adding an entry is the whole change. This is
+the extension point for a second engine.
+
+### Untrusted-data readers
+
+Anything parsed from outside — engine stdout, the registry — goes through
+`infrastructure/json/JsonRecord.ts`: `unknown` in, a typed value with a stated
+fallback out. No `as` casts on foreign data.
+
+## Naming
+
+The names are a pattern, not a preference, and are checked by
+`@typescript-eslint/naming-convention` where a linter can check them.
+
+### Files
+
+- One primary export per file; the filename is the subject in `PascalCase`
+  (`CatalogService.ts`, `GameDto.ts`).
+- A file whose primary export is a constant table is named for the table, and the
+  export is its `UPPER_SNAKE_CASE` form (`IpcChannels.ts` exports `IPC_CHANNELS`).
+- Directories are lowercase and plural where they hold several of a kind (`models`,
+  `ports`, `views`, `services`).
+
+### Types and classes
+
+| Kind | Pattern | Example |
+|---|---|---|
+| Domain model | plain noun, no suffix | `Game`, `InstalledStore` |
+| Port | `<Subject>Repository` / `Gateway` / `Locator` / `Installer` / `Launcher` | `StoreCatalogGateway` |
+| Adapter | `<Technology><Port>` | `PythonStoreCatalogGateway`, `HttpStoreRegistryRepository`, `FileSystemInstalledStoreRepository` |
+| Service | `<Area>Service` | `CatalogService` |
+| Mapper | `<Subject>Mapper` / `<Subject>DtoMapper` | `EngineGameMapper`, `GameDtoMapper` |
+| Wire type | `<Subject>Dto` | `CatalogListingDto` |
+| IPC controller | `<Domain>IpcController` | `CatalogIpcController` |
+| Renderer controller | `<Area>Controller` | `StoreController` |
+| View | `<Region>View` | `SideMenuView`, `GameCardView` |
+| Factory | `<Product>Factory` | `MainWindowFactory` |
+| Error | `<Cause>Error` | `PythonMissingError` |
+| Callback bag | `<Owner>Callbacks` | `SideMenuViewCallbacks` |
+| Type parameter | `T`-prefixed | `TResult`, `TElement` |
+
+Interfaces carry no `I` prefix: a port is named for what it does, and its
+implementations say what they are made of.
+
+### Methods
+
+The verb states the contract, so a caller knows what a name will do before reading it.
+
+| Prefix | Contract |
+|---|---|
+| `find…` | returns the thing or `null` / an array; absence is normal |
+| `require…` | returns the thing or **throws**; absence is a fault |
+| `read…` | fetches from a store, a file or a process |
+| `list…` | returns a collection from somewhere outside |
+| `install…`, `sync…`, `remove…`, `select…`, `update…` | changes something |
+| `apply…` | writes to the renderer state store |
+| `render…` | draws (views only) |
+| `handle…` | an IPC or DOM event handler |
+| `on…` | a callback property or subscription |
+| `to…` / `from…` | a mapper conversion |
+| `is…`, `has…`, `can…` | a boolean |
+| `describe…` | turns something into a message for a person |
+
+Booleans read as assertions (`supported`, `installed`, `launchable`, `busy`), never
+`flag` or `status`.
+
+## Type rules
+
+- `strict`, plus `noUncheckedIndexedAccess`, `exactOptionalPropertyTypes`,
+  `noImplicitOverride`, `noImplicitReturns`, `noPropertyAccessFromIndexSignature`,
+  `noFallthroughCasesInSwitch`, `isolatedModules`.
+- **Every signature is annotated** — parameters, return types, class properties —
+  including where inference would manage: `explicit-function-return-type`,
+  `explicit-module-boundary-types` and `typedef` are errors.
+- Data is `readonly`: DTO and model fields, and arrays as `readonly T[]`.
+- No `any`, no non-null `!`, no unchecked casts. Foreign data goes through
+  `JsonRecord`; DOM lookups go through `requireElement`, which checks the element type
+  it was asked for.
+- Exhaustive `switch` over union types, checked by `switch-exhaustiveness-check` — the
+  sync-event union is handled that way on purpose.
+
+`erasableSyntaxOnly` is deliberately **off**: constructor parameter properties are how
+dependencies are declared here, and that is worth more than being strippable by
+`node --experimental-strip-types`.
+
+## How to add things
+
+**A new bridge call.** Add the channel to `IPC_CHANNELS`, the method to `BridgeApi`,
+the implementation to `preload.ts`, a `handle…` method to the right controller, and the
+behaviour to a service. The compiler names every file you missed.
+
+**A new engine (e.g. RetroArch).** Add an entry to `STORE_ENGINES`. The store
+discovery, the home suffix and the launcher name all read from that table; the CLI has
+the same command shape, so `PythonStoreCatalogGateway` is unchanged.
+
+**A new field from the engine.** `EngineGameMapper` reads it into the model, `GameDto`
+and `GameDtoMapper` carry it across if the window needs it, and a view renders it.
+
+**A new language.** Add `<Language>Messages.ts` typed as `MessageBundle`, add the code
+to `LOCALES` and the bundle to `TranslationCatalog`. A missing key will not compile.
+
+## Build layout
+
+`tsc` compiles the main process to CommonJS in `build/`. The preload and the renderer
+are **bundled** by esbuild into one file each (`build/preload/preload.js`,
+`build/renderer/app.js`), because a sandboxed preload may not require its own modules
+and a module script over `file://` is blocked by the page's origin rules. `index.html`
+and `style.css` are copied. `electron-builder` ships `build/**` and nothing else.
+
+`make check` is the gate: `typecheck`, `lint`, then the two test suites — the cheapest
+check that can fail runs first.

eslint.config.mjs

@@ -0,0 +1,49 @@
+// Strict on purpose: this is a client that drives a program which deletes files,
+// so an implicit `any` crossing a layer boundary is not a style question.
+import tseslint from 'typescript-eslint'
+
+export default tseslint.config(
+  { ignores: ['build/**', 'dist/**', 'node_modules/**', 'scripts/*.js', 'scripts/*.mjs', 'eslint.config.mjs'] },
+  ...tseslint.configs.strictTypeChecked,
+  ...tseslint.configs.stylisticTypeChecked,
+  {
+    languageOptions: {
+      parserOptions: { projectService: true, tsconfigRootDir: import.meta.dirname }
+    },
+    rules: {
+      // Types everywhere, including the ones TypeScript would happily infer: a
+      // signature is the layer's contract, and it should be readable without
+      // running the compiler in your head.
+      '@typescript-eslint/explicit-function-return-type': ['error', { allowExpressions: false }],
+      '@typescript-eslint/explicit-module-boundary-types': 'error',
+      '@typescript-eslint/typedef': ['error', { parameter: true, propertyDeclaration: true }],
+      // typedef and no-inferrable-types disagree about `fallback: string = ''`. The
+      // annotation wins: a signature states its types even where TypeScript could
+      // guess them.
+      '@typescript-eslint/no-inferrable-types': ['error', { ignoreParameters: true }],
+      '@typescript-eslint/consistent-type-definitions': ['error', 'interface'],
+      '@typescript-eslint/prefer-readonly': 'error',
+      '@typescript-eslint/no-floating-promises': 'error',
+      '@typescript-eslint/no-unnecessary-condition': 'error',
+      '@typescript-eslint/switch-exhaustiveness-check': 'error',
+
+      // The naming patterns STRUCTURE.md documents, enforced rather than trusted.
+      '@typescript-eslint/naming-convention': ['error',
+        { selector: 'default', format: ['camelCase'] },
+        { selector: 'variable', format: ['camelCase', 'UPPER_CASE'] },
+        { selector: 'parameter', format: ['camelCase'], leadingUnderscore: 'allow' },
+        { selector: 'typeLike', format: ['PascalCase'] },
+        { selector: 'enumMember', format: ['UPPER_CASE'] },
+        { selector: 'objectLiteralProperty', format: null },
+        { selector: 'typeProperty', format: ['camelCase'] },
+        { selector: 'classProperty', modifiers: ['static', 'readonly'], format: ['UPPER_CASE'] },
+        { selector: 'classMethod', format: ['camelCase'] },
+        { selector: 'function', format: ['camelCase'] }
+      ],
+
+      'no-console': 'off',
+      curly: ['error', 'multi-line'],
+      eqeqeq: ['error', 'always']
+    }
+  }
+)

lib/bootstrap.js

@@ -1,159 +0,0 @@
-'use strict'
-// Setting up a store when there is none yet.
-//
-// This is the reason the client exists on Windows at all: the shell installer is
-// `curl … | sh`, which Windows does not have. The three files it would place are
-// downloaded here instead, into the very same store home — so the CLI and the
-// client stay one installation, and running install.sh afterwards only adds the
-// launcher script.
-//
-// Which store, though, is not baked in. The client asks a registry — `GET
-// /api/stores` on the site — and each record says what the store is called, which
-// catalog it serves and where its configuration lives. A different site, or a
-// second store on ours, needs no change here. The registry address is the one
-// address the client does know, and even that is overridable.
-
-const fs = require('node:fs')
-const https = require('node:https')
-const http = require('node:http')
-const path = require('node:path')
-
-// Where the engine itself comes from. Not part of the registry: this is the
-// client's own machinery, the same for every store it can drive.
-const FORGE = process.env.FORGE_BASE || 'https://git.teletypegames.org'
-const ENGINE_SOURCES = {
-  'desktop_store.py': `${FORGE}/stores/warp-engine-desktop-store/raw/branch/master/desktop_store.py`,
-  'warpstore.py': `${FORGE}/engines/warpstore/raw/branch/master/warpstore.py`
-}
-
-// The registry. One address, and the only thing about a particular site left in
-// the client.
-const REGISTRY_URL = process.env.STORES_API || 'https://teletypegames.org/api/stores'
-
-/** GET a URL as a string, following redirects — a moved repo answers 301. */
-function fetchText (url, redirects = 5) {
-  return new Promise((resolve, reject) => {
-    const client = url.startsWith('http://') ? http : https
-    const request = client.get(url, { headers: { 'User-Agent': 'warp-engine-desktop-gui' } }, (res) => {
-      if (res.statusCode >= 300 && res.statusCode < 400 && res.headers.location) {
-        res.resume()
-        if (redirects <= 0) return reject(new Error(`too many redirects for ${url}`))
-        return fetchText(new URL(res.headers.location, url).toString(), redirects - 1).then(resolve, reject)
-      }
-      if (res.statusCode !== 200) {
-        res.resume()
-        const error = new Error(`${url} answered ${res.statusCode}`)
-        error.statusCode = res.statusCode
-        return reject(error)
-      }
-      let body = ''
-      res.setEncoding('utf8')
-      res.on('data', (chunk) => { body += chunk })
-      res.on('end', () => resolve(body))
-    })
-    request.setTimeout(60000, () => request.destroy(new Error(`${url} timed out`)))
-    request.on('error', reject)
-  })
-}
-
-/**
- * The stores this client can install, from the site's registry.
- *
- * Each record carries a name, the catalog it serves and the repository holding
- * its config. Anything without those three is dropped rather than half-used.
- */
-async function registry (url = REGISTRY_URL) {
-  const body = await fetchText(url)
-  const rows = JSON.parse(body)
-  if (!Array.isArray(rows)) throw new Error(`${url} did not answer with a list of stores`)
-  return rows
-    .map((row) => ({
-      name: String(row.name || '').trim(),
-      catalogUrl: String(row.catalogUrl || row.catalog_url || '').trim(),
-      storeRepositoryUrl: String(row.storeRepositoryUrl || row.store_repository_url || '').trim()
-    }))
-    .filter((row) => row.name && row.catalogUrl && row.storeRepositoryUrl)
-}
-
-/** `…/stores/ttg-desktop-store` -> the raw config.json on its default branch. */
-function configUrl (repositoryUrl, branch = 'master') {
-  return `${repositoryUrl.replace(/\/+$/, '')}/raw/branch/${branch}/config.json`
-}
-
-/**
- * A store id from its repository name: `ttg-desktop-store` -> `ttg`.
- *
- * The id names the store home and the folder the games land in, so it has to be
- * short and filesystem-safe. The repository name is the best source we have; the
- * store's own config.json overrides it whenever it exists.
- */
-function storeId (store) {
-  const last = store.storeRepositoryUrl.replace(/\/+$/, '').split('/').pop() || ''
-  const base = last.replace(/-(desktop-)?store$/, '') || store.name
-  return base.toLowerCase().replace(/[^a-z0-9._-]+/g, '-').replace(/^-+|-+$/g, '') || 'store'
-}
-
-/**
- * The store's configuration.
- *
- * Its repository is the authority on how the store behaves — which platforms,
- * which statuses, where things land. A repository without a config.json still
- * works: the engine merges whatever it is given onto its own defaults, so a
- * three-field config is a complete one.
- */
-async function storeConfig (store, { onLog = () => {} } = {}) {
-  const id = storeId(store)
-  let config = null
-  try {
-    onLog(`reading the store config from ${store.storeRepositoryUrl}`)
-    config = JSON.parse(await fetchText(configUrl(store.storeRepositoryUrl)))
-  } catch (err) {
-    if (err.statusCode !== 404) throw err
-    onLog('no config.json in the store repository — using the engine defaults')
-    config = { paths: { subfolder: id }, catalog: { statuses: ['released', 'archived', 'demo'] } }
-  }
-  // The registry is the authority on identity and on which catalog to read, so
-  // those two win over whatever the file says.
-  config.store = { ...(config.store || {}) }
-  config.store.id = config.store.id || id
-  config.store.name = store.name
-  config.store.base_url = store.catalogUrl
-  return config
-}
-
-/** Where this store's home goes. */
-function homeFor (store, root) {
-  return path.join(root, `${storeId(store)}-desktop`)
-}
-
-/**
- * Install the engine, the shared core and the store's config into `home`.
- *
- * `onLog` reports each step, because on a slow line this takes a few seconds and
- * silence looks like a hang.
- */
-async function install (home, store, { onLog = () => {} } = {}) {
-  if (!store) throw new Error('no store was chosen')
-  fs.mkdirSync(home, { recursive: true })
-
-  for (const [file, url] of Object.entries(ENGINE_SOURCES)) {
-    onLog(`downloading ${file}`)
-    const body = await fetchText(url)
-    if (!body.startsWith('#!/usr/bin/env python3')) {
-      throw new Error(`${file} does not look like the store engine — refusing to install it`)
-    }
-    fs.writeFileSync(path.join(home, file), body, { mode: 0o755 })
-  }
-
-  const configPath = path.join(home, 'config.json')
-  const config = await storeConfig(store, { onLog })
-  fs.writeFileSync(configPath, `${JSON.stringify(config, null, 2)}\n`)
-
-  onLog(`${store.name} is set up in ${home}`)
-  return { home, config: configPath, script: path.join(home, 'desktop_store.py'), id: config.store.id }
-}
-
-module.exports = {
-  ENGINE_SOURCES, FORGE, REGISTRY_URL,
-  configUrl, fetchText, homeFor, install, registry, storeConfig, storeId
-}

lib/i18n.js

@@ -1,130 +0,0 @@
-'use strict'
-// Two languages, the way the public site has them. The CLI and the docs stay
-// English; this is the one end-user surface where Hungarian matters.
-//
-// Catalog text — titles, descriptions — is never translated here: it arrives
-// from the store as it was published.
-
-const STRINGS = {
-  en: {
-    appName: 'WarpEngine Store',
-    syncAll: 'Install all',
-    refresh: 'Refresh',
-    install: 'Install',
-    update: 'Update',
-    play: 'Play',
-    open: 'Open',
-    remove: 'Remove',
-    installed: 'installed',
-    native: 'native',
-    hosted: 'hosted',
-    hostedHint: 'Opens in your browser — needs the network',
-    nativeHint: 'Installed on this machine — works offline',
-    updateAvailable: 'update available',
-    log: 'Log',
-    menu: 'Menu',
-    stores: 'Stores',
-    addStore: 'Add a store…',
-    switchFailed: 'That store could not be opened',
-    actions: 'Actions',
-    categories: 'Categories',
-    catAll: 'Everything',
-    catInstalled: 'Installed',
-    catUpdates: 'Updates',
-    catAvailable: 'Not installed',
-    catPlatform: 'Platform',
-    catMode: 'Kind',
-    language: 'Language',
-    noGames: 'No installable titles in the catalog.',
-    noMatch: 'Nothing in this category.',
-    setupTitle: 'Set up a store',
-    setupBody: 'No store on this machine yet. Pick one and it will be downloaded — the same files the shell installer would place, in the same folder.',
-    setupAction: 'Download the store',
-    setupWorking: 'Setting up…',
-    setupChoose: 'Store',
-    registryFailed: 'The list of stores could not be fetched',
-    registryEmpty: 'The list of stores came back empty. Nothing to install from yet.',
-    registryRetry: 'Try again',
-    oldEngineTitle: 'The store needs refreshing',
-    oldEngineBody: 'The store engine on this machine is older than this client can drive. Refreshing it downloads the current engine and keeps your settings and installed games.',
-    oldEngineAction: 'Refresh the store',
-    noPythonTitle: 'Python 3 is required',
-    noPythonBody: 'The store is a Python program, so Python 3 has to be installed. Install it, then reopen this window.',
-    pythonLink: 'python.org/downloads',
-    paths: 'Where things go',
-    openStoreFolder: 'Open the store folder',
-    openMenuFolder: 'Open the menu folder',
-    busy: 'Working…',
-    failed: 'failed',
-    removed: 'removed',
-    upToDate: 'Everything is up to date.',
-    of: 'of'
-  },
-  hu: {
-    appName: 'WarpEngine Store',
-    syncAll: 'Mind telepítése',
-    refresh: 'Frissítés',
-    install: 'Telepítés',
-    update: 'Frissítés',
-    play: 'Indítás',
-    open: 'Megnyitás',
-    remove: 'Eltávolítás',
-    installed: 'telepítve',
-    native: 'natív',
-    hosted: 'hosztolt',
-    hostedHint: 'A böngészőben nyílik meg — internet kell hozzá',
-    nativeHint: 'Erre a gépre telepítve — internet nélkül is megy',
-    updateAvailable: 'frissítés elérhető',
-    log: 'Napló',
-    menu: 'Menü',
-    stores: 'Store-ok',
-    addStore: 'Store hozzáadása…',
-    switchFailed: 'Ez a store nem nyitható meg',
-    actions: 'Műveletek',
-    categories: 'Kategóriák',
-    catAll: 'Minden',
-    catInstalled: 'Telepítve',
-    catUpdates: 'Frissítés',
-    catAvailable: 'Nincs telepítve',
-    catPlatform: 'Platform',
-    catMode: 'Fajta',
-    language: 'Nyelv',
-    noGames: 'Nincs telepíthető cím a katalógusban.',
-    noMatch: 'Ebben a kategóriában nincs semmi.',
-    setupTitle: 'Store beállítása',
-    setupBody: 'Ezen a gépen még nincs store. Válassz egyet, és letöltöm — ugyanazokat a fájlokat, ugyanabba a könyvtárba, ahová a shell-telepítő tenné.',
-    setupAction: 'Store letöltése',
-    setupWorking: 'Beállítás…',
-    setupChoose: 'Store',
-    registryFailed: 'A store-ok listája nem érhető el',
-    registryEmpty: 'A store-ok listája üresen jött vissza. Egyelőre nincs miből telepíteni.',
-    registryRetry: 'Újra',
-    oldEngineTitle: 'A store frissítésre vár',
-    oldEngineBody: 'A gépen lévő store-motor régebbi, mint amit ez a kliens vezérelni tud. A frissítés letölti a mostani motort, a beállításaid és a telepített játékok pedig megmaradnak.',
-    oldEngineAction: 'Store frissítése',
-    noPythonTitle: 'Python 3 kell hozzá',
-    noPythonBody: 'A store egy Python program, tehát Python 3 kell a gépre. Telepítsd, majd nyisd meg újra ezt az ablakot.',
-    pythonLink: 'python.org/downloads',
-    paths: 'Hova kerül',
-    openStoreFolder: 'Store könyvtár megnyitása',
-    openMenuFolder: 'Menü könyvtár megnyitása',
-    busy: 'Dolgozom…',
-    failed: 'hiba',
-    removed: 'eltávolítva',
-    upToDate: 'Minden naprakész.',
-    of: '/'
-  }
-}
-
-const FALLBACK = 'en'
-
-function pick (locale) {
-  const short = String(locale || '').slice(0, 2).toLowerCase()
-  return STRINGS[short] ? short : FALLBACK
-}
-
-function dict (locale) {
-  return STRINGS[pick(locale)]
-}
-
-module.exports = { FALLBACK, STRINGS, dict, pick, languages: Object.keys(STRINGS) }

lib/store.js

@@ -1,258 +0,0 @@
-'use strict'
-// The bridge to the store CLI.
-//
-// The CLI is the product; this file only finds it and talks to it. Every
-// operation is `desktop_store.py --json …`, which puts data on stdout and its
-// log on stderr — so nothing here parses a sentence meant for a person.
-//
-// Shaped for more than one engine on purpose: ENGINES is a list today with one
-// entry, and the RetroArch store could be added without touching the callers.
-
-const { spawn, spawnSync } = require('node:child_process')
-const fs = require('node:fs')
-const os = require('node:os')
-const path = require('node:path')
-
-const ENGINES = [
-  {
-    id: 'desktop',
-    script: 'desktop_store.py',
-    // The installer names the store home `<store id>-desktop`, so the RetroArch
-    // engine can share the same root without sharing config.json and state.json.
-    homeSuffix: '-desktop',
-    launcherSuffix: '-desktop-store'
-  }
-]
-
-/** The roots the shell installers use, in the same order they would. */
-function storeRoots () {
-  const home = os.homedir()
-  const roots = []
-  if (process.env.STORE_ROOT) roots.push(process.env.STORE_ROOT)
-  if (process.env.XDG_DATA_HOME) {
-    roots.push(path.join(process.env.XDG_DATA_HOME, 'warp-engine-store'))
-  }
-  roots.push(path.join(home, '.local', 'share', 'warp-engine-store'))
-  if (process.platform === 'darwin') {
-    roots.push(path.join(home, 'Library', 'Application Support', 'warp-engine-store'))
-  }
-  if (process.platform === 'win32' && process.env.LOCALAPPDATA) {
-    roots.push(path.join(process.env.LOCALAPPDATA, 'warp-engine-store'))
-  }
-  return [...new Set(roots)]
-}
-
-/** Every installed store this client can drive. */
-function findStores () {
-  const found = []
-  for (const root of storeRoots()) {
-    let entries = []
-    try {
-      entries = fs.readdirSync(root, { withFileTypes: true })
-    } catch { continue }
-    for (const entry of entries) {
-      if (!entry.isDirectory()) continue
-      const home = path.join(root, entry.name)
-      for (const engine of ENGINES) {
-        const script = path.join(home, engine.script)
-        const config = path.join(home, 'config.json')
-        if (fs.existsSync(script) && fs.existsSync(config)) {
-          found.push({ engine: engine.id, id: entry.name.replace(engine.homeSuffix, ''), home, script, config })
-        }
-      }
-    }
-  }
-  return found
-}
-
-/**
- * The store to drive: the one asked for by home if it is still there, otherwise
- * the first one found. The client remembers the choice, so a machine with two
- * stores reopens on the one last used rather than on whichever sorts first.
- */
-function findStore (preferredHome) {
-  const stores = findStores()
-  if (preferredHome) {
-    const wanted = stores.find((store) => store.home === preferredHome)
-    if (wanted) return wanted
-  }
-  return stores[0] || null
-}
-
-/**
- * The store's own name, from the config the installer wrote. Worth reading here
- * rather than waiting for `paths`: the switcher lists every store on the machine,
- * and starting a Python process per entry to learn its name would be absurd.
- */
-function storeName (store) {
-  try {
-    const config = JSON.parse(fs.readFileSync(store.config, 'utf8'))
-    return (config.store && config.store.name) || store.id
-  } catch {
-    return store.id
-  }
-}
-
-/** An installed store as the window needs it. */
-function describe (store) {
-  return store && { id: store.id, home: store.home, engine: store.engine, name: storeName(store) }
-}
-
-/** Where a store would be installed if there is none yet. */
-function defaultHome (storeId = 'ttg') {
-  const engine = ENGINES[0]
-  return path.join(storeRoots()[0], `${storeId}${engine.homeSuffix}`)
-}
-
-// Python 3 is what the CLI needs, and its name differs per platform. `py -3` is
-// the Windows launcher, which is often the only one on PATH.
-const PYTHON_CANDIDATES = process.platform === 'win32'
-  ? [['py', ['-3']], ['python', []], ['python3', []]]
-  : [['python3', []], ['python', []]]
-
-let cachedPython = null
-
-function findPython () {
-  if (cachedPython !== undefined && cachedPython !== null) return cachedPython
-  for (const [cmd, args] of PYTHON_CANDIDATES) {
-    try {
-      const probe = spawnSync(cmd, [...args, '--version'], { encoding: 'utf8', timeout: 10000 })
-      const out = `${probe.stdout || ''}${probe.stderr || ''}`
-      if (probe.status === 0 && /Python 3\./.test(out)) {
-        cachedPython = { cmd, args, version: out.trim() }
-        return cachedPython
-      }
-    } catch { /* try the next one */ }
-  }
-  cachedPython = null
-  return null
-}
-
-class StoreError extends Error {
-  constructor (message, code) {
-    super(message)
-    this.code = code
-  }
-}
-
-// The oldest engine that speaks `--json`. An older one is not broken, it simply
-// cannot be driven from a window — and it will be met in the wild, because the
-// CLI shipped before this client did.
-const MIN_ENGINE = [1, 1, 0]
-
-function parseVersion (text) {
-  const match = /(\d+)\.(\d+)\.(\d+)/.exec(String(text || ''))
-  return match ? match.slice(1, 4).map(Number) : null
-}
-
-function atLeast (version, minimum) {
-  if (!version) return false
-  for (let i = 0; i < minimum.length; i += 1) {
-    if ((version[i] || 0) > minimum[i]) return true
-    if ((version[i] || 0) < minimum[i]) return false
-  }
-  return true
-}
-
-/** The installed engine's version string, and whether this client can drive it. */
-function engineVersion (store) {
-  const python = findPython()
-  if (!python || !store) return null
-  try {
-    const probe = spawnSync(python.cmd, [...python.args, store.script, '--version'],
-      { encoding: 'utf8', timeout: 15000 })
-    const text = `${probe.stdout || ''}${probe.stderr || ''}`.trim()
-    if (probe.status !== 0 || !text) return null
-    return { text, version: parseVersion(text), ok: atLeast(parseVersion(text), MIN_ENGINE) }
-  } catch {
-    return null
-  }
-}
-
-/**
- * Run one CLI command.
- *
- * `onLine` gets every stdout line already parsed (the CLI emits one JSON object
- * per line), `onLog` every stderr line as text. Resolves with the parsed lines.
- */
-function run (store, args, { onLine, onLog, signal } = {}) {
-  const python = findPython()
-  if (!python) throw new StoreError('python3 was not found on this machine', 'NO_PYTHON')
-  if (!store) throw new StoreError('no store is installed yet', 'NO_STORE')
-
-  const argv = [...python.args, store.script, '--config', store.config, '--json', ...args]
-  return new Promise((resolve, reject) => {
-    const child = spawn(python.cmd, argv, {
-      env: { ...process.env, DESKTOP_STORE_HOME: store.home },
-      signal
-    })
-    const lines = []
-    let stdoutRest = ''
-    let stderrRest = ''
-
-    const takeStdout = (chunk) => {
-      stdoutRest += chunk
-      const parts = stdoutRest.split('\n')
-      stdoutRest = parts.pop()
-      for (const part of parts) {
-        if (!part.trim()) continue
-        let value
-        try {
-          value = JSON.parse(part)
-        } catch {
-          // Not ours to interpret — hand it on as a log line rather than crash.
-          if (onLog) onLog(part)
-          continue
-        }
-        lines.push(value)
-        if (onLine) onLine(value)
-      }
-    }
-    const takeStderr = (chunk) => {
-      stderrRest += chunk
-      const parts = stderrRest.split('\n')
-      stderrRest = parts.pop()
-      for (const part of parts) if (part.trim() && onLog) onLog(part)
-    }
-
-    child.stdout.setEncoding('utf8')
-    child.stderr.setEncoding('utf8')
-    child.stdout.on('data', takeStdout)
-    child.stderr.on('data', takeStderr)
-    child.on('error', (err) => reject(new StoreError(err.message, 'SPAWN_FAILED')))
-    child.on('close', (code) => {
-      takeStdout('\n')
-      takeStderr('\n')
-      if (code === 0) resolve(lines)
-      else reject(new StoreError(`the store exited with code ${code}`, 'CLI_FAILED'))
-    })
-  })
-}
-
-async function list (store, hooks) {
-  const lines = await run(store, ['list'], hooks)
-  return lines[lines.length - 1] || { games: [], skipped: [] }
-}
-
-async function paths (store, hooks) {
-  const lines = await run(store, ['paths'], hooks)
-  return lines[lines.length - 1] || {}
-}
-
-function sync (store, names = [], hooks) {
-  return run(store, ['sync', ...names], hooks)
-}
-
-function remove (store, name, hooks) {
-  return run(store, ['remove', name], hooks)
-}
-
-function purge (store, hooks) {
-  return run(store, ['purge'], hooks)
-}
-
-module.exports = {
-  ENGINES, MIN_ENGINE, StoreError, atLeast, defaultHome, describe, engineVersion,
-  findPython, findStore, findStores, list, parseVersion, paths, purge, remove, run,
-  storeName, storeRoots, sync
-}

