import type { SubtitleCue } from "@umt/contracts";

// 预览用的纯解析函数(FM-2):编码探测、字幕(SRT/VTT/ASS/SSA/PGS)、图片尺寸。
// 输入都是已按上限截取的字节,不做 IO;非法输入一律返回空结果而不是抛错。

export type PreviewKind = "text" | "subtitle" | "torrent" | "image";

const EXT_PREVIEW: Record<string, PreviewKind> = {};
for (const e of "nfo txt log md markdown json xml yaml yml ini conf cfg csv tsv cue sfv md5 sha1 sha256 url".split(" "))
  EXT_PREVIEW[e] = "text";
for (const e of "srt vtt ass ssa sup".split(" ")) EXT_PREVIEW[e] = "subtitle";
for (const e of "jpg jpeg png webp avif gif bmp".split(" ")) EXT_PREVIEW[e] = "image";
EXT_PREVIEW.torrent = "torrent";

export const extOf = (name: string) => /\.([A-Za-z0-9]{1,8})$/.exec(name)?.[1]?.toLowerCase() ?? "";
export const previewKindOf = (name: string): PreviewKind | null => EXT_PREVIEW[extOf(name)] ?? null;

// ── 编码探测 ──

function tryDecode(label: string, buf: Uint8Array): string | null {
  try {
    return new TextDecoder(label, { fatal: true, ignoreBOM: true }).decode(buf);
  } catch {
    return null;
  }
}

/** 截断读取时末尾可能落在多字节字符中间:最多去掉 3 个字节再试 */
function tryDecodeTail(label: string, buf: Uint8Array, truncated: boolean): string | null {
  const max = truncated ? 3 : 0;
  for (let cut = 0; cut <= max && cut <= buf.length; cut++) {
    const t = tryDecode(label, cut ? buf.subarray(0, buf.length - cut) : buf);
    if (t !== null) return t;
  }
  return null;
}

/** 双字节编码的"像不像":常用汉字越多越像,生僻区/私用区/控制字符扣分 */
function cjkScore(s: string): number {
  let score = 0;
  for (const ch of s) {
    const c = ch.codePointAt(0) ?? 0;
    if (c >= 0x4e00 && c <= 0x9fa5) score += 1;
    else if (c >= 0x3000 && c <= 0x303f) score += 1;
    else if (c >= 0xff00 && c <= 0xffef) score += 0.5;
    else if ((c >= 0x3400 && c <= 0x4dbf) || (c >= 0xe000 && c <= 0xf8ff) || c > 0xffff) score -= 3;
    else if (c < 0x20 && c !== 9 && c !== 10 && c !== 13) score -= 3;
  }
  return score;
}

function utf16Guess(buf: Uint8Array): "utf-16le" | "utf-16be" | null {
  const n = Math.min(buf.length, 4096) & ~1;
  if (n < 4) return null;
  let evenZero = 0;
  let oddZero = 0;
  for (let i = 0; i < n; i += 2) {
    if (buf[i] === 0) evenZero++;
    if (buf[i + 1] === 0) oddZero++;
  }
  const pairs = n / 2;
  if (oddZero > pairs * 0.3 && evenZero < pairs * 0.05) return "utf-16le";
  if (evenZero > pairs * 0.3 && oddZero < pairs * 0.05) return "utf-16be";
  return null;
}

/** 按 BOM → UTF-16 零字节分布 → UTF-8 → GB18030/Big5(择优)→ windows-1252 顺序探测 */
export function decodeText(buf: Uint8Array, truncated = false): { text: string; encoding: string } {
  if (buf[0] === 0xef && buf[1] === 0xbb && buf[2] === 0xbf)
    return { text: new TextDecoder("utf-8").decode(buf.subarray(3)), encoding: "utf-8" };
  if (buf[0] === 0xff && buf[1] === 0xfe)
    return { text: new TextDecoder("utf-16le").decode(buf.subarray(2)), encoding: "utf-16le" };
  if (buf[0] === 0xfe && buf[1] === 0xff)
    return { text: new TextDecoder("utf-16be").decode(buf.subarray(2)), encoding: "utf-16be" };
  const u16 = utf16Guess(buf);
  if (u16) return { text: new TextDecoder(u16).decode(buf.subarray(0, buf.length & ~1)), encoding: u16 };
  const utf8 = tryDecodeTail("utf-8", buf, truncated);
  if (utf8 !== null) return { text: utf8, encoding: "utf-8" };
  const cands = (["gb18030", "big5"] as const)
    .map((enc) => ({ enc, text: tryDecodeTail(enc, buf, truncated) }))
    .filter((c): c is { enc: "gb18030" | "big5"; text: string } => c.text !== null)
    .map((c) => ({ ...c, score: cjkScore(c.text) }))
    .sort((a, b) => b.score - a.score);
  const best = cands[0];
  if (best && best.score > 0) return { text: best.text, encoding: best.enc };
  return { text: new TextDecoder("windows-1252").decode(buf), encoding: "windows-1252" };
}

