fix: address CodeRabbit review feedback

src/core/services/youtube/kinds.ts

@@ -0,0 +1 @@
+export type YoutubeTrackKind = 'manual' | 'auto';

src/core/services/youtube/labels.ts

@@ -1,4 +1,6 @@
-export type YoutubeTrackKind = 'manual' | 'auto';
+import type { YoutubeTrackKind } from './kinds';
+
+export type { YoutubeTrackKind };
 
 export function normalizeYoutubeLangCode(value: string): string {
   return value.trim().toLowerCase().replace(/_/g, '-').replace(/[^a-z0-9-]+/g, '');
@@ -37,4 +39,3 @@ export function formatYoutubeTrackLabel(input: {
   const base = input.title?.trim() || language;
   return `${base} (${input.kind})`;
 }
-

src/core/services/youtube/retime.test.ts

@@ -6,10 +6,6 @@ import path from 'node:path';
 import { retimeYoutubeSubtitle } from './retime';
 
 test('retimeYoutubeSubtitle uses the downloaded subtitle path as-is', async () => {
-  if (process.platform === 'win32') {
-    return;
-  }
-
   const root = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-youtube-retime-'));
   try {
     const primaryPath = path.join(root, 'primary.vtt');

src/core/services/youtube/retime.ts

@@ -1,7 +1,7 @@
 export async function retimeYoutubeSubtitle(input: {
   primaryPath: string;
   secondaryPath: string | null;
-}): Promise<{ ok: boolean; path: string; strategy: 'none'; message: string }> {
+}): Promise<{ ok: boolean; path: string; strategy: 'none' | 'alass' | 'ffsubsync'; message: string }> {
   return {
     ok: true,
     path: input.primaryPath,

src/core/services/youtube/timedtext.ts

@@ -74,16 +74,31 @@ export function convertYoutubeTimedTextToVtt(xml: string): string {
     return 'WEBVTT\n';
   }
 
-  const blocks = rows.map((row, index) => {
+  const blocks: string[] = [];
+  let previousText = '';
+  for (let index = 0; index < rows.length; index += 1) {
+    const row = rows[index]!;
     const nextRow = rows[index + 1];
     const unclampedEnd = row.startMs + row.durationMs;
     const clampedEnd =
       nextRow && unclampedEnd > nextRow.startMs
         ? Math.max(row.startMs, nextRow.startMs - 1)
         : unclampedEnd;
+    if (clampedEnd <= row.startMs) {
+      previousText = row.text;
+      continue;
+    }
 
-    return `${formatVttTimestamp(row.startMs)} --> ${formatVttTimestamp(clampedEnd)}\n${row.text}`;
-  });
+    const text =
+      previousText && row.text.startsWith(previousText)
+        ? row.text.slice(previousText.length).trimStart()
+        : row.text;
+    previousText = row.text;
+    if (!text) {
+      continue;
+    }
+    blocks.push(`${formatVttTimestamp(row.startMs)} --> ${formatVttTimestamp(clampedEnd)}\n${text}`);
+  }
 
   return `WEBVTT\n\n${blocks.join('\n\n')}\n`;
 }

src/core/services/youtube/track-download.test.ts

@@ -470,3 +470,48 @@ test('downloadYoutubeSubtitleTracks prefers direct download URLs when available'
     );
   });
 });
+
+test('downloadYoutubeSubtitleTracks keeps duplicate source-language direct downloads distinct', async () => {
+  await withTempDir(async (root) => {
+    const seen: string[] = [];
+    await withStubFetch(
+      async (url) => {
+        seen.push(url);
+        return new Response(`WEBVTT\n${url}\n`, { status: 200 });
+      },
+      async () => {
+        const result = await downloadYoutubeSubtitleTracks({
+          targetUrl: 'https://www.youtube.com/watch?v=abc123',
+          outputDir: path.join(root, 'out'),
+          tracks: [
+            {
+              id: 'auto:ja-orig',
+              language: 'ja',
+              sourceLanguage: 'ja-orig',
+              kind: 'auto',
+              label: 'Japanese (auto)',
+              downloadUrl: 'https://example.com/subs/ja-auto.vtt',
+              fileExtension: 'vtt',
+            },
+            {
+              id: 'manual:ja-orig',
+              language: 'ja',
+              sourceLanguage: 'ja-orig',
+              kind: 'manual',
+              label: 'Japanese (manual)',
+              downloadUrl: 'https://example.com/subs/ja-manual.vtt',
+              fileExtension: 'vtt',
+            },
+          ],
+          mode: 'download',
+        });
+
+        assert.deepEqual(seen, [
+          'https://example.com/subs/ja-auto.vtt',
+          'https://example.com/subs/ja-manual.vtt',
+        ]);
+        assert.notEqual(result.get('auto:ja-orig'), result.get('manual:ja-orig'));
+      },
+    );
+  });
+});