main.js

@@ -1,357 +0,0 @@
-'use strict'
-// Main process: one window, and the IPC that lets it drive the store CLI.
-//
-// The renderer gets no Node access at all (contextIsolation on, nodeIntegration
-// off, sandbox on); everything it can do is in preload.js and handled here.
-
-const { app, BrowserWindow, ipcMain, shell, dialog } = require('electron')
-const fs = require('node:fs')
-const path = require('node:path')
-const { spawn } = require('node:child_process')
-
-const store = require('./lib/store')
-const bootstrap = require('./lib/bootstrap')
-const i18n = require('./lib/i18n')
-
-let win = null
-let current = null          // the store we are driving
-let busy = false            // one CLI call at a time
-const prefsFile = () => path.join(app.getPath('userData'), 'prefs.json')
-
-function loadPrefs () {
-  try {
-    return JSON.parse(fs.readFileSync(prefsFile(), 'utf8'))
-  } catch {
-    return {}
-  }
-}
-
-function savePrefs (prefs) {
-  try {
-    fs.mkdirSync(path.dirname(prefsFile()), { recursive: true })
-    fs.writeFileSync(prefsFile(), JSON.stringify(prefs, null, 2))
-  } catch { /* a lost preference is not worth an error dialog */ }
-}
-
-function send (channel, payload) {
-  if (win && !win.isDestroyed()) win.webContents.send(channel, payload)
-}
-
-const hooks = () => ({
-  onLog: (line) => send('store:log', line),
-  onLine: (event) => send('store:event', event)
-})
-
-/** One CLI call at a time: the store writes files, and two writers would race. */
-async function guarded (fn) {
-  if (busy) throw new Error('busy')
-  busy = true
-  send('store:busy', true)
-  try {
-    return await fn()
-  } finally {
-    busy = false
-    send('store:busy', false)
-  }
-}
-
-// `--selftest` drives the window once and reports what rendered, so the UI has a
-// check that does not need a pair of eyes. It is the only way a renderer error
-// would otherwise be noticed: the main process log stays empty.
-const SELFTEST = process.argv.includes('--selftest')
-
-// A test run must never be swallowed by a copy the user already has open: it gets
-// its own user-data directory and skips the single-instance lock. Without this the
-// second process exits silently with status 0, which reads as a passing test.
-if (SELFTEST) {
-  app.setPath('userData', path.join(app.getPath('temp'), 'warpstore-gui-selftest'))
-}
-
-async function selftest () {
-  const result = await win.webContents.executeJavaScript(`(() => ({
-    cards: document.querySelectorAll('.card').length,
-    installed: document.querySelectorAll('.card.is-installed').length,
-    buttons: document.querySelectorAll('.card .actions button').length,
-    gateVisible: !document.getElementById('gate').hidden,
-    gateTitle: document.getElementById('gate-title').textContent,
-    gateChoices: [...document.getElementById('gate-select').options].map((o) => o.text),
-    gateAction: document.getElementById('gate-action').textContent,
-    appName: document.getElementById('app-name').textContent,
-    storeId: document.getElementById('store-id').textContent,
-    navOpen: !document.body.classList.contains('nav-closed'),
-    stores: [...document.querySelectorAll('#store-list .store-row')].map((n) => n.textContent),
-    categories: [...document.querySelectorAll('#cats .cat')].map((n) => n.textContent),
-    activeCategory: (document.querySelector('#cats .cat.is-active') || {}).textContent || null,
-    paths: document.getElementById('log-paths').textContent.slice(0, 120),
-    logLines: document.querySelectorAll('.log-line').length,
-    locales: [...document.getElementById('locale').options].map((o) => o.value)
-  }))()`)
-  console.log(JSON.stringify(result, null, 2))
-
-  // With two stores on the machine the switcher is the thing most likely to be
-  // broken without anyone noticing, so the test uses it: click the store that is
-  // not open and see whether the window follows. Skipped when there is only one,
-  // which is the normal case — a single store cannot be switched away from.
-  let switched = null
-  if (result.stores.length > 1) {
-    switched = await win.webContents.executeJavaScript(`(async () => {
-      const other = [...document.querySelectorAll('#store-list .store-row')]
-        .find((row) => !row.classList.contains('is-active'))
-      other.click()
-      await new Promise((done) => setTimeout(done, 8000))
-      return {
-        storeId: document.getElementById('store-id').textContent,
-        active: (document.querySelector('#store-list .store-row.is-active') || {}).textContent || null,
-        cards: document.querySelectorAll('.card').length,
-        categories: document.querySelectorAll('#cats .cat').length
-      }
-    })()`)
-    console.log(`switched: ${JSON.stringify(switched)}`)
-  }
-
-  // A layout mistake does not show up in the DOM counts above, so on request the
-  // window photographs itself — the terminal cannot screenshot it from outside.
-  if (process.env.SELFTEST_SHOT) {
-    // capturePage hands back the last painted frame, so a window that is behind
-    // others — or still loading box art — photographs as a half-drawn page. Focus
-    // it, wait for the images, then let one frame go by.
-    win.show()
-    win.focus()
-    await win.webContents.executeJavaScript(`(async () => {
-      await Promise.all([...document.images].map((img) => img.complete
-        ? null
-        : new Promise((done) => { img.onload = done; img.onerror = done })))
-      await new Promise((done) => requestAnimationFrame(() => setTimeout(done, 400)))
-      return document.images.length
-    })()`)
-    const image = await win.webContents.capturePage()
-    fs.writeFileSync(process.env.SELFTEST_SHOT, image.toPNG())
-    console.log(`shot: ${process.env.SELFTEST_SHOT}`)
-  }
-
-  // Either outcome is a pass: a grid when a store is installed — with the side
-  // menu populated, which is the part a blank render would silently lose — or the
-  // setup gate with something to choose from when there is none.
-  const good = result.locales.length > 1 && (
-    (result.cards > 0 && !result.gateVisible &&
-      result.stores.length > 0 && result.categories.length > 0 && result.activeCategory) ||
-    (result.gateVisible && result.gateChoices.length > 0 && result.gateAction))
-  const switchGood = switched === null || (
-    switched.storeId && switched.storeId !== result.storeId &&
-    switched.cards > 0 && switched.categories > 0)
-  console.log(good && switchGood ? 'SELFTEST OK' : 'SELFTEST FAILED')
-  app.exit(good && switchGood ? 0 : 1)
-}
-
-function createWindow () {
-  win = new BrowserWindow({
-    width: 1040,
-    height: 720,
-    minWidth: 760,
-    minHeight: 520,
-    backgroundColor: '#11151c',
-    title: 'WarpEngine Store',
-    webPreferences: {
-      preload: path.join(__dirname, 'preload.js'),
-      contextIsolation: true,
-      nodeIntegration: false,
-      sandbox: true,
-      webSecurity: true
-    }
-  })
-
-  win.loadFile(path.join(__dirname, 'renderer', 'index.html'))
-
-  // A renderer error is invisible from here otherwise.
-  win.webContents.on('console-message', (_event, level, message) => {
-    if (level >= 2 || SELFTEST) console.log(`[renderer] ${message}`)
-  })
-  win.webContents.on('render-process-gone', (_event, details) => {
-    console.log(`[renderer] gone: ${details.reason}`)
-    if (SELFTEST) app.exit(1)
-  })
-  if (SELFTEST) {
-    // The first list() has to finish before there is anything to look at.
-    win.webContents.once('did-finish-load', () => setTimeout(() => {
-      selftest().catch((err) => { console.log(`SELFTEST ERROR ${err.message}`); app.exit(1) })
-    }, 6000))
-  }
-
-  // Nothing in this app should ever navigate away or open a second window; a
-  // link the user clicks goes to their browser instead.
-  win.webContents.setWindowOpenHandler(({ url }) => {
-    if (/^https:\/\//.test(url)) shell.openExternal(url)
-    return { action: 'deny' }
-  })
-  win.webContents.on('will-navigate', (event, url) => {
-    if (url !== win.webContents.getURL()) {
-      event.preventDefault()
-      if (/^https:\/\//.test(url)) shell.openExternal(url)
-    }
-  })
-}
-
-// --- IPC ------------------------------------------------------------------
-
-ipcMain.handle('app:state', () => {
-  const prefs = loadPrefs()
-  const python = store.findPython()
-  // Every store on the machine, because the window offers a switch between them —
-  // and the remembered one wins, so reopening lands where the user left off.
-  const stores = store.findStores()
-  current = store.findStore(prefs.store)
-  // An engine that predates `--json` cannot be driven from a window; the client
-  // says so and offers to refresh it rather than failing on the first call.
-  const engine = current ? store.engineVersion(current) : null
-  return {
-    locale: i18n.pick(prefs.locale || app.getLocale()),
-    languages: i18n.languages,
-    strings: i18n.dict(prefs.locale || app.getLocale()),
-    nav: prefs.nav !== false,
-    python: python ? python.version : null,
-    store: store.describe(current),
-    stores: stores.map(store.describe),
-    engine: engine ? { text: engine.text, ok: engine.ok } : null,
-    minEngine: store.MIN_ENGINE.join('.'),
-    registryUrl: bootstrap.REGISTRY_URL,
-    storeRoot: store.storeRoots()[0],
-    version: app.getVersion()
-  }
-})
-
-// The side menu's open/closed state is worth keeping between runs; it is the one
-// preference the window sets that is not a language.
-ipcMain.handle('app:setNav', (_event, open) => {
-  const prefs = loadPrefs()
-  prefs.nav = Boolean(open)
-  savePrefs(prefs)
-  return prefs.nav
-})
-
-/**
- * Switch to another installed store.
- *
- * The choice is remembered, and the engine is checked here rather than in the
- * window: two stores on one machine can be at different versions, and the one
- * being switched to may be the older one.
- */
-ipcMain.handle('store:use', (_event, home) => {
-  const wanted = store.findStores().find((candidate) => candidate.home === home)
-  if (!wanted) throw new Error('that store is no longer on this machine')
-  current = wanted
-  const prefs = loadPrefs()
-  prefs.store = wanted.home
-  savePrefs(prefs)
-  const engine = store.engineVersion(current)
-  return {
-    store: store.describe(current),
-    engine: engine ? { text: engine.text, ok: engine.ok } : null
-  }
-})
-
-ipcMain.handle('app:setLocale', (_event, locale) => {
-  const prefs = loadPrefs()
-  prefs.locale = i18n.pick(locale)
-  savePrefs(prefs)
-  return { locale: prefs.locale, strings: i18n.dict(prefs.locale) }
-})
-
-ipcMain.handle('store:list', () => guarded(() => store.list(current, hooks())))
-ipcMain.handle('store:paths', () => guarded(() => store.paths(current, hooks())))
-
-ipcMain.handle('store:sync', (_event, names) =>
-  guarded(() => store.sync(current, Array.isArray(names) ? names : [], hooks())))
-
-ipcMain.handle('store:remove', (_event, name) =>
-  guarded(() => store.remove(current, String(name), hooks())))
-
-// The stores this client can install, from the site's registry rather than from
-// anything baked in here. A separate call because it needs the network: the first
-// window paints without waiting for it.
-ipcMain.handle('store:registry', async () => {
-  try {
-    return { stores: await bootstrap.registry() }
-  } catch (err) {
-    return { stores: [], error: err.message, url: bootstrap.REGISTRY_URL }
-  }
-})
-
-ipcMain.handle('store:bootstrap', (_event, chosen) => guarded(async () => {
-  if (!chosen) throw new Error('no store was chosen')
-  const home = bootstrap.homeFor(chosen, store.storeRoots()[0])
-  const result = await bootstrap.install(home, chosen, { onLog: (line) => send('store:log', line) })
-  current = { engine: 'desktop', ...result }
-  const prefs = loadPrefs()
-  prefs.store = current.home
-  savePrefs(prefs)
-  return { ...store.describe(current), name: chosen.name }
-}))
-
-/**
- * Launch what was installed.
- *
- * A hosted title is a URL, so it goes to the browser. A native one is whatever
- * the store recorded: on macOS the app bundle through `open`, elsewhere the
- * executable from its own directory — the same working directory the menu entry
- * uses, because games load their assets relative to it.
- */
-ipcMain.handle('store:launch', async (_event, game) => {
-  if (!game) return false
-  if (game.mode === 'web' && game.url) {
-    await shell.openExternal(game.url)
-    return true
-  }
-  const target = game.menu_entry || game.exe
-  if (!target || !fs.existsSync(target)) return false
-  if (process.platform === 'darwin' && target.endsWith('.app')) {
-    spawn('open', [target], { detached: true, stdio: 'ignore' }).unref()
-    return true
-  }
-  if (process.platform === 'win32' || target.endsWith('.desktop')) {
-    const error = await shell.openPath(target)
-    if (!error) return true
-  }
-  const exe = game.exe || target
-  spawn(exe, [], { cwd: path.dirname(exe), detached: true, stdio: 'ignore' }).unref()
-  return true
-})
-
-ipcMain.handle('app:openFolder', async (_event, dir) => {
-  if (!dir) return false
-  const error = await shell.openPath(dir)
-  return !error
-})
-
-ipcMain.handle('app:openExternal', async (_event, url) => {
-  if (!/^https:\/\//.test(String(url))) return false
-  await shell.openExternal(String(url))
-  return true
-})
-
-// --- lifecycle ------------------------------------------------------------
-
-if (!SELFTEST && !app.requestSingleInstanceLock()) {
-  app.quit()
-} else {
-  app.on('second-instance', () => {
-    if (win) {
-      if (win.isMinimized()) win.restore()
-      win.focus()
-    }
-  })
-
-  app.whenReady().then(() => {
-    createWindow()
-    app.on('activate', () => {
-      if (BrowserWindow.getAllWindows().length === 0) createWindow()
-    })
-  })
-
-  app.on('window-all-closed', () => {
-    if (process.platform !== 'darwin') app.quit()
-  })
-
-  process.on('unhandledRejection', (reason) => {
-    dialog.showErrorBox('WarpEngine Store', String(reason && reason.message ? reason.message : reason))
-  })
-}

package.json

@@ -1,36 +1,43 @@
 {
   "name": "warp-engine-desktop-gui",
   "productName": "WarpEngine Store",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "description": "Graphical client for a WarpEngine desktop store: install the catalog into your own application menu.",
   "license": "MIT",
   "author": "Teletype Games <games@teletype.hu>",
   "homepage": "https://git.teletypegames.org/stores/warp-engine-desktop-gui",
-  "main": "main.js",
+  "main": "build/main/main.js",
   "engines": {
     "node": ">=22"
   },
   "scripts": {
-    "start": "electron .",
-    "smoke": "node scripts/smoke.js",
-    "dist": "electron-builder",
-    "dist:mac": "electron-builder --mac",
-    "dist:win": "electron-builder --win",
-    "dist:linux": "electron-builder --linux",
-    "uitest": "electron . --selftest"
+    "build": "tsc -p tsconfig.build.json && node scripts/build-assets.mjs",
+    "typecheck": "tsc -p tsconfig.json --noEmit",
+    "lint": "eslint .",
+    "lint:fix": "eslint . --fix",
+    "start": "npm run build && electron .",
+    "smoke": "npm run build && node build/scripts/SmokeTest.js",
+    "uitest": "npm run build && electron . --selftest",
+    "dist": "npm run build && electron-builder",
+    "dist:mac": "npm run build && electron-builder --mac",
+    "dist:win": "npm run build && electron-builder --win",
+    "dist:linux": "npm run build && electron-builder --linux"
   },
   "devDependencies": {
+    "@types/node": "^26.2.0",
     "electron": "^43.4.0",
-    "electron-builder": "^26.15.3"
+    "electron-builder": "^26.15.3",
+    "esbuild": "^0.28.2",
+    "eslint": "^10.8.1",
+    "typescript": "^6.0.3",
+    "typescript-eslint": "^8.67.0"
   },
   "build": {
     "appId": "org.teletypegames.warpstore.gui",
     "productName": "WarpEngine Store",
     "files": [
-      "main.js",
-      "preload.js",
-      "lib/**/*",
-      "renderer/**/*"
+      "build/**/*",
+      "package.json"
     ],
     "mac": {
       "category": "public.app-category.games",
@@ -55,6 +62,7 @@
     "afterPack": "scripts/after-pack.js"
   },
   "allowScripts": {
-    "electron@43.4.0": true
+    "electron@43.4.0": true,
+    "esbuild@0.28.2": true
   }
 }

preload.js

@@ -1,29 +0,0 @@
-'use strict'
-// The whole surface the renderer gets. No Node, no fs, no child_process — just
-// these calls and two event streams.
-
-const { contextBridge, ipcRenderer } = require('electron')
-
-contextBridge.exposeInMainWorld('storeApi', {
-  state: () => ipcRenderer.invoke('app:state'),
-  setLocale: (locale) => ipcRenderer.invoke('app:setLocale', locale),
-  setNav: (open) => ipcRenderer.invoke('app:setNav', open),
-
-  list: () => ipcRenderer.invoke('store:list'),
-  paths: () => ipcRenderer.invoke('store:paths'),
-  sync: (names) => ipcRenderer.invoke('store:sync', names),
-  remove: (name) => ipcRenderer.invoke('store:remove', name),
-  use: (home) => ipcRenderer.invoke('store:use', home),
-  registry: () => ipcRenderer.invoke('store:registry'),
-  bootstrap: (store) => ipcRenderer.invoke('store:bootstrap', store),
-  launch: (game) => ipcRenderer.invoke('store:launch', game),
-
-  openFolder: (dir) => ipcRenderer.invoke('app:openFolder', dir),
-  openExternal: (url) => ipcRenderer.invoke('app:openExternal', url),
-
-  // Streams from the running CLI: `log` is a line a person can read, `event` is
-  // one of the store's JSON progress events.
-  onLog: (fn) => ipcRenderer.on('store:log', (_e, line) => fn(line)),
-  onEvent: (fn) => ipcRenderer.on('store:event', (_e, event) => fn(event)),
-  onBusy: (fn) => ipcRenderer.on('store:busy', (_e, value) => fn(value))
-})

renderer/app.js

@@ -1,555 +0,0 @@
-'use strict'
-// The whole renderer. No framework and no build step: a side menu on the left
-// decides what is shown, a grid of cards on the right shows it, and every action
-// is one call over the bridge in preload.js.
-
-const api = window.storeApi
-const el = (id) => document.getElementById(id)
-
-let T = {}                 // the active string table
-let state = null           // what the main process knows: stores, python, engine
-let games = []
-let paths = null
-let busy = false
-let plan = null            // { total, done } while a sync is running
-
-// What the grid is narrowed down to. One category at a time on purpose: a matrix
-// of filters would need explaining, and a catalog of this size does not earn it.
-let filter = { kind: 'group', value: 'all' }
-
-// --- helpers --------------------------------------------------------------
-
-function text (node, value) {
-  node.textContent = value == null ? '' : String(value)
-}
-
-function imageUrl (game) {
-  if (!game.image_url) return null
-  if (/^https?:\/\//.test(game.image_url)) return game.image_url
-  const base = (paths && paths.store && paths.store.base_url) || ''
-  return base ? `${base}${game.image_url}` : null
-}
-
-function logLine (line) {
-  const box = el('log-lines')
-  const row = document.createElement('div')
-  row.className = 'log-line'
-  text(row, line)
-  box.appendChild(row)
-  while (box.childElementCount > 400) box.removeChild(box.firstChild)
-  box.scrollTop = box.scrollHeight
-}
-
-// While the CLI runs, anything that would start a second call is disabled. The
-// menu toggle, the log drawer and the category filters are not among them: they
-// only change what is on screen.
-function setBusy (value) {
-  busy = value
-  for (const node of document.querySelectorAll('button')) {
-    if (node.id === 'log-toggle' || node.id === 'nav-toggle') continue
-    if (node.classList.contains('cat')) continue
-    node.disabled = value
-  }
-  const progress = el('progress')
-  if (!value) {
-    progress.hidden = true
-    plan = null
-  }
-}
-
-function showProgress (label) {
-  const progress = el('progress')
-  progress.hidden = false
-  text(progress, label)
-}
-
-// --- the side menu --------------------------------------------------------
-
-function setNav (open) {
-  document.body.classList.toggle('nav-closed', !open)
-  el('nav-toggle').setAttribute('aria-expanded', String(open))
-}
-
-function renderStores () {
-  const box = el('store-list')
-  const stores = (state && state.stores) || []
-  const active = state && state.store ? state.store.home : null
-  // Two stores can carry the same id in different roots — the same catalog
-  // installed twice. Then the id says nothing and the folder is what tells them
-  // apart, so that is what the row shows.
-  const ambiguous = new Set(stores
-    .filter((store, index) => stores.findIndex((other) => other.id === store.id) !== index)
-    .map((store) => store.id))
-  box.replaceChildren(...stores.map((store) => {
-    const row = document.createElement('button')
-    row.className = 'store-row'
-    if (store.home === active) row.classList.add('is-active')
-    const name = document.createElement('span')
-    name.className = 'store-row-name'
-    text(name, store.name)
-    row.appendChild(name)
-    const id = document.createElement('span')
-    id.className = 'store-row-id'
-    text(id, ambiguous.has(store.id) ? store.home : store.id)
-    row.appendChild(id)
-    row.title = store.home
-    row.addEventListener('click', () => {
-      if (store.home !== active) switchStore(store.home)
-    })
-    return row
-  }))
-  el('add-store').hidden = false
-}
-
-/**
- * The categories, built from what the catalog actually contains.
- *
- * There is no genre in a WarpEngine catalog, so the useful axes are the state of
- * a title on this machine, the platform it was built with, and whether it runs
- * here or in a browser. Empty axes are left out rather than shown as zeroes.
- */
-function categories () {
-  const count = (fn) => games.filter(fn).length
-  const sections = [{
-    group: null,
-    items: [
-      { kind: 'group', value: 'all', label: T.catAll, count: games.length },
-      { kind: 'group', value: 'installed', label: T.catInstalled, count: count((g) => g.installed) },
-      { kind: 'group', value: 'updates', label: T.catUpdates, count: count((g) => g.update_available) },
-      { kind: 'group', value: 'available', label: T.catAvailable, count: count((g) => !g.installed) }
-    ].filter((item) => item.value === 'all' || item.count > 0)
-  }]
-
-  const platforms = [...new Set(games.map((g) => g.platform).filter(Boolean))].sort()
-  if (platforms.length > 1) {
-    sections.push({
-      group: T.catPlatform,
-      items: platforms.map((platform) => ({
-        kind: 'platform', value: platform, label: platform, count: count((g) => g.platform === platform)
-      }))
-    })
-  }
-
-  const modes = [...new Set(games.map((g) => g.mode).filter(Boolean))]
-  if (modes.length > 1) {
-    sections.push({
-      group: T.catMode,
-      items: modes.map((mode) => ({
-        kind: 'mode', value: mode, label: mode === 'web' ? T.hosted : T.native, count: count((g) => g.mode === mode)
-      }))
-    })
-  }
-  return sections
-}
-
-function matches (game) {
-  if (filter.kind === 'platform') return game.platform === filter.value
-  if (filter.kind === 'mode') return game.mode === filter.value
-  if (filter.value === 'installed') return Boolean(game.installed)
-  if (filter.value === 'updates') return Boolean(game.update_available)
-  if (filter.value === 'available') return !game.installed
-  return true
-}
-
-function renderCats () {
-  const box = el('cats')
-  const sections = categories()
-
-  // A category can vanish under us — the last title of a platform is removed, or
-  // an update is applied — and a filter matching nothing would look like an empty
-  // catalog. Falling back to everything is the honest answer.
-  const known = sections.flatMap((section) => section.items)
-    .some((item) => item.kind === filter.kind && item.value === filter.value)
-  if (!known) filter = { kind: 'group', value: 'all' }
-
-  const nodes = []
-  for (const section of sections) {
-    if (section.group) {
-      const head = document.createElement('div')
-      head.className = 'cat-group'
-      text(head, section.group)
-      nodes.push(head)
-    }
-    for (const item of section.items) {
-      const button = document.createElement('button')
-      button.className = 'cat'
-      if (item.kind === filter.kind && item.value === filter.value) button.classList.add('is-active')
-      const label = document.createElement('span')
-      label.className = 'cat-label'
-      text(label, item.label)
-      button.appendChild(label)
-      const count = document.createElement('span')
-      count.className = 'cat-count'
-      text(count, item.count)
-      button.appendChild(count)
-      button.addEventListener('click', () => {
-        filter = { kind: item.kind, value: item.value }
-        renderCats()
-        renderGrid()
-      })
-      nodes.push(button)
-    }
-  }
-  box.replaceChildren(...nodes)
-}
-
-// --- the card grid --------------------------------------------------------
-
-function card (game) {
-  const node = document.createElement('article')
-  node.className = 'card'
-  if (game.installed) node.classList.add('is-installed')
-
-  const art = document.createElement('div')
-  art.className = 'art'
-  const src = imageUrl(game)
-  if (src) {
-    const img = document.createElement('img')
-    img.src = src
-    img.alt = ''
-    img.loading = 'lazy'
-    art.appendChild(img)
-  } else {
-    // No box art in the catalog: the first letter, on the same band an image
-    // would fill, so a row of cards stays aligned either way.
-    const glyph = document.createElement('span')
-    glyph.className = 'art-glyph'
-    text(glyph, game.title.slice(0, 1).toUpperCase())
-    art.appendChild(glyph)
-  }
-  node.appendChild(art)
-
-  const body = document.createElement('div')
-  body.className = 'body'
-
-  const title = document.createElement('h2')
-  text(title, game.title)
-  body.appendChild(title)
-
-  const meta = document.createElement('div')
-  meta.className = 'meta'
-  const mode = document.createElement('span')
-  mode.className = `badge badge-${game.mode}`
-  text(mode, game.mode === 'web' ? T.hosted : T.native)
-  mode.title = game.mode === 'web' ? T.hostedHint : T.nativeHint
-  meta.appendChild(mode)
-  const platform = document.createElement('span')
-  platform.className = 'badge badge-plain'
-  text(platform, game.platform)
-  meta.appendChild(platform)
-  const version = document.createElement('span')
-  version.className = 'version'
-  text(version, game.installed && game.installed_version
-    ? `${game.installed_version} · ${T.installed}`
-    : game.version)
-  meta.appendChild(version)
-  body.appendChild(meta)
-
-  if (game.desc) {
-    const desc = document.createElement('p')
-    desc.className = 'desc'
-    text(desc, game.desc)
-    body.appendChild(desc)
-  }
-
-  const actions = document.createElement('div')
-  actions.className = 'actions'
-
-  if (game.installed && !game.update_available) {
-    const play = document.createElement('button')
-    play.className = 'btn btn-primary'
-    text(play, game.mode === 'web' ? T.open : T.play)
-    play.addEventListener('click', () => api.launch(game))
-    actions.appendChild(play)
-  } else {
-    const install = document.createElement('button')
-    install.className = 'btn btn-primary'
-    text(install, game.update_available ? T.update : T.install)
-    install.addEventListener('click', () => runSync([game.name]))
-    actions.appendChild(install)
-  }
-
-  if (game.installed) {
-    const remove = document.createElement('button')
-    remove.className = 'btn btn-ghost'
-    text(remove, T.remove)
-    remove.addEventListener('click', () => runRemove(game.name))
-    actions.appendChild(remove)
-  }
-
-  body.appendChild(actions)
-  node.appendChild(body)
-  return node
-}
-
-function renderGrid () {
-  const shown = games.filter(matches)
-  const grid = el('grid')
-  grid.replaceChildren(...shown.map(card))
-  grid.hidden = shown.length === 0
-  grid.scrollTop = 0
-  const empty = el('empty')
-  empty.hidden = shown.length !== 0
-  text(empty, games.length === 0 ? T.noGames : T.noMatch)
-}
-
-function renderPaths () {
-  const box = el('log-paths')
-  box.replaceChildren()
-  if (!paths) return
-  const line = document.createElement('div')
-  line.className = 'paths-line'
-  text(line, `${T.paths}: ${paths.store_folder} · ${paths.menu_group}`)
-  box.appendChild(line)
-
-  for (const [label, dir] of [[T.openStoreFolder, paths.store_folder],
-                              [T.openMenuFolder, paths.menu_group]]) {
-    const button = document.createElement('button')
-    button.className = 'btn btn-tiny'
-    text(button, label)
-    button.addEventListener('click', () => api.openFolder(dir))
-    box.appendChild(button)
-  }
-}
-
-// --- actions --------------------------------------------------------------
-
-async function refresh () {
-  try {
-    const result = await api.list()
-    games = result.games || []
-    paths = result.paths || paths
-    renderCats()
-    renderGrid()
-    renderPaths()
-    for (const reason of result.skipped || []) logLine(`skipped ${reason}`)
-  } catch (err) {
-    logLine(String(err && err.message ? err.message : err))
-  }
-}
-
-async function runSync (names) {
-  try {
-    await api.sync(names || [])
-  } catch (err) {
-    logLine(String(err && err.message ? err.message : err))
-  }
-  await refresh()
-}
-
-async function runRemove (name) {
-  try {
-    await api.remove(name)
-  } catch (err) {
-    logLine(String(err && err.message ? err.message : err))
-  }
-  await refresh()
-}
-
-/** Open another store that is already on this machine. */
-async function switchStore (home) {
-  try {
-    const next = await api.use(home)
-    state.store = next.store
-    state.engine = next.engine
-    text(el('store-id'), next.store.id)
-    renderStores()
-    games = []
-    paths = null
-    filter = { kind: 'group', value: 'all' }
-    if (next.engine && !next.engine.ok) {
-      renderCats()
-      showOldEngineGate()
-      return
-    }
-    hideGate()
-    await refresh()
-  } catch (err) {
-    logLine(`${T.switchFailed}: ${err && err.message ? err.message : err}`)
-  }
-}
-
-/** Pick up a store that appeared since the window opened. */
-async function reloadState () {
-  state = await api.state()
-  text(el('store-id'), state.store ? state.store.id : '')
-  renderStores()
-}
-
-// --- gate: no python, no store yet, or an engine too old ------------------
-
-function showGate (title, body, action, link, choices) {
-  el('grid').hidden = true
-  el('empty').hidden = true
-  const gate = el('gate')
-  gate.hidden = false
-  text(el('gate-title'), title)
-  text(el('gate-body'), body)
-
-  // Only shown when the registry offers more than one store; with a single one
-  // there is nothing to decide.
-  const choice = el('gate-choice')
-  const select = el('gate-select')
-  choice.hidden = !choices || choices.length < 2
-  if (!choice.hidden) {
-    text(el('gate-choice-label'), T.setupChoose)
-    select.replaceChildren(...choices.map((store, index) => {
-      const option = document.createElement('option')
-      option.value = String(index)
-      option.textContent = store.name
-      return option
-    }))
-  }
-
-  const button = el('gate-action')
-  button.hidden = !action
-  if (action) {
-    text(button, action.label)
-    button.onclick = () => action.onClick(choices ? choices[Number(select.value) || 0] : undefined)
-  }
-  const anchor = el('gate-link')
-  anchor.hidden = !link
-  if (link) {
-    text(anchor, link.label)
-    anchor.onclick = (event) => { event.preventDefault(); api.openExternal(link.url) }
-  }
-}
-
-function hideGate () {
-  el('gate').hidden = true
-}
-
-function showOldEngineGate () {
-  showGate(T.oldEngineTitle,
-    `${T.oldEngineBody}\n\n${state.engine.text} → ${state.minEngine}`,
-    { label: T.oldEngineAction, onClick: offerStores })
-}
-
-async function setUpStore (chosen) {
-  showProgress(T.setupWorking)
-  try {
-    await api.bootstrap(chosen)
-    await reloadState()
-    hideGate()
-    await refresh()
-  } catch (err) {
-    logLine(String(err && err.message ? err.message : err))
-  }
-}
-
-// Which stores exist is the site's answer, not this client's: the registry is
-// asked for it, and its records carry the catalog and the config repository.
-async function offerStores () {
-  const result = await api.registry()
-  if (result.error) {
-    showGate(`${T.registryFailed}`, `${result.url}\n\n${result.error}`,
-      { label: T.registryRetry, onClick: offerStores })
-    return
-  }
-  if (!result.stores.length) {
-    showGate(T.setupTitle, `${T.registryEmpty}\n\n${result.url}`, null)
-    return
-  }
-  showGate(T.setupTitle,
-    `${T.setupBody}\n\n${state.storeRoot}`,
-    { label: T.setupAction, onClick: async (chosen) => { await setUpStore(chosen); await runSync([]) } },
-    null,
-    result.stores)
-}
-
-// --- boot -----------------------------------------------------------------
-
-function applyStrings (strings) {
-  T = strings
-  text(el('app-name'), T.appName)
-  text(el('sync-all'), T.syncAll)
-  text(el('refresh'), T.refresh)
-  text(el('log-toggle'), T.log)
-  text(el('head-stores'), T.stores)
-  text(el('head-actions'), T.actions)
-  text(el('head-cats'), T.categories)
-  text(el('head-lang'), T.language)
-  text(el('add-store'), T.addStore)
-  el('nav-toggle').title = T.menu
-  el('nav-toggle').setAttribute('aria-label', T.menu)
-  renderPaths()
-  if (state) renderStores()
-  if (games.length) {
-    renderCats()
-    renderGrid()
-  }
-}
-
-async function boot () {
-  state = await api.state()
-  applyStrings(state.strings)
-  setNav(state.nav !== false)
-  renderStores()
-
-  const select = el('locale')
-  select.replaceChildren(...state.languages.map((code) => {
-    const option = document.createElement('option')
-    option.value = code
-    option.textContent = code.toUpperCase()
-    if (code === state.locale) option.selected = true
-    return option
-  }))
-  select.addEventListener('change', async () => {
-    const next = await api.setLocale(select.value)
-    applyStrings(next.strings)
-  })
-
-  if (!state.python) {
-    showGate(T.noPythonTitle, T.noPythonBody, null,
-      { label: T.pythonLink, url: 'https://www.python.org/downloads/' })
-    return
-  }
-
-  if (!state.store) {
-    await offerStores()
-    return
-  }
-
-  if (state.engine && !state.engine.ok) {
-    showOldEngineGate()
-    return
-  }
-
-  text(el('store-id'), state.store.id)
-  hideGate()
-  await refresh()
-}
-
-el('sync-all').addEventListener('click', () => runSync([]))
-el('refresh').addEventListener('click', () => refresh())
-el('add-store').addEventListener('click', () => offerStores())
-el('nav-toggle').addEventListener('click', () => {
-  const open = document.body.classList.contains('nav-closed')
-  setNav(open)
-  api.setNav(open)
-})
-el('log-toggle').addEventListener('click', () => {
-  const box = el('log-lines')
-  box.hidden = !box.hidden
-  el('log-toggle').setAttribute('aria-expanded', String(!box.hidden))
-})
-
-api.onLog(logLine)
-api.onBusy(setBusy)
-api.onEvent((event) => {
-  if (event.event === 'plan') {
-    plan = { total: event.count, done: 0 }
-    showProgress(`0 ${T.of} ${event.count}`)
-  } else if (event.event === 'begin' && plan) {
-    showProgress(`${plan.done + 1} ${T.of} ${plan.total} · ${event.title}`)
-  } else if (event.event === 'installed' && plan) {
-    plan.done += 1
-    logLine(`${event.title} — ${event.changed ? T.installed : T.upToDate}`)
-  } else if (event.event === 'failed') {
-    logLine(`${event.name}: ${T.failed} — ${event.error}`)
-  } else if (event.event === 'removed') {
-    logLine(`${event.name} — ${T.removed}`)
-  }
-})
-
-boot()