// ── 字幕 ──

export const CUE_LIMIT = 200;

const TIME_RE = /(?:(\d{1,2}):)?(\d{1,2}):(\d{2})[.,](\d{1,3})/;
function parseTime(s: string): number | null {
  const m = TIME_RE.exec(s);
  if (!m) return null;
  const [, h, mi, se, frac] = m;
  const ms = Number((frac ?? "0").padEnd(3, "0"));
  return ((Number(h ?? 0) * 60 + Number(mi)) * 60 + Number(se)) * 1000 + ms;
}

const stripTags = (s: string) =>
  s
    .replace(/\{\\[^}]*\}/g, "")
    .replace(/<[^>]+>/g, "")
    .trim();

/** SRT 与 WebVTT:按空行分块,取含 --> 的时间行 */
export function parseSrtLike(text: string): SubtitleCue[] {
  const out: SubtitleCue[] = [];
  for (const block of text.replace(/\r\n?/g, "\n").split(/\n{2,}/)) {
    const lines = block.split("\n");
    const i = lines.findIndex((l) => l.includes("-->"));
    if (i < 0) continue;
    const [a, b] = (lines[i] ?? "").split("-->");
    const start = parseTime(a ?? "");
    const end = parseTime(b ?? "");
    if (start === null || end === null) continue;
    out.push({ start, end, text: stripTags(lines.slice(i + 1).join("\n")) });
  }
  return out;
}

/** ASS/SSA:[Events] 段的 Format 决定 Start/End/Text 列;Text 是最后一列,可含逗号 */
export function parseAss(text: string): { cues: SubtitleCue[]; title: string | null } {
  const cues: SubtitleCue[] = [];
  let title: string | null = null;
  let section = "";
  let fields: string[] = ["layer", "start", "end", "style", "name", "marginl", "marginr", "marginv", "effect", "text"];
  for (const raw of text.replace(/\r\n?/g, "\n").split("\n")) {
    const line = raw.trim();
    if (/^\[.+\]$/.test(line)) {
      section = line.toLowerCase();
      continue;
    }
    if (section === "[script info]" && /^title\s*:/i.test(line)) title = line.replace(/^title\s*:/i, "").trim() || null;
    if (section !== "[events]") continue;
    if (/^format\s*:/i.test(line)) {
      fields = line
        .replace(/^format\s*:/i, "")
        .split(",")
        .map((f) => f.trim().toLowerCase());
      continue;
    }
    if (!/^dialogue\s*:/i.test(line)) continue;
    const parts = line.replace(/^dialogue\s*:/i, "").split(",");
    const textIdx = fields.indexOf("text");
    const vals = [...parts.slice(0, textIdx), parts.slice(textIdx).join(",")];
    const start = parseTime(vals[fields.indexOf("start")] ?? "");
    const end = parseTime(vals[fields.indexOf("end")] ?? "");
    if (start === null || end === null) continue;
    const body = (vals[textIdx] ?? "")
      .replace(/\{[^}]*\}/g, "")
      .replace(/\\[Nn]/g, "\n")
      .replace(/\\h/g, " ")
      .trim();
    cues.push({ start, end, text: body });
  }
  return { cues, title };
}

/**
 * PGS(.sup):段头 "PG" + PTS(90 kHz)+ DTS + 类型 + 长度。
 * 类型 0x16 是显示组合段:带对象的算一条起点,之后第一个不带对象的算终点。
 */
export function parseSup(buf: Uint8Array): SubtitleCue[] {
  const cues: SubtitleCue[] = [];
  let open: number | null = null;
  let p = 0;
  while (p + 13 <= buf.length) {
    if (buf[p] !== 0x50 || buf[p + 1] !== 0x47) break;
    const pts = (((buf[p + 2]! << 24) >>> 0) + (buf[p + 3]! << 16) + (buf[p + 4]! << 8) + buf[p + 5]!) / 90;
    const type = buf[p + 10];
    const len = (buf[p + 11]! << 8) + buf[p + 12]!;
    const body = p + 13;
    if (body + len > buf.length) break;
    if (type === 0x16 && len >= 11) {
      const objects = buf[body + 10] ?? 0;
      const t = Math.round(pts);
      if (objects > 0 && open === null) open = t;
      else if (objects === 0 && open !== null) {
        cues.push({ start: open, end: Math.max(open, t), text: "" });
        open = null;
      }
    }
    p = body + len;
  }
  return cues;
}

