/** 附属文件(字幕/外挂音轨)的语言标签,按主干名剥离后与主视频配对 */
const LANG_TAG: Record<string, "zh-Hans" | "zh-Hant" | "en" | "ja" | "ko" | "flag"> = {
  chs: "zh-Hans",
  sc: "zh-Hans",
  gb: "zh-Hans",
  chi: "zh-Hans",
  zho: "zh-Hans",
  zh: "zh-Hans",
  "zh-cn": "zh-Hans",
  "zh-hans": "zh-Hans",
  "zh-sg": "zh-Hans",
  简体: "zh-Hans",
  简中: "zh-Hans",
  简: "zh-Hans",
  cht: "zh-Hant",
  tc: "zh-Hant",
  big5: "zh-Hant",
  "zh-tw": "zh-Hant",
  "zh-hk": "zh-Hant",
  "zh-hant": "zh-Hant",
  繁体: "zh-Hant",
  繁體: "zh-Hant",
  繁中: "zh-Hant",
  繁: "zh-Hant",
  eng: "en",
  en: "en",
  english: "en",
  jpn: "ja",
  ja: "ja",
  jp: "ja",
  kor: "ko",
  ko: "ko",
  default: "flag",
  forced: "flag",
  sdh: "flag",
  cc: "flag",
  简英: "zh-Hans",
  繁英: "zh-Hant",
  中英: "zh-Hans",
  双语: "zh-Hans",
  简繁: "zh-Hans",
};

export const basename = (p: string) => p.replace(/\\/g, "/").split("/").pop() ?? p;
export const dirname = (p: string) => {
  const s = p.replace(/\\/g, "/");
  const i = s.lastIndexOf("/");
  return i <= 0 ? (i === 0 ? "/" : "") : s.slice(0, i);
};
export const splitExt = (name: string): [string, string] => {
  const i = name.lastIndexOf(".");
  return i > 0 ? [name.slice(0, i), name.slice(i + 1)] : [name, ""];
};

/** 字幕主干名:去扩展名后逐级剥掉 .chs/.eng/.default 等语言标签,返回小写主干与剥下的标签 */
export function sidecarStem(name: string): { stem: string; tags: string[] } {
  let [stem] = splitExt(basename(name));
  const tags: string[] = [];
  for (;;) {
    const i = stem.lastIndexOf(".");
    if (i <= 0) break;
    const tag = stem.slice(i + 1).toLowerCase();
    if (!(tag in LANG_TAG)) break;
    tags.unshift(tag);
    stem = stem.slice(0, i);
  }
  return { stem: stem.toLowerCase(), tags };
}

/** 默认字幕语言(对照 MP DEFAULT_SUB):命中的随行字幕加 .default,Jellyfin/Plex/Emby 都认 */
export type DefaultSubtitleLang = "zh-cn" | "zh-tw" | "en" | "ja" | "ko";

const DEFAULT_LANG_SUFFIX: Record<DefaultSubtitleLang, string> = {
  "zh-cn": ".chi.zh-cn",
  "zh-tw": ".zh-tw",
  en: ".eng",
  ja: ".ja",
  ko: ".ko",
};

/**
 * 目标字幕后缀(对照 MP:繁体优先判定 → .zh-tw;简体 → .chi.zh-cn;英 → .eng;日 → .ja)。
 * 源文件自带 .default,或语言与 defaultLang 一致时加 .default。
 */
export function sidecarLanguageSuffix(tags: readonly string[], defaultLang?: DefaultSubtitleLang): string {
  const langs = tags.map((t) => LANG_TAG[t]);
  let s = "";
  if (langs.includes("zh-Hant")) s = ".zh-tw";
  else if (langs.includes("zh-Hans")) s = ".chi.zh-cn";
  else if (langs.includes("en")) s = ".eng";
  else if (langs.includes("ja")) s = ".ja";
  else if (langs.includes("ko")) s = ".ko";
  if (tags.includes("default") || (defaultLang && s !== "" && s === DEFAULT_LANG_SUFFIX[defaultLang])) s += ".default";
  if (tags.includes("forced")) s += ".forced";
  return s;
}