scripts/build-assets.mjs

@@ -0,0 +1,54 @@
+// The two bundles and the two static files.
+//
+// tsc compiles the main process, where CommonJS and `require` are fine. The preload
+// and the renderer cannot work that way: a sandboxed preload may not require its own
+// modules, and a module script over file:// is blocked by the page's own origin
+// rules. So both are bundled into one file each — the layering stays in src/, the
+// window gets a single script.
+import { build } from 'esbuild'
+import { copyFile, mkdir } from 'node:fs/promises'
+import { dirname, join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const root = dirname(dirname(fileURLToPath(import.meta.url)))
+const outDir = join(root, 'build')
+
+const bundles = [
+  {
+    label: 'preload',
+    entryPoints: [join(root, 'src/preload/preload.ts')],
+    outfile: join(outDir, 'preload/preload.js'),
+    platform: 'node',
+    format: 'cjs',
+    // Provided by Electron at runtime; bundling it would break the sandbox.
+    external: ['electron']
+  },
+  {
+    label: 'renderer',
+    entryPoints: [join(root, 'src/renderer/main.ts')],
+    outfile: join(outDir, 'renderer/app.js'),
+    platform: 'browser',
+    format: 'iife',
+    external: []
+  }
+]
+
+for (const bundle of bundles) {
+  await build({
+    entryPoints: bundle.entryPoints,
+    outfile: bundle.outfile,
+    bundle: true,
+    platform: bundle.platform,
+    format: bundle.format,
+    external: bundle.external,
+    target: 'es2023',
+    logLevel: 'warning'
+  })
+  console.log(`bundled ${bundle.label} -> ${bundle.outfile.replace(`${root}/`, '')}`)
+}
+
+await mkdir(join(outDir, 'renderer'), { recursive: true })
+for (const asset of ['index.html', 'style.css']) {
+  await copyFile(join(root, 'src/renderer', asset), join(outDir, 'renderer', asset))
+  console.log(`copied ${asset}`)
+}

scripts/release.sh

@@ -99,27 +99,44 @@ RELEASE_ID="$(release_id)"
 [ -n "$RELEASE_ID" ] || die "the release $TAG could not be created or found"
 
 # --- the attachments -------------------------------------------------------
-while IFS= read -r asset; do
-  [ -n "$asset" ] || continue
-  [ -f "$asset" ] || die "no such file: $asset"
-  name="$(basename "$asset")"
-
-  # Replacing rather than refusing: a second run after a rebuild should land.
-  old="$(tea api "/repos/$REPO/releases/$RELEASE_ID/assets" | python3 -c "
+# Anything already attached under this name, dropped: replacing rather than
+# refusing is what makes a rebuild-and-upload repeatable. Called before every
+# attempt, so a retry cannot leave two copies behind.
+drop_existing() {
+  ids="$(tea api "/repos/$REPO/releases/$RELEASE_ID/assets" | python3 -c "
 import json, sys
 name = sys.argv[1]
 for a in json.load(sys.stdin):
     if a['name'] == name:
         print(a['id'])
-" "$name")"
-  for id in $old; do
-    say "replacing $name"
+" "$1")"
+  for id in $ids; do
+    say "replacing $1"
     tea api -X DELETE "/repos/$REPO/releases/$RELEASE_ID/assets/$id" >/dev/null
   done
+}
 
+while IFS= read -r asset; do
+  [ -n "$asset" ] || continue
+  [ -f "$asset" ] || die "no such file: $asset"
+  name="$(basename "$asset")"
   size="$(python3 -c "import os,sys; print(f'{os.path.getsize(sys.argv[1])/1e6:.0f} MB')" "$asset")"
+
+  # Retried, because a 100 MB upload does fail on its own: publishing 1.2.0 got
+  # "invalid username, password or token" on the second package while the first
+  # had just gone up with the same token, and the identical command succeeded on
+  # the next run. One flake should not cost a rebuild.
+  attempt=1
+  while :; do
+    drop_existing "$name"
     say "uploading $name ($size) — large packages take a few minutes"
-  tea releases assets create --login "$LOGIN" --repo "$REPO" "$TAG" "$asset" >/dev/null
+    if tea releases assets create --login "$LOGIN" --repo "$REPO" "$TAG" "$asset" >/dev/null; then
+      break
+    fi
+    [ "$attempt" -lt 3 ] || die "$name could not be uploaded after $attempt attempts"
+    attempt=$((attempt + 1))
+    say "that failed — attempt $attempt of 3"
+  done
 done < "$LIST"
 
 say "done:"

scripts/smoke.js

@@ -1,128 +0,0 @@
-#!/usr/bin/env node
-'use strict'
-// Drives the bridge without Electron: no window, no packaging, just the part
-// that talks to the store. This is where an integration mistake shows up first,
-// so it is the check to run after touching lib/store.js or the CLI.
-//
-//   npm run smoke                       the store installed on this machine
-//   SMOKE_HOME=/path/to/store-home npm run smoke     a sandbox store
-
-const path = require('node:path')
-const fs = require('node:fs')
-const store = require('../lib/store')
-const bootstrap = require('../lib/bootstrap')
-const i18n = require('../lib/i18n')
-
-function ok (label, value) {
-  console.log(`  ok    ${label}${value === undefined ? '' : `: ${value}`}`)
-}
-function bad (label, value) {
-  console.log(`  FAIL  ${label}${value === undefined ? '' : `: ${value}`}`)
-  process.exitCode = 1
-}
-
-async function main () {
-  console.log('warp-engine-desktop-gui smoke test')
-
-  const python = store.findPython()
-  if (python) ok('python', python.version)
-  else return bad('python', 'not found — the store cannot run')
-
-  for (const lang of i18n.languages) {
-    const dict = i18n.dict(lang)
-    const missing = Object.keys(i18n.STRINGS[i18n.FALLBACK]).filter((k) => !dict[k])
-    if (missing.length) bad(`strings:${lang}`, `missing ${missing.join(', ')}`)
-    else ok(`strings:${lang}`, `${Object.keys(dict).length} keys`)
-  }
-
-  // The registry is what decides which stores exist, so it is checked before
-  // anything that depends on one being installed.
-  try {
-    const stores = await bootstrap.registry()
-    if (!stores.length) bad('registry', `${bootstrap.REGISTRY_URL} returned no stores`)
-    else {
-      ok('registry', `${stores.length} store(s) from ${bootstrap.REGISTRY_URL}`)
-      for (const store of stores) {
-        ok(`  ${store.name}`, `${store.catalogUrl} · ${bootstrap.storeId(store)}`)
-        const url = bootstrap.configUrl(store.storeRepositoryUrl)
-        try {
-          const config = JSON.parse(await bootstrap.fetchText(url))
-          ok('  config.json', `${Object.keys(config).length} sections`)
-        } catch (err) {
-          // Not fatal: the engine merges onto its defaults, so a store without a
-          // config file still installs.
-          ok('  config.json', `absent (${err.statusCode || err.message}) — defaults would be used`)
-        }
-      }
-    }
-  } catch (err) {
-    bad('registry', `${bootstrap.REGISTRY_URL}: ${err.message}`)
-  }
-
-  let target = null
-  if (process.env.SMOKE_HOME) {
-    const home = path.resolve(process.env.SMOKE_HOME)
-    target = {
-      engine: 'desktop',
-      id: path.basename(home).replace(/-desktop$/, ''),
-      home,
-      script: path.join(home, 'desktop_store.py'),
-      config: path.join(home, 'config.json')
-    }
-    for (const file of [target.script, target.config]) {
-      if (!fs.existsSync(file)) return bad('SMOKE_HOME', `${file} is missing`)
-    }
-    ok('store (SMOKE_HOME)', target.home)
-  } else {
-    const stores = store.findStores()
-    if (!stores.length) {
-      console.log('  skip  no store installed — run the app once, or set SMOKE_HOME')
-      console.log(`        it would be installed in ${store.defaultHome()}`)
-      return
-    }
-    target = stores[0]
-    ok('store found', `${target.id} in ${target.home}`)
-  }
-
-  const logs = []
-  const paths = await store.paths(target, { onLog: (l) => logs.push(l) })
-  if (paths.os && paths.store_folder) ok('paths', `${paths.os} → ${paths.store_folder}`)
-  else bad('paths', JSON.stringify(paths))
-
-  const listing = await store.list(target, { onLog: (l) => logs.push(l) })
-  const games = listing.games || []
-  if (!games.length) return bad('list', 'no games came back')
-
-  const modes = games.reduce((acc, g) => {
-    acc[g.mode] = (acc[g.mode] || 0) + 1
-    return acc
-  }, {})
-  ok('list', `${games.length} titles (${Object.entries(modes).map(([m, n]) => `${m}:${n}`).join(', ')})`)
-
-  const required = ['name', 'title', 'platform', 'version', 'mode', 'kind', 'installed', 'update_available']
-  const broken = games.filter((g) => required.some((k) => g[k] === undefined))
-  if (broken.length) bad('game shape', `${broken.length} entries miss a field`)
-  else ok('game shape', required.join(', '))
-
-  const hosted = games.filter((g) => g.mode === 'web')
-  if (hosted.length && !hosted.every((g) => /^https?:\/\//.test(g.url || ''))) {
-    bad('hosted urls', 'a web title has no usable url')
-  } else if (hosted.length) {
-    ok('hosted urls', hosted[0].url)
-  }
-
-  const installed = games.filter((g) => g.installed)
-  ok('installed', `${installed.length} of ${games.length}`)
-  if (installed.length) {
-    const withTarget = installed.filter((g) => g.menu_entry || g.exe || g.url)
-    if (withTarget.length !== installed.length) bad('launch targets', 'an installed title has nothing to launch')
-    else ok('launch targets', 'every installed title has one')
-  }
-
-  if (logs.length) ok('stderr log', `${logs.length} lines (kept off stdout)`)
-}
-
-main().catch((err) => {
-  console.log(`  FAIL  ${err && err.code ? err.code : 'error'}: ${err && err.message ? err.message : err}`)
-  process.exitCode = 1
-})

src/application/mappers/EngineVersionDtoMapper.ts

@@ -0,0 +1,8 @@
+import type { EngineVersion } from '../../domain/models/EngineVersion'
+import type { EngineVersionDto } from '../../shared/contracts/dto/EngineVersionDto'
+
+export class EngineVersionDtoMapper {
+  public toDto (version: EngineVersion): EngineVersionDto {
+    return { text: version.text, supported: version.supported }
+  }
+}

src/application/mappers/GameDtoMapper.ts

@@ -0,0 +1,48 @@
+import type { Game } from '../../domain/models/Game'
+import type { GameDto } from '../../shared/contracts/dto/GameDto'
+
+const ABSOLUTE_URL = /^https?:\/\//
+
+/**
+ * A title as the window may see it.
+ *
+ * Two decisions live here rather than in the renderer: the box art is resolved
+ * against the catalog's base URL, and whether a title can be launched is answered
+ * here — so the window never receives a filesystem path it could be talked into
+ * opening.
+ */
+export class GameDtoMapper {
+  public toDto (game: Game, catalogBaseUrl: string): GameDto {
+    return {
+      name: game.name,
+      title: game.title,
+      platform: game.platform,
+      version: game.version,
+      mode: game.mode,
+      kind: game.kind,
+      description: game.description,
+      author: game.author,
+      imageUrl: this.resolveImageUrl(game, catalogBaseUrl),
+      installed: game.installed,
+      updateAvailable: game.updateAvailable,
+      installedVersion: game.installedVersion,
+      launchable: this.isLaunchable(game)
+    }
+  }
+
+  public toDtoList (games: readonly Game[], catalogBaseUrl: string): readonly GameDto[] {
+    return games.map((game: Game): GameDto => this.toDto(game, catalogBaseUrl))
+  }
+
+  private resolveImageUrl (game: Game, catalogBaseUrl: string): string | null {
+    if (game.imagePath === null) return null
+    if (ABSOLUTE_URL.test(game.imagePath)) return game.imagePath
+    return catalogBaseUrl.length > 0 ? `${catalogBaseUrl}${game.imagePath}` : null
+  }
+
+  private isLaunchable (game: Game): boolean {
+    if (!game.installed) return false
+    if (game.mode === 'web') return game.hostedUrl !== null
+    return game.menuEntryPath !== null || game.executablePath !== null
+  }
+}

src/application/mappers/InstalledStoreDtoMapper.ts

@@ -0,0 +1,12 @@
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import type { InstalledStoreDto } from '../../shared/contracts/dto/InstalledStoreDto'
+
+export class InstalledStoreDtoMapper {
+  public toDto (store: InstalledStore): InstalledStoreDto {
+    return { id: store.id, name: store.name, home: store.home, engine: store.engine }
+  }
+
+  public toDtoList (stores: readonly InstalledStore[]): readonly InstalledStoreDto[] {
+    return stores.map((store: InstalledStore): InstalledStoreDto => this.toDto(store))
+  }
+}

src/application/mappers/RegistryStoreDtoMapper.ts

@@ -0,0 +1,27 @@
+import type { RegistryStore } from '../../domain/models/RegistryStore'
+import { deriveStoreId } from '../../domain/models/StoreIdentity'
+import type { RegistryStoreDto } from '../../shared/contracts/dto/RegistryStoreDto'
+
+export class RegistryStoreDtoMapper {
+  public toDto (store: RegistryStore): RegistryStoreDto {
+    return {
+      name: store.name,
+      catalogUrl: store.catalogUrl,
+      storeRepositoryUrl: store.storeRepositoryUrl,
+      storeId: deriveStoreId(store)
+    }
+  }
+
+  public toDtoList (stores: readonly RegistryStore[]): readonly RegistryStoreDto[] {
+    return stores.map((store: RegistryStore): RegistryStoreDto => this.toDto(store))
+  }
+
+  /** The window hands a record straight back when asking for an install. */
+  public toModel (dto: RegistryStoreDto): RegistryStore {
+    return {
+      name: dto.name,
+      catalogUrl: dto.catalogUrl,
+      storeRepositoryUrl: dto.storeRepositoryUrl
+    }
+  }
+}

src/application/mappers/StorePathsDtoMapper.ts

@@ -0,0 +1,16 @@
+import type { StorePaths } from '../../domain/models/StorePaths'
+import type { StorePathsDto } from '../../shared/contracts/dto/StorePathsDto'
+
+export class StorePathsDtoMapper {
+  public toDto (paths: StorePaths): StorePathsDto {
+    return {
+      operatingSystem: paths.operatingSystem,
+      architecture: paths.architecture,
+      storeFolder: paths.storeFolder,
+      menuGroup: paths.menuGroup,
+      catalogBaseUrl: paths.catalogBaseUrl,
+      storeName: paths.storeName,
+      storeId: paths.storeId
+    }
+  }
+}

src/application/services/ApplicationStateService.ts

@@ -0,0 +1,54 @@
+import { MINIMUM_ENGINE_VERSION, formatVersion } from '../../domain/models/EngineVersion'
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import type { ApplicationEnvironment } from '../../domain/ports/ApplicationEnvironment'
+import type { PythonRuntimeLocator } from '../../domain/ports/PythonRuntimeLocator'
+import type { AppStateDto } from '../../shared/contracts/dto/AppStateDto'
+import { TranslationCatalog } from '../../shared/i18n/TranslationCatalog'
+import { EngineVersionDtoMapper } from '../mappers/EngineVersionDtoMapper'
+import { InstalledStoreDtoMapper } from '../mappers/InstalledStoreDtoMapper'
+import type { PreferencesService } from './PreferencesService'
+import type { StoreProvisioningService } from './StoreProvisioningService'
+import type { StoreSelectionService } from './StoreSelectionService'
+
+/**
+ * Everything the window needs before it can paint anything, in one answer.
+ *
+ * One call rather than six, because the first frame should not be a sequence of
+ * round trips — and because the decisions the window makes from it (no Python, no
+ * store, an engine too old) all depend on each other.
+ */
+export class ApplicationStateService {
+  public constructor (
+    private readonly preferences: PreferencesService,
+    private readonly selection: StoreSelectionService,
+    private readonly provisioning: StoreProvisioningService,
+    private readonly pythonLocator: PythonRuntimeLocator,
+    private readonly environment: ApplicationEnvironment,
+    private readonly translations: TranslationCatalog = new TranslationCatalog(),
+    private readonly storeMapper: InstalledStoreDtoMapper = new InstalledStoreDtoMapper(),
+    private readonly engineMapper: EngineVersionDtoMapper = new EngineVersionDtoMapper()
+  ) {}
+
+  public readState (): AppStateDto {
+    const locale = this.preferences.readLocale()
+    const stores = this.selection.listStores()
+    const current: InstalledStore | null = this.selection.findCurrentStore()
+    const engine = current === null ? null : this.selection.findEngineVersion(current)
+    const runtime = this.pythonLocator.findRuntime()
+
+    return {
+      locale,
+      locales: this.translations.locales,
+      messages: this.translations.readBundle(locale),
+      navigationOpen: this.preferences.readNavigationOpen(),
+      pythonVersion: runtime === null ? null : runtime.version,
+      currentStore: current === null ? null : this.storeMapper.toDto(current),
+      stores: this.storeMapper.toDtoList(stores),
+      engine: engine === null ? null : this.engineMapper.toDto(engine),
+      minimumEngineVersion: formatVersion(MINIMUM_ENGINE_VERSION),
+      registryUrl: this.provisioning.registryUrl,
+      defaultStoreRoot: this.selection.readDefaultStoreRoot(),
+      appVersion: this.environment.readVersion()
+    }
+  }
+}

src/application/services/CatalogService.ts

@@ -0,0 +1,54 @@
+import type { CatalogListing } from '../../domain/models/CatalogListing'
+import type { EngineProgressListener } from '../../domain/models/EngineProgress'
+import type { Game } from '../../domain/models/Game'
+import type { StorePaths } from '../../domain/models/StorePaths'
+import type { StoreCatalogGateway } from '../../domain/ports/StoreCatalogGateway'
+import type { StoreSelectionService } from './StoreSelectionService'
+
+/**
+ * The catalog of the store that is open.
+ *
+ * The last listing is kept so a launch can be resolved by name: the window asks
+ * for "pong", and the paths it would need to start it never leave this process.
+ */
+export class CatalogService {
+  private lastListing: CatalogListing | null = null
+
+  public constructor (
+    private readonly catalogGateway: StoreCatalogGateway,
+    private readonly selection: StoreSelectionService
+  ) {}
+
+  public async listGames (progress?: EngineProgressListener): Promise<CatalogListing> {
+    const listing = await this.catalogGateway.listGames(this.selection.requireCurrentStore(), progress)
+    this.lastListing = listing
+    return listing
+  }
+
+  public async readPaths (progress?: EngineProgressListener): Promise<StorePaths> {
+    return this.catalogGateway.readPaths(this.selection.requireCurrentStore(), progress)
+  }
+
+  public async syncGames (names: readonly string[], progress?: EngineProgressListener): Promise<void> {
+    await this.catalogGateway.syncGames(this.selection.requireCurrentStore(), names, progress)
+    this.forgetListing()
+  }
+
+  public async removeGame (name: string, progress?: EngineProgressListener): Promise<void> {
+    await this.catalogGateway.removeGame(this.selection.requireCurrentStore(), name, progress)
+    this.forgetListing()
+  }
+
+  public findGame (name: string): Game | null {
+    return this.lastListing?.games.find((game: Game): boolean => game.name === name) ?? null
+  }
+
+  public findCatalogBaseUrl (): string {
+    return this.lastListing?.paths?.catalogBaseUrl ?? ''
+  }
+
+  /** After a write the listing is stale; the window refreshes anyway. */
+  public forgetListing (): void {
+    this.lastListing = null
+  }
+}

src/application/services/GameLaunchService.ts

@@ -0,0 +1,29 @@
+import type { GameLauncher } from '../../domain/ports/GameLauncher'
+import type { CatalogService } from './CatalogService'
+
+/**
+ * Starting a title the window asked for by name.
+ *
+ * The name is all the window has; the launch target comes from the catalog this
+ * process last read.
+ */
+export class GameLaunchService {
+  public constructor (
+    private readonly launcher: GameLauncher,
+    private readonly catalog: CatalogService
+  ) {}
+
+  public async launchGame (name: string): Promise<boolean> {
+    const game = this.catalog.findGame(name)
+    if (game === null) return false
+    return this.launcher.launchGame(game)
+  }
+
+  public async openFolder (directory: string): Promise<boolean> {
+    return this.launcher.openFolder(directory)
+  }
+
+  public async openUrl (url: string): Promise<boolean> {
+    return this.launcher.openUrl(url)
+  }
+}

src/application/services/PreferencesService.ts

@@ -0,0 +1,51 @@
+import type { Preferences } from '../../domain/models/Preferences'
+import type { ApplicationEnvironment } from '../../domain/ports/ApplicationEnvironment'
+import type { PreferencesRepository } from '../../domain/ports/PreferencesRepository'
+import { TranslationCatalog } from '../../shared/i18n/TranslationCatalog'
+import type { Locale } from '../../shared/i18n/MessageBundle'
+
+/**
+ * What the client remembers, and what it falls back to.
+ *
+ * The reads never fail: an unreadable file, a language that no longer exists and a
+ * fresh install all produce the same defaults.
+ */
+export class PreferencesService {
+  public constructor (
+    private readonly repository: PreferencesRepository,
+    private readonly environment: ApplicationEnvironment,
+    private readonly translations: TranslationCatalog = new TranslationCatalog()
+  ) {}
+
+  public readLocale (): Locale {
+    const stored = this.repository.read().locale
+    return this.translations.resolveLocale(stored ?? this.environment.readSystemLocale())
+  }
+
+  public updateLocale (candidate: string): Locale {
+    const locale = this.translations.resolveLocale(candidate)
+    this.merge({ locale })
+    return locale
+  }
+
+  public readNavigationOpen (): boolean {
+    return this.repository.read().navigationOpen ?? true
+  }
+
+  public updateNavigationOpen (open: boolean): boolean {
+    this.merge({ navigationOpen: open })
+    return open
+  }
+
+  public readStoreHome (): string | null {
+    return this.repository.read().storeHome ?? null
+  }
+
+  public updateStoreHome (home: string): void {
+    this.merge({ storeHome: home })
+  }
+
+  private merge (changes: Preferences): void {
+    this.repository.write({ ...this.repository.read(), ...changes })
+  }
+}

