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>

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
+  }
+}