// ── 图片尺寸 ──

const u16be = (b: Uint8Array, o: number) => (b[o]! << 8) | b[o + 1]!;
const u16le = (b: Uint8Array, o: number) => b[o]! | (b[o + 1]! << 8);
const u32be = (b: Uint8Array, o: number) => ((b[o]! << 24) >>> 0) + (b[o + 1]! << 16) + (b[o + 2]! << 8) + b[o + 3]!;
const u24le = (b: Uint8Array, o: number) => b[o]! | (b[o + 1]! << 8) | (b[o + 2]! << 16);
const ascii = (b: Uint8Array, o: number, n: number) => String.fromCharCode(...b.subarray(o, o + n));

export const IMAGE_MIME: Record<string, string> = {
  jpg: "image/jpeg",
  jpeg: "image/jpeg",
  png: "image/png",
  webp: "image/webp",
  avif: "image/avif",
  gif: "image/gif",
  bmp: "image/bmp",
};

/** 读文件头里的宽高(PNG/JPEG/GIF/BMP/WebP/AVIF);认不出返回 null */
export function imageSize(b: Uint8Array): { width: number; height: number } | null {
  if (b.length < 24) return null;
  if (b[0] === 0x89 && ascii(b, 1, 3) === "PNG") return { width: u32be(b, 16), height: u32be(b, 20) };
  if (ascii(b, 0, 3) === "GIF") return { width: u16le(b, 6), height: u16le(b, 8) };
  if (ascii(b, 0, 2) === "BM" && b.length >= 26)
    return {
      width: Math.abs(new DataView(b.buffer, b.byteOffset).getInt32(18, true)),
      height: Math.abs(new DataView(b.buffer, b.byteOffset).getInt32(22, true)),
    };
  if (ascii(b, 0, 4) === "RIFF" && ascii(b, 8, 4) === "WEBP") {
    const chunk = ascii(b, 12, 4);
    if (chunk === "VP8 " && b.length >= 30) return { width: u16le(b, 26) & 0x3fff, height: u16le(b, 28) & 0x3fff };
    if (chunk === "VP8L" && b.length >= 25) {
      const bits = b[21]! | (b[22]! << 8) | (b[23]! << 16) | (b[24]! << 24);
      return { width: (bits & 0x3fff) + 1, height: ((bits >> 14) & 0x3fff) + 1 };
    }
    if (chunk === "VP8X" && b.length >= 30) return { width: u24le(b, 24) + 1, height: u24le(b, 27) + 1 };
    return null;
  }
  if (b[0] === 0xff && b[1] === 0xd8) {
    let p = 2;
    while (p + 9 < b.length) {
      if (b[p] !== 0xff) {
        p++;
        continue;
      }
      const marker = b[p + 1]!;
      if (marker === 0xff) {
        p++;
        continue;
      }
      if (marker === 0xd8 || marker === 0x01 || (marker >= 0xd0 && marker <= 0xd7)) {
        p += 2;
        continue;
      }
      const len = u16be(b, p + 2);
      const sof = marker >= 0xc0 && marker <= 0xcf && marker !== 0xc4 && marker !== 0xc8 && marker !== 0xcc;
      if (sof) return { width: u16be(b, p + 7), height: u16be(b, p + 5) };
      p += 2 + len;
    }
    return null;
  }
  if (ascii(b, 4, 4) === "ftyp") {
    // AVIF/HEIF:在头部里找 ispe(image spatial extents)盒
    for (let p = 8; p + 20 <= b.length; p++) {
      if (b[p] === 0x69 && ascii(b, p, 4) === "ispe") return { width: u32be(b, p + 8), height: u32be(b, p + 12) };
    }
  }
  return null;
}

// ── tracker ──

const SECRET_KEY = /pass|key|token|auth|secret|sign|uid|hash/i;

/** tracker 地址里的 passkey 不外露:敏感参数值与路径里的长十六进制/Base64 段替换成 *** */
export function maskTracker(url: string): string {
  let u: URL;
  try {
    u = new URL(url);
  } catch {
    return url.replace(/[0-9a-f]{16,}/gi, "***");
  }
  for (const [k] of [...u.searchParams]) if (SECRET_KEY.test(k)) u.searchParams.set(k, "***");
  u.pathname = u.pathname
    .split("/")
    .map((seg) => (/^[0-9a-z_-]{16,}$/i.test(seg) && /\d/.test(seg) ? "***" : seg))
    .join("/");
  u.username = "";
  u.password = "";
  return decodeURIComponent(u.toString());
}