src/application/services/StoreProvisioningService.ts

@@ -0,0 +1,41 @@
+import type { EngineProgressListener } from '../../domain/models/EngineProgress'
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import type { RegistryStore } from '../../domain/models/RegistryStore'
+import { deriveStoreId } from '../../domain/models/StoreIdentity'
+import type { InstalledStoreRepository } from '../../domain/ports/InstalledStoreRepository'
+import type { StoreEngineInstaller } from '../../domain/ports/StoreEngineInstaller'
+import type { StoreRegistryRepository } from '../../domain/ports/StoreRegistryRepository'
+import type { StoreSelectionService } from './StoreSelectionService'
+
+/**
+ * Getting a store onto this machine.
+ *
+ * Which stores exist is the site's answer — this asks the registry and installs
+ * what was chosen, into the folder the shell installer would have used. The newly
+ * installed store becomes the open one, so the window can carry straight on.
+ */
+export class StoreProvisioningService {
+  public constructor (
+    private readonly registry: StoreRegistryRepository,
+    private readonly installer: StoreEngineInstaller,
+    private readonly stores: InstalledStoreRepository,
+    private readonly selection: StoreSelectionService
+  ) {}
+
+  public get registryUrl (): string {
+    return this.registry.sourceUrl
+  }
+
+  public async listAvailableStores (): Promise<readonly RegistryStore[]> {
+    return this.registry.listStores()
+  }
+
+  public async installStore (
+    store: RegistryStore,
+    progress?: EngineProgressListener
+  ): Promise<InstalledStore> {
+    const home = this.stores.resolveDefaultHome(deriveStoreId(store))
+    const installed = await this.installer.installEngine(home, store, progress)
+    return this.selection.adoptStore(installed)
+  }
+}

src/application/services/StoreSelectionService.ts

@@ -0,0 +1,73 @@
+import { StoreMissingError } from '../../domain/errors/StoreMissingError'
+import type { EngineVersion } from '../../domain/models/EngineVersion'
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import type { InstalledStoreRepository } from '../../domain/ports/InstalledStoreRepository'
+import type { StoreCatalogGateway } from '../../domain/ports/StoreCatalogGateway'
+import type { PreferencesService } from './PreferencesService'
+
+/**
+ * Which store is open.
+ *
+ * A machine can carry several: two catalogs, or the same catalog installed twice.
+ * The remembered one wins, so the window reopens where it was left; the current
+ * store is cached because every catalog call needs it and re-scanning the disk per
+ * call would be silly.
+ */
+export class StoreSelectionService {
+  private current: InstalledStore | null = null
+
+  public constructor (
+    private readonly stores: InstalledStoreRepository,
+    private readonly catalogGateway: StoreCatalogGateway,
+    private readonly preferences: PreferencesService
+  ) {}
+
+  public listStores (): readonly InstalledStore[] {
+    return this.stores.findAll()
+  }
+
+  /** The store to drive, remembering the choice across runs. Null when there is none. */
+  public findCurrentStore (): InstalledStore | null {
+    const known = this.stores.findAll()
+    const preferredHome = this.preferences.readStoreHome()
+    const remembered = preferredHome === null
+      ? undefined
+      : known.find((store: InstalledStore): boolean => store.home === preferredHome)
+    this.current = remembered ?? known[0] ?? null
+    return this.current
+  }
+
+  public requireCurrentStore (): InstalledStore {
+    const store = this.current ?? this.findCurrentStore()
+    if (store === null) throw new StoreMissingError()
+    return store
+  }
+
+  public selectStore (home: string): InstalledStore {
+    const store = this.stores.findByHome(home)
+    if (store === null) throw new StoreMissingError(home)
+    this.current = store
+    this.preferences.updateStoreHome(store.home)
+    return store
+  }
+
+  /** Adopt a store that was just installed, without a disk scan. */
+  public adoptStore (store: InstalledStore): InstalledStore {
+    this.current = store
+    this.preferences.updateStoreHome(store.home)
+    return store
+  }
+
+  /**
+   * The engine version of a store, checked per store rather than once: two stores
+   * on one machine can be at different versions, and the one being switched to may
+   * be the older one.
+   */
+  public findEngineVersion (store: InstalledStore): EngineVersion | null {
+    return this.catalogGateway.readEngineVersion(store)
+  }
+
+  public readDefaultStoreRoot (): string {
+    return this.stores.readRoots()[0] ?? ''
+  }
+}

src/domain/errors/BusyError.ts

@@ -0,0 +1,10 @@
+import { DomainError } from './DomainError'
+
+/** A second engine call while one is running. The store writes files; two writers race. */
+export class BusyError extends DomainError {
+  public override readonly code: string = 'BUSY'
+
+  public constructor () {
+    super('the store is busy with another operation')
+  }
+}

src/domain/errors/DomainError.ts

@@ -0,0 +1,14 @@
+/**
+ * The base for every error this application raises on purpose.
+ *
+ * `code` is what crosses the bridge: the window shows its own sentence for a code
+ * it knows, and the message only ever ends up in the log drawer.
+ */
+export abstract class DomainError extends Error {
+  public abstract readonly code: string
+
+  protected constructor (message: string) {
+    super(message)
+    this.name = new.target.name
+  }
+}

src/domain/errors/EngineInvocationError.ts

@@ -0,0 +1,10 @@
+import { DomainError } from './DomainError'
+
+/** The engine ran and failed: a non-zero exit, or a process that never started. */
+export class EngineInvocationError extends DomainError {
+  public override readonly code: string = 'ENGINE_FAILED'
+
+  public constructor (message: string, public readonly exitCode: number | null = null) {
+    super(message)
+  }
+}

src/domain/errors/PythonMissingError.ts

@@ -0,0 +1,9 @@
+import { DomainError } from './DomainError'
+
+export class PythonMissingError extends DomainError {
+  public override readonly code: string = 'PYTHON_MISSING'
+
+  public constructor () {
+    super('python3 was not found on this machine')
+  }
+}

src/domain/errors/RegistryUnavailableError.ts

@@ -0,0 +1,9 @@
+import { DomainError } from './DomainError'
+
+export class RegistryUnavailableError extends DomainError {
+  public override readonly code: string = 'REGISTRY_UNAVAILABLE'
+
+  public constructor (public readonly sourceUrl: string, reason: string) {
+    super(`${sourceUrl}: ${reason}`)
+  }
+}

src/domain/errors/StoreMissingError.ts

@@ -0,0 +1,9 @@
+import { DomainError } from './DomainError'
+
+export class StoreMissingError extends DomainError {
+  public override readonly code: string = 'STORE_MISSING'
+
+  public constructor (home?: string) {
+    super(home === undefined ? 'no store is installed yet' : `no store at ${home}`)
+  }
+}

src/domain/models/CatalogListing.ts

@@ -0,0 +1,9 @@
+import type { Game } from './Game'
+import type { StorePaths } from './StorePaths'
+
+/** One reading of a store's catalog. */
+export interface CatalogListing {
+  readonly games: readonly Game[]
+  readonly skipped: readonly string[]
+  readonly paths: StorePaths | null
+}

src/domain/models/EngineProgress.ts

@@ -0,0 +1,13 @@
+import type { SyncEventDto } from '../../shared/contracts/dto/SyncEventDto'
+
+/**
+ * How a long-running engine call reports itself.
+ *
+ * `onLog` is a line a person can read (the engine's stderr), `onEvent` one of its
+ * JSON progress events. Both are optional: a caller that only wants the result
+ * passes neither.
+ */
+export interface EngineProgressListener {
+  readonly onLog?: (line: string) => void
+  readonly onEvent?: (event: SyncEventDto) => void
+}

src/domain/models/EngineVersion.ts

@@ -0,0 +1,34 @@
+/**
+ * The engine version this client found, and whether it can drive it.
+ *
+ * `--json` arrived with engine 1.1.0. An older engine is not broken, it simply
+ * cannot be driven from a window — and it will be met in the wild, because the CLI
+ * shipped before this client did.
+ */
+export interface EngineVersion {
+  readonly text: string
+  readonly numbers: readonly number[] | null
+  readonly supported: boolean
+}
+
+export const MINIMUM_ENGINE_VERSION: readonly number[] = [1, 1, 0]
+
+export function parseVersionNumbers (text: string): readonly number[] | null {
+  const match = /(\d+)\.(\d+)\.(\d+)/.exec(text)
+  return match ? match.slice(1, 4).map((part: string): number => Number(part)) : null
+}
+
+export function isAtLeast (version: readonly number[] | null, minimum: readonly number[]): boolean {
+  if (version === null) return false
+  for (let index = 0; index < minimum.length; index += 1) {
+    const found = version[index] ?? 0
+    const needed = minimum[index] ?? 0
+    if (found > needed) return true
+    if (found < needed) return false
+  }
+  return true
+}
+
+export function formatVersion (numbers: readonly number[]): string {
+  return numbers.join('.')
+}

src/domain/models/Game.ts

@@ -0,0 +1,27 @@
+/** How a title runs: unpacked on this machine, or served as a web build. */
+export type GameMode = 'app' | 'web'
+
+/**
+ * A catalog entry, with what the store did about it on this machine.
+ *
+ * The launch targets live here and nowhere nearer the window: resolving what to
+ * open is the main process's job.
+ */
+export interface Game {
+  readonly name: string
+  readonly title: string
+  readonly platform: string
+  readonly version: string
+  readonly mode: GameMode
+  readonly kind: string
+  readonly description: string
+  readonly author: string
+  /** Relative to the catalog's base URL, as published. */
+  readonly imagePath: string | null
+  readonly installed: boolean
+  readonly updateAvailable: boolean
+  readonly installedVersion: string | null
+  readonly menuEntryPath: string | null
+  readonly executablePath: string | null
+  readonly hostedUrl: string | null
+}

src/domain/models/InstalledStore.ts

@@ -0,0 +1,9 @@
+/** A store engine installed on this machine, with everything needed to run it. */
+export interface InstalledStore {
+  readonly id: string
+  readonly name: string
+  readonly home: string
+  readonly scriptPath: string
+  readonly configPath: string
+  readonly engine: string
+}

src/domain/models/Preferences.ts

@@ -0,0 +1,9 @@
+import type { Locale } from '../../shared/i18n/MessageBundle'
+
+/** What the client remembers between runs. Every field optional: a fresh install has none. */
+export interface Preferences {
+  readonly locale?: Locale
+  readonly navigationOpen?: boolean
+  /** The home of the store last opened, so the window reopens where it was left. */
+  readonly storeHome?: string
+}

src/domain/models/PythonRuntime.ts

@@ -0,0 +1,6 @@
+/** The Python 3 this machine has, and how to invoke it. */
+export interface PythonRuntime {
+  readonly command: string
+  readonly arguments: readonly string[]
+  readonly version: string
+}

src/domain/models/RegistryStore.ts

@@ -0,0 +1,11 @@
+/**
+ * A store the site's registry offers.
+ *
+ * Three fields, because that is what a record is: what it is called, which
+ * catalog it serves, and where its configuration lives.
+ */
+export interface RegistryStore {
+  readonly name: string
+  readonly catalogUrl: string
+  readonly storeRepositoryUrl: string
+}

src/domain/models/StoreEngine.ts

@@ -0,0 +1,23 @@
+/**
+ * A store engine this client knows how to drive.
+ *
+ * There is one today. The table exists because the RetroArch store has the same
+ * command shape, so a second entry — not a second code path — is what adding it
+ * would take.
+ */
+export interface StoreEngine {
+  readonly id: string
+  readonly scriptFileName: string
+  /** The installer names a store home `<store id><homeSuffix>`. */
+  readonly homeSuffix: string
+  readonly launcherSuffix: string
+}
+
+export const DESKTOP_STORE_ENGINE: StoreEngine = {
+  id: 'desktop',
+  scriptFileName: 'desktop_store.py',
+  homeSuffix: '-desktop',
+  launcherSuffix: '-desktop-store'
+}
+
+export const STORE_ENGINES: readonly StoreEngine[] = [DESKTOP_STORE_ENGINE]

src/domain/models/StoreIdentity.ts

@@ -0,0 +1,15 @@
+import type { RegistryStore } from './RegistryStore'
+
+/**
+ * A store id from its repository name: `ttg-desktop-store` becomes `ttg`.
+ *
+ * The id names the store home and the folder games land in, so it has to be short
+ * and filesystem-safe. The repository name is the best source available before
+ * anything is downloaded; the store's own config.json overrides it once it is.
+ */
+export function deriveStoreId (store: RegistryStore): string {
+  const lastSegment = store.storeRepositoryUrl.replace(/\/+$/, '').split('/').pop() ?? ''
+  const base = lastSegment.replace(/-(desktop-)?store$/, '') || store.name
+  const slug = base.toLowerCase().replace(/[^a-z0-9._-]+/g, '-').replace(/^-+|-+$/g, '')
+  return slug || 'store'
+}

src/domain/models/StorePaths.ts

@@ -0,0 +1,12 @@
+/** The store's resolved locations on this machine, as the engine reports them. */
+export interface StorePaths {
+  readonly operatingSystem: string
+  readonly architecture: string
+  readonly installRoot: string
+  readonly menuDirectory: string
+  readonly storeFolder: string
+  readonly menuGroup: string
+  readonly catalogBaseUrl: string
+  readonly storeName: string
+  readonly storeId: string
+}

src/domain/ports/ApplicationEnvironment.ts

@@ -0,0 +1,6 @@
+/** What the host application knows about itself: its version, locale and storage. */
+export interface ApplicationEnvironment {
+  readVersion: () => string
+  readSystemLocale: () => string
+  resolveUserDataPath: (fileName: string) => string
+}

src/domain/ports/GameLauncher.ts

@@ -0,0 +1,8 @@
+import type { Game } from '../models/Game'
+
+/** Opening things outside this application: a game, a folder, a page. */
+export interface GameLauncher {
+  launchGame: (game: Game) => Promise<boolean>
+  openFolder: (directory: string) => Promise<boolean>
+  openUrl: (url: string) => Promise<boolean>
+}

src/domain/ports/InstalledStoreRepository.ts

@@ -0,0 +1,10 @@
+import type { InstalledStore } from '../models/InstalledStore'
+
+/** The stores present on this machine, wherever the shell installer would put them. */
+export interface InstalledStoreRepository {
+  findAll: () => readonly InstalledStore[]
+  findByHome: (home: string) => InstalledStore | null
+  /** The roots that are searched, in the order the shell installer would use them. */
+  readRoots: () => readonly string[]
+  resolveDefaultHome: (storeId: string) => string
+}

src/domain/ports/PreferencesRepository.ts

@@ -0,0 +1,6 @@
+import type { Preferences } from '../models/Preferences'
+
+export interface PreferencesRepository {
+  read: () => Preferences
+  write: (preferences: Preferences) => void
+}

src/domain/ports/PythonRuntimeLocator.ts

@@ -0,0 +1,5 @@
+import type { PythonRuntime } from '../models/PythonRuntime'
+
+export interface PythonRuntimeLocator {
+  findRuntime: () => PythonRuntime | null
+}

src/domain/ports/StoreCatalogGateway.ts

@@ -0,0 +1,19 @@
+import type { CatalogListing } from '../models/CatalogListing'
+import type { EngineProgressListener } from '../models/EngineProgress'
+import type { EngineVersion } from '../models/EngineVersion'
+import type { InstalledStore } from '../models/InstalledStore'
+import type { StorePaths } from '../models/StorePaths'
+
+/**
+ * The store engine, as an interface.
+ *
+ * Every catalog operation this client performs is one call on this port; the CLI
+ * behind it stays the product, and nothing above this line knows it is Python.
+ */
+export interface StoreCatalogGateway {
+  listGames: (store: InstalledStore, progress?: EngineProgressListener) => Promise<CatalogListing>
+  readPaths: (store: InstalledStore, progress?: EngineProgressListener) => Promise<StorePaths>
+  syncGames: (store: InstalledStore, names: readonly string[], progress?: EngineProgressListener) => Promise<void>
+  removeGame: (store: InstalledStore, name: string, progress?: EngineProgressListener) => Promise<void>
+  readEngineVersion: (store: InstalledStore) => EngineVersion | null
+}

src/domain/ports/StoreEngineInstaller.ts

@@ -0,0 +1,17 @@
+import type { EngineProgressListener } from '../models/EngineProgress'
+import type { InstalledStore } from '../models/InstalledStore'
+import type { RegistryStore } from '../models/RegistryStore'
+
+/**
+ * Setting up a store where there is none.
+ *
+ * This is why the client exists on Windows at all: the store's own installer is
+ * `curl … | sh`, which Windows does not have.
+ */
+export interface StoreEngineInstaller {
+  installEngine: (
+    home: string,
+    store: RegistryStore,
+    progress?: EngineProgressListener
+  ) => Promise<InstalledStore>
+}

src/domain/ports/StoreRegistryRepository.ts

@@ -0,0 +1,7 @@
+import type { RegistryStore } from '../models/RegistryStore'
+
+/** Which stores exist at all — the site's answer, not this client's. */
+export interface StoreRegistryRepository {
+  readonly sourceUrl: string
+  listStores: () => Promise<readonly RegistryStore[]>
+}

src/infrastructure/electron/ElectronApplicationEnvironment.ts

@@ -0,0 +1,20 @@
+import path from 'node:path'
+import type { App } from 'electron'
+import type { ApplicationEnvironment } from '../../domain/ports/ApplicationEnvironment'
+
+/** The host application, as the services see it. Keeps `electron` out of them. */
+export class ElectronApplicationEnvironment implements ApplicationEnvironment {
+  public constructor (private readonly app: App) {}
+
+  public readVersion (): string {
+    return this.app.getVersion()
+  }
+
+  public readSystemLocale (): string {
+    return this.app.getLocale()
+  }
+
+  public resolveUserDataPath (fileName: string): string {
+    return path.join(this.app.getPath('userData'), fileName)
+  }
+}

src/infrastructure/electron/ElectronGameLauncher.ts

@@ -0,0 +1,58 @@
+import { spawn } from 'node:child_process'
+import fs from 'node:fs'
+import path from 'node:path'
+import type { Shell } from 'electron'
+import type { Game } from '../../domain/models/Game'
+import type { GameLauncher } from '../../domain/ports/GameLauncher'
+
+/**
+ * Launching what was installed.
+ *
+ * A hosted title is a URL, so it goes to the browser. A native one is whatever the
+ * store recorded: on macOS the app bundle through `open`, elsewhere the executable
+ * from its own directory — the same working directory the menu entry uses, because
+ * games load their assets relative to it.
+ */
+export class ElectronGameLauncher implements GameLauncher {
+  public constructor (private readonly shell: Shell) {}
+
+  public async launchGame (game: Game): Promise<boolean> {
+    if (game.mode === 'web' && game.hostedUrl !== null) {
+      await this.shell.openExternal(game.hostedUrl)
+      return true
+    }
+
+    const target = game.menuEntryPath ?? game.executablePath
+    if (target === null || !fs.existsSync(target)) return false
+
+    if (process.platform === 'darwin' && target.endsWith('.app')) {
+      this.spawnDetached('open', [target], path.dirname(target))
+      return true
+    }
+
+    if (process.platform === 'win32' || target.endsWith('.desktop')) {
+      const failure = await this.shell.openPath(target)
+      if (failure === '') return true
+    }
+
+    const executable = game.executablePath ?? target
+    this.spawnDetached(executable, [], path.dirname(executable))
+    return true
+  }
+
+  public async openFolder (directory: string): Promise<boolean> {
+    if (directory.length === 0) return false
+    const failure = await this.shell.openPath(directory)
+    return failure === ''
+  }
+
+  public async openUrl (url: string): Promise<boolean> {
+    if (!url.startsWith('https://')) return false
+    await this.shell.openExternal(url)
+    return true
+  }
+
+  private spawnDetached (command: string, commandArguments: readonly string[], cwd: string): void {
+    spawn(command, [...commandArguments], { cwd, detached: true, stdio: 'ignore' }).unref()
+  }
+}

src/infrastructure/http/HttpTextClient.ts

@@ -0,0 +1,60 @@
+import http from 'node:http'
+import https from 'node:https'
+
+const REQUEST_TIMEOUT_MS = 60_000
+const MAX_REDIRECTS = 5
+const USER_AGENT = 'warp-engine-desktop-gui'
+
+/** A response that arrived but said no. The status matters: 404 is not a failure everywhere. */
+export class HttpStatusError extends Error {
+  public constructor (public readonly url: string, public readonly statusCode: number) {
+    super(`${url} answered ${String(statusCode)}`)
+    this.name = 'HttpStatusError'
+  }
+}
+
+/**
+ * GET a URL as text, following redirects.
+ *
+ * Node's own client rather than `fetch`, because this runs in the main process
+ * where the proxy and certificate settings are the system's, and because a moved
+ * repository answers 301.
+ */
+export class HttpTextClient {
+  public async readText (url: string, redirectsLeft: number = MAX_REDIRECTS): Promise<string> {
+    return new Promise<string>((resolve: (body: string) => void, reject: (error: Error) => void): void => {
+      const client = url.startsWith('http://') ? http : https
+      const request = client.get(url, { headers: { 'User-Agent': USER_AGENT } }, (response): void => {
+        const status = response.statusCode ?? 0
+        const location = response.headers.location
+
+        if (status >= 300 && status < 400 && location !== undefined) {
+          response.resume()
+          if (redirectsLeft <= 0) {
+            reject(new Error(`too many redirects for ${url}`))
+            return
+          }
+          const next = new URL(location, url).toString()
+          this.readText(next, redirectsLeft - 1).then(resolve, reject)
+          return
+        }
+
+        if (status !== 200) {
+          response.resume()
+          reject(new HttpStatusError(url, status))
+          return
+        }
+
+        let body = ''
+        response.setEncoding('utf8')
+        response.on('data', (chunk: string): void => { body += chunk })
+        response.on('end', (): void => { resolve(body) })
+      })
+
+      request.setTimeout(REQUEST_TIMEOUT_MS, (): void => {
+        request.destroy(new Error(`${url} timed out`))
+      })
+      request.on('error', reject)
+    })
+  }
+}

src/infrastructure/json/JsonRecord.ts

@@ -0,0 +1,53 @@
+/**
+ * Reading JSON that came from somewhere else.
+ *
+ * The engine's stdout and the site's registry are both outside this program, so
+ * their shape is a claim, not a fact. These readers turn `unknown` into typed
+ * values with a stated fallback, which keeps every parser honest and every mapper
+ * free of casts.
+ */
+export type JsonRecord = Readonly<Record<string, unknown>>
+
+export function asRecord (value: unknown): JsonRecord | null {
+  return typeof value === 'object' && value !== null && !Array.isArray(value)
+    ? (value as JsonRecord)
+    : null
+}
+
+export function readString (record: JsonRecord, key: string, fallback: string = ''): string {
+  const value = record[key]
+  return typeof value === 'string' ? value : fallback
+}
+
+export function readOptionalString (record: JsonRecord, key: string): string | null {
+  const value = record[key]
+  return typeof value === 'string' && value.length > 0 ? value : null
+}
+
+export function readBoolean (record: JsonRecord, key: string, fallback: boolean = false): boolean {
+  const value = record[key]
+  return typeof value === 'boolean' ? value : fallback
+}
+
+export function readNumber (record: JsonRecord, key: string, fallback: number = 0): number {
+  const value = record[key]
+  return typeof value === 'number' && Number.isFinite(value) ? value : fallback
+}
+
+export function readStringArray (record: JsonRecord, key: string): readonly string[] {
+  const value = record[key]
+  if (!Array.isArray(value)) return []
+  return value.filter((item: unknown): item is string => typeof item === 'string')
+}
+
+export function readRecordArray (record: JsonRecord, key: string): readonly JsonRecord[] {
+  const value = record[key]
+  if (!Array.isArray(value)) return []
+  return value
+    .map((item: unknown): JsonRecord | null => asRecord(item))
+    .filter((item: JsonRecord | null): item is JsonRecord => item !== null)
+}
+
+export function readRecord (record: JsonRecord, key: string): JsonRecord | null {
+  return asRecord(record[key])
+}

src/infrastructure/mappers/EngineGameMapper.ts

@@ -0,0 +1,36 @@
+import type { Game, GameMode } from '../../domain/models/Game'
+import {
+  readBoolean, readOptionalString, readString, type JsonRecord
+} from '../json/JsonRecord'
+
+/**
+ * One engine JSON entry to one domain model.
+ *
+ * The engine speaks snake_case and this is the only place that knows it: rename a
+ * field there and this mapper is the single file that follows.
+ */
+export class EngineGameMapper {
+  public toModel (record: JsonRecord): Game {
+    return {
+      name: readString(record, 'name'),
+      title: readString(record, 'title'),
+      platform: readString(record, 'platform'),
+      version: readString(record, 'version'),
+      mode: this.toMode(readString(record, 'mode')),
+      kind: readString(record, 'kind'),
+      description: readString(record, 'desc'),
+      author: readString(record, 'author'),
+      imagePath: readOptionalString(record, 'image_url'),
+      installed: readBoolean(record, 'installed'),
+      updateAvailable: readBoolean(record, 'update_available'),
+      installedVersion: readOptionalString(record, 'installed_version'),
+      menuEntryPath: readOptionalString(record, 'menu_entry'),
+      executablePath: readOptionalString(record, 'exe'),
+      hostedUrl: readOptionalString(record, 'url')
+    }
+  }
+
+  private toMode (value: string): GameMode {
+    return value === 'web' ? 'web' : 'app'
+  }
+}

src/infrastructure/mappers/EngineStorePathsMapper.ts

@@ -0,0 +1,20 @@
+import type { StorePaths } from '../../domain/models/StorePaths'
+import { readRecord, readString, type JsonRecord } from '../json/JsonRecord'
+
+/** The engine's `paths` answer to one domain model. */
+export class EngineStorePathsMapper {
+  public toModel (record: JsonRecord): StorePaths {
+    const store = readRecord(record, 'store')
+    return {
+      operatingSystem: readString(record, 'os'),
+      architecture: readString(record, 'arch'),
+      installRoot: readString(record, 'install_root'),
+      menuDirectory: readString(record, 'menu_dir'),
+      storeFolder: readString(record, 'store_folder'),
+      menuGroup: readString(record, 'menu_group'),
+      catalogBaseUrl: store === null ? '' : readString(store, 'base_url'),
+      storeName: store === null ? '' : readString(store, 'name'),
+      storeId: store === null ? '' : readString(store, 'id')
+    }
+  }
+}

src/infrastructure/process/PythonEngineProcessRunner.ts

@@ -0,0 +1,128 @@
+import { spawn, spawnSync } from 'node:child_process'
+import { EngineInvocationError } from '../../domain/errors/EngineInvocationError'
+import { PythonMissingError } from '../../domain/errors/PythonMissingError'
+import type { EngineProgressListener } from '../../domain/models/EngineProgress'
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import type { PythonRuntimeLocator } from '../../domain/ports/PythonRuntimeLocator'
+import type { SyncEventDto } from '../../shared/contracts/dto/SyncEventDto'
+import { asRecord, type JsonRecord } from '../json/JsonRecord'
+
+const VERSION_PROBE_TIMEOUT_MS = 15_000
+
+/**
+ * Runs one engine command and reads its two streams.
+ *
+ * The engine's contract with any client is `--json`: data on stdout, one JSON
+ * object per line, and the human-readable log on stderr. So nothing here parses a
+ * sentence meant for a person, and a line that is not JSON is handed to the log
+ * rather than crashing the call.
+ */
+export class PythonEngineProcessRunner {
+  public constructor (private readonly runtimeLocator: PythonRuntimeLocator) {}
+
+  public async runCommand (
+    store: InstalledStore,
+    commandArguments: readonly string[],
+    progress: EngineProgressListener = {}
+  ): Promise<readonly JsonRecord[]> {
+    const runtime = this.runtimeLocator.findRuntime()
+    if (runtime === null) throw new PythonMissingError()
+
+    const argv = [
+      ...runtime.arguments,
+      store.scriptPath,
+      '--config', store.configPath,
+      '--json',
+      ...commandArguments
+    ]
+
+    return new Promise<readonly JsonRecord[]>((
+      resolve: (records: readonly JsonRecord[]) => void,
+      reject: (error: Error) => void
+    ): void => {
+      const child = spawn(runtime.command, argv, {
+        env: { ...process.env, DESKTOP_STORE_HOME: store.home }
+      })
+      const records: JsonRecord[] = []
+      let stdoutRest = ''
+      let stderrRest = ''
+
+      const takeStdout = (chunk: string): void => {
+        stdoutRest += chunk
+        const parts = stdoutRest.split('\n')
+        stdoutRest = parts.pop() ?? ''
+        for (const part of parts) this.consumeStdoutLine(part, records, progress)
+      }
+
+      const takeStderr = (chunk: string): void => {
+        stderrRest += chunk
+        const parts = stderrRest.split('\n')
+        stderrRest = parts.pop() ?? ''
+        for (const part of parts) {
+          if (part.trim().length > 0) progress.onLog?.(part)
+        }
+      }
+
+      child.stdout.setEncoding('utf8')
+      child.stderr.setEncoding('utf8')
+      child.stdout.on('data', takeStdout)
+      child.stderr.on('data', takeStderr)
+      child.on('error', (error: Error): void => {
+        reject(new EngineInvocationError(error.message))
+      })
+      child.on('close', (code: number | null): void => {
+        takeStdout('\n')
+        takeStderr('\n')
+        if (code === 0) resolve(records)
+        else reject(new EngineInvocationError(`the store exited with code ${String(code)}`, code))
+      })
+    })
+  }
+
+  /** The engine's `--version`, read synchronously because it gates the first paint. */
+  public readVersionText (store: InstalledStore): string | null {
+    const runtime = this.runtimeLocator.findRuntime()
+    if (runtime === null) return null
+    try {
+      const probe = spawnSync(runtime.command, [...runtime.arguments, store.scriptPath, '--version'], {
+        encoding: 'utf8',
+        timeout: VERSION_PROBE_TIMEOUT_MS
+      })
+      const text = `${probe.stdout}${probe.stderr}`.trim()
+      return probe.status === 0 && text.length > 0 ? text : null
+    } catch {
+      return null
+    }
+  }
+
+  private consumeStdoutLine (
+    line: string,
+    records: JsonRecord[],
+    progress: EngineProgressListener
+  ): void {
+    if (line.trim().length === 0) return
+    let parsed: unknown
+    try {
+      parsed = JSON.parse(line)
+    } catch {
+      // Not ours to interpret — hand it on as a log line rather than fail the call.
+      progress.onLog?.(line)
+      return
+    }
+    const record = asRecord(parsed)
+    if (record === null) return
+    records.push(record)
+    const event = this.asSyncEvent(record)
+    if (event !== null) progress.onEvent?.(event)
+  }
+
+  /**
+   * A progress line, or null for the final result object.
+   *
+   * The engine tags its stream events with `event`; the listing and paths answers
+   * carry no such field, which is exactly the difference.
+   */
+  private asSyncEvent (record: JsonRecord): SyncEventDto | null {
+    return typeof record['event'] === 'string' ? (record as unknown as SyncEventDto) : null
+  }
+}

