fix: address coderabbit review findings

src/main/runtime/mpv-client-event-bindings.test.ts

@@ -71,6 +71,8 @@ test('mpv event bindings register all expected events', () => {
     onSubtitleChange: () => {},
     onSubtitleAssChange: () => {},
     onSecondarySubtitleChange: () => {},
+    onSubtitleTrackChange: () => {},
+    onSubtitleTrackListChange: () => {},
     onSubtitleTiming: () => {},
     onMediaPathChange: () => {},
     onMediaTitleChange: () => {},
@@ -92,6 +94,8 @@ test('mpv event bindings register all expected events', () => {
     'subtitle-change',
     'subtitle-ass-change',
     'secondary-subtitle-change',
+    'subtitle-track-change',
+    'subtitle-track-list-change',
     'subtitle-timing',
     'media-path-change',
     'media-title-change',

src/main/runtime/mpv-client-event-bindings.ts

@@ -3,6 +3,8 @@ type MpvBindingEventName =
   | 'subtitle-change'
   | 'subtitle-ass-change'
   | 'secondary-subtitle-change'
+  | 'subtitle-track-change'
+  | 'subtitle-track-list-change'
   | 'subtitle-timing'
   | 'media-path-change'
   | 'media-title-change'
@@ -69,6 +71,8 @@ export function createBindMpvClientEventHandlers(deps: {
   onSubtitleChange: (payload: { text: string }) => void;
   onSubtitleAssChange: (payload: { text: string }) => void;
   onSecondarySubtitleChange: (payload: { text: string }) => void;
+  onSubtitleTrackChange: (payload: { sid: number | null }) => void;
+  onSubtitleTrackListChange: (payload: { trackList: unknown[] | null }) => void;
   onSubtitleTiming: (payload: { text: string; start: number; end: number }) => void;
   onMediaPathChange: (payload: { path: string | null }) => void;
   onMediaTitleChange: (payload: { title: string | null }) => void;
@@ -83,6 +87,8 @@ export function createBindMpvClientEventHandlers(deps: {
     mpvClient.on('subtitle-change', deps.onSubtitleChange);
     mpvClient.on('subtitle-ass-change', deps.onSubtitleAssChange);
     mpvClient.on('secondary-subtitle-change', deps.onSecondarySubtitleChange);
+    mpvClient.on('subtitle-track-change', deps.onSubtitleTrackChange);
+    mpvClient.on('subtitle-track-list-change', deps.onSubtitleTrackListChange);
     mpvClient.on('subtitle-timing', deps.onSubtitleTiming);
     mpvClient.on('media-path-change', deps.onMediaPathChange);
     mpvClient.on('media-title-change', deps.onMediaTitleChange);

src/main/runtime/mpv-main-event-bindings.test.ts

@@ -34,6 +34,8 @@ test('main mpv event binder wires callbacks through to runtime deps', () => {
     setCurrentSubAssText: (text) => calls.push(`set-ass:${text}`),
     broadcastSubtitleAss: (text) => calls.push(`broadcast-ass:${text}`),
     broadcastSecondarySubtitle: (text) => calls.push(`broadcast-secondary:${text}`),
+    onSubtitleTrackChange: () => calls.push('subtitle-track-change'),
+    onSubtitleTrackListChange: () => calls.push('subtitle-track-list-change'),
 
     updateCurrentMediaPath: (path) => calls.push(`media-path:${path}`),
     restoreMpvSubVisibility: () => calls.push('restore-mpv-sub'),
@@ -65,6 +67,8 @@ test('main mpv event binder wires callbacks through to runtime deps', () => {
   });
 
   handlers.get('subtitle-change')?.({ text: 'line' });
+  handlers.get('subtitle-track-change')?.({ sid: 3 });
+  handlers.get('subtitle-track-list-change')?.({ trackList: [] });
   handlers.get('media-path-change')?.({ path: '' });
   handlers.get('media-title-change')?.({ title: 'Episode 1' });
   handlers.get('time-pos-change')?.({ time: 2.5 });
@@ -73,6 +77,8 @@ test('main mpv event binder wires callbacks through to runtime deps', () => {
   assert.ok(calls.includes('set-sub:line'));
   assert.ok(calls.includes('broadcast-sub:line'));
   assert.ok(calls.includes('subtitle-change:line'));
+  assert.ok(calls.includes('subtitle-track-change'));
+  assert.ok(calls.includes('subtitle-track-list-change'));
   assert.ok(calls.includes('media-title:Episode 1'));
   assert.ok(calls.includes('restore-mpv-sub'));
   assert.ok(calls.includes('reset-guess-state'));

src/main/runtime/mpv-main-event-bindings.ts

@@ -42,6 +42,8 @@ export function createBindMpvMainEventHandlersHandler(deps: {
   setCurrentSubAssText: (text: string) => void;
   broadcastSubtitleAss: (text: string) => void;
   broadcastSecondarySubtitle: (text: string) => void;
+  onSubtitleTrackChange?: (sid: number | null) => void;
+  onSubtitleTrackListChange?: (trackList: unknown[] | null) => void;
 
