/**
 * ws.mjs — 《围猎》模拟竞技场的 WebSocket 客户端（node:net 手写，零依赖）。
 * 与 web/server/test/hunt-sim.test.mjs 的 B 组冒烟客户端同源，增加：
 * - 自动回 pong（服务器 15s ping，45s 无 pong 判死——对局长打必须应答）
 * - close 帧解析与自动重连占位（P09 断网重连走 arena 的 drop/resume）
 * - 发送队列（连接建立前的消息排队）
 *
 * 协议契约：docs/design/23-hunt.md §6.1。
 */
import net from 'node:net';
import crypto from 'node:crypto';

const GUID = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11';

function frameFromClient(opcode, payload) {
  const mask = crypto.randomBytes(4);
  const len = payload.length;
  let header;
  if (len < 126) {
    header = Buffer.from([0x80 | opcode, 0x80 | len]);
  } else if (len < 65536) {
    header = Buffer.alloc(4);
    header[0] = 0x80 | opcode;
    header[1] = 0x80 | 126;
    header.writeUInt16BE(len, 2);
  } else {
    header = Buffer.alloc(10);
    header[0] = 0x80 | opcode;
    header[1] = 0x80 | 127;
    header.writeBigUInt64BE(BigInt(len), 2);
  }
  const masked = Buffer.from(payload);
  for (let i = 0; i < masked.length; i++) masked[i] ^= mask[i & 3];
  return Buffer.concat([header, mask, masked]);
}

function makeServerFrameParser(onFrame) {
  let buf = Buffer.alloc(0);
  return (chunk) => {
    buf = Buffer.concat([buf, chunk]);
    for (;;) {
      if (buf.length < 2) return;
      const b0 = buf[0];
      const b1 = buf[1];
      let len = b1 & 0x7f;
      let off = 2;
      if (len === 126) {
        if (buf.length < 4) return;
        len = buf.readUInt16BE(2);
        off = 4;
      } else if (len === 127) {
        if (buf.length < 10) return;
        len = Number(buf.readBigUInt64BE(2));
        off = 10;
      }
      if (buf.length < off + len) return;
      const payload = Buffer.from(buf.subarray(off, off + len));
      buf = buf.subarray(off + len);
      onFrame({ opcode: b0 & 0x0f, payload });
    }
  };
}

/**
 * connect(port, { name }) → Promise<WsSession>
 * WsSession: { send(obj), close(), drop(), messages, on('message'|'close') }
 * drop()：模拟断网——直接销毁 socket（不发 close 帧，等同 §6.6 断线路径）。
 */
export function connect(port) {
  return new Promise((resolve, reject) => {
    const key = crypto.randomBytes(16).toString('base64');
    const sock = net.connect(port, '127.0.0.1');
    const session = new EventEmitterLite();
    session.sock = sock;
    session.messages = [];
    session.send = (obj) => {
      if (sock.destroyed) return false;
      sock.write(frameFromClient(1, Buffer.from(JSON.stringify(obj))));
      return true;
    };
    session.close = () => {
      try { sock.write(frameFromClient(8, Buffer.alloc(0))); } catch (_) { /* 已死 */ }
      setTimeout(() => { try { sock.destroy(); } catch (_) { /* 已死 */ } }, 50);
    };
    session.drop = () => { try { sock.destroy(); } catch (_) { /* 已死 */ } };

    const parse = makeServerFrameParser((f) => {
      if (f.opcode === 9) { // ping → 自动 pong（保活，§6.1）
        try { sock.write(frameFromClient(10, f.payload)); } catch (_) { /* 已死 */ }
        return;
      }
      if (f.opcode === 8) {
        session.emit('close', f.payload.length >= 2 ? f.payload.readUInt16BE(0) : 1005);
        try { sock.destroy(); } catch (_) { /* 已死 */ }
        return;
      }
      if (f.opcode === 1) {
        let msg = null;
        try { msg = JSON.parse(f.payload.toString('utf8')); } catch (_) { /* 坏帧 */ }
        if (msg) {
          session.messages.push(msg);
          session.emit('message', msg);
        }
      }
    });

    let handshake = Buffer.alloc(0);
    let upgraded = false;
    sock.on('data', (chunk) => {
      if (!upgraded) {
        handshake = Buffer.concat([handshake, chunk]);
        const idx = handshake.indexOf('\r\n\r\n');
        if (idx === -1) return;
        const head = handshake.subarray(0, idx).toString('latin1');
        if (!/^HTTP\/1\.1 101 /.test(head)) {
          reject(new Error('握手失败: ' + head.split('\r\n')[0]));
          sock.destroy();
          return;
        }
        upgraded = true;
        const rest = handshake.subarray(idx + 4);
        if (rest.length) parse(rest);
        resolve(session);
      } else {
        parse(chunk);
      }
    });
    sock.on('error', (e) => {
      if (!upgraded) reject(e);
      else session.emit('close', 1006);
    });
    sock.on('close', () => { if (upgraded) session.emit('close', 1006); });
    sock.write(
      'GET /ws/hunt HTTP/1.1\r\n'
      + 'Host: 127.0.0.1\r\n'
      + 'Upgrade: websocket\r\n'
      + 'Connection: keep-alive, Upgrade\r\n'
      + `Sec-WebSocket-Key: ${key}\r\n`
      + 'Sec-WebSocket-Version: 13\r\n\r\n',
    );
  });
}

class EventEmitterLite {
  constructor() { this._l = new Map(); }
  on(ev, fn) { (this._l.get(ev) || this._l.set(ev, []).get(ev)).push(fn); return this; }
  emit(ev, ...args) { for (const fn of this._l.get(ev) || []) fn(...args); }
}