src/infrastructure/process/SystemPythonRuntimeLocator.ts

@@ -0,0 +1,63 @@
+import { spawnSync } from 'node:child_process'
+import type { PythonRuntime } from '../../domain/models/PythonRuntime'
+import type { PythonRuntimeLocator } from '../../domain/ports/PythonRuntimeLocator'
+
+interface RuntimeCandidate {
+  readonly command: string
+  readonly arguments: readonly string[]
+}
+
+/** `py -3` is the Windows launcher, and often the only Python on PATH there. */
+const WINDOWS_CANDIDATES: readonly RuntimeCandidate[] = [
+  { command: 'py', arguments: ['-3'] },
+  { command: 'python', arguments: [] },
+  { command: 'python3', arguments: [] }
+]
+
+const POSIX_CANDIDATES: readonly RuntimeCandidate[] = [
+  { command: 'python3', arguments: [] },
+  { command: 'python', arguments: [] }
+]
+
+const PROBE_TIMEOUT_MS = 10_000
+
+/**
+ * Finds the Python 3 the store needs.
+ *
+ * The answer is cached: the probe spawns processes, and the window asks for it on
+ * every state read.
+ */
+export class SystemPythonRuntimeLocator implements PythonRuntimeLocator {
+  private cached: PythonRuntime | null = null
+  private probed = false
+
+  public findRuntime (): PythonRuntime | null {
+    if (this.probed) return this.cached
+    this.probed = true
+    const candidates = process.platform === 'win32' ? WINDOWS_CANDIDATES : POSIX_CANDIDATES
+    for (const candidate of candidates) {
+      const runtime = this.probeCandidate(candidate)
+      if (runtime !== null) {
+        this.cached = runtime
+        return runtime
+      }
+    }
+    return null
+  }
+
+  private probeCandidate (candidate: RuntimeCandidate): PythonRuntime | null {
+    try {
+      const probe = spawnSync(candidate.command, [...candidate.arguments, '--version'], {
+        encoding: 'utf8',
+        timeout: PROBE_TIMEOUT_MS
+      })
+      const output = `${probe.stdout}${probe.stderr}`
+      if (probe.status === 0 && output.includes('Python 3.')) {
+        return { command: candidate.command, arguments: candidate.arguments, version: output.trim() }
+      }
+    } catch {
+      // An absent interpreter is the normal case, not an error worth reporting.
+    }
+    return null
+  }
+}

src/infrastructure/repositories/FileSystemInstalledStoreRepository.ts

@@ -0,0 +1,107 @@
+import fs from 'node:fs'
+import os from 'node:os'
+import path from 'node:path'
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import { DESKTOP_STORE_ENGINE, STORE_ENGINES } from '../../domain/models/StoreEngine'
+import type { InstalledStoreRepository } from '../../domain/ports/InstalledStoreRepository'
+import { asRecord, readString } from '../json/JsonRecord'
+
+const STORE_DIRECTORY_NAME = 'warp-engine-store'
+const CONFIG_FILE_NAME = 'config.json'
+
+/**
+ * Finds stores where the shell installers put them.
+ *
+ * The roots are searched in the installers' own order, and `STORE_ROOT` comes
+ * first so a sandbox can be driven without touching a working installation — which
+ * is how this repository is tested.
+ */
+export class FileSystemInstalledStoreRepository implements InstalledStoreRepository {
+  public findAll (): readonly InstalledStore[] {
+    const found: InstalledStore[] = []
+    for (const root of this.readRoots()) {
+      for (const entry of this.readDirectories(root)) {
+        const home = path.join(root, entry)
+        const store = this.readStoreAt(home, entry)
+        if (store !== null) found.push(store)
+      }
+    }
+    return found
+  }
+
+  public findByHome (home: string): InstalledStore | null {
+    return this.findAll().find((store: InstalledStore): boolean => store.home === home) ?? null
+  }
+
+  public readRoots (): readonly string[] {
+    const home = os.homedir()
+    const roots: string[] = []
+    const override = process.env['STORE_ROOT']
+    if (override !== undefined && override.length > 0) roots.push(override)
+    const xdgDataHome = process.env['XDG_DATA_HOME']
+    if (xdgDataHome !== undefined && xdgDataHome.length > 0) {
+      roots.push(path.join(xdgDataHome, STORE_DIRECTORY_NAME))
+    }
+    roots.push(path.join(home, '.local', 'share', STORE_DIRECTORY_NAME))
+    if (process.platform === 'darwin') {
+      roots.push(path.join(home, 'Library', 'Application Support', STORE_DIRECTORY_NAME))
+    }
+    const localAppData = process.env['LOCALAPPDATA']
+    if (process.platform === 'win32' && localAppData !== undefined && localAppData.length > 0) {
+      roots.push(path.join(localAppData, STORE_DIRECTORY_NAME))
+    }
+    return [...new Set(roots)]
+  }
+
+  public resolveDefaultHome (storeId: string): string {
+    const root = this.readRoots()[0] ?? path.join(os.homedir(), '.local', 'share', STORE_DIRECTORY_NAME)
+    return path.join(root, `${storeId}${DESKTOP_STORE_ENGINE.homeSuffix}`)
+  }
+
+  private readDirectories (root: string): readonly string[] {
+    try {
+      return fs.readdirSync(root, { withFileTypes: true })
+        .filter((entry: fs.Dirent): boolean => entry.isDirectory())
+        .map((entry: fs.Dirent): string => entry.name)
+    } catch {
+      // A root that does not exist is the normal case on a fresh machine.
+      return []
+    }
+  }
+
+  private readStoreAt (home: string, directoryName: string): InstalledStore | null {
+    for (const engine of STORE_ENGINES) {
+      const scriptPath = path.join(home, engine.scriptFileName)
+      const configPath = path.join(home, CONFIG_FILE_NAME)
+      if (!fs.existsSync(scriptPath) || !fs.existsSync(configPath)) continue
+      const id = directoryName.replace(engine.homeSuffix, '')
+      return {
+        id,
+        name: this.readStoreName(configPath, id),
+        home,
+        scriptPath,
+        configPath,
+        engine: engine.id
+      }
+    }
+    return null
+  }
+
+  /**
+   * The store's own name, from the config the installer wrote.
+   *
+   * Read here rather than asked of the engine: the switcher lists every store on
+   * the machine, and starting a Python process per entry to learn its name would
+   * be absurd.
+   */
+  private readStoreName (configPath: string, fallback: string): string {
+    try {
+      const config = asRecord(JSON.parse(fs.readFileSync(configPath, 'utf8')))
+      const store = config === null ? null : asRecord(config['store'])
+      const name = store === null ? '' : readString(store, 'name')
+      return name.length > 0 ? name : fallback
+    } catch {
+      return fallback
+    }
+  }
+}

src/infrastructure/repositories/HttpStoreEngineInstaller.ts

@@ -0,0 +1,117 @@
+import fs from 'node:fs'
+import path from 'node:path'
+import type { EngineProgressListener } from '../../domain/models/EngineProgress'
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import type { RegistryStore } from '../../domain/models/RegistryStore'
+import { DESKTOP_STORE_ENGINE } from '../../domain/models/StoreEngine'
+import { deriveStoreId } from '../../domain/models/StoreIdentity'
+import type { StoreEngineInstaller } from '../../domain/ports/StoreEngineInstaller'
+import { asRecord, readString } from '../json/JsonRecord'
+import { HttpStatusError, type HttpTextClient } from '../http/HttpTextClient'
+
+const CONFIG_FILE_NAME = 'config.json'
+const SCRIPT_MODE = 0o755
+const PYTHON_SHEBANG = '#!/usr/bin/env python3'
+const DEFAULT_FORGE_BASE = 'https://git.teletypegames.org'
+const DEFAULT_BRANCH = 'master'
+
+/**
+ * Downloads the engine, the shared core and a store config into a store home.
+ *
+ * The same three files, in the same folder, the shell installer would place — so
+ * the CLI and this client stay one installation, and running install.sh afterwards
+ * only adds the launcher script. No launcher is written here: the window is it.
+ */
+export class HttpStoreEngineInstaller implements StoreEngineInstaller {
+  private readonly forgeBase: string
+
+  public constructor (private readonly httpClient: HttpTextClient, forgeBase?: string) {
+    const configured = process.env['FORGE_BASE']
+    this.forgeBase = forgeBase ?? (configured !== undefined && configured.length > 0
+      ? configured
+      : DEFAULT_FORGE_BASE)
+  }
+
+  public async installEngine (
+    home: string,
+    store: RegistryStore,
+    progress: EngineProgressListener = {}
+  ): Promise<InstalledStore> {
+    fs.mkdirSync(home, { recursive: true })
+
+    for (const [fileName, url] of Object.entries(this.engineSources())) {
+      progress.onLog?.(`downloading ${fileName}`)
+      const body = await this.httpClient.readText(url)
+      if (!body.startsWith(PYTHON_SHEBANG)) {
+        throw new Error(`${fileName} does not look like the store engine — refusing to install it`)
+      }
+      fs.writeFileSync(path.join(home, fileName), body, { mode: SCRIPT_MODE })
+    }
+
+    const config = await this.readStoreConfig(store, progress)
+    const configPath = path.join(home, CONFIG_FILE_NAME)
+    fs.writeFileSync(configPath, `${JSON.stringify(config, null, 2)}\n`)
+
+    progress.onLog?.(`${store.name} is set up in ${home}`)
+    const configStore = asRecord(config['store'])
+    return {
+      id: configStore === null ? deriveStoreId(store) : readString(configStore, 'id', deriveStoreId(store)),
+      name: store.name,
+      home,
+      scriptPath: path.join(home, DESKTOP_STORE_ENGINE.scriptFileName),
+      configPath,
+      engine: DESKTOP_STORE_ENGINE.id
+    }
+  }
+
+  /** Where the engine itself comes from: this client's own machinery, not the registry's. */
+  private engineSources (): Readonly<Record<string, string>> {
+    return {
+      [DESKTOP_STORE_ENGINE.scriptFileName]:
+        `${this.forgeBase}/stores/warp-engine-desktop-store/raw/branch/${DEFAULT_BRANCH}/${DESKTOP_STORE_ENGINE.scriptFileName}`,
+      'warpstore.py': `${this.forgeBase}/engines/warpstore/raw/branch/${DEFAULT_BRANCH}/warpstore.py`
+    }
+  }
+
+  /**
+   * The store's configuration.
+   *
+   * Its repository is the authority on how the store behaves — which platforms,
+   * which statuses, where things land. A repository without a config.json still
+   * works: the engine merges whatever it is given onto its own defaults, so a
+   * three-field config is a complete one. The registry wins on identity and on
+   * which catalog to read.
+   */
+  private async readStoreConfig (
+    store: RegistryStore,
+    progress: EngineProgressListener
+  ): Promise<Record<string, unknown>> {
+    const storeId = deriveStoreId(store)
+    let config: Record<string, unknown>
+    try {
+      progress.onLog?.(`reading the store config from ${store.storeRepositoryUrl}`)
+      const body = await this.httpClient.readText(this.configUrl(store.storeRepositoryUrl))
+      config = { ...(asRecord(JSON.parse(body)) ?? {}) }
+    } catch (error: unknown) {
+      if (!(error instanceof HttpStatusError) || error.statusCode !== 404) throw error
+      progress.onLog?.('no config.json in the store repository — using the engine defaults')
+      config = {
+        paths: { subfolder: storeId },
+        catalog: { statuses: ['released', 'archived', 'demo'] }
+      }
+    }
+
+    const existing = asRecord(config['store']) ?? {}
+    config['store'] = {
+      ...existing,
+      id: readString(existing, 'id', storeId),
+      name: store.name,
+      base_url: store.catalogUrl
+    }
+    return config
+  }
+
+  private configUrl (repositoryUrl: string, branch: string = DEFAULT_BRANCH): string {
+    return `${repositoryUrl.replace(/\/+$/, '')}/raw/branch/${branch}/${CONFIG_FILE_NAME}`
+  }
+}

src/infrastructure/repositories/HttpStoreRegistryRepository.ts

@@ -0,0 +1,47 @@
+import { RegistryUnavailableError } from '../../domain/errors/RegistryUnavailableError'
+import type { RegistryStore } from '../../domain/models/RegistryStore'
+import type { StoreRegistryRepository } from '../../domain/ports/StoreRegistryRepository'
+import { asRecord, readString, type JsonRecord } from '../json/JsonRecord'
+import type { HttpTextClient } from '../http/HttpTextClient'
+
+const DEFAULT_REGISTRY_URL = 'https://teletypegames.org/api/stores'
+
+/**
+ * The registry: `GET /api/stores` on the site.
+ *
+ * The one address this client knows, and even that is overridable — `STORES_API`
+ * points it at another site or at a local endpoint. Records missing any of the
+ * three fields are dropped rather than half-used.
+ */
+export class HttpStoreRegistryRepository implements StoreRegistryRepository {
+  public readonly sourceUrl: string
+
+  public constructor (private readonly httpClient: HttpTextClient, sourceUrl?: string) {
+    const configured = process.env['STORES_API']
+    this.sourceUrl = sourceUrl ?? (configured !== undefined && configured.length > 0
+      ? configured
+      : DEFAULT_REGISTRY_URL)
+  }
+
+  public async listStores (): Promise<readonly RegistryStore[]> {
+    const body = await this.httpClient.readText(this.sourceUrl)
+    const parsed: unknown = JSON.parse(body)
+    if (!Array.isArray(parsed)) {
+      throw new RegistryUnavailableError(this.sourceUrl, 'the answer was not a list of stores')
+    }
+    return parsed
+      .map((row: unknown): JsonRecord | null => asRecord(row))
+      .filter((row: JsonRecord | null): row is JsonRecord => row !== null)
+      .map((row: JsonRecord): RegistryStore => ({
+        name: readString(row, 'name').trim(),
+        // Both spellings, because a registry is someone else's API: ours answers
+        // camelCase, and a hand-rolled one may not.
+        catalogUrl: (readString(row, 'catalogUrl') || readString(row, 'catalog_url')).trim(),
+        storeRepositoryUrl: (
+          readString(row, 'storeRepositoryUrl') || readString(row, 'store_repository_url')
+        ).trim()
+      }))
+      .filter((store: RegistryStore): boolean =>
+        store.name.length > 0 && store.catalogUrl.length > 0 && store.storeRepositoryUrl.length > 0)
+  }
+}

src/infrastructure/repositories/JsonFilePreferencesRepository.ts

@@ -0,0 +1,56 @@
+import fs from 'node:fs'
+import path from 'node:path'
+import type { Preferences } from '../../domain/models/Preferences'
+import type { ApplicationEnvironment } from '../../domain/ports/ApplicationEnvironment'
+import type { PreferencesRepository } from '../../domain/ports/PreferencesRepository'
+import { LOCALES, type Locale } from '../../shared/i18n/MessageBundle'
+import { asRecord, readBoolean, readOptionalString } from '../json/JsonRecord'
+
+const PREFERENCES_FILE_NAME = 'prefs.json'
+
+/**
+ * Preferences in one small JSON file next to the application's own data.
+ *
+ * A lost preference is not worth an error dialog, so both directions swallow their
+ * failures — the defaults are always usable.
+ */
+export class JsonFilePreferencesRepository implements PreferencesRepository {
+  public constructor (private readonly environment: ApplicationEnvironment) {}
+
+  public read (): Preferences {
+    try {
+      const parsed = asRecord(JSON.parse(fs.readFileSync(this.filePath(), 'utf8')))
+      if (parsed === null) return {}
+      const locale = readOptionalString(parsed, 'locale')
+      const storeHome = readOptionalString(parsed, 'storeHome')
+      const preferences: {
+        locale?: Locale
+        navigationOpen?: boolean
+        storeHome?: string
+      } = {}
+      const known = LOCALES.find((candidate: Locale): boolean => candidate === locale)
+      if (known !== undefined) preferences.locale = known
+      if (storeHome !== null) preferences.storeHome = storeHome
+      if (typeof parsed['navigationOpen'] === 'boolean') {
+        preferences.navigationOpen = readBoolean(parsed, 'navigationOpen', true)
+      }
+      return preferences
+    } catch {
+      return {}
+    }
+  }
+
+  public write (preferences: Preferences): void {
+    try {
+      const target = this.filePath()
+      fs.mkdirSync(path.dirname(target), { recursive: true })
+      fs.writeFileSync(target, `${JSON.stringify(preferences, null, 2)}\n`)
+    } catch {
+      // Not worth interrupting the session over.
+    }
+  }
+
+  private filePath (): string {
+    return this.environment.resolveUserDataPath(PREFERENCES_FILE_NAME)
+  }
+}

src/infrastructure/repositories/PythonStoreCatalogGateway.ts

@@ -0,0 +1,87 @@
+import type { CatalogListing } from '../../domain/models/CatalogListing'
+import type { EngineProgressListener } from '../../domain/models/EngineProgress'
+import {
+  MINIMUM_ENGINE_VERSION, isAtLeast, parseVersionNumbers, type EngineVersion
+} from '../../domain/models/EngineVersion'
+import type { Game } from '../../domain/models/Game'
+import type { InstalledStore } from '../../domain/models/InstalledStore'
+import type { StorePaths } from '../../domain/models/StorePaths'
+import type { StoreCatalogGateway } from '../../domain/ports/StoreCatalogGateway'
+import { readRecord, readRecordArray, readStringArray, type JsonRecord } from '../json/JsonRecord'
+import { EngineGameMapper } from '../mappers/EngineGameMapper'
+import { EngineStorePathsMapper } from '../mappers/EngineStorePathsMapper'
+import type { PythonEngineProcessRunner } from '../process/PythonEngineProcessRunner'
+
+/**
+ * The store engine, driven as a child process.
+ *
+ * The only adapter that knows the CLI exists. Everything above it sees the port.
+ */
+export class PythonStoreCatalogGateway implements StoreCatalogGateway {
+  public constructor (
+    private readonly runner: PythonEngineProcessRunner,
+    private readonly gameMapper: EngineGameMapper = new EngineGameMapper(),
+    private readonly pathsMapper: EngineStorePathsMapper = new EngineStorePathsMapper()
+  ) {}
+
+  public async listGames (
+    store: InstalledStore,
+    progress?: EngineProgressListener
+  ): Promise<CatalogListing> {
+    const records = await this.runner.runCommand(store, ['list'], progress)
+    const answer = this.lastRecord(records)
+    if (answer === null) return { games: [], skipped: [], paths: null }
+    const games: readonly Game[] = readRecordArray(answer, 'games')
+      .map((record: JsonRecord): Game => this.gameMapper.toModel(record))
+    const paths = readRecord(answer, 'paths')
+    return {
+      games,
+      skipped: readStringArray(answer, 'skipped'),
+      paths: paths === null ? null : this.pathsMapper.toModel(paths)
+    }
+  }
+
+  public async readPaths (
+    store: InstalledStore,
+    progress?: EngineProgressListener
+  ): Promise<StorePaths> {
+    const records = await this.runner.runCommand(store, ['paths'], progress)
+    const answer = this.lastRecord(records)
+    return this.pathsMapper.toModel(answer ?? {})
+  }
+
+  public async syncGames (
+    store: InstalledStore,
+    names: readonly string[],
+    progress?: EngineProgressListener
+  ): Promise<void> {
+    await this.runner.runCommand(store, ['sync', ...names], progress)
+  }
+
+  public async removeGame (
+    store: InstalledStore,
+    name: string,
+    progress?: EngineProgressListener
+  ): Promise<void> {
+    await this.runner.runCommand(store, ['remove', name], progress)
+  }
+
+  public readEngineVersion (store: InstalledStore): EngineVersion | null {
+    const text = this.runner.readVersionText(store)
+    if (text === null) return null
+    const numbers = parseVersionNumbers(text)
+    return { text, numbers, supported: isAtLeast(numbers, MINIMUM_ENGINE_VERSION) }
+  }
+
+  /**
+   * The result object is the last line: the stream events come first, and both
+   * arrive on the same pipe.
+   */
+  private lastRecord (records: readonly JsonRecord[]): JsonRecord | null {
+    for (let index = records.length - 1; index >= 0; index -= 1) {
+      const record = records[index]
+      if (record !== undefined && typeof record['event'] !== 'string') return record
+    }
+    return null
+  }
+}

src/main/ElectronApplication.ts

@@ -0,0 +1,96 @@
+import path from 'node:path'
+import { BrowserWindow, dialog, type App, type IpcMain, type Shell } from 'electron'
+import { ServiceContainer } from './composition/ServiceContainer'
+import { MainWindowFactory } from './MainWindowFactory'
+import { SelfTestRunner } from './diagnostics/SelfTestRunner'
+
+const SELFTEST_FLAG = '--selftest'
+const SELFTEST_USER_DATA_DIRECTORY = 'warpstore-gui-selftest'
+const PRODUCT_NAME = 'WarpEngine Store'
+
+/**
+ * The application's lifecycle.
+ *
+ * Thin on purpose: it owns the window and the process events, and hands everything
+ * else to the container. The self-test mode is part of the lifecycle because it has
+ * to bypass two of its rules — see below.
+ */
+export class ElectronApplication {
+  private readonly selfTest: boolean
+  private readonly container: ServiceContainer
+  private readonly windowFactory: MainWindowFactory
+  private window: BrowserWindow | null = null
+
+  public constructor (
+    private readonly app: App,
+    private readonly ipc: IpcMain,
+    shell: Shell,
+    argv: readonly string[] = process.argv
+  ) {
+    this.selfTest = argv.includes(SELFTEST_FLAG)
+    this.container = new ServiceContainer(app, shell)
+    this.windowFactory = new MainWindowFactory((message: string, level: number): void => {
+      if (level >= 2 || this.selfTest) console.log(`[renderer] ${message}`)
+    })
+  }
+
+  public start (): void {
+    // A test run must never be swallowed by a copy the user already has open: it
+    // gets its own user-data directory and skips the single-instance lock. Without
+    // this the second process exits silently with status 0, which reads as a pass.
+    if (this.selfTest) {
+      this.app.setPath('userData', path.join(this.app.getPath('temp'), SELFTEST_USER_DATA_DIRECTORY))
+    } else if (!this.app.requestSingleInstanceLock()) {
+      this.app.quit()
+      return
+    }
+
+    this.container.registerIpc(this.ipc)
+    this.app.on('second-instance', (): void => { this.focusWindow() })
+    this.app.on('activate', (): void => {
+      if (BrowserWindow.getAllWindows().length === 0) this.openWindow()
+    })
+    this.app.on('window-all-closed', (): void => {
+      if (process.platform !== 'darwin') this.app.quit()
+    })
+    process.on('unhandledRejection', (reason: unknown): void => {
+      dialog.showErrorBox(PRODUCT_NAME, reason instanceof Error ? reason.message : String(reason))
+    })
+
+    void this.app.whenReady().then((): void => { this.openWindow() })
+  }
+
+  private openWindow (): void {
+    const window = this.windowFactory.createWindow()
+    this.window = window
+    this.container.streams.attachWindow(window)
+    window.on('closed', (): void => {
+      this.container.streams.detachWindow()
+      this.window = null
+    })
+    if (this.selfTest) this.scheduleSelfTest(window)
+  }
+
+  private scheduleSelfTest (window: BrowserWindow): void {
+    const runner = new SelfTestRunner(window)
+    window.webContents.once('did-finish-load', (): void => {
+      // The first listing has to finish before there is anything to look at.
+      setTimeout((): void => {
+        runner.run().then(
+          (passed: boolean): void => { this.app.exit(passed ? 0 : 1) },
+          (error: unknown): void => {
+            console.log(`SELFTEST ERROR ${error instanceof Error ? error.message : String(error)}`)
+            this.app.exit(1)
+          }
+        )
+      }, runner.settleDelayMs)
+    })
+  }
+
+  private focusWindow (): void {
+    const window = this.window
+    if (window === null) return
+    if (window.isMinimized()) window.restore()
+    window.focus()
+  }
+}

src/main/MainWindowFactory.ts

@@ -0,0 +1,63 @@
+import path from 'node:path'
+import { BrowserWindow, shell, type BrowserWindowConstructorOptions } from 'electron'
+
+const WINDOW_OPTIONS: BrowserWindowConstructorOptions = {
+  width: 1040,
+  height: 720,
+  minWidth: 760,
+  minHeight: 520,
+  backgroundColor: '#11151c',
+  title: 'WarpEngine Store'
+}
+
+/**
+ * The one window.
+ *
+ * Locked down deliberately: context isolation on, node integration off, sandbox on,
+ * and the page carries a CSP of its own. Nothing here should ever navigate away or
+ * open a second window — a link the user clicks goes to their browser instead.
+ */
+export class MainWindowFactory {
+  public constructor (private readonly onRendererMessage: (message: string, level: number) => void) {}
+
+  public createWindow (): BrowserWindow {
+    const window = new BrowserWindow({
+      ...WINDOW_OPTIONS,
+      webPreferences: {
+        preload: path.join(__dirname, '..', 'preload', 'preload.js'),
+        contextIsolation: true,
+        nodeIntegration: false,
+        sandbox: true,
+        webSecurity: true
+      }
+    })
+
+    void window.loadFile(path.join(__dirname, '..', 'renderer', 'index.html'))
+    this.forwardRendererDiagnostics(window)
+    this.denyNavigation(window)
+    return window
+  }
+
+  /** A renderer error is invisible from the main process otherwise. */
+  private forwardRendererDiagnostics (window: BrowserWindow): void {
+    window.webContents.on('console-message', (details): void => {
+      const level = details.level === 'error' ? 3 : details.level === 'warning' ? 2 : 1
+      this.onRendererMessage(details.message, level)
+    })
+    window.webContents.on('render-process-gone', (_event, details): void => {
+      this.onRendererMessage(`gone: ${details.reason}`, 3)
+    })
+  }
+
+  private denyNavigation (window: BrowserWindow): void {
+    window.webContents.setWindowOpenHandler(({ url }: { url: string }): { action: 'deny' } => {
+      if (url.startsWith('https://')) void shell.openExternal(url)
+      return { action: 'deny' }
+    })
+    window.webContents.on('will-navigate', (event, url: string): void => {
+      if (url === window.webContents.getURL()) return
+      event.preventDefault()
+      if (url.startsWith('https://')) void shell.openExternal(url)
+    })
+  }
+}

