feat(overlay): add optional subtitle selection modal (#265)

src/main/runtime/subtitle-selection.ts

@@ -0,0 +1,117 @@
+import type { IpcMain, WebContents } from 'electron';
+import { IPC_CHANNELS } from '../../shared/ipc/contracts';
+import {
+  parseSubtitleSelectionRequest,
+  type SubtitleSelectionState,
+} from '../../shared/subtitle-selection';
+import { openOverlayHostedModal, retryOverlayModalOpen } from './overlay-hosted-modal-open';
+
+interface SelectionMpvClient {
+  connected: boolean;
+  requestProperty: (name: string) => Promise<unknown>;
+  request: (command: unknown[]) => Promise<{ error?: string }>;
+}
+
+export function openSubtitleSelectionModal(
+  deps: Parameters<typeof openOverlayHostedModal>[0] & Parameters<typeof retryOverlayModalOpen>[0],
+): Promise<boolean> {
+  return retryOverlayModalOpen(deps, {
+    modal: 'subtitle-selection',
+    timeoutMs: 1500,
+    retryWarning: 'Subtitle selection modal did not acknowledge opening; retrying.',
+    sendOpen: () =>
+      openOverlayHostedModal(deps, {
+        channel: IPC_CHANNELS.event.subtitleSelectionOpen,
+        modal: 'subtitle-selection',
+        preferModalWindow: true,
+      }),
+  });
+}
+
+export function createSubtitleSelectionRuntime(deps: {
+  isEnabled: () => boolean;
+  getMpvClient: () => SelectionMpvClient | null;
+}) {
+  function getClient(): SelectionMpvClient {
+    if (!deps.isEnabled()) throw new Error('Enable subtitle selection in Settings first.');
+    const client = deps.getMpvClient();
+    if (!client?.connected) throw new Error('Connect to mpv first.');
+    return client;
+  }
+
+  async function readState(client: SelectionMpvClient): Promise<SubtitleSelectionState> {
+    const mediaPath = await client.requestProperty('path');
+    if (typeof mediaPath !== 'string' || !mediaPath) throw new Error('Open a video first.');
+    const [rawTracks, primary, secondary] = await Promise.all([
+      client.requestProperty('track-list'),
+      client.requestProperty('sid'),
+      client.requestProperty('secondary-sid'),
+    ]);
+    const tracks: SubtitleSelectionState['tracks'] = [];
+    const candidates: unknown[] = Array.isArray(rawTracks) ? rawTracks : [];
+    for (const track of candidates) {
+      if (
+        typeof track !== 'object' ||
+        track === null ||
+        !('type' in track) ||
+        track.type !== 'sub' ||
+        !('id' in track) ||
+        typeof track.id !== 'number' ||
+        !Number.isSafeInteger(track.id) ||
+        track.id <= 0
+      )
+        continue;
+      const details = [
+        'title' in track ? track.title : undefined,
+        'lang' in track ? track.lang : undefined,
+        'codec' in track ? track.codec : undefined,
+      ].filter((value): value is string => typeof value === 'string' && value.length > 0);
+      if ('external' in track && track.external === true) details.push('external');
+      tracks.push({ id: track.id, label: `#${track.id} · ${details.join(' · ') || 'Subtitle'}` });
+    }
+    if ((await client.requestProperty('path')) !== mediaPath)
+      throw new Error('The video changed. Reopen subtitle selection.');
+    const selected = (value: unknown): number | null =>
+      tracks.find((track) => track.id === value)?.id ?? null;
+    return { mediaPath, tracks, primary: selected(primary), secondary: selected(secondary) };
+  }
+
+  async function apply(value: unknown): Promise<void> {
+    const selection = parseSubtitleSelectionRequest(value);
+    const client = getClient();
+    const current = await readState(client);
+    if (current.mediaPath !== selection.mediaPath)
+      throw new Error('The video changed. Reopen subtitle selection.');
+    for (const id of [selection.primary, selection.secondary]) {
+      if (id !== null && !current.tracks.some((track) => track.id === id))
+        throw new Error('A selected track is no longer available. Reopen subtitle selection.');
+    }
+    const set = async (property: string, id: number | null): Promise<void> => {
+      const response = await client.request(['set_property', property, id ?? 'no']);
+      if (response.error && response.error !== 'success') throw new Error(response.error);
+    };
+    // Clear secondary first so swapping the two tracks works in mpv.
+    await set('secondary-sid', null);
+    await set('sid', selection.primary);
+    await set('secondary-sid', selection.secondary);
+  }
+
+  return { getState: async () => readState(getClient()), apply };
+}
+
+export function registerSubtitleSelectionIpc(deps: {
+  ipc: Pick<IpcMain, 'handle'>;
+  isAllowedSender: (sender: WebContents) => boolean;
+  runtime: ReturnType<typeof createSubtitleSelectionRuntime>;
+}): void {
+  deps.ipc.handle(IPC_CHANNELS.request.getSubtitleSelection, (event) => {
+    if (!deps.isAllowedSender(event.sender))
+      throw new Error('Subtitle selection requires the overlay.');
+    return deps.runtime.getState();
+  });
+  deps.ipc.handle(IPC_CHANNELS.request.applySubtitleSelection, (event, value: unknown) => {
+    if (!deps.isAllowedSender(event.sender))
+      throw new Error('Subtitle selection requires the overlay.');
+    return deps.runtime.apply(value);
+  });
+}