feat: add multilingual subtitle tracks

2026-08-28 19:37:03 +00:00 · 2026-06-26 14:34:10 +00:00
parent 7ce7941712
commit 22871f6679
13 changed files with 486 additions and 89 deletions
@@ -0,0 +1,144 @@
+import { basename, extname } from 'path'
+
+export type SubtitleFormat = 'vtt' | 'srt'
+
+export type SubtitleTrackInput = {
+  src: string
+  lang: string
+  label: string
+  format: SubtitleFormat
+  isDefault: boolean
+}
+
+const LANGUAGE_LABELS: Record<string, string> = {
+  en: 'English',
+  es: 'Spanish',
+  fr: 'French',
+  de: 'German',
+  it: 'Italian',
+  pt: 'Portuguese',
+  'pt-BR': 'Portuguese (Brazil)',
+  zh: 'Chinese',
+  'zh-CN': 'Chinese (Simplified)',
+  'zh-TW': 'Chinese (Traditional)',
+  ja: 'Japanese',
+  ko: 'Korean',
+  fil: 'Filipino',
+  tl: 'Tagalog',
+  id: 'Indonesian',
+  ms: 'Malay',
+  th: 'Thai',
+  vi: 'Vietnamese',
+  ar: 'Arabic',
+  hi: 'Hindi',
+  ru: 'Russian',
+}
+
+export function normalizeSubtitleLang(code: string): string {
+  const trimmed = code.trim().replace(/_/g, '-')
+  if (!trimmed) return 'en'
+
+  const [language, region, ...rest] = trimmed.split('-')
+  const normalizedLanguage = language.toLowerCase()
+  const normalizedRegion = region ? region.toUpperCase() : undefined
+  const normalizedRest = rest.map(part => part.length === 2 ? part.toUpperCase() : part)
+
+  return [normalizedLanguage, normalizedRegion, ...normalizedRest]
+    .filter(Boolean)
+    .join('-')
+}
+
+export function languageCodeToLabel(code: string): string {
+  const normalized = normalizeSubtitleLang(code)
+  if (LANGUAGE_LABELS[normalized]) return LANGUAGE_LABELS[normalized]
+
+  const baseLanguage = normalized.split('-')[0]
+  if (LANGUAGE_LABELS[baseLanguage]) {
+    const region = normalized.split('-')[1]
+    return region ? `${LANGUAGE_LABELS[baseLanguage]} (${region})` : LANGUAGE_LABELS[baseLanguage]
+  }
+
+  return normalized
+    .split('-')
+    .map(part => part.charAt(0).toUpperCase() + part.slice(1))
+    .join(' ')
+}
+
+export function getSubtitleFormat(fileName: string): SubtitleFormat | null {
+  const ext = extname(fileName).slice(1).toLowerCase()
+  return ext === 'vtt' || ext === 'srt' ? ext : null
+}
+
+export function parseSubtitleForVideo(
+  videoBaseName: string,
+  subtitleFileName: string,
+  src: string
+): SubtitleTrackInput | null {
+  const format = getSubtitleFormat(subtitleFileName)
+  if (!format) return null
+
+  const subtitleBaseName = basename(subtitleFileName, extname(subtitleFileName))
+
+  if (subtitleBaseName === videoBaseName) {
+    return {
+      src,
+      lang: 'en',
+      label: 'English',
+      format,
+      isDefault: true,
+    }
+  }
+
+  const languagePrefix = `${videoBaseName}.`
+  if (!subtitleBaseName.startsWith(languagePrefix)) return null
+
+  const rawLanguage = subtitleBaseName.slice(languagePrefix.length)
+  if (!rawLanguage || rawLanguage.includes('/')) return null
+
+  const lang = normalizeSubtitleLang(rawLanguage)
+  return {
+    src,
+    lang,
+    label: languageCodeToLabel(lang),
+    format,
+    isDefault: lang === 'en',
+  }
+}
+
+export function buildSubtitleTrackMap(
+  videoFileNames: string[],
+  subtitleFileNames: string[],
+  toRelativePath: (fileName: string) => string
+): Map<string, SubtitleTrackInput[]> {
+  const map = new Map<string, SubtitleTrackInput[]>()
+  const videoBaseNames = videoFileNames.map(fileName => basename(fileName, extname(fileName)))
+
+  for (const videoBaseName of videoBaseNames) {
+    for (const subtitleFileName of subtitleFileNames) {
+      const track = parseSubtitleForVideo(
+        videoBaseName,
+        subtitleFileName,
+        toRelativePath(subtitleFileName)
+      )
+      if (!track) continue
+
+      const existingTracks = map.get(videoBaseName) || []
+      const duplicate = existingTracks.some(existing => existing.lang === track.lang && existing.src === track.src)
+      if (!duplicate) {
+        existingTracks.push(track)
+      }
+      map.set(videoBaseName, sortSubtitleTracks(existingTracks))
+    }
+  }
+
+  return map
+}
+
+export function sortSubtitleTracks(tracks: SubtitleTrackInput[]): SubtitleTrackInput[] {
+  return [...tracks].sort((a, b) => {
+    if (a.isDefault !== b.isDefault) return a.isDefault ? -1 : 1
+    if (a.lang === 'en' && b.lang !== 'en') return -1
+    if (b.lang === 'en' && a.lang !== 'en') return 1
+    return a.label.localeCompare(b.label)
+  })
+}