src/main/composition/ServiceContainer.ts

@@ -0,0 +1,78 @@
+import type { App, IpcMain, Shell } from 'electron'
+import { ApplicationStateService } from '../../application/services/ApplicationStateService'
+import { CatalogService } from '../../application/services/CatalogService'
+import { GameLaunchService } from '../../application/services/GameLaunchService'
+import { PreferencesService } from '../../application/services/PreferencesService'
+import { StoreProvisioningService } from '../../application/services/StoreProvisioningService'
+import { StoreSelectionService } from '../../application/services/StoreSelectionService'
+import { ElectronApplicationEnvironment } from '../../infrastructure/electron/ElectronApplicationEnvironment'
+import { ElectronGameLauncher } from '../../infrastructure/electron/ElectronGameLauncher'
+import { HttpTextClient } from '../../infrastructure/http/HttpTextClient'
+import { PythonEngineProcessRunner } from '../../infrastructure/process/PythonEngineProcessRunner'
+import { SystemPythonRuntimeLocator } from '../../infrastructure/process/SystemPythonRuntimeLocator'
+import { FileSystemInstalledStoreRepository } from '../../infrastructure/repositories/FileSystemInstalledStoreRepository'
+import { HttpStoreEngineInstaller } from '../../infrastructure/repositories/HttpStoreEngineInstaller'
+import { HttpStoreRegistryRepository } from '../../infrastructure/repositories/HttpStoreRegistryRepository'
+import { JsonFilePreferencesRepository } from '../../infrastructure/repositories/JsonFilePreferencesRepository'
+import { PythonStoreCatalogGateway } from '../../infrastructure/repositories/PythonStoreCatalogGateway'
+import { AppIpcController } from '../ipc/AppIpcController'
+import { CatalogIpcController } from '../ipc/CatalogIpcController'
+import { IpcRouter } from '../ipc/IpcRouter'
+import { SingleFlightGuard } from '../ipc/SingleFlightGuard'
+import { StoreIpcController } from '../ipc/StoreIpcController'
+import { WindowStreamBroadcaster } from '../streams/WindowStreamBroadcaster'
+
+/**
+ * The composition root: the only file that knows which implementation backs which
+ * port.
+ *
+ * Every layer above depends on interfaces, so swapping the engine for a stub or the
+ * registry for a local endpoint is a change here and nowhere else.
+ */
+export class ServiceContainer {
+  public readonly streams: WindowStreamBroadcaster
+  public readonly guard: SingleFlightGuard
+  public readonly catalog: CatalogService
+  public readonly selection: StoreSelectionService
+  public readonly provisioning: StoreProvisioningService
+  public readonly state: ApplicationStateService
+  public readonly launching: GameLaunchService
+
+  private readonly controllers: readonly { register: (router: IpcRouter) => void }[]
+
+  public constructor (app: App, shell: Shell) {
+    this.streams = new WindowStreamBroadcaster()
+    this.guard = new SingleFlightGuard((busy: boolean): void => { this.streams.publishBusyChanged(busy) })
+
+    const environment = new ElectronApplicationEnvironment(app)
+    const httpClient = new HttpTextClient()
+    const pythonLocator = new SystemPythonRuntimeLocator()
+    const engineRunner = new PythonEngineProcessRunner(pythonLocator)
+
+    const stores = new FileSystemInstalledStoreRepository()
+    const catalogGateway = new PythonStoreCatalogGateway(engineRunner)
+    const registry = new HttpStoreRegistryRepository(httpClient)
+    const installer = new HttpStoreEngineInstaller(httpClient)
+    const preferencesRepository = new JsonFilePreferencesRepository(environment)
+
+    const preferences = new PreferencesService(preferencesRepository, environment)
+    this.selection = new StoreSelectionService(stores, catalogGateway, preferences)
+    this.catalog = new CatalogService(catalogGateway, this.selection)
+    this.provisioning = new StoreProvisioningService(registry, installer, stores, this.selection)
+    this.launching = new GameLaunchService(new ElectronGameLauncher(shell), this.catalog)
+    this.state = new ApplicationStateService(
+      preferences, this.selection, this.provisioning, pythonLocator, environment
+    )
+
+    this.controllers = [
+      new AppIpcController(this.state, preferences, this.launching),
+      new CatalogIpcController(this.catalog, this.launching, this.guard, this.streams),
+      new StoreIpcController(this.provisioning, this.selection, this.guard, this.streams)
+    ]
+  }
+
+  public registerIpc (ipc: IpcMain): void {
+    const router = new IpcRouter(ipc)
+    for (const controller of this.controllers) controller.register(router)
+  }
+}

src/main/diagnostics/SelfTestRunner.ts

@@ -0,0 +1,173 @@
+import fs from 'node:fs'
+import type { BrowserWindow } from 'electron'
+import {
+  asRecord, readBoolean, readNumber, readOptionalString, readString, readStringArray
+} from '../../infrastructure/json/JsonRecord'
+
+const SETTLE_DELAY_MS = 6_000
+const SWITCH_SETTLE_DELAY_MS = 8_000
+const SHOT_FRAME_DELAY_MS = 400
+
+/** What the window says about itself once it has painted. */
+interface SelfTestReport {
+  readonly cards: number
+  readonly installed: number
+  readonly buttons: number
+  readonly gateVisible: boolean
+  readonly gateTitle: string
+  readonly gateChoices: readonly string[]
+  readonly gateAction: string
+  readonly appName: string
+  readonly storeId: string
+  readonly navOpen: boolean
+  readonly stores: readonly string[]
+  readonly categories: readonly string[]
+  readonly activeCategory: string | null
+  readonly paths: string
+  readonly logLines: number
+  readonly locales: readonly string[]
+}
+
+/** What changed after clicking a store that was not open. */
+interface StoreSwitchReport {
+  readonly storeId: string
+  readonly active: string | null
+  readonly cards: number
+  readonly categories: number
+}
+
+/**
+ * Drives the window once and reports what rendered.
+ *
+ * This is the only check that would notice a renderer error at all: the main
+ * process log stays empty when the page throws. Counting nodes is not enough on its
+ * own — the collapsed-grid bug passed every count while showing neither box art nor
+ * buttons — so `SELFTEST_SHOT` has the window photograph itself for a human to look
+ * at.
+ */
+export class SelfTestRunner {
+  public constructor (
+    private readonly window: BrowserWindow,
+    private readonly shotPath: string | null = process.env['SELFTEST_SHOT'] ?? null
+  ) {}
+
+  public get settleDelayMs (): number {
+    return SETTLE_DELAY_MS
+  }
+
+  /** True when the window is in a state a user could work with. */
+  public async run (): Promise<boolean> {
+    const report = await this.readReport()
+    console.log(JSON.stringify(report, null, 2))
+
+    const switched = report.stores.length > 1 ? await this.switchStore() : null
+    if (switched !== null) console.log(`switched: ${JSON.stringify(switched)}`)
+
+    if (this.shotPath !== null) await this.captureShot(this.shotPath)
+
+    const rendered = report.locales.length > 1 && (
+      (report.cards > 0 && !report.gateVisible && report.stores.length > 0 &&
+        report.categories.length > 0 && report.activeCategory !== null) ||
+      (report.gateVisible && report.gateChoices.length > 0 && report.gateAction.length > 0))
+    const switchedWell = switched === null || (
+      switched.storeId.length > 0 && switched.storeId !== report.storeId &&
+      switched.cards > 0 && switched.categories > 0)
+
+    const passed = rendered && switchedWell
+    console.log(passed ? 'SELFTEST OK' : 'SELFTEST FAILED')
+    return passed
+  }
+
+  private async readReport (): Promise<SelfTestReport> {
+    const record = asRecord(JSON.parse(await this.evaluate(`JSON.stringify({
+      cards: document.querySelectorAll('.card').length,
+      installed: document.querySelectorAll('.card.is-installed').length,
+      buttons: document.querySelectorAll('.card .actions button').length,
+      gateVisible: !document.getElementById('gate').hidden,
+      gateTitle: document.getElementById('gate-title').textContent,
+      gateChoices: [...document.getElementById('gate-select').options].map((option) => option.text),
+      gateAction: document.getElementById('gate-action').textContent,
+      appName: document.getElementById('app-name').textContent,
+      storeId: document.getElementById('store-id').textContent,
+      navOpen: !document.body.classList.contains('nav-closed'),
+      stores: [...document.querySelectorAll('#store-list .store-row')].map((row) => row.textContent),
+      categories: [...document.querySelectorAll('#cats .cat')].map((cat) => cat.textContent),
+      activeCategory: (document.querySelector('#cats .cat.is-active') || {}).textContent || null,
+      paths: document.getElementById('log-paths').textContent.slice(0, 120),
+      logLines: document.querySelectorAll('.log-line').length,
+      locales: [...document.getElementById('locale').options].map((option) => option.value)
+    })`))) ?? {}
+
+    return {
+      cards: readNumber(record, 'cards'),
+      installed: readNumber(record, 'installed'),
+      buttons: readNumber(record, 'buttons'),
+      gateVisible: readBoolean(record, 'gateVisible'),
+      gateTitle: readString(record, 'gateTitle'),
+      gateChoices: readStringArray(record, 'gateChoices'),
+      gateAction: readString(record, 'gateAction'),
+      appName: readString(record, 'appName'),
+      storeId: readString(record, 'storeId'),
+      navOpen: readBoolean(record, 'navOpen'),
+      stores: readStringArray(record, 'stores'),
+      categories: readStringArray(record, 'categories'),
+      activeCategory: readOptionalString(record, 'activeCategory'),
+      paths: readString(record, 'paths'),
+      logLines: readNumber(record, 'logLines'),
+      locales: readStringArray(record, 'locales')
+    }
+  }
+
+  /**
+   * With two stores on the machine the switcher is the thing most likely to break
+   * without anyone noticing, so the test uses it. Skipped with one store, which
+   * cannot be switched away from.
+   */
+  private async switchStore (): Promise<StoreSwitchReport> {
+    const record = asRecord(JSON.parse(await this.evaluate(`(async () => {
+      const other = [...document.querySelectorAll('#store-list .store-row')]
+        .find((row) => !row.classList.contains('is-active'))
+      other.click()
+      await new Promise((done) => setTimeout(done, ${String(SWITCH_SETTLE_DELAY_MS)}))
+      return JSON.stringify({
+        storeId: document.getElementById('store-id').textContent,
+        active: (document.querySelector('#store-list .store-row.is-active') || {}).textContent || null,
+        cards: document.querySelectorAll('.card').length,
+        categories: document.querySelectorAll('#cats .cat').length
+      })
+    })()`))) ?? {}
+
+    return {
+      storeId: readString(record, 'storeId'),
+      active: readOptionalString(record, 'active'),
+      cards: readNumber(record, 'cards'),
+      categories: readNumber(record, 'categories')
+    }
+  }
+
+  /**
+   * capturePage hands back the last painted frame, so a window that is behind
+   * others — or still loading box art — photographs as a half-drawn page. Focus it,
+   * wait for the images, then let one frame go by.
+   */
+  private async captureShot (target: string): Promise<void> {
+    this.window.show()
+    this.window.focus()
+    await this.evaluate(`(async () => {
+      await Promise.all([...document.images].map((image) => image.complete
+        ? null
+        : new Promise((done) => { image.onload = done; image.onerror = done })))
+      await new Promise((done) => requestAnimationFrame(() => setTimeout(done, ${String(SHOT_FRAME_DELAY_MS)})))
+      return String(document.images.length)
+    })()`)
+    const image = await this.window.webContents.capturePage()
+    fs.writeFileSync(target, image.toPNG())
+    console.log(`shot: ${target}`)
+  }
+
+  /** Every probe returns a JSON string, so nothing untyped crosses back. */
+  private async evaluate (script: string): Promise<string> {
+    const result: unknown = await this.window.webContents.executeJavaScript(script)
+    return typeof result === 'string' ? result : JSON.stringify(result ?? null)
+  }
+}

src/main/ipc/AppIpcController.ts

@@ -0,0 +1,52 @@
+import type { ApplicationStateService } from '../../application/services/ApplicationStateService'
+import type { GameLaunchService } from '../../application/services/GameLaunchService'
+import type { PreferencesService } from '../../application/services/PreferencesService'
+import { IPC_CHANNELS } from '../../shared/contracts/IpcChannels'
+import type { AppStateDto } from '../../shared/contracts/dto/AppStateDto'
+import type { LocaleSelectionDto } from '../../shared/contracts/dto/LocaleSelectionDto'
+import { TranslationCatalog } from '../../shared/i18n/TranslationCatalog'
+import { requireBoolean, requireString } from './IpcArguments'
+import type { IpcRouter } from './IpcRouter'
+
+/** The window's own concerns: what it needs to paint, its language, its menu state. */
+export class AppIpcController {
+  public constructor (
+    private readonly state: ApplicationStateService,
+    private readonly preferences: PreferencesService,
+    private readonly launching: GameLaunchService,
+    private readonly translations: TranslationCatalog = new TranslationCatalog()
+  ) {}
+
+  public register (router: IpcRouter): void {
+    router.handle(IPC_CHANNELS.appReadState, (): AppStateDto => this.handleReadState())
+    router.handle(IPC_CHANNELS.appUpdateLocale, (locale: unknown): LocaleSelectionDto =>
+      this.handleUpdateLocale(requireString(locale, 'locale')))
+    router.handle(IPC_CHANNELS.appUpdateNavOpen, (open: unknown): boolean =>
+      this.handleUpdateNavOpen(requireBoolean(open, 'open')))
+    router.handle(IPC_CHANNELS.appOpenFolder, async (directory: unknown): Promise<boolean> =>
+      this.handleOpenFolder(requireString(directory, 'directory')))
+    router.handle(IPC_CHANNELS.appOpenUrl, async (url: unknown): Promise<boolean> =>
+      this.handleOpenUrl(requireString(url, 'url')))
+  }
+
+  private handleReadState (): AppStateDto {
+    return this.state.readState()
+  }
+
+  private handleUpdateLocale (candidate: string): LocaleSelectionDto {
+    const locale = this.preferences.updateLocale(candidate)
+    return { locale, messages: this.translations.readBundle(locale) }
+  }
+
+  private handleUpdateNavOpen (open: boolean): boolean {
+    return this.preferences.updateNavigationOpen(open)
+  }
+
+  private async handleOpenFolder (directory: string): Promise<boolean> {
+    return this.launching.openFolder(directory)
+  }
+
+  private async handleOpenUrl (url: string): Promise<boolean> {
+    return this.launching.openUrl(url)
+  }
+}

src/main/ipc/CatalogIpcController.ts

@@ -0,0 +1,74 @@
+import type { CatalogService } from '../../application/services/CatalogService'
+import type { GameLaunchService } from '../../application/services/GameLaunchService'
+import { GameDtoMapper } from '../../application/mappers/GameDtoMapper'
+import { StorePathsDtoMapper } from '../../application/mappers/StorePathsDtoMapper'
+import { IPC_CHANNELS } from '../../shared/contracts/IpcChannels'
+import type { CatalogListingDto } from '../../shared/contracts/dto/CatalogListingDto'
+import type { StorePathsDto } from '../../shared/contracts/dto/StorePathsDto'
+import type { WindowStreamBroadcaster } from '../streams/WindowStreamBroadcaster'
+import { requireString, requireStringArray } from './IpcArguments'
+import type { IpcRouter } from './IpcRouter'
+import type { SingleFlightGuard } from './SingleFlightGuard'
+
+/**
+ * Everything that touches the catalog.
+ *
+ * The four engine calls go through the guard; launching does not, because it starts
+ * someone else's program and writes nothing.
+ */
+export class CatalogIpcController {
+  public constructor (
+    private readonly catalog: CatalogService,
+    private readonly launching: GameLaunchService,
+    private readonly guard: SingleFlightGuard,
+    private readonly streams: WindowStreamBroadcaster,
+    private readonly gameMapper: GameDtoMapper = new GameDtoMapper(),
+    private readonly pathsMapper: StorePathsDtoMapper = new StorePathsDtoMapper()
+  ) {}
+
+  public register (router: IpcRouter): void {
+    router.handle(IPC_CHANNELS.catalogListGames, async (): Promise<CatalogListingDto> =>
+      this.handleListGames())
+    router.handle(IPC_CHANNELS.catalogReadPaths, async (): Promise<StorePathsDto> =>
+      this.handleReadPaths())
+    router.handle(IPC_CHANNELS.catalogSyncGames, async (names: unknown): Promise<void> =>
+      this.handleSyncGames(names === undefined ? [] : requireStringArray(names, 'names')))
+    router.handle(IPC_CHANNELS.catalogRemoveGame, async (name: unknown): Promise<void> =>
+      this.handleRemoveGame(requireString(name, 'name')))
+    router.handle(IPC_CHANNELS.catalogLaunchGame, async (name: unknown): Promise<boolean> =>
+      this.handleLaunchGame(requireString(name, 'name')))
+  }
+
+  private async handleListGames (): Promise<CatalogListingDto> {
+    return this.guard.run(async (): Promise<CatalogListingDto> => {
+      const listing = await this.catalog.listGames(this.streams.asProgressListener())
+      const baseUrl = listing.paths?.catalogBaseUrl ?? ''
+      return {
+        games: this.gameMapper.toDtoList(listing.games, baseUrl),
+        skipped: listing.skipped,
+        paths: listing.paths === null ? null : this.pathsMapper.toDto(listing.paths)
+      }
+    })
+  }
+
+  private async handleReadPaths (): Promise<StorePathsDto> {
+    return this.guard.run(async (): Promise<StorePathsDto> =>
+      this.pathsMapper.toDto(await this.catalog.readPaths(this.streams.asProgressListener())))
+  }
+
+  private async handleSyncGames (names: readonly string[]): Promise<void> {
+    await this.guard.run(async (): Promise<void> => {
+      await this.catalog.syncGames(names, this.streams.asProgressListener())
+    })
+  }
+
+  private async handleRemoveGame (name: string): Promise<void> {
+    await this.guard.run(async (): Promise<void> => {
+      await this.catalog.removeGame(name, this.streams.asProgressListener())
+    })
+  }
+
+  private async handleLaunchGame (name: string): Promise<boolean> {
+    return this.launching.launchGame(name)
+  }
+}

src/main/ipc/IpcArguments.ts

@@ -0,0 +1,40 @@
+import { asRecord, readString } from '../../infrastructure/json/JsonRecord'
+import type { RegistryStoreDto } from '../../shared/contracts/dto/RegistryStoreDto'
+
+/**
+ * Reading what came over the bridge.
+ *
+ * The window is ours, but the channel is an interface: a payload is checked here
+ * once, so no service below has to wonder whether a string is really a string.
+ */
+export function requireString (value: unknown, name: string): string {
+  if (typeof value !== 'string' || value.length === 0) {
+    throw new TypeError(`${name} must be a non-empty string`)
+  }
+  return value
+}
+
+export function requireBoolean (value: unknown, name: string): boolean {
+  if (typeof value !== 'boolean') throw new TypeError(`${name} must be a boolean`)
+  return value
+}
+
+export function requireStringArray (value: unknown, name: string): readonly string[] {
+  if (!Array.isArray(value)) throw new TypeError(`${name} must be an array of strings`)
+  return value.map((item: unknown, index: number): string => requireString(item, `${name}[${String(index)}]`))
+}
+
+export function requireRegistryStore (value: unknown): RegistryStoreDto {
+  const record = asRecord(value)
+  if (record === null) throw new TypeError('a store record is required')
+  const store: RegistryStoreDto = {
+    name: readString(record, 'name'),
+    catalogUrl: readString(record, 'catalogUrl'),
+    storeRepositoryUrl: readString(record, 'storeRepositoryUrl'),
+    storeId: readString(record, 'storeId')
+  }
+  if (store.name.length === 0 || store.catalogUrl.length === 0 || store.storeRepositoryUrl.length === 0) {
+    throw new TypeError('a store record needs a name, a catalog URL and a repository URL')
+  }
+  return store
+}

src/main/ipc/IpcRouter.ts

@@ -0,0 +1,37 @@
+import type { IpcMain, IpcMainInvokeEvent } from 'electron'
+import { DomainError } from '../../domain/errors/DomainError'
+import type { IpcChannel } from '../../shared/contracts/IpcChannels'
+
+/** What a channel does with the arguments it was invoked with. */
+export type IpcHandler<TResult> = (...args: readonly unknown[]) => Promise<TResult> | TResult
+
+/**
+ * The one place a channel is registered.
+ *
+ * Errors are normalised on the way out: a domain error crosses as `CODE: message`
+ * so the log drawer shows something a person can act on, and an unexpected one is
+ * logged here rather than vanishing into a rejected promise the window cannot read.
+ */
+export class IpcRouter {
+  public constructor (private readonly ipc: IpcMain) {}
+
+  public handle<TResult>(channel: IpcChannel, handler: IpcHandler<TResult>): void {
+    this.ipc.handle(channel, async (_event: IpcMainInvokeEvent, ...args: readonly unknown[]): Promise<TResult> => {
+      try {
+        return await handler(...args)
+      } catch (error: unknown) {
+        throw this.describe(channel, error)
+      }
+    })
+  }
+
+  private describe (channel: IpcChannel, error: unknown): Error {
+    if (error instanceof DomainError) return new Error(`${error.code}: ${error.message}`)
+    if (error instanceof Error) {
+      console.error(`[ipc] ${channel} failed: ${error.message}`)
+      return error
+    }
+    console.error(`[ipc] ${channel} failed: ${String(error)}`)
+    return new Error(String(error))
+  }
+}

src/main/ipc/SingleFlightGuard.ts

@@ -0,0 +1,30 @@
+import { BusyError } from '../../domain/errors/BusyError'
+
+/**
+ * One engine call at a time.
+ *
+ * The store writes files, and two writers would race. Callers are told which state
+ * the guard is in, so the window can disable exactly what would start a second
+ * call and leave the rest alive.
+ */
+export class SingleFlightGuard {
+  private running = false
+
+  public constructor (private readonly onBusyChanged: (busy: boolean) => void) {}
+
+  public get busy (): boolean {
+    return this.running
+  }
+
+  public async run<TResult>(task: () => Promise<TResult>): Promise<TResult> {
+    if (this.running) throw new BusyError()
+    this.running = true
+    this.onBusyChanged(true)
+    try {
+      return await task()
+    } finally {
+      this.running = false
+      this.onBusyChanged(false)
+    }
+  }
+}

src/main/ipc/StoreIpcController.ts

@@ -0,0 +1,73 @@
+import { InstalledStoreDtoMapper } from '../../application/mappers/InstalledStoreDtoMapper'
+import { EngineVersionDtoMapper } from '../../application/mappers/EngineVersionDtoMapper'
+import { RegistryStoreDtoMapper } from '../../application/mappers/RegistryStoreDtoMapper'
+import type { StoreProvisioningService } from '../../application/services/StoreProvisioningService'
+import type { StoreSelectionService } from '../../application/services/StoreSelectionService'
+import { IPC_CHANNELS } from '../../shared/contracts/IpcChannels'
+import type { InstalledStoreDto } from '../../shared/contracts/dto/InstalledStoreDto'
+import type { RegistryResultDto } from '../../shared/contracts/dto/RegistryResultDto'
+import type { StoreSelectionDto } from '../../shared/contracts/dto/StoreSelectionDto'
+import type { WindowStreamBroadcaster } from '../streams/WindowStreamBroadcaster'
+import { requireRegistryStore, requireString } from './IpcArguments'
+import type { IpcRouter } from './IpcRouter'
+import type { SingleFlightGuard } from './SingleFlightGuard'
+
+/** Which stores exist, which one is open, and installing a new one. */
+export class StoreIpcController {
+  public constructor (
+    private readonly provisioning: StoreProvisioningService,
+    private readonly selection: StoreSelectionService,
+    private readonly guard: SingleFlightGuard,
+    private readonly streams: WindowStreamBroadcaster,
+    private readonly registryMapper: RegistryStoreDtoMapper = new RegistryStoreDtoMapper(),
+    private readonly storeMapper: InstalledStoreDtoMapper = new InstalledStoreDtoMapper(),
+    private readonly engineMapper: EngineVersionDtoMapper = new EngineVersionDtoMapper()
+  ) {}
+
+  public register (router: IpcRouter): void {
+    router.handle(IPC_CHANNELS.storeListRegistry, async (): Promise<RegistryResultDto> =>
+      this.handleListRegistry())
+    router.handle(IPC_CHANNELS.storeInstallStore, async (store: unknown): Promise<InstalledStoreDto> =>
+      this.handleInstallStore(store))
+    router.handle(IPC_CHANNELS.storeSelectStore, (home: unknown): StoreSelectionDto =>
+      this.handleSelectStore(requireString(home, 'home')))
+  }
+
+  /**
+   * The registry lookup never rejects: the window has to say *why* there is nothing
+   * to install, and an unreachable site and an empty list need different words.
+   */
+  private async handleListRegistry (): Promise<RegistryResultDto> {
+    try {
+      const stores = await this.provisioning.listAvailableStores()
+      return {
+        stores: this.registryMapper.toDtoList(stores),
+        sourceUrl: this.provisioning.registryUrl,
+        error: null
+      }
+    } catch (error: unknown) {
+      return {
+        stores: [],
+        sourceUrl: this.provisioning.registryUrl,
+        error: error instanceof Error ? error.message : String(error)
+      }
+    }
+  }
+
+  private async handleInstallStore (payload: unknown): Promise<InstalledStoreDto> {
+    const chosen = this.registryMapper.toModel(requireRegistryStore(payload))
+    return this.guard.run(async (): Promise<InstalledStoreDto> => {
+      const installed = await this.provisioning.installStore(chosen, this.streams.asProgressListener())
+      return this.storeMapper.toDto(installed)
+    })
+  }
+
+  private handleSelectStore (home: string): StoreSelectionDto {
+    const store = this.selection.selectStore(home)
+    const engine = this.selection.findEngineVersion(store)
+    return {
+      store: this.storeMapper.toDto(store),
+      engine: engine === null ? null : this.engineMapper.toDto(engine)
+    }
+  }
+}

src/main/main.ts

@@ -0,0 +1,5 @@
+import { app, ipcMain, shell } from 'electron'
+import { ElectronApplication } from './ElectronApplication'
+
+// The entry point does one thing: everything else is a class with a name.
+new ElectronApplication(app, ipcMain, shell).start()

src/main/streams/WindowStreamBroadcaster.ts

@@ -0,0 +1,49 @@
+import type { BrowserWindow } from 'electron'
+import type { EngineProgressListener } from '../../domain/models/EngineProgress'
+import { IPC_CHANNELS } from '../../shared/contracts/IpcChannels'
+import type { SyncEventDto } from '../../shared/contracts/dto/SyncEventDto'
+
+/**
+ * The three one-way streams to the window: log lines, progress events, busy state.
+ *
+ * Holds no window of its own — the reference is handed in when one exists and
+ * cleared when it does not, so a stream that outlives the window is a no-op rather
+ * than a crash.
+ */
+export class WindowStreamBroadcaster {
+  private window: BrowserWindow | null = null
+
+  public attachWindow (window: BrowserWindow): void {
+    this.window = window
+  }
+
+  public detachWindow (): void {
+    this.window = null
+  }
+
+  public publishLog (line: string): void {
+    this.send(IPC_CHANNELS.streamLog, line)
+  }
+
+  public publishSyncEvent (event: SyncEventDto): void {
+    this.send(IPC_CHANNELS.streamSyncEvent, event)
+  }
+
+  public publishBusyChanged (busy: boolean): void {
+    this.send(IPC_CHANNELS.streamBusyChanged, busy)
+  }
+
+  /** A progress listener wired to these streams, for handing to the engine. */
+  public asProgressListener (): EngineProgressListener {
+    return {
+      onLog: (line: string): void => { this.publishLog(line) },
+      onEvent: (event: SyncEventDto): void => { this.publishSyncEvent(event) }
+    }
+  }
+
+  private send (channel: string, payload: unknown): void {
+    const window = this.window
+    if (window === null || window.isDestroyed()) return
+    window.webContents.send(channel, payload)
+  }
+}