src/core/services/youtube/track-download.ts

@@ -7,12 +7,28 @@ import { convertYoutubeTimedTextToVtt, isYoutubeTimedTextExtension } from './tim
 
 const YOUTUBE_SUBTITLE_EXTENSIONS = new Set(['.srt', '.vtt', '.ass']);
 const YOUTUBE_BATCH_PREFIX = 'youtube-batch';
+const YOUTUBE_DOWNLOAD_TIMEOUT_MS = 15_000;
 
-function runCapture(command: string, args: string[]): Promise<{ stdout: string; stderr: string }> {
+function createFetchTimeoutSignal(timeoutMs: number): AbortSignal | undefined {
+  if (typeof AbortSignal !== 'undefined' && typeof AbortSignal.timeout === 'function') {
+    return AbortSignal.timeout(timeoutMs);
+  }
+  return undefined;
+}
+
+function runCapture(
+  command: string,
+  args: string[],
+  timeoutMs = YOUTUBE_DOWNLOAD_TIMEOUT_MS,
+): Promise<{ stdout: string; stderr: string }> {
   return new Promise((resolve, reject) => {
     const proc = spawn(command, args, { stdio: ['ignore', 'pipe', 'pipe'] });
     let stdout = '';
     let stderr = '';
+    const timer = setTimeout(() => {
+      proc.kill();
+      reject(new Error(`yt-dlp timed out after ${timeoutMs}ms`));
+    }, timeoutMs);
     proc.stdout.setEncoding('utf8');
     proc.stderr.setEncoding('utf8');
     proc.stdout.on('data', (chunk) => {
@@ -21,8 +37,12 @@ function runCapture(command: string, args: string[]): Promise<{ stdout: string;
     proc.stderr.on('data', (chunk) => {
       stderr += String(chunk);
     });
-    proc.once('error', reject);
+    proc.once('error', (error) => {
+      clearTimeout(timer);
+      reject(error);
+    });
     proc.once('close', (code) => {
+      clearTimeout(timer);
       if (code === 0) {
         resolve({ stdout, stderr });
         return;
@@ -35,11 +55,16 @@ function runCapture(command: string, args: string[]): Promise<{ stdout: string;
 function runCaptureDetailed(
   command: string,
   args: string[],
+  timeoutMs = YOUTUBE_DOWNLOAD_TIMEOUT_MS,
 ): Promise<{ stdout: string; stderr: string; code: number }> {
   return new Promise((resolve, reject) => {
     const proc = spawn(command, args, { stdio: ['ignore', 'pipe', 'pipe'] });
     let stdout = '';
     let stderr = '';
+    const timer = setTimeout(() => {
+      proc.kill();
+      reject(new Error(`yt-dlp timed out after ${timeoutMs}ms`));
+    }, timeoutMs);
     proc.stdout.setEncoding('utf8');
     proc.stderr.setEncoding('utf8');
     proc.stdout.on('data', (chunk) => {
@@ -48,8 +73,12 @@ function runCaptureDetailed(
     proc.stderr.on('data', (chunk) => {
       stderr += String(chunk);
     });
-    proc.once('error', reject);
+    proc.once('error', (error) => {
+      clearTimeout(timer);
+      reject(error);
+    });
     proc.once('close', (code) => {
+      clearTimeout(timer);
       resolve({ stdout, stderr, code: code ?? 1 });
     });
   });
@@ -125,8 +154,13 @@ async function downloadSubtitleFromUrl(input: {
     : YOUTUBE_SUBTITLE_EXTENSIONS.has(`.${ext}`)
       ? ext
       : 'vtt';
-  const targetPath = path.join(input.outputDir, `${input.prefix}.${input.track.sourceLanguage}.${safeExt}`);
-  const response = await fetch(input.track.downloadUrl);
+  const targetPath = path.join(
+    input.outputDir,
+    `${input.prefix}.${input.track.sourceLanguage}.${safeExt}`,
+  );
+  const response = await fetch(input.track.downloadUrl, {
+    signal: createFetchTimeoutSignal(YOUTUBE_DOWNLOAD_TIMEOUT_MS),
+  });
   if (!response.ok) {
     throw new Error(`HTTP ${response.status} while downloading ${input.track.sourceLanguage}`);
   }
@@ -195,6 +229,8 @@ export async function downloadYoutubeSubtitleTracks(input: {
   mode: YoutubeFlowMode;
 }): Promise<Map<string, string>> {
   fs.mkdirSync(input.outputDir, { recursive: true });
+  const hasDuplicateSourceLanguages =
+    new Set(input.tracks.map((track) => track.sourceLanguage)).size !== input.tracks.length;
   for (const name of fs.readdirSync(input.outputDir)) {
     if (name.startsWith(`${YOUTUBE_BATCH_PREFIX}.`)) {
       try {
@@ -204,12 +240,12 @@ export async function downloadYoutubeSubtitleTracks(input: {
       }
     }
   }
-  if (input.tracks.every(canDownloadSubtitleFromUrl)) {
+  if (hasDuplicateSourceLanguages || input.tracks.every(canDownloadSubtitleFromUrl)) {
     const results = new Map<string, string>();
     for (const track of input.tracks) {
       const download = await downloadSubtitleFromUrl({
         outputDir: input.outputDir,
-        prefix: YOUTUBE_BATCH_PREFIX,
+        prefix: track.id.replace(/[^a-z0-9_-]+/gi, '-'),
         track,
       });
       results.set(track.id, download.path);