   updateCurrentMediaPath: (path: string) => void;
   restoreMpvSubVisibility: () => void;
@@ -146,6 +148,8 @@ export function createBindMpvMainEventHandlersHandler(deps: {
       onSubtitleChange: handleMpvSubtitleChange,
       onSubtitleAssChange: handleMpvSubtitleAssChange,
       onSecondarySubtitleChange: handleMpvSecondarySubtitleChange,
+      onSubtitleTrackChange: ({ sid }) => deps.onSubtitleTrackChange?.(sid),
+      onSubtitleTrackListChange: ({ trackList }) => deps.onSubtitleTrackListChange?.(trackList),
       onSubtitleTiming: handleMpvSubtitleTiming,
       onMediaPathChange: handleMpvMediaPathChange,
       onMediaTitleChange: handleMpvMediaTitleChange,

src/main/runtime/mpv-main-event-main-deps.ts

@@ -35,6 +35,8 @@ export function createBuildBindMpvMainEventHandlersMainDepsHandler(deps: {
   logSubtitleTimingError: (message: string, error: unknown) => void;
   broadcastToOverlayWindows: (channel: string, payload: unknown) => void;
   onSubtitleChange: (text: string) => void;
+  onSubtitleTrackChange?: (sid: number | null) => void;
+  onSubtitleTrackListChange?: (trackList: unknown[] | null) => void;
   updateCurrentMediaPath: (path: string) => void;
   restoreMpvSubVisibility: () => void;
   getCurrentAnilistMediaKey: () => string | null;
@@ -101,6 +103,12 @@ export function createBuildBindMpvMainEventHandlersMainDepsHandler(deps: {
     broadcastSubtitle: (payload: { text: string; tokens: null }) =>
       deps.broadcastToOverlayWindows('subtitle:set', payload),
     onSubtitleChange: (text: string) => deps.onSubtitleChange(text),
+    onSubtitleTrackChange: deps.onSubtitleTrackChange
+      ? (sid: number | null) => deps.onSubtitleTrackChange!(sid)
+      : undefined,
+    onSubtitleTrackListChange: deps.onSubtitleTrackListChange
+      ? (trackList: unknown[] | null) => deps.onSubtitleTrackListChange!(trackList)
+      : undefined,
     refreshDiscordPresence: () => deps.refreshDiscordPresence(),
     setCurrentSubAssText: (text: string) => {
       deps.appState.currentSubAssText = text;

src/main/runtime/subtitle-prefetch-source.test.ts

@@ -0,0 +1,41 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  getActiveExternalSubtitleSource,
+  resolveSubtitleSourcePath,
+} from './subtitle-prefetch-source';
+
+test('getActiveExternalSubtitleSource returns the active external subtitle path', () => {
+  const source = getActiveExternalSubtitleSource(
+    [
+      { type: 'sub', id: 1, external: false },
+      { type: 'sub', id: 2, external: true, 'external-filename': ' https://host/subs.ass ' },
+    ],
+    '2',
+  );
+
+  assert.equal(source, 'https://host/subs.ass');
+});
+
+test('getActiveExternalSubtitleSource returns null when the selected track is not external', () => {
+  const source = getActiveExternalSubtitleSource(
+    [{ type: 'sub', id: 2, external: false, 'external-filename': '/tmp/subs.ass' }],
+    2,
+  );
+
+  assert.equal(source, null);
+});
+
+test('resolveSubtitleSourcePath converts file URLs with spaces into filesystem paths', () => {
+  const fileUrl = process.platform === 'win32'
+    ? 'file:///C:/Users/test/Sub%20Folder/subs.ass'
+    : 'file:///tmp/Sub%20Folder/subs.ass';
+
+  const resolved = resolveSubtitleSourcePath(fileUrl);
+
+  assert.ok(resolved.endsWith('/Sub Folder/subs.ass') || resolved.endsWith('\\Sub Folder\\subs.ass'));
+});
+
+test('resolveSubtitleSourcePath leaves non-file sources unchanged', () => {
+  assert.equal(resolveSubtitleSourcePath('/tmp/subs.ass'), '/tmp/subs.ass');
+});

src/main/runtime/subtitle-prefetch-source.ts

@@ -0,0 +1,34 @@
+import { fileURLToPath } from 'node:url';
+
+export function getActiveExternalSubtitleSource(
+  trackListRaw: unknown,
+  sidRaw: unknown,
+): string | null {
+  if (!Array.isArray(trackListRaw) || sidRaw == null) {
+    return null;
+  }
+
+  const sid =
+    typeof sidRaw === 'number' ? sidRaw : typeof sidRaw === 'string' ? Number(sidRaw) : null;
+  if (sid == null || !Number.isFinite(sid)) {
+    return null;
+  }
+
+  const activeTrack = trackListRaw.find((entry: unknown) => {
+    if (!entry || typeof entry !== 'object') {
+      return false;
+    }
+    const track = entry as Record<string, unknown>;
+    return track.type === 'sub' && track.id === sid && track.external === true;
+  }) as Record<string, unknown> | undefined;
+
+  const externalFilename =
+    typeof activeTrack?.['external-filename'] === 'string'
+      ? activeTrack['external-filename'].trim()
+      : '';
+  return externalFilename || null;
+}
+
+export function resolveSubtitleSourcePath(source: string): string {
+  return source.startsWith('file://') ? fileURLToPath(new URL(source)) : source;
+}