src/preload/preload.ts

@@ -0,0 +1,72 @@
+import { contextBridge, ipcRenderer, type IpcRendererEvent } from 'electron'
+import {
+  BRIDGE_GLOBAL_NAME, type BridgeApi, type StreamListener
+} from '../shared/contracts/BridgeApi'
+import { IPC_CHANNELS } from '../shared/contracts/IpcChannels'
+import type { AppStateDto } from '../shared/contracts/dto/AppStateDto'
+import type { CatalogListingDto } from '../shared/contracts/dto/CatalogListingDto'
+import type { InstalledStoreDto } from '../shared/contracts/dto/InstalledStoreDto'
+import type { LocaleSelectionDto } from '../shared/contracts/dto/LocaleSelectionDto'
+import type { RegistryResultDto } from '../shared/contracts/dto/RegistryResultDto'
+import type { RegistryStoreDto } from '../shared/contracts/dto/RegistryStoreDto'
+import type { StorePathsDto } from '../shared/contracts/dto/StorePathsDto'
+import type { StoreSelectionDto } from '../shared/contracts/dto/StoreSelectionDto'
+import type { SyncEventDto } from '../shared/contracts/dto/SyncEventDto'
+
+/**
+ * The bridge, and nothing else.
+ *
+ * This file is the whole surface the window gets: no Node, no filesystem, no child
+ * processes. It is bundled into a single script on purpose — a sandboxed preload
+ * cannot require its own modules — and it implements `BridgeApi`, so the renderer
+ * and the main process are compiled against the same contract.
+ */
+const bridge: BridgeApi = {
+  readState: async (): Promise<AppStateDto> =>
+    ipcRenderer.invoke(IPC_CHANNELS.appReadState) as Promise<AppStateDto>,
+  updateLocale: async (locale: string): Promise<LocaleSelectionDto> =>
+    ipcRenderer.invoke(IPC_CHANNELS.appUpdateLocale, locale) as Promise<LocaleSelectionDto>,
+  updateNavOpen: async (open: boolean): Promise<boolean> =>
+    ipcRenderer.invoke(IPC_CHANNELS.appUpdateNavOpen, open) as Promise<boolean>,
+
+  listGames: async (): Promise<CatalogListingDto> =>
+    ipcRenderer.invoke(IPC_CHANNELS.catalogListGames) as Promise<CatalogListingDto>,
+  readPaths: async (): Promise<StorePathsDto> =>
+    ipcRenderer.invoke(IPC_CHANNELS.catalogReadPaths) as Promise<StorePathsDto>,
+  syncGames: async (names: readonly string[]): Promise<void> =>
+    ipcRenderer.invoke(IPC_CHANNELS.catalogSyncGames, names) as Promise<void>,
+  removeGame: async (name: string): Promise<void> =>
+    ipcRenderer.invoke(IPC_CHANNELS.catalogRemoveGame, name) as Promise<void>,
+  launchGame: async (name: string): Promise<boolean> =>
+    ipcRenderer.invoke(IPC_CHANNELS.catalogLaunchGame, name) as Promise<boolean>,
+
+  listRegistryStores: async (): Promise<RegistryResultDto> =>
+    ipcRenderer.invoke(IPC_CHANNELS.storeListRegistry) as Promise<RegistryResultDto>,
+  installStore: async (store: RegistryStoreDto): Promise<InstalledStoreDto> =>
+    ipcRenderer.invoke(IPC_CHANNELS.storeInstallStore, store) as Promise<InstalledStoreDto>,
+  selectStore: async (home: string): Promise<StoreSelectionDto> =>
+    ipcRenderer.invoke(IPC_CHANNELS.storeSelectStore, home) as Promise<StoreSelectionDto>,
+
+  openFolder: async (directory: string): Promise<boolean> =>
+    ipcRenderer.invoke(IPC_CHANNELS.appOpenFolder, directory) as Promise<boolean>,
+  openUrl: async (url: string): Promise<boolean> =>
+    ipcRenderer.invoke(IPC_CHANNELS.appOpenUrl, url) as Promise<boolean>,
+
+  onLog: (listener: StreamListener<string>): void => {
+    ipcRenderer.on(IPC_CHANNELS.streamLog, (_event: IpcRendererEvent, line: string): void => {
+      listener(line)
+    })
+  },
+  onSyncEvent: (listener: StreamListener<SyncEventDto>): void => {
+    ipcRenderer.on(IPC_CHANNELS.streamSyncEvent, (_event: IpcRendererEvent, payload: SyncEventDto): void => {
+      listener(payload)
+    })
+  },
+  onBusyChanged: (listener: StreamListener<boolean>): void => {
+    ipcRenderer.on(IPC_CHANNELS.streamBusyChanged, (_event: IpcRendererEvent, busy: boolean): void => {
+      listener(busy)
+    })
+  }
+}
+
+contextBridge.exposeInMainWorld(BRIDGE_GLOBAL_NAME, bridge)

src/renderer/BridgeAccess.ts

@@ -0,0 +1,21 @@
+import { BRIDGE_GLOBAL_NAME, type BridgeApi } from '../shared/contracts/BridgeApi'
+
+declare global {
+  interface Window {
+    readonly storeApi?: BridgeApi
+  }
+}
+
+/**
+ * The bridge the preload published.
+ *
+ * Absent means the preload did not run, which is a packaging fault rather than a
+ * runtime condition — so it fails here, once, with a sentence that says what happened.
+ */
+export function requireBridge (): BridgeApi {
+  const bridge = window.storeApi
+  if (bridge === undefined) {
+    throw new Error(`window.${BRIDGE_GLOBAL_NAME} is missing — the preload script did not run`)
+  }
+  return bridge
+}

src/renderer/RendererApplication.ts

@@ -0,0 +1,106 @@
+import type { BridgeApi } from '../shared/contracts/BridgeApi'
+import { requireBridge } from './BridgeAccess'
+import { CatalogController } from './controllers/CatalogController'
+import { EngineStreamController } from './controllers/EngineStreamController'
+import { PreferencesController } from './controllers/PreferencesController'
+import { StoreController } from './controllers/StoreController'
+import { AppStore, type AppState } from './state/AppStore'
+import { buildCategorySections, resolveFilter, type CategoryFilter } from './state/CategoryFilter'
+import { CatalogGridView } from './views/CatalogGridView'
+import { GameCardView } from './views/GameCardView'
+import { GateView } from './views/GateView'
+import { LogDrawerView } from './views/LogDrawerView'
+import { SideMenuView } from './views/SideMenuView'
+import { TopBarView } from './views/TopBarView'
+
+/**
+ * The window, assembled.
+ *
+ * The flow is one direction only: a control calls a controller, the controller calls
+ * the bridge and writes to the store, and the store re-renders every view. No view
+ * reads another view, and nothing but the store decides what is on screen.
+ */
+export class RendererApplication {
+  private readonly store = new AppStore()
+  private readonly bridge: BridgeApi
+  private readonly log: LogDrawerView
+  private readonly gate: GateView
+  private readonly grid: CatalogGridView
+  private readonly topBar: TopBarView
+  private readonly sideMenu: SideMenuView
+  private readonly catalog: CatalogController
+  private readonly stores: StoreController
+  private readonly preferences: PreferencesController
+  private readonly streams: EngineStreamController
+
+  public constructor (bridge: BridgeApi = requireBridge()) {
+    this.bridge = bridge
+
+    this.log = new LogDrawerView({
+      onOpenFolder: (directory: string): void => { void this.bridge.openFolder(directory) }
+    })
+    this.gate = new GateView((url: string): void => { void this.bridge.openUrl(url) })
+    this.catalog = new CatalogController(this.bridge, this.store, this.log)
+    this.stores = new StoreController(this.bridge, this.store, this.gate, this.log, this.catalog)
+    this.preferences = new PreferencesController(this.bridge, this.store)
+    this.streams = new EngineStreamController(this.bridge, this.store, this.log)
+
+    this.grid = new CatalogGridView(new GameCardView({
+      onInstall: (name: string): void => { void this.catalog.syncGames([name]) },
+      onLaunch: (name: string): void => { void this.catalog.launchGame(name) },
+      onRemove: (name: string): void => { void this.catalog.removeGame(name) }
+    }))
+    this.topBar = new TopBarView({
+      onToggleNavigation: (): void => { void this.preferences.toggleNavigation() }
+    })
+    this.sideMenu = new SideMenuView({
+      onSelectStore: (home: string): void => { void this.stores.selectStore(home) },
+      onAddStore: (): void => { void this.stores.offerStores() },
+      onSyncAll: (): void => { void this.catalog.syncGames([]) },
+      onRefresh: (): void => { void this.catalog.refresh() },
+      onSelectCategory: (filter: CategoryFilter): void => { this.store.applyFilter(filter) },
+      onSelectLocale: (locale: string): void => { void this.preferences.selectLocale(locale) }
+    })
+
+    this.store.subscribe((state: AppState): void => { this.render(state) })
+    this.streams.subscribe()
+  }
+
+  /** Decides what the window is showing, then hands over to the views. */
+  public async start (): Promise<void> {
+    this.store.applyAppState(await this.bridge.readState())
+    const state = this.store.readState()
+
+    if (state.pythonVersion === null) {
+      this.stores.showMissingPythonGate()
+      return
+    }
+    if (state.currentStore === null) {
+      await this.stores.offerStores()
+      return
+    }
+    if (state.engine !== null && !state.engine.supported) {
+      this.stores.showOutdatedEngineGate()
+      return
+    }
+    this.gate.hide()
+    await this.catalog.refresh()
+  }
+
+  private render (state: AppState): void {
+    // The filter is corrected before anything is drawn from it, so the menu and the
+    // grid can never disagree about which category is active.
+    const corrected = resolveFilter(state.filter, buildCategorySections(state.games, state.messages))
+    if (corrected !== state.filter) {
+      this.store.applyFilter(corrected)
+      return
+    }
+
+    document.body.classList.toggle('nav-closed', !state.navigationOpen)
+    this.topBar.render(state)
+    this.sideMenu.render(state)
+    this.log.render(state)
+    if (this.gate.visible) this.grid.hide()
+    else this.grid.render(state)
+  }
+}

src/renderer/controllers/CatalogController.ts

@@ -0,0 +1,59 @@
+import type { BridgeApi } from '../../shared/contracts/BridgeApi'
+import type { CatalogListingDto } from '../../shared/contracts/dto/CatalogListingDto'
+import type { AppStore } from '../state/AppStore'
+import type { LogDrawerView } from '../views/LogDrawerView'
+
+/**
+ * The catalog operations, as the window performs them.
+ *
+ * Every one of them ends in a refresh: the engine is the authority on what is
+ * installed, so the window asks again rather than guessing what changed.
+ */
+export class CatalogController {
+  public constructor (
+    private readonly bridge: BridgeApi,
+    private readonly store: AppStore,
+    private readonly log: LogDrawerView
+  ) {}
+
+  public async refresh (): Promise<void> {
+    try {
+      const listing: CatalogListingDto = await this.bridge.listGames()
+      this.store.applyCatalog(listing.games, listing.paths)
+      for (const reason of listing.skipped) this.log.appendLine(`skipped ${reason}`)
+    } catch (error: unknown) {
+      this.reportFailure(error)
+    }
+  }
+
+  public async syncGames (names: readonly string[]): Promise<void> {
+    try {
+      await this.bridge.syncGames(names)
+    } catch (error: unknown) {
+      this.reportFailure(error)
+    }
+    await this.refresh()
+  }
+
+  public async removeGame (name: string): Promise<void> {
+    try {
+      await this.bridge.removeGame(name)
+    } catch (error: unknown) {
+      this.reportFailure(error)
+    }
+    await this.refresh()
+  }
+
+  public async launchGame (name: string): Promise<void> {
+    try {
+      const launched = await this.bridge.launchGame(name)
+      if (!launched) this.log.appendLine(`${name}: ${this.store.readState().messages.failed}`)
+    } catch (error: unknown) {
+      this.reportFailure(error)
+    }
+  }
+
+  private reportFailure (error: unknown): void {
+    this.log.appendLine(error instanceof Error ? error.message : String(error))
+  }
+}

src/renderer/controllers/EngineStreamController.ts

@@ -0,0 +1,67 @@
+import type { BridgeApi } from '../../shared/contracts/BridgeApi'
+import type { SyncEventDto } from '../../shared/contracts/dto/SyncEventDto'
+import type { AppStore, SyncProgress } from '../state/AppStore'
+import type { LogDrawerView } from '../views/LogDrawerView'
+
+/**
+ * The engine's own voice: its log, its progress events, and whether it is busy.
+ *
+ * Subscribed once at boot. The counter is derived from the events rather than
+ * guessed: `plan` says how many titles there are, `begin` and `installed` move it.
+ */
+export class EngineStreamController {
+  private progress: SyncProgress | null = null
+
+  public constructor (
+    private readonly bridge: BridgeApi,
+    private readonly store: AppStore,
+    private readonly log: LogDrawerView
+  ) {}
+
+  public subscribe (): void {
+    this.bridge.onLog((line: string): void => { this.log.appendLine(line) })
+    this.bridge.onBusyChanged((busy: boolean): void => {
+      if (!busy) this.progress = null
+      this.store.applyBusy(busy)
+    })
+    this.bridge.onSyncEvent((event: SyncEventDto): void => { this.handleEvent(event) })
+  }
+
+  private handleEvent (event: SyncEventDto): void {
+    const messages = this.store.readState().messages
+    switch (event.event) {
+      case 'plan':
+        this.progress = { total: event.count, done: 0, label: `0 ${messages.of} ${String(event.count)}` }
+        this.store.applyProgress(this.progress)
+        return
+      case 'begin': {
+        const current = this.progress
+        if (current === null) return
+        this.progress = {
+          ...current,
+          label: `${String(current.done + 1)} ${messages.of} ${String(current.total)} · ${event.title}`
+        }
+        this.store.applyProgress(this.progress)
+        return
+      }
+      case 'installed': {
+        const current = this.progress
+        if (current !== null) {
+          this.progress = { ...current, done: current.done + 1 }
+          this.store.applyProgress(this.progress)
+        }
+        this.log.appendLine(`${event.title} — ${event.changed ? messages.installed : messages.upToDate}`)
+        return
+      }
+      case 'failed':
+        this.log.appendLine(`${event.name}: ${messages.failed} — ${event.error}`)
+        return
+      case 'removed':
+        this.log.appendLine(`${event.name} — ${messages.removed}`)
+        return
+      case 'pruned':
+      case 'finished':
+        return
+    }
+  }
+}

src/renderer/controllers/PreferencesController.ts

@@ -0,0 +1,21 @@
+import type { BridgeApi } from '../../shared/contracts/BridgeApi'
+import type { AppStore } from '../state/AppStore'
+
+/** The two things the window remembers: its language and whether the menu is open. */
+export class PreferencesController {
+  public constructor (
+    private readonly bridge: BridgeApi,
+    private readonly store: AppStore
+  ) {}
+
+  public async selectLocale (candidate: string): Promise<void> {
+    const selection = await this.bridge.updateLocale(candidate)
+    this.store.applyMessages(selection.locale, selection.messages)
+  }
+
+  public async toggleNavigation (): Promise<void> {
+    const open = !this.store.readState().navigationOpen
+    this.store.applyNavigationOpen(open)
+    await this.bridge.updateNavOpen(open)
+  }
+}

src/renderer/controllers/StoreController.ts

@@ -0,0 +1,114 @@
+import type { BridgeApi } from '../../shared/contracts/BridgeApi'
+import type { RegistryStoreDto } from '../../shared/contracts/dto/RegistryStoreDto'
+import type { AppStore } from '../state/AppStore'
+import type { GateView } from '../views/GateView'
+import type { LogDrawerView } from '../views/LogDrawerView'
+import type { CatalogController } from './CatalogController'
+
+/**
+ * Which store the window drives, and how one gets onto the machine.
+ *
+ * The gate screens live here because they are all the same decision seen from
+ * different angles: there is no store to show a catalog for, and this is what can be
+ * done about it.
+ */
+export class StoreController {
+  public constructor (
+    private readonly bridge: BridgeApi,
+    private readonly store: AppStore,
+    private readonly gate: GateView,
+    private readonly log: LogDrawerView,
+    private readonly catalog: CatalogController
+  ) {}
+
+  /** Open another store that is already on this machine. */
+  public async selectStore (home: string): Promise<void> {
+    const messages = this.store.readState().messages
+    try {
+      const selection = await this.bridge.selectStore(home)
+      this.store.applySelectedStore(selection.store, selection.engine)
+      if (selection.engine !== null && !selection.engine.supported) {
+        this.showOutdatedEngineGate()
+        return
+      }
+      this.gate.hide()
+      await this.catalog.refresh()
+    } catch (error: unknown) {
+      this.log.appendLine(`${messages.switchFailed}: ${error instanceof Error ? error.message : String(error)}`)
+    }
+  }
+
+  /**
+   * Which stores exist is the site's answer, not this client's: the registry is asked
+   * for it, and its records carry the catalog and the config repository.
+   */
+  public async offerStores (): Promise<void> {
+    const state = this.store.readState()
+    const messages = state.messages
+    const result = await this.bridge.listRegistryStores()
+
+    if (result.error !== null) {
+      this.gate.show({
+        title: messages.registryFailed,
+        body: `${result.sourceUrl}\n\n${result.error}`,
+        action: { label: messages.registryRetry, perform: (): void => { void this.offerStores() } }
+      }, messages)
+      return
+    }
+
+    if (result.stores.length === 0) {
+      this.gate.show({
+        title: messages.setupTitle,
+        body: `${messages.registryEmpty}\n\n${result.sourceUrl}`
+      }, messages)
+      return
+    }
+
+    this.gate.show({
+      title: messages.setupTitle,
+      body: `${messages.setupBody}\n\n${state.defaultStoreRoot}`,
+      action: {
+        label: messages.setupAction,
+        perform: (chosen: RegistryStoreDto | null): void => {
+          if (chosen !== null) void this.installStore(chosen)
+        }
+      },
+      choices: result.stores
+    }, messages)
+  }
+
+  public showOutdatedEngineGate (): void {
+    const state = this.store.readState()
+    const engineText = state.engine === null ? '' : state.engine.text
+    this.gate.show({
+      title: state.messages.oldEngineTitle,
+      body: `${state.messages.oldEngineBody}\n\n${engineText} → ${state.minimumEngineVersion}`,
+      action: { label: state.messages.oldEngineAction, perform: (): void => { void this.offerStores() } }
+    }, state.messages)
+  }
+
+  public showMissingPythonGate (): void {
+    const messages = this.store.readState().messages
+    this.gate.show({
+      title: messages.noPythonTitle,
+      body: messages.noPythonBody,
+      link: { label: messages.pythonLink, url: 'https://www.python.org/downloads/' }
+    }, messages)
+  }
+
+  private async installStore (chosen: RegistryStoreDto): Promise<void> {
+    const messages = this.store.readState().messages
+    this.store.applyProgress({ total: 0, done: 0, label: messages.setupWorking })
+    try {
+      await this.bridge.installStore(chosen)
+      this.store.applyAppState(await this.bridge.readState())
+      this.gate.hide()
+      await this.catalog.refresh()
+      await this.catalog.syncGames([])
+    } catch (error: unknown) {
+      this.log.appendLine(error instanceof Error ? error.message : String(error))
+    } finally {
+      this.store.applyProgress(null)
+    }
+  }
+}

src/renderer/dom/Dom.ts

@@ -0,0 +1,36 @@
+/**
+ * The DOM chores this window has, in one place.
+ *
+ * `requireElement` throws rather than returning null, and checks what it found
+ * against the element type asked for: every id it is called with is in index.html, so
+ * a missing or retyped one is a mistake in this repository and should say so loudly
+ * instead of silently rendering half a window.
+ */
+export function requireElement<TElement extends HTMLElement> (
+  id: string,
+  type: abstract new () => TElement
+): TElement {
+  const found = document.getElementById(id)
+  if (found === null) throw new Error(`the element #${id} is missing from index.html`)
+  if (!(found instanceof type)) throw new Error(`#${id} is not a ${type.name}`)
+  return found
+}
+
+export function createElement<TTag extends keyof HTMLElementTagNameMap> (
+  tag: TTag,
+  className?: string,
+  text?: string
+): HTMLElementTagNameMap[TTag] {
+  const node = document.createElement(tag)
+  if (className !== undefined) node.className = className
+  if (text !== undefined) node.textContent = text
+  return node
+}
+
+export function setText (node: HTMLElement, value: string | number | null): void {
+  node.textContent = value === null ? '' : String(value)
+}
+
+export function setHidden (node: HTMLElement, hidden: boolean): void {
+  node.hidden = hidden
+}

src/renderer/main.ts

@@ -0,0 +1,7 @@
+import { RendererApplication } from './RendererApplication'
+
+// The renderer's entry point. Errors here would otherwise be invisible: the main
+// process log stays empty when the page throws, so the window says it out loud.
+void new RendererApplication().start().catch((error: unknown): void => {
+  console.error(error instanceof Error ? error.message : String(error))
+})

src/renderer/state/AppStore.ts

@@ -0,0 +1,133 @@
+import type { AppStateDto } from '../../shared/contracts/dto/AppStateDto'
+import type { EngineVersionDto } from '../../shared/contracts/dto/EngineVersionDto'
+import type { GameDto } from '../../shared/contracts/dto/GameDto'
+import type { InstalledStoreDto } from '../../shared/contracts/dto/InstalledStoreDto'
+import type { StorePathsDto } from '../../shared/contracts/dto/StorePathsDto'
+import { ENGLISH_MESSAGES } from '../../shared/i18n/EnglishMessages'
+import type { Locale, MessageBundle } from '../../shared/i18n/MessageBundle'
+import { ALL_CATEGORIES, type CategoryFilter } from './CategoryFilter'
+
+/** How far a running sync has got, for the counter in the bar. */
+export interface SyncProgress {
+  readonly total: number
+  readonly done: number
+  readonly label: string
+}
+
+/** Everything the window draws itself from. Read-only to everyone but the store. */
+export interface AppState {
+  readonly locale: Locale
+  readonly locales: readonly Locale[]
+  readonly messages: MessageBundle
+  readonly navigationOpen: boolean
+  readonly pythonVersion: string | null
+  readonly stores: readonly InstalledStoreDto[]
+  readonly currentStore: InstalledStoreDto | null
+  readonly engine: EngineVersionDto | null
+  readonly minimumEngineVersion: string
+  readonly registryUrl: string
+  readonly defaultStoreRoot: string
+  readonly games: readonly GameDto[]
+  readonly paths: StorePathsDto | null
+  readonly filter: CategoryFilter
+  readonly busy: boolean
+  readonly progress: SyncProgress | null
+}
+
+const INITIAL_STATE: AppState = {
+  locale: 'en',
+  locales: ['en'],
+  messages: ENGLISH_MESSAGES,
+  navigationOpen: true,
+  pythonVersion: null,
+  stores: [],
+  currentStore: null,
+  engine: null,
+  minimumEngineVersion: '',
+  registryUrl: '',
+  defaultStoreRoot: '',
+  games: [],
+  paths: null,
+  filter: ALL_CATEGORIES,
+  busy: false,
+  progress: null
+}
+
+export type AppStateListener = (state: AppState) => void
+
+/**
+ * The window's single source of truth.
+ *
+ * Every mutator is named after what it changes, and every one of them notifies: the
+ * views re-render from the state rather than being poked individually, so there is no
+ * way to update the model and forget the screen.
+ */
+export class AppStore {
+  private state: AppState = INITIAL_STATE
+  private readonly listeners: AppStateListener[] = []
+
+  public readState (): AppState {
+    return this.state
+  }
+
+  public subscribe (listener: AppStateListener): void {
+    this.listeners.push(listener)
+  }
+
+  public applyAppState (dto: AppStateDto): void {
+    this.state = {
+      ...this.state,
+      locale: dto.locale,
+      locales: dto.locales,
+      messages: dto.messages,
+      navigationOpen: dto.navigationOpen,
+      pythonVersion: dto.pythonVersion,
+      stores: dto.stores,
+      currentStore: dto.currentStore,
+      engine: dto.engine,
+      minimumEngineVersion: dto.minimumEngineVersion,
+      registryUrl: dto.registryUrl,
+      defaultStoreRoot: dto.defaultStoreRoot
+    }
+    this.notify()
+  }
+
+  public applyMessages (locale: Locale, messages: MessageBundle): void {
+    this.state = { ...this.state, locale, messages }
+    this.notify()
+  }
+
+  public applyNavigationOpen (open: boolean): void {
+    this.state = { ...this.state, navigationOpen: open }
+    this.notify()
+  }
+
+  public applyCatalog (games: readonly GameDto[], paths: StorePathsDto | null): void {
+    this.state = { ...this.state, games, paths: paths ?? this.state.paths }
+    this.notify()
+  }
+
+  public applySelectedStore (store: InstalledStoreDto, engine: EngineVersionDto | null): void {
+    this.state = { ...this.state, currentStore: store, engine, games: [], paths: null, filter: ALL_CATEGORIES }
+    this.notify()
+  }
+
+  public applyFilter (filter: CategoryFilter): void {
+    this.state = { ...this.state, filter }
+    this.notify()
+  }
+
+  public applyBusy (busy: boolean): void {
+    this.state = { ...this.state, busy, progress: busy ? this.state.progress : null }
+    this.notify()
+  }
+
+  public applyProgress (progress: SyncProgress | null): void {
+    this.state = { ...this.state, progress }
+    this.notify()
+  }
+
+  private notify (): void {
+    for (const listener of this.listeners) listener(this.state)
+  }
+}

src/renderer/state/CategoryFilter.ts

@@ -0,0 +1,122 @@
+import type { GameDto } from '../../shared/contracts/dto/GameDto'
+import type { MessageBundle } from '../../shared/i18n/MessageBundle'
+
+/** Which axis a category narrows the grid along. */
+export type CategoryKind = 'group' | 'platform' | 'mode'
+
+export interface CategoryFilter {
+  readonly kind: CategoryKind
+  readonly value: string
+}
+
+export interface CategoryItem extends CategoryFilter {
+  readonly label: string
+  readonly count: number
+}
+
+export interface CategorySection {
+  readonly title: string | null
+  readonly items: readonly CategoryItem[]
+}
+
+export const ALL_CATEGORIES: CategoryFilter = { kind: 'group', value: 'all' }
+
+export function isSameFilter (left: CategoryFilter, right: CategoryFilter): boolean {
+  return left.kind === right.kind && left.value === right.value
+}
+
+export function matchesFilter (game: GameDto, filter: CategoryFilter): boolean {
+  switch (filter.kind) {
+    case 'platform':
+      return game.platform === filter.value
+    case 'mode':
+      return game.mode === filter.value
+    case 'group':
+      return matchesGroup(game, filter.value)
+  }
+}
+
+function matchesGroup (game: GameDto, group: string): boolean {
+  switch (group) {
+    case 'installed':
+      return game.installed
+    case 'updates':
+      return game.updateAvailable
+    case 'available':
+      return !game.installed
+    default:
+      return true
+  }
+}
+
+/**
+ * The categories, built from what the catalog actually contains.
+ *
+ * There is no genre in a WarpEngine catalog, so the useful axes are the state of a
+ * title on this machine, the platform it was built with, and whether it runs here or
+ * in a browser. Empty axes are left out rather than shown as zeroes, and an axis with
+ * a single value is left out too — a filter that changes nothing is noise.
+ */
+export function buildCategorySections (
+  games: readonly GameDto[],
+  messages: MessageBundle
+): readonly CategorySection[] {
+  const count = (predicate: (game: GameDto) => boolean): number => games.filter(predicate).length
+  const sections: CategorySection[] = []
+
+  const groups: readonly CategoryItem[] = [
+    { kind: 'group', value: 'all', label: messages.catAll, count: games.length },
+    { kind: 'group', value: 'installed', label: messages.catInstalled, count: count((game: GameDto): boolean => game.installed) },
+    { kind: 'group', value: 'updates', label: messages.catUpdates, count: count((game: GameDto): boolean => game.updateAvailable) },
+    { kind: 'group', value: 'available', label: messages.catAvailable, count: count((game: GameDto): boolean => !game.installed) }
+  ]
+  sections.push({
+    title: null,
+    items: groups.filter((item: CategoryItem): boolean => item.value === 'all' || item.count > 0)
+  })
+
+  const platforms = [...new Set(games.map((game: GameDto): string => game.platform))]
+    .filter((platform: string): boolean => platform.length > 0)
+    .sort((left: string, right: string): number => left.localeCompare(right))
+  if (platforms.length > 1) {
+    sections.push({
+      title: messages.catPlatform,
+      items: platforms.map((platform: string): CategoryItem => ({
+        kind: 'platform',
+        value: platform,
+        label: platform,
+        count: count((game: GameDto): boolean => game.platform === platform)
+      }))
+    })
+  }
+
+  const modes = [...new Set(games.map((game: GameDto): string => game.mode))]
+  if (modes.length > 1) {
+    sections.push({
+      title: messages.catMode,
+      items: modes.map((mode: string): CategoryItem => ({
+        kind: 'mode',
+        value: mode,
+        label: mode === 'web' ? messages.hosted : messages.native,
+        count: count((game: GameDto): boolean => game.mode === mode)
+      }))
+    })
+  }
+
+  return sections
+}
+
+/**
+ * A category can vanish under us — the last title of a platform is removed, or an
+ * update is applied — and a filter matching nothing would look like an empty
+ * catalog. Falling back to everything is the honest answer.
+ */
+export function resolveFilter (
+  filter: CategoryFilter,
+  sections: readonly CategorySection[]
+): CategoryFilter {
+  const known = sections
+    .flatMap((section: CategorySection): readonly CategoryItem[] => section.items)
+    .some((item: CategoryItem): boolean => isSameFilter(item, filter))
+  return known ? filter : ALL_CATEGORIES
+}

src/renderer/views/CatalogGridView.ts

@@ -0,0 +1,28 @@
+import type { GameDto } from '../../shared/contracts/dto/GameDto'
+import { requireElement, setHidden, setText } from '../dom/Dom'
+import type { AppState } from '../state/AppStore'
+import { matchesFilter } from '../state/CategoryFilter'
+import type { GameCardView } from './GameCardView'
+
+/** The grid, and the sentence that stands in for it when there is nothing to show. */
+export class CatalogGridView {
+  private readonly grid = requireElement('grid', HTMLElement)
+  private readonly empty = requireElement('empty', HTMLElement)
+
+  public constructor (private readonly cards: GameCardView) {}
+
+  public render (state: AppState): void {
+    const shown = state.games.filter((game: GameDto): boolean => matchesFilter(game, state.filter))
+    this.grid.replaceChildren(...shown.map((game: GameDto): HTMLElement =>
+      this.cards.createCard(game, state.messages, state.busy)))
+    setHidden(this.grid, shown.length === 0)
+    this.grid.scrollTop = 0
+    setHidden(this.empty, shown.length !== 0)
+    setText(this.empty, state.games.length === 0 ? state.messages.noGames : state.messages.noMatch)
+  }
+
+  public hide (): void {
+    setHidden(this.grid, true)
+    setHidden(this.empty, true)
+  }
+}

