feat(animetosho): add English/Japanese subtitle download integration (#159)

src/animetosho/lang.ts

@@ -0,0 +1,70 @@
+// Pure language-code helpers shared between the main-process Animetosho client
+// and the overlay renderer. Must stay free of node imports so the renderer
+// bundle can use it.
+
+const LANG_FILENAME_SUFFIXES: Record<string, string> = {
+  eng: 'en',
+  jpn: 'ja',
+  ger: 'de',
+  deu: 'de',
+  spa: 'es',
+  por: 'pt',
+  fre: 'fr',
+  fra: 'fr',
+  ita: 'it',
+  rus: 'ru',
+  ara: 'ar',
+  chi: 'zh',
+  zho: 'zh',
+  kor: 'ko',
+};
+
+const LANG_DISPLAY_NAMES: Record<string, string> = {
+  en: 'English',
+  ja: 'Japanese',
+  de: 'German',
+  es: 'Spanish',
+  pt: 'Portuguese',
+  fr: 'French',
+  it: 'Italian',
+  ru: 'Russian',
+  ar: 'Arabic',
+  zh: 'Chinese',
+  ko: 'Korean',
+};
+
+export function normalizeAnimetoshoLangCode(code: string): string {
+  const base = code.trim().toLowerCase().split(/[-_]/)[0] ?? '';
+  return LANG_FILENAME_SUFFIXES[base] ?? base;
+}
+
+export function animetoshoLangToFilenameSuffix(lang: string | undefined): string {
+  const normalized = normalizeAnimetoshoLangCode(lang ?? '');
+  if (!normalized || normalized === 'und') return 'en';
+  return normalized;
+}
+
+export function animetoshoTrackMatchesLanguages(
+  trackLang: string,
+  configuredLanguages: string[],
+): boolean {
+  const normalizedTrack = normalizeAnimetoshoLangCode(trackLang);
+  // Unlabeled tracks cannot be classified; keep them visible rather than
+  // hiding them behind a tab that never shows them.
+  if (!normalizedTrack || normalizedTrack === 'und') return true;
+  return configuredLanguages.some(
+    (candidate) => normalizeAnimetoshoLangCode(candidate) === normalizedTrack,
+  );
+}
+
+export function describeAnimetoshoTabLanguages(configuredLanguages: string[]): string {
+  const normalized = [
+    ...new Set(
+      configuredLanguages
+        .map((candidate) => normalizeAnimetoshoLangCode(candidate))
+        .filter(Boolean),
+    ),
+  ];
+  if (normalized.length === 0) return 'English';
+  return normalized.map((code) => LANG_DISPLAY_NAMES[code] ?? code.toUpperCase()).join(' / ');
+}