src/core/services/youtube/track-probe.test.ts

@@ -16,11 +16,15 @@ async function withTempDir<T>(fn: (dir: string) => Promise<T>): Promise<T> {
 
 function makeFakeYtDlpScript(dir: string, payload: unknown): void {
   const scriptPath = path.join(dir, 'yt-dlp');
+  const stdoutBody = typeof payload === 'string' ? payload : JSON.stringify(payload);
   const script = `#!/usr/bin/env node
-process.stdout.write(${JSON.stringify(JSON.stringify(payload))});
+process.stdout.write(${JSON.stringify(stdoutBody)});
 `;
   fs.writeFileSync(scriptPath, script, 'utf8');
-  fs.chmodSync(scriptPath, 0o755);
+  if (process.platform !== 'win32') {
+    fs.chmodSync(scriptPath, 0o755);
+  }
+  fs.writeFileSync(scriptPath + '.cmd', `@echo off\r\nnode "${scriptPath}"\r\n`, 'utf8');
 }
 
 async function withFakeYtDlp<T>(payload: unknown, fn: () => Promise<T>): Promise<T> {
@@ -78,3 +82,12 @@ test('probeYoutubeTracks keeps preferring srt for manual captions', async () =>
     },
   );
 });
+
+test('probeYoutubeTracks reports malformed yt-dlp JSON with context', async () => {
+  await withFakeYtDlp('not-json', async () => {
+    await assert.rejects(
+      async () => await probeYoutubeTracks('https://www.youtube.com/watch?v=abc123'),
+      /Failed to parse yt-dlp output as JSON/,
+    );
+  });
+});

src/core/services/youtube/track-probe.ts

@@ -1,10 +1,6 @@
 import { spawn } from 'node:child_process';
 import type { YoutubeTrackOption } from '../../../types';
-import {
-  formatYoutubeTrackLabel,
-  normalizeYoutubeLangCode,
-  type YoutubeTrackKind,
-} from './labels';
+import { formatYoutubeTrackLabel, normalizeYoutubeLangCode, type YoutubeTrackKind } from './labels';
 
 export type YoutubeTrackProbeResult = {
   videoId: string;
@@ -102,7 +98,21 @@ export type { YoutubeTrackOption };
 
 export async function probeYoutubeTracks(targetUrl: string): Promise<YoutubeTrackProbeResult> {
   const { stdout } = await runCapture('yt-dlp', ['--dump-single-json', '--no-warnings', targetUrl]);
-  const info = JSON.parse(stdout) as YtDlpInfo;
+  const trimmedStdout = stdout.trim();
+  if (!trimmedStdout) {
+    throw new Error('yt-dlp returned empty output while probing subtitle tracks');
+  }
+  let info: YtDlpInfo;
+  try {
+    info = JSON.parse(trimmedStdout) as YtDlpInfo;
+  } catch (error) {
+    const snippet = trimmedStdout.slice(0, 200);
+    throw new Error(
+      `Failed to parse yt-dlp output as JSON: ${
+        error instanceof Error ? error.message : String(error)
+      }${snippet ? `; stdout=${snippet}` : ''}`,
+    );
+  }
   const tracks = [...toTracks(info.subtitles, 'manual'), ...toTracks(info.automatic_captions, 'auto')];
   return {
     videoId: info.id || '',