src/renderer/views/GameCardView.ts

@@ -0,0 +1,92 @@
+import type { GameDto } from '../../shared/contracts/dto/GameDto'
+import type { MessageBundle } from '../../shared/i18n/MessageBundle'
+import { createElement } from '../dom/Dom'
+
+export interface GameCardViewCallbacks {
+  readonly onInstall: (name: string) => void
+  readonly onLaunch: (name: string) => void
+  readonly onRemove: (name: string) => void
+}
+
+/**
+ * One card.
+ *
+ * A card is a function of a title and the strings: it holds no state of its own, so
+ * the grid can throw the lot away and rebuild after every listing.
+ */
+export class GameCardView {
+  public constructor (private readonly callbacks: GameCardViewCallbacks) {}
+
+  public createCard (game: GameDto, messages: MessageBundle, busy: boolean): HTMLElement {
+    const card = createElement('article', 'card')
+    if (game.installed) card.classList.add('is-installed')
+    card.appendChild(this.createArt(game))
+    card.appendChild(this.createBody(game, messages, busy))
+    return card
+  }
+
+  private createArt (game: GameDto): HTMLElement {
+    const art = createElement('div', 'art')
+    if (game.imageUrl !== null) {
+      const image = createElement('img')
+      image.src = game.imageUrl
+      image.alt = ''
+      image.loading = 'lazy'
+      art.appendChild(image)
+      return art
+    }
+    // No box art in the catalog: the first letter, on the same band an image would
+    // fill, so a row of cards stays aligned either way.
+    art.appendChild(createElement('span', 'art-glyph', game.title.slice(0, 1).toUpperCase()))
+    return art
+  }
+
+  private createBody (game: GameDto, messages: MessageBundle, busy: boolean): HTMLElement {
+    const body = createElement('div', 'body')
+    body.appendChild(createElement('h2', undefined, game.title))
+    body.appendChild(this.createMeta(game, messages))
+    if (game.description.length > 0) {
+      body.appendChild(createElement('p', 'desc', game.description))
+    }
+    body.appendChild(this.createActions(game, messages, busy))
+    return body
+  }
+
+  private createMeta (game: GameDto, messages: MessageBundle): HTMLElement {
+    const meta = createElement('div', 'meta')
+    const mode = createElement('span', `badge badge-${game.mode}`,
+      game.mode === 'web' ? messages.hosted : messages.native)
+    mode.title = game.mode === 'web' ? messages.hostedHint : messages.nativeHint
+    meta.appendChild(mode)
+    meta.appendChild(createElement('span', 'badge badge-plain', game.platform))
+    meta.appendChild(createElement('span', 'version',
+      game.installed && game.installedVersion !== null
+        ? `${game.installedVersion} · ${messages.installed}`
+        : game.version))
+    return meta
+  }
+
+  private createActions (game: GameDto, messages: MessageBundle, busy: boolean): HTMLElement {
+    const actions = createElement('div', 'actions')
+    const primary = createElement('button', 'btn btn-primary')
+    primary.disabled = busy
+
+    if (game.installed && !game.updateAvailable) {
+      primary.textContent = game.mode === 'web' ? messages.open : messages.play
+      primary.disabled = busy || !game.launchable
+      primary.addEventListener('click', (): void => { this.callbacks.onLaunch(game.name) })
+    } else {
+      primary.textContent = game.updateAvailable ? messages.update : messages.install
+      primary.addEventListener('click', (): void => { this.callbacks.onInstall(game.name) })
+    }
+    actions.appendChild(primary)
+
+    if (game.installed) {
+      const remove = createElement('button', 'btn btn-ghost', messages.remove)
+      remove.disabled = busy
+      remove.addEventListener('click', (): void => { this.callbacks.onRemove(game.name) })
+      actions.appendChild(remove)
+    }
+    return actions
+  }
+}

src/renderer/views/GateView.ts

@@ -0,0 +1,91 @@
+import type { RegistryStoreDto } from '../../shared/contracts/dto/RegistryStoreDto'
+import { createElement, requireElement, setHidden, setText } from '../dom/Dom'
+import type { MessageBundle } from '../../shared/i18n/MessageBundle'
+
+/** A button on the gate, and what choosing it does. */
+export interface GateAction {
+  readonly label: string
+  readonly perform: (chosen: RegistryStoreDto | null) => void
+}
+
+export interface GateLink {
+  readonly label: string
+  readonly url: string
+}
+
+export interface GatePresentation {
+  readonly title: string
+  readonly body: string
+  readonly action?: GateAction
+  readonly link?: GateLink
+  readonly choices?: readonly RegistryStoreDto[]
+}
+
+/**
+ * The screen shown instead of the grid when there is nothing to drive: no Python, no
+ * store yet, an engine too old, or a registry that cannot be reached.
+ */
+export class GateView {
+  private readonly section = requireElement('gate', HTMLElement)
+  private readonly title = requireElement('gate-title', HTMLElement)
+  private readonly body = requireElement('gate-body', HTMLElement)
+  private readonly choice = requireElement('gate-choice', HTMLElement)
+  private readonly choiceLabel = requireElement('gate-choice-label', HTMLElement)
+  private readonly select = requireElement('gate-select', HTMLSelectElement)
+  private readonly button = requireElement('gate-action', HTMLButtonElement)
+  private readonly link = requireElement('gate-link', HTMLAnchorElement)
+
+  public constructor (private readonly onOpenUrl: (url: string) => void) {}
+
+  public show (presentation: GatePresentation, messages: MessageBundle): void {
+    setHidden(this.section, false)
+    setText(this.title, presentation.title)
+    setText(this.body, presentation.body)
+    this.renderChoices(presentation.choices ?? [], messages)
+    this.renderAction(presentation)
+    this.renderLink(presentation.link ?? null)
+  }
+
+  public hide (): void {
+    setHidden(this.section, true)
+  }
+
+  public get visible (): boolean {
+    return !this.section.hidden
+  }
+
+  /** Only shown when the registry offers more than one store; with a single one there is nothing to decide. */
+  private renderChoices (choices: readonly RegistryStoreDto[], messages: MessageBundle): void {
+    setHidden(this.choice, choices.length < 2)
+    if (choices.length < 2) return
+    setText(this.choiceLabel, messages.setupChoose)
+    this.select.replaceChildren(...choices.map((store: RegistryStoreDto, index: number): HTMLOptionElement => {
+      const option = createElement('option', undefined, store.name)
+      option.value = String(index)
+      return option
+    }))
+  }
+
+  private renderAction (presentation: GatePresentation): void {
+    const action = presentation.action
+    setHidden(this.button, action === undefined)
+    this.button.disabled = false
+    if (action === undefined) return
+    setText(this.button, action.label)
+    this.button.onclick = (): void => {
+      const choices = presentation.choices ?? []
+      const index = Number(this.select.value)
+      action.perform(choices[Number.isFinite(index) ? index : 0] ?? choices[0] ?? null)
+    }
+  }
+
+  private renderLink (link: GateLink | null): void {
+    setHidden(this.link, link === null)
+    if (link === null) return
+    setText(this.link, link.label)
+    this.link.onclick = (event: MouseEvent): void => {
+      event.preventDefault()
+      this.onOpenUrl(link.url)
+    }
+  }
+}

src/renderer/views/LogDrawerView.ts

@@ -0,0 +1,52 @@
+import { createElement, requireElement, setText } from '../dom/Dom'
+import type { AppState } from '../state/AppStore'
+
+const MAX_LOG_LINES = 400
+
+export interface LogDrawerViewCallbacks {
+  readonly onOpenFolder: (directory: string) => void
+}
+
+/** The store's own output, verbatim, and the folders everything lands in. */
+export class LogDrawerView {
+  private readonly toggle = requireElement('log-toggle', HTMLButtonElement)
+  private readonly lines = requireElement('log-lines', HTMLElement)
+  private readonly pathsBox = requireElement('log-paths', HTMLElement)
+
+  public constructor (private readonly callbacks: LogDrawerViewCallbacks) {
+    this.toggle.addEventListener('click', (): void => {
+      this.lines.hidden = !this.lines.hidden
+      this.toggle.setAttribute('aria-expanded', String(!this.lines.hidden))
+    })
+  }
+
+  public render (state: AppState): void {
+    setText(this.toggle, state.messages.log)
+    this.pathsBox.replaceChildren()
+    const paths = state.paths
+    if (paths === null) return
+
+    this.pathsBox.appendChild(createElement('div', 'paths-line',
+      `${state.messages.paths}: ${paths.storeFolder} · ${paths.menuGroup}`))
+
+    const folders: readonly (readonly [string, string])[] = [
+      [state.messages.openStoreFolder, paths.storeFolder],
+      [state.messages.openMenuFolder, paths.menuGroup]
+    ]
+    for (const [label, directory] of folders) {
+      const button = createElement('button', 'btn btn-tiny', label)
+      button.addEventListener('click', (): void => { this.callbacks.onOpenFolder(directory) })
+      this.pathsBox.appendChild(button)
+    }
+  }
+
+  public appendLine (line: string): void {
+    this.lines.appendChild(createElement('div', 'log-line', line))
+    while (this.lines.childElementCount > MAX_LOG_LINES) {
+      const first = this.lines.firstElementChild
+      if (first === null) break
+      first.remove()
+    }
+    this.lines.scrollTop = this.lines.scrollHeight
+  }
+}

src/renderer/views/SideMenuView.ts

@@ -0,0 +1,124 @@
+import { createElement, requireElement, setText } from '../dom/Dom'
+import type { InstalledStoreDto } from '../../shared/contracts/dto/InstalledStoreDto'
+import type { Locale } from '../../shared/i18n/MessageBundle'
+import {
+  buildCategorySections, isSameFilter, type CategoryFilter, type CategoryItem
+} from '../state/CategoryFilter'
+import type { AppState } from '../state/AppStore'
+
+export interface SideMenuViewCallbacks {
+  readonly onSelectStore: (home: string) => void
+  readonly onAddStore: () => void
+  readonly onSyncAll: () => void
+  readonly onRefresh: () => void
+  readonly onSelectCategory: (filter: CategoryFilter) => void
+  readonly onSelectLocale: (locale: string) => void
+}
+
+/**
+ * The side menu: which store, what to do with it, and what to look at.
+ *
+ * Everything that is not a title lives here, and the bar's button folds it away.
+ */
+export class SideMenuView {
+  private readonly storesHead = requireElement('head-stores', HTMLElement)
+  private readonly actionsHead = requireElement('head-actions', HTMLElement)
+  private readonly categoriesHead = requireElement('head-cats', HTMLElement)
+  private readonly languageHead = requireElement('head-lang', HTMLElement)
+  private readonly storeList = requireElement('store-list', HTMLElement)
+  private readonly addStore = requireElement('add-store', HTMLButtonElement)
+  private readonly syncAll = requireElement('sync-all', HTMLButtonElement)
+  private readonly refresh = requireElement('refresh', HTMLButtonElement)
+  private readonly categories = requireElement('cats', HTMLElement)
+  private readonly locale = requireElement('locale', HTMLSelectElement)
+
+  public constructor (private readonly callbacks: SideMenuViewCallbacks) {
+    this.addStore.addEventListener('click', callbacks.onAddStore)
+    this.syncAll.addEventListener('click', callbacks.onSyncAll)
+    this.refresh.addEventListener('click', callbacks.onRefresh)
+    this.locale.addEventListener('change', (): void => { callbacks.onSelectLocale(this.locale.value) })
+  }
+
+  public render (state: AppState): void {
+    setText(this.storesHead, state.messages.stores)
+    setText(this.actionsHead, state.messages.actions)
+    setText(this.categoriesHead, state.messages.categories)
+    setText(this.languageHead, state.messages.language)
+    setText(this.addStore, state.messages.addStore)
+    setText(this.syncAll, state.messages.syncAll)
+    setText(this.refresh, state.messages.refresh)
+
+    this.renderStores(state)
+    this.renderCategories(state)
+    this.renderLocales(state)
+    this.renderEnabled(state)
+  }
+
+  private renderStores (state: AppState): void {
+    const activeHome = state.currentStore === null ? null : state.currentStore.home
+    // Two stores can carry the same id in different roots — the same catalog
+    // installed twice. Then the id says nothing and the folder is what tells them
+    // apart, so that is what the row shows.
+    const ambiguousIds = new Set(state.stores
+      .filter((store: InstalledStoreDto, index: number): boolean =>
+        state.stores.findIndex((other: InstalledStoreDto): boolean => other.id === store.id) !== index)
+      .map((store: InstalledStoreDto): string => store.id))
+
+    this.storeList.replaceChildren(...state.stores.map((store: InstalledStoreDto): HTMLElement => {
+      const row = createElement('button', 'store-row')
+      if (store.home === activeHome) row.classList.add('is-active')
+      row.appendChild(createElement('span', 'store-row-name', store.name))
+      row.appendChild(createElement('span', 'store-row-id',
+        ambiguousIds.has(store.id) ? store.home : store.id))
+      row.title = store.home
+      row.addEventListener('click', (): void => {
+        if (store.home !== activeHome) this.callbacks.onSelectStore(store.home)
+      })
+      return row
+    }))
+  }
+
+  private renderCategories (state: AppState): void {
+    const sections = buildCategorySections(state.games, state.messages)
+    const nodes: HTMLElement[] = []
+    for (const section of sections) {
+      if (section.title !== null) nodes.push(createElement('div', 'cat-group', section.title))
+      for (const item of section.items) nodes.push(this.createCategoryRow(item, state.filter))
+    }
+    this.categories.replaceChildren(...nodes)
+  }
+
+  private createCategoryRow (item: CategoryItem, active: CategoryFilter): HTMLElement {
+    const row = createElement('button', 'cat')
+    if (isSameFilter(item, active)) row.classList.add('is-active')
+    row.appendChild(createElement('span', 'cat-label', item.label))
+    row.appendChild(createElement('span', 'cat-count', String(item.count)))
+    row.addEventListener('click', (): void => {
+      this.callbacks.onSelectCategory({ kind: item.kind, value: item.value })
+    })
+    return row
+  }
+
+  private renderLocales (state: AppState): void {
+    const current = this.locale.value
+    if (current === state.locale && this.locale.options.length === state.locales.length) return
+    this.locale.replaceChildren(...state.locales.map((locale: Locale): HTMLOptionElement => {
+      const option = createElement('option', undefined, locale.toUpperCase())
+      option.value = locale
+      option.selected = locale === state.locale
+      return option
+    }))
+  }
+
+  /**
+   * While the store is working only what would start a second call is disabled; the
+   * filters stay live because they change what is on screen and nothing on disk.
+   */
+  private renderEnabled (state: AppState): void {
+    const hasStore = state.currentStore !== null
+    this.syncAll.disabled = state.busy || !hasStore
+    this.refresh.disabled = state.busy || !hasStore
+    this.addStore.disabled = state.busy
+    for (const row of this.storeList.querySelectorAll('button')) row.disabled = state.busy
+  }
+}

src/renderer/views/TopBarView.ts

@@ -0,0 +1,30 @@
+import { requireElement, setHidden, setText } from '../dom/Dom'
+import type { AppState } from '../state/AppStore'
+
+export interface TopBarViewCallbacks {
+  readonly onToggleNavigation: () => void
+}
+
+/** The bar: what this is, which store is open, and how far a sync has got. */
+export class TopBarView {
+  private readonly appName = requireElement('app-name', HTMLElement)
+  private readonly storeId = requireElement('store-id', HTMLElement)
+  private readonly progress = requireElement('progress', HTMLElement)
+  private readonly navToggle = requireElement('nav-toggle', HTMLButtonElement)
+
+  public constructor (callbacks: TopBarViewCallbacks) {
+    this.navToggle.addEventListener('click', callbacks.onToggleNavigation)
+  }
+
+  public render (state: AppState): void {
+    setText(this.appName, state.messages.appName)
+    setText(this.storeId, state.currentStore === null ? '' : state.currentStore.id)
+    this.navToggle.title = state.messages.menu
+    this.navToggle.setAttribute('aria-label', state.messages.menu)
+    this.navToggle.setAttribute('aria-expanded', String(state.navigationOpen))
+
+    const progress = state.progress
+    setHidden(this.progress, progress === null)
+    setText(this.progress, progress === null ? '' : progress.label)
+  }
+}

src/scripts/SmokeTest.ts

@@ -0,0 +1,209 @@
+import fs from 'node:fs'
+import path from 'node:path'
+import { GameDtoMapper } from '../application/mappers/GameDtoMapper'
+import type { CatalogListing } from '../domain/models/CatalogListing'
+import type { InstalledStore } from '../domain/models/InstalledStore'
+import type { RegistryStore } from '../domain/models/RegistryStore'
+import { DESKTOP_STORE_ENGINE } from '../domain/models/StoreEngine'
+import { deriveStoreId } from '../domain/models/StoreIdentity'
+import { HttpTextClient } from '../infrastructure/http/HttpTextClient'
+import { PythonEngineProcessRunner } from '../infrastructure/process/PythonEngineProcessRunner'
+import { SystemPythonRuntimeLocator } from '../infrastructure/process/SystemPythonRuntimeLocator'
+import { FileSystemInstalledStoreRepository } from '../infrastructure/repositories/FileSystemInstalledStoreRepository'
+import { HttpStoreRegistryRepository } from '../infrastructure/repositories/HttpStoreRegistryRepository'
+import { PythonStoreCatalogGateway } from '../infrastructure/repositories/PythonStoreCatalogGateway'
+import type { GameDto } from '../shared/contracts/dto/GameDto'
+import { ENGLISH_MESSAGES } from '../shared/i18n/EnglishMessages'
+import { HUNGARIAN_MESSAGES } from '../shared/i18n/HungarianMessages'
+import { LOCALES } from '../shared/i18n/MessageBundle'
+
+/**
+ * Drives the store with no window and no Electron at all.
+ *
+ * This is the second composition root, and the reason the layers are worth having:
+ * the same services the window uses are assembled here against the same ports, so an
+ * integration mistake shows up in a terminal rather than in a screenshot.
+ *
+ *   npm run smoke                                       the store on this machine
+ *   SMOKE_HOME=/path/to/store-home npm run smoke        a sandbox store
+ */
+class SmokeTest {
+  private failed = false
+
+  private readonly stores = new FileSystemInstalledStoreRepository()
+  private readonly pythonLocator = new SystemPythonRuntimeLocator()
+  private readonly catalogGateway = new PythonStoreCatalogGateway(
+    new PythonEngineProcessRunner(this.pythonLocator)
+  )
+  private readonly httpClient = new HttpTextClient()
+  private readonly registry = new HttpStoreRegistryRepository(this.httpClient)
+  private readonly gameMapper = new GameDtoMapper()
+
+  public async run (): Promise<number> {
+    console.log('warp-engine-desktop-gui smoke test')
+
+    if (!this.checkPython()) return 1
+    this.checkMessages()
+    await this.checkRegistry()
+
+    const store = this.findStore()
+    if (store === null) return this.failed ? 1 : 0
+    await this.checkCatalog(store)
+
+    return this.failed ? 1 : 0
+  }
+
+  private checkPython (): boolean {
+    const runtime = this.pythonLocator.findRuntime()
+    if (runtime === null) {
+      this.reportBad('python', 'not found — the store cannot run')
+      return false
+    }
+    this.reportOk('python', runtime.version)
+    return true
+  }
+
+  /** The bundles are typed against one key set, so this only counts them. */
+  private checkMessages (): void {
+    const english = Object.keys(ENGLISH_MESSAGES).length
+    const hungarian = Object.keys(HUNGARIAN_MESSAGES).length
+    if (english === hungarian) this.reportOk('strings', `${String(english)} keys × ${String(LOCALES.length)} languages`)
+    else this.reportBad('strings', `en has ${String(english)}, hu has ${String(hungarian)}`)
+  }
+
+  private async checkRegistry (): Promise<void> {
+    try {
+      const stores = await this.registry.listStores()
+      if (stores.length === 0) {
+        this.reportBad('registry', `${this.registry.sourceUrl} returned no stores`)
+        return
+      }
+      this.reportOk('registry', `${String(stores.length)} store(s) from ${this.registry.sourceUrl}`)
+      for (const store of stores) {
+        this.reportOk(`  ${store.name}`, `${store.catalogUrl} · ${deriveStoreId(store)}`)
+        await this.checkStoreConfig(store)
+      }
+    } catch (error: unknown) {
+      this.reportBad('registry', `${this.registry.sourceUrl}: ${this.describe(error)}`)
+    }
+  }
+
+  /**
+   * A store repository without a config.json still installs — the engine merges what
+   * it is given onto its defaults — so an absent file is reported, not failed.
+   */
+  private async checkStoreConfig (store: RegistryStore): Promise<void> {
+    const url = `${store.storeRepositoryUrl.replace(/\/+$/, '')}/raw/branch/master/config.json`
+    try {
+      const config: unknown = JSON.parse(await this.httpClient.readText(url))
+      const sections = typeof config === 'object' && config !== null ? Object.keys(config).length : 0
+      this.reportOk('  config.json', `${String(sections)} sections`)
+    } catch (error: unknown) {
+      this.reportOk('  config.json', `absent (${this.describe(error)}) — defaults would be used`)
+    }
+  }
+
+  private findStore (): InstalledStore | null {
+    const sandbox = process.env['SMOKE_HOME']
+    if (sandbox !== undefined && sandbox.length > 0) {
+      const home = path.resolve(sandbox)
+      const store: InstalledStore = {
+        id: path.basename(home).replace(DESKTOP_STORE_ENGINE.homeSuffix, ''),
+        name: path.basename(home),
+        home,
+        scriptPath: path.join(home, DESKTOP_STORE_ENGINE.scriptFileName),
+        configPath: path.join(home, 'config.json'),
+        engine: DESKTOP_STORE_ENGINE.id
+      }
+      for (const file of [store.scriptPath, store.configPath]) {
+        if (!fs.existsSync(file)) {
+          this.reportBad('SMOKE_HOME', `${file} is missing`)
+          return null
+        }
+      }
+      this.reportOk('store (SMOKE_HOME)', store.home)
+      return store
+    }
+
+    const found = this.stores.findAll()[0]
+    if (found === undefined) {
+      console.log('  skip  no store installed — run the app once, or set SMOKE_HOME')
+      console.log(`        it would be installed in ${this.stores.resolveDefaultHome('ttg')}`)
+      return null
+    }
+    this.reportOk('store found', `${found.id} in ${found.home}`)
+    return found
+  }
+
+  private async checkCatalog (store: InstalledStore): Promise<void> {
+    const logLines: string[] = []
+    const progress = { onLog: (line: string): void => { logLines.push(line) } }
+
+    const engine = this.catalogGateway.readEngineVersion(store)
+    if (engine === null) this.reportBad('engine', 'the store did not answer --version')
+    else if (!engine.supported) this.reportBad('engine', `${engine.text} is too old for this client`)
+    else this.reportOk('engine', engine.text)
+
+    const paths = await this.catalogGateway.readPaths(store, progress)
+    if (paths.operatingSystem.length > 0 && paths.storeFolder.length > 0) {
+      this.reportOk('paths', `${paths.operatingSystem} → ${paths.storeFolder}`)
+    } else {
+      this.reportBad('paths', JSON.stringify(paths))
+    }
+
+    const listing: CatalogListing = await this.catalogGateway.listGames(store, progress)
+    if (listing.games.length === 0) {
+      this.reportBad('list', 'no games came back')
+      return
+    }
+    const games = this.gameMapper.toDtoList(listing.games, listing.paths?.catalogBaseUrl ?? '')
+    this.reportListing(games)
+
+    if (logLines.length > 0) this.reportOk('stderr log', `${String(logLines.length)} lines (kept off stdout)`)
+  }
+
+  private reportListing (games: readonly GameDto[]): void {
+    const native = games.filter((game: GameDto): boolean => game.mode === 'app').length
+    const hosted = games.length - native
+    this.reportOk('list', `${String(games.length)} titles (app:${String(native)}, web:${String(hosted)})`)
+
+    const withoutTitle = games.filter((game: GameDto): boolean =>
+      game.name.length === 0 || game.title.length === 0 || game.platform.length === 0)
+    if (withoutTitle.length > 0) this.reportBad('game shape', `${String(withoutTitle.length)} entries are incomplete`)
+    else this.reportOk('game shape', 'name, title, platform, version, mode, installed, updateAvailable')
+
+    const installed = games.filter((game: GameDto): boolean => game.installed)
+    this.reportOk('installed', `${String(installed.length)} of ${String(games.length)}`)
+
+    const unlaunchable = installed.filter((game: GameDto): boolean => !game.launchable)
+    if (unlaunchable.length > 0) this.reportBad('launch targets', `${String(unlaunchable.length)} installed titles have nothing to launch`)
+    else if (installed.length > 0) this.reportOk('launch targets', 'every installed title has one')
+
+    const withArt = games.filter((game: GameDto): boolean => game.imageUrl !== null)
+    if (withArt.length > 0) {
+      const first = withArt[0]
+      if (first !== undefined) this.reportOk('box art', first.imageUrl ?? '')
+    }
+  }
+
+  private describe (error: unknown): string {
+    return error instanceof Error ? error.message : String(error)
+  }
+
+  private reportOk (label: string, value?: string): void {
+    console.log(`  ok    ${label}${value === undefined ? '' : `: ${value}`}`)
+  }
+
+  private reportBad (label: string, value: string): void {
+    this.failed = true
+    console.log(`  FAIL  ${label}: ${value}`)
+  }
+}
+
+void new SmokeTest().run().then(
+  (code: number): void => { process.exitCode = code },
+  (error: unknown): void => {
+    console.log(`  FAIL  error: ${error instanceof Error ? error.message : String(error)}`)
+    process.exitCode = 1
+  }
+)

src/shared/contracts/BridgeApi.ts

@@ -0,0 +1,46 @@
+import type { AppStateDto } from './dto/AppStateDto'
+import type { CatalogListingDto } from './dto/CatalogListingDto'
+import type { InstalledStoreDto } from './dto/InstalledStoreDto'
+import type { LocaleSelectionDto } from './dto/LocaleSelectionDto'
+import type { RegistryResultDto } from './dto/RegistryResultDto'
+import type { RegistryStoreDto } from './dto/RegistryStoreDto'
+import type { StorePathsDto } from './dto/StorePathsDto'
+import type { StoreSelectionDto } from './dto/StoreSelectionDto'
+import type { SyncEventDto } from './dto/SyncEventDto'
+
+/** A stream the main process pushes; the window subscribes and never replies. */
+export type StreamListener<TPayload> = (payload: TPayload) => void
+
+/**
+ * The entire surface the window gets.
+ *
+ * Nothing else reaches it: no Node, no filesystem, no child processes. Both sides
+ * compile against this interface, so a method the preload does not expose is a
+ * compile error in the renderer rather than an `undefined is not a function` at
+ * runtime.
+ */
+export interface BridgeApi {
+  readState: () => Promise<AppStateDto>
+  updateLocale: (locale: string) => Promise<LocaleSelectionDto>
+  updateNavOpen: (open: boolean) => Promise<boolean>
+
+  listGames: () => Promise<CatalogListingDto>
+  readPaths: () => Promise<StorePathsDto>
+  syncGames: (names: readonly string[]) => Promise<void>
+  removeGame: (name: string) => Promise<void>
+  launchGame: (name: string) => Promise<boolean>
+
+  listRegistryStores: () => Promise<RegistryResultDto>
+  installStore: (store: RegistryStoreDto) => Promise<InstalledStoreDto>
+  selectStore: (home: string) => Promise<StoreSelectionDto>
+
+  openFolder: (directory: string) => Promise<boolean>
+  openUrl: (url: string) => Promise<boolean>
+
+  onLog: (listener: StreamListener<string>) => void
+  onSyncEvent: (listener: StreamListener<SyncEventDto>) => void
+  onBusyChanged: (listener: StreamListener<boolean>) => void
+}
+
+/** The name the bridge is published under on `window`. */
+export const BRIDGE_GLOBAL_NAME = 'storeApi'

src/shared/contracts/IpcChannels.ts

@@ -0,0 +1,32 @@
+/**
+ * Every channel name, in one frozen table.
+ *
+ * The pattern is `<domain>:<verb><Subject>` — the same verbs the services use, so
+ * a channel, the bridge method it backs and the service call behind it read as one
+ * sentence. Renderer and main both import this table; a typo cannot make a channel
+ * that only one side knows about.
+ */
+export const IPC_CHANNELS = {
+  appReadState: 'app:readState',
+  appUpdateLocale: 'app:updateLocale',
+  appUpdateNavOpen: 'app:updateNavOpen',
+  appOpenFolder: 'app:openFolder',
+  appOpenUrl: 'app:openUrl',
+
+  catalogListGames: 'catalog:listGames',
+  catalogReadPaths: 'catalog:readPaths',
+  catalogSyncGames: 'catalog:syncGames',
+  catalogRemoveGame: 'catalog:removeGame',
+  catalogLaunchGame: 'catalog:launchGame',
+
+  storeListRegistry: 'store:listRegistry',
+  storeInstallStore: 'store:installStore',
+  storeSelectStore: 'store:selectStore',
+
+  /** Main to renderer, one way. */
+  streamLog: 'stream:log',
+  streamSyncEvent: 'stream:syncEvent',
+  streamBusyChanged: 'stream:busyChanged'
+} as const
+
+export type IpcChannel = (typeof IPC_CHANNELS)[keyof typeof IPC_CHANNELS]