var request = require('../utils/request')

var MQTT_BROKER = 'wxs://iotcloud.tencent.com/socket/mqtt'
var _socketTask = null
var _connected = false
var _subscriptions = {}
var _listeners = {}
var _reconnectTimer = null
var _heartbeatTimer = null
var _userId = null

function on(event, callback) {
  if (!_listeners[event]) _listeners[event] = []
  _listeners[event].push(callback)
}

function off(event, callback) {
  if (!_listeners[event]) return
  if (callback) {
    _listeners[event] = _listeners[event].filter(function (cb) { return cb !== callback })
  } else {
    _listeners[event] = []
  }
}

function emit(event, data) {
  if (!_listeners[event]) return
  _listeners[event].forEach(function (cb) {
    try { cb(data) } catch (e) { console.error('mqtt emit error:', e) }
  })
}

function connect(userId) {
  _userId = userId
  var clientId = 'user_' + userId
  var token = wx.getStorageSync('token')

  _socketTask = wx.connectSocket({
    url: MQTT_BROKER,
    header: {
      'Authorization': 'Bearer ' + token
    },
    success: function () {
      console.log('mqtt connecting...')
    },
    fail: function () {
      emit('error', { msg: 'MQTT连接失败' })
      scheduleReconnect()
    }
  })

  _socketTask.onOpen(function () {
    _connected = true
    startHeartbeat()
    subscribeUserTopics()
    emit('connected')
  })

  _socketTask.onMessage(function (res) {
    handleMessage(res.data)
  })

  _socketTask.onClose(function () {
    _connected = false
    stopHeartbeat()
    emit('disconnected')
    scheduleReconnect()
  })

  _socketTask.onError(function () {
    _connected = false
    emit('error', { msg: 'MQTT连接异常' })
  })
}

function subscribeUserTopics() {
  if (!_userId) return
  subscribe('users/' + _userId + '/subscription')
  subscribe('users/' + _userId + '/devices')
  subscribe('users/' + _userId + '/notification')
}

function subscribe(topic) {
  _subscriptions[topic] = true
}

function unsubscribe(topic) {
  delete _subscriptions[topic]
}

function handleMessage(data) {
  try {
    var msg = JSON.parse(data)
    var topic = msg.topic

    if (topic && _subscriptions[topic]) {
      if (topic.indexOf('/subscription') !== -1) {
        emit('subscription_change', msg.payload || msg)
      } else if (topic.indexOf('/devices') !== -1) {
        emit('devices_change', msg.payload || msg)
      } else if (topic.indexOf('/notification') !== -1) {
        emit('notification', msg.payload || msg)
      } else {
        emit('message', msg.payload || msg)
      }
    }
  } catch (e) {
    console.error('mqtt parse error:', e)
  }
}

function publish(topic, payload) {
  if (!_connected || !_socketTask) return
  _socketTask.send({
    data: JSON.stringify({ topic: topic, payload: payload })
  })
}

function startHeartbeat() {
  stopHeartbeat()
  _heartbeatTimer = setInterval(function () {
    if (_connected && _socketTask) {
      _socketTask.send({ data: JSON.stringify({ type: 'ping' }) })
    }
  }, 30000)
}

function stopHeartbeat() {
  if (_heartbeatTimer) {
    clearInterval(_heartbeatTimer)
    _heartbeatTimer = null
  }
}

function scheduleReconnect() {
  if (_reconnectTimer) return
  _reconnectTimer = setTimeout(function () {
    _reconnectTimer = null
    if (_userId) connect(_userId)
  }, 5000)
}

function disconnect() {
  if (_reconnectTimer) {
    clearTimeout(_reconnectTimer)
    _reconnectTimer = null
  }
  stopHeartbeat()
  if (_socketTask) {
    _socketTask.close({})
    _socketTask = null
  }
  _connected = false
  _subscriptions = {}
  _listeners = {}
  _userId = null
}

function isConnected() {
  return _connected
}

module.exports = {
  connect: connect,
  disconnect: disconnect,
  subscribe: subscribe,
  unsubscribe: unsubscribe,
  publish: publish,
  on: on,
  off: off,
  isConnected: isConnected
}