/**
 * Edge TTS — zero-dependency Microsoft Edge neural text-to-speech for Bun/Node.
 * Produces 24kHz 48kbit mono MP3 for Vietnamese voices:
 *   vi-VN-HoaiMyNeural  (female, "Hoài My")
 *   vi-VN-NamMinhNeural (male,   "Nam Minh")
 */
import { createHash, randomUUID, randomBytes } from "node:crypto";

const TRUSTED_CLIENT_TOKEN = "6A5AA1D4EAFF4E9FB37E23D68491D6F4";
const WIN_EPOCH = 11644473600;
const WSS_URL =
  "wss://speech.platform.bing.com/consumer/speech/synthesize/readaloud/edge/v1";
const SEC_MS_GEC_VERSION = "1-143.0.3650.75";
const CHROME_VER = "143";

const UA =
  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 " +
  `(KHTML, like Gecko) Chrome/${CHROME_VER}.0.0.0 Safari/537.36 Edg/${CHROME_VER}.0.0.0`;

function generateSecMsGec() {
  let ticks = Date.now() / 1000 + WIN_EPOCH;
  ticks -= ticks % 300;
  ticks *= 1e7;
  return createHash("sha256")
    .update(`${ticks.toFixed(0)}${TRUSTED_CLIENT_TOKEN}`, "ascii")
    .digest("hex")
    .toUpperCase();
}

function dateToString() {
  const d = new Date();
  const days = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"];
  const months = ["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"];
  const p = (n) => String(n).padStart(2, "0");
  return `${days[d.getUTCDay()]} ${months[d.getUTCMonth()]} ${p(d.getUTCDate())} ` +
         `${d.getUTCFullYear()} ${p(d.getUTCHours())}:${p(d.getUTCMinutes())}:${p(d.getUTCSeconds())} ` +
         `GMT+0000 (Coordinated Universal Time)`;
}

function buildSSML(text, voice, { pitch = "+0Hz", rate = "+0%", volume = "+0%" } = {}) {
  const esc = String(text).replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
  return `<speak version='1.0' xmlns='http://www.w3.org/2001/10/synthesis' xml:lang='en-US'>` +
         `<voice name='${voice}'><prosody pitch='${pitch}' rate='${rate}' volume='${volume}'>` +
         `${esc}</prosody></voice></speak>`;
}

/** Split long text at sentence boundaries (Edge caps ~3000 chars/request). */
function splitText(text, max = 2800) {
  if (text.length <= max) return [text];
  const parts = [];
  let rest = text;
  while (rest.length > max) {
    let cut = rest.lastIndexOf(". ", max);
    if (cut < max * 0.5) cut = rest.lastIndexOf(" ", max);
    if (cut <= 0) cut = max;
    parts.push(rest.slice(0, cut + 1));
    rest = rest.slice(cut + 1).trimStart();
  }
  if (rest) parts.push(rest);
  return parts;
}

/**
 * Synthesize text to mp3 bytes.
 * @param {string} text
 * @param {string} voice  e.g. "vi-VN-HoaiMyNeural" | "vi-VN-NamMinhNeural"
 * @returns {Promise<Uint8Array>}
 */
export async function synthesize(text, voice = "vi-VN-HoaiMyNeural") {
  const clean = String(text || "").trim().replace(/\s+/g, " ").replace(/\*\*?|`|_{1,2}/g, "");
  if (!clean) return new Uint8Array(0);
  const parts = splitText(clean);
  const buffers = [];
  for (const part of parts) {
    buffers.push(await synthesizeOne(part, voice));
  }
  const total = buffers.reduce((n, b) => n + b.length, 0);
  const out = new Uint8Array(total);
  let off = 0;
  for (const b of buffers) { out.set(b, off); off += b.length; }
  return out;
}

function synthesizeOne(text, voice) {
  const reqId = randomUUID().replace(/-/g, "");
  const sec = generateSecMsGec();
  const url =
    `${WSS_URL}?TrustedClientToken=${TRUSTED_CLIENT_TOKEN}` +
    `&Sec-MS-GEC=${sec}&Sec-MS-GEC-Version=${SEC_MS_GEC_VERSION}` +
    `&ConnectionId=${randomUUID().replace(/-/g, "")}`;

  const headers = {
    "User-Agent": UA,
    "Origin": "chrome-extension://jdiccldimpdaibmpdkjnbmckianbfold",
    "Pragma": "no-cache",
    "Cache-Control": "no-cache",
    "Cookie": `muid=${randomBytes(16).toString("hex").toUpperCase()};`,
  };

  // Bun native WebSocket accepts options with headers as 2nd arg.
  const ws = new WebSocket(url, { headers });

  return new Promise((resolve, reject) => {
    const chunks = [];
    let opened = false;
    const timer = setTimeout(() => {
      try { ws.close(); } catch {}
      reject(new Error("Edge TTS timeout"));
    }, 20000);

    ws.onopen = () => {
      opened = true;
      ws.send(
        `X-Timestamp:${dateToString()}\r\n` +
        "Content-Type:application/json; charset=utf-8\r\n" +
        "Path:speech.config\r\n\r\n" +
        '{"context":{"synthesis":{"audio":{"metadataoptions":' +
        '{"sentenceBoundaryEnabled":"true","wordBoundaryEnabled":"false"},' +
        '"outputFormat":"audio-24khz-48kbitrate-mono-mp3"}}}}\r\n'
      );
      ws.send(
        `X-RequestId:${reqId}\r\n` +
        "Content-Type:application/ssml+xml\r\n" +
        `X-Timestamp:${dateToString()}Z\r\n` +
        "Path:ssml\r\n\r\n" +
        buildSSML(text, voice)
      );
    };

    ws.onmessage = (ev) => {
      const data = ev.data;
      if (typeof data === "string") return;
      const buf = Buffer.isBuffer(data) ? data : Buffer.from(data);
      if (buf.length < 2) return;
      const hl = buf.readUInt16BE(0);
      const header = buf.subarray(0, hl + 2).toString("latin1");
      const body = buf.subarray(hl + 2);
      if (header.includes("Path:audio")) chunks.push(body);
      else if (header.includes("Path:turn.end")) {
        clearTimeout(timer);
        try { ws.close(); } catch {}
        resolve(Buffer.concat(chunks));
      }
    };

    ws.onerror = (e) => { if (!opened) { clearTimeout(timer); reject(e); } };
    ws.onclose = () => {
      if (chunks.length) { clearTimeout(timer); resolve(Buffer.concat(chunks)); }
      else clearTimeout(timer);
    };
  });
}