/**
 * WxTransport — 微信小程序 wx.connectSocket 实现的 TerminalTransport。
 *
 * 帧协议与 Web 端 GatewayTransport 完全一致（§8.2）：
 *   入站：{ type: 'init'|'stdin'|'resize'|'control', ... }
 *   出站：{ type: 'stdout'|'stderr'|'control'|'error', ... }
 *
 * 使用方式：
 *   const t = new WxTransport({ gatewayUrl, gatewayToken });
 *   const off = t.on(event => { ... });
 *   await t.connect({ host, port, username, password });
 *   t.send("ls -la\r");
 *   t.resize(80, 24);
 *   t.disconnect();
 */

const { sanitizeTerminalOutput } = require('../../../packages/terminal-core/dist-miniprogram/index');

function buildWsUrl(rawUrl, token) {
  let base = String(rawUrl || '').trim();
  if (!base) throw new Error('WxTransport: 网关地址为空');
  if (base.startsWith('http://'))  base = 'ws://'  + base.slice(7);
  if (base.startsWith('https://')) base = 'wss://' + base.slice(8);
  if (!base.startsWith('ws://') && !base.startsWith('wss://')) {
    base = 'wss://' + base;
  }
  base = base.replace(/\/+$/, '');
  return base + '/ws/terminal?token=' + encodeURIComponent(String(token || ''));
}

function WxTransport(options) {
  const cfg = options || {};
  this._gatewayUrl   = cfg.gatewayUrl   || '';
  this._gatewayToken = cfg.gatewayToken || '';

  this._state     = 'idle';       // SessionState
  this._sessionId = '';
  this._socket    = null;         // wx.SocketTask
  this._listeners = [];           // Array<(event) => void>
  this._pingTimer = null;
  this._pingAt    = 0;
}

// ── 接口实现 ──────────────────────────────────────────────────────────────────

/**
 * 连接网关并发送 init 帧。
 * 返回 Promise，在 control.connected 帧到达后 resolve，错误时 reject。
 */
WxTransport.prototype.connect = function(params) {
  const self = this;
  return new Promise(function(resolve, reject) {
    if (self._state === 'connecting' || self._state === 'connected') {
      resolve();
      return;
    }

    self._state = 'connecting';
    const sessionId = 'wx_' + Date.now() + '_' + Math.random().toString(36).slice(2);
    self._sessionId = sessionId;
    const url = buildWsUrl(self._gatewayUrl, self._gatewayToken);

    const task = wx.connectSocket({
      url: url,
      protocols: ['v1.terminal'],
      success: function() { /* socket created */ },
      fail: function(err) {
        self._state = 'error';
        self._emit({ type: 'error', code: 'HOST_UNREACHABLE', message: JSON.stringify(err) });
        reject(new Error('wx.connectSocket fail: ' + JSON.stringify(err)));
      }
    });

    self._socket = task;
    let resolved = false;

    task.onOpen(function() {
      // 发送 init 帧
      self._sendFrame({ type: 'init', sessionId: sessionId, params: params });
      // 启动心跳
      self._startPing();
    });

    task.onMessage(function(res) {
      let frame;
      try {
        frame = JSON.parse(res.data);
      } catch(e) {
        return;
      }

      if (frame.type === 'stdout' || frame.type === 'stderr') {
        const raw = typeof frame.data === 'string' ? frame.data : '';
        const sanitized = sanitizeTerminalOutput(raw);
        if (sanitized) self._emit({ type: frame.type, data: sanitized });
      } else if (frame.type === 'control') {
        if (frame.action === 'connected') {
          self._state = 'connected';
          self._emit({ type: 'control', action: 'connected', data: frame.data });
          if (!resolved) { resolved = true; resolve(); }
        } else if (frame.action === 'disconnect') {
          self._cleanup();
          self._state = 'disconnected';
          self._emit({ type: 'control', action: 'disconnect' });
        } else if (frame.action === 'pong') {
          self._emit({ type: 'control', action: 'pong' });
        }
      } else if (frame.type === 'error') {
        self._state = 'error';
        self._emit({ type: 'error', code: frame.code || 'INTERNAL_ERROR', message: frame.message || '' });
        if (!resolved) { resolved = true; reject(new Error(frame.message)); }
      }
    });

    task.onError(function(err) {
      self._cleanup();
      self._state = 'error';
      self._emit({ type: 'error', code: 'HOST_UNREACHABLE', message: JSON.stringify(err) });
      if (!resolved) { resolved = true; reject(new Error(JSON.stringify(err))); }
    });

    task.onClose(function() {
      self._cleanup();
      if (self._state !== 'disconnected' && self._state !== 'error') {
        self._state = 'disconnected';
        self._emit({ type: 'control', action: 'disconnect' });
      }
    });
  });
};

WxTransport.prototype.send = function(data, meta) {
  if (this._state !== 'connected') return;
  this._sendFrame({ type: 'stdin', data: data, meta: meta });
};

WxTransport.prototype.resize = function(cols, rows) {
  if (this._state !== 'connected') return;
  this._sendFrame({ type: 'resize', cols: cols, rows: rows });
};

WxTransport.prototype.disconnect = function(reason) {
  this._sendFrame({ type: 'control', action: 'disconnect', reason: reason || 'manual' });
  this._cleanup();
  this._state = 'disconnected';
};

WxTransport.prototype.on = function(listener) {
  const self = this;
  self._listeners.push(listener);
  return function() {
    const idx = self._listeners.indexOf(listener);
    if (idx >= 0) self._listeners.splice(idx, 1);
  };
};

WxTransport.prototype.getState = function() {
  return this._state;
};

// ── 私有方法 ──────────────────────────────────────────────────────────────────

WxTransport.prototype._emit = function(event) {
  for (let i = 0; i < this._listeners.length; i++) {
    try { this._listeners[i](event); } catch(e) { /* 单个监听器异常不影响其他 */ }
  }
};

WxTransport.prototype._sendFrame = function(frame) {
  if (!this._socket) return;
  try {
    this._socket.send({ data: JSON.stringify(frame) });
  } catch(e) { /* 忽略发送时 socket 已关闭 */ }
};

WxTransport.prototype._startPing = function() {
  const self = this;
  self._clearPing();
  self._pingTimer = setInterval(function() {
    if (self._state !== 'connected') return;
    self._pingAt = Date.now();
    self._sendFrame({ type: 'control', action: 'ping' });
  }, 10000);
};

WxTransport.prototype._clearPing = function() {
  if (this._pingTimer !== null) {
    clearInterval(this._pingTimer);
    this._pingTimer = null;
  }
};

WxTransport.prototype._cleanup = function() {
  this._clearPing();
  if (this._socket) {
    try { this._socket.close(); } catch(e) { /* ignore */ }
    this._socket = null;
  }
};

module.exports = { WxTransport: WxTransport };