refactor(youtube): extract subtitle generation pipeline

launcher/youtube/manual-subs.ts

@@ -0,0 +1,99 @@
+import fs from 'node:fs';
+import path from 'node:path';
+
+import type { SubtitleCandidate } from '../types.js';
+import { YOUTUBE_SUB_EXTENSIONS } from '../types.js';
+import { escapeRegExp, runExternalCommand } from '../util.js';
+
+function filenameHasLanguageTag(filenameLower: string, langCode: string): boolean {
+  const escaped = escapeRegExp(langCode);
+  const pattern = new RegExp(`(^|[._-])${escaped}([._-]|$)`);
+  return pattern.test(filenameLower);
+}
+
+function classifyLanguage(
+  filename: string,
+  primaryLangCodes: string[],
+  secondaryLangCodes: string[],
+): 'primary' | 'secondary' | null {
+  const lower = filename.toLowerCase();
+  const primary = primaryLangCodes.some((code) => filenameHasLanguageTag(lower, code));
+  const secondary = secondaryLangCodes.some((code) => filenameHasLanguageTag(lower, code));
+  if (primary && !secondary) return 'primary';
+  if (secondary && !primary) return 'secondary';
+  return null;
+}
+
+export function toYtdlpLangPattern(langCodes: string[]): string {
+  return langCodes.map((lang) => `${lang}.*`).join(',');
+}
+
+export function scanSubtitleCandidates(
+  tempDir: string,
+  knownSet: Set<string>,
+  source: SubtitleCandidate['source'],
+  primaryLangCodes: string[],
+  secondaryLangCodes: string[],
+): SubtitleCandidate[] {
+  const entries = fs.readdirSync(tempDir);
+  const out: SubtitleCandidate[] = [];
+  for (const name of entries) {
+    const fullPath = path.join(tempDir, name);
+    if (knownSet.has(fullPath)) continue;
+    let stat: fs.Stats;
+    try {
+      stat = fs.statSync(fullPath);
+    } catch {
+      continue;
+    }
+    if (!stat.isFile()) continue;
+    const ext = path.extname(fullPath).toLowerCase();
+    if (!YOUTUBE_SUB_EXTENSIONS.has(ext)) continue;
+    const lang = classifyLanguage(name, primaryLangCodes, secondaryLangCodes);
+    if (!lang) continue;
+    out.push({ path: fullPath, lang, ext, size: stat.size, source });
+  }
+  return out;
+}
+
+export function pickBestCandidate(candidates: SubtitleCandidate[]): SubtitleCandidate | null {
+  if (candidates.length === 0) return null;
+  const scored = [...candidates].sort((a, b) => {
+    const srtA = a.ext === '.srt' ? 1 : 0;
+    const srtB = b.ext === '.srt' ? 1 : 0;
+    if (srtA !== srtB) return srtB - srtA;
+    return b.size - a.size;
+  });
+  return scored[0] ?? null;
+}
+
+export async function downloadManualSubtitles(
+  target: string,
+  tempDir: string,
+  langPattern: string,
+  logLevel: import('../types.js').LogLevel,
+  childTracker?: Set<ReturnType<typeof import('node:child_process').spawn>>,
+): Promise<void> {
+  await runExternalCommand(
+    'yt-dlp',
+    [
+      '--skip-download',
+      '--no-warnings',
+      '--write-subs',
+      '--sub-format',
+      'srt/vtt/best',
+      '--sub-langs',
+      langPattern,
+      '-o',
+      path.join(tempDir, '%(id)s.%(ext)s'),
+      target,
+    ],
+    {
+      allowFailure: true,
+      logLevel,
+      commandLabel: 'yt-dlp:manual-subs',
+      streamOutput: true,
+    },
+    childTracker,
+  );
+}