feat(subtitle-sidebar): add sidebar config surface (#28)

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

@@ -1,5 +1,16 @@
 import { fileURLToPath } from 'node:url';
 
+function parseTrackId(value: unknown): number | null {
+  if (typeof value === 'number' && Number.isInteger(value)) {
+    return value;
+  }
+  if (typeof value === 'string') {
+    const parsed = Number(value.trim());
+    return Number.isInteger(parsed) ? parsed : null;
+  }
+  return null;
+}
+
 export function getActiveExternalSubtitleSource(
   trackListRaw: unknown,
   sidRaw: unknown,
@@ -8,9 +19,8 @@ export function getActiveExternalSubtitleSource(
     return null;
   }
 
-  const sid =
-    typeof sidRaw === 'number' ? sidRaw : typeof sidRaw === 'string' ? Number(sidRaw) : null;
-  if (sid == null || !Number.isFinite(sid)) {
+  const sid = parseTrackId(sidRaw);
+  if (sid === null) {
     return null;
   }
 
@@ -19,7 +29,7 @@ export function getActiveExternalSubtitleSource(
       return false;
     }
     const track = entry as Record<string, unknown>;
-    return track.type === 'sub' && track.id === sid && track.external === true;
+    return track.type === 'sub' && parseTrackId(track.id) === sid && track.external === true;
   }) as Record<string, unknown> | undefined;
 
   const externalFilename =
@@ -40,3 +50,21 @@ export function resolveSubtitleSourcePath(source: string): string {
     return source;
   }
 }
+
+export function buildSubtitleSidebarSourceKey(
+  videoPath: string,
+  track: unknown,
+  fallbackSourcePath?: string,
+): string {
+  const normalizedVideoPath = videoPath.trim();
+  if (track && typeof track === 'object' && normalizedVideoPath) {
+    const subtitleTrack = track as Record<string, unknown>;
+    const trackId = parseTrackId(subtitleTrack.id);
+    const ffIndex = parseTrackId(subtitleTrack['ff-index']);
+    if (trackId !== null || ffIndex !== null) {
+      return `internal:${normalizedVideoPath}:track:${trackId ?? 'unknown'}:ff:${ffIndex ?? 'unknown'}`;
+    }
+  }
+
+  return fallbackSourcePath ?? normalizedVideoPath;
+}