import { KEFU_BASE_URL } from '@/utils/config.js'

const RECONNECT_DELAYS = [2000, 4000, 8000, 15000, 30000]

function getSocketBaseUrl() {
  const override = uni.getStorageSync('kefu-socket-base-url')
  let baseUrl = String(override || KEFU_BASE_URL).replace(/\/+$/, '')
  // H5 本地环境的客服地址是相对路径 /api，WebSocket 必须使用完整的 ws:// URL。
  if (baseUrl.startsWith('/') && typeof window !== 'undefined' && window.location) {
    baseUrl = `${window.location.origin}${baseUrl}`
  }
  return baseUrl.replace(/^http:/, 'ws:').replace(/^https:/, 'wss:')
}

export class KefuSocket {
  constructor(options = {}) {
    this.options = options
    this.socketTask = null
    this.connectionParams = null
    this.manualClose = false
    this.networkOnline = true
    this.reconnectCount = 0
    this.reconnectTimer = null
    this.heartbeatTimer = null
    this.networkListener = status => this.handleNetworkChange(status)
    this.browserOnlineListener = () => this.handleNetworkChange({ isConnected: true })
    this.browserOfflineListener = () => this.handleNetworkChange({ isConnected: false })
    this.bindNetworkListeners()
  }

  connect(params = {}) {
    this.connectionParams = { ...params }
    const { userId, mchId = 1002, conversationId } = this.connectionParams
    if (!userId || this.manualClose || this.socketTask || !this.networkOnline) return

    this.options.onStatus && this.options.onStatus('connecting')
    const query = [
      'userType=member',
      `userId=${encodeURIComponent(userId)}`,
      `mchId=${encodeURIComponent(mchId || 1002)}`,
      conversationId ? `conversationId=${encodeURIComponent(conversationId)}` : ''
    ].filter(Boolean).join('&')

    const task = uni.connectSocket({
      url: `${getSocketBaseUrl()}/ws/kefu?${query}`,
      complete: () => {}
    })
    this.socketTask = task

    task.onOpen(() => {
      if (this.socketTask !== task) return
      this.reconnectCount = 0
      this.options.onStatus && this.options.onStatus('online')
      this.startHeartbeat(task)
    })
    task.onMessage(event => {
      if (this.socketTask === task) this.handleMessage(event.data)
    })
    task.onError(() => this.handleDisconnect(task))
    task.onClose(() => this.handleDisconnect(task))
  }

  handleMessage(raw) {
    let event = raw
    if (typeof raw === 'string') {
      try {
        event = JSON.parse(raw)
      } catch (error) {
        return
      }
    }
    if (event && event.type === 'pong') return
    this.options.onEvent && this.options.onEvent(event)
  }

  startHeartbeat(task) {
    this.stopHeartbeat()
    this.heartbeatTimer = setInterval(() => {
      if (this.socketTask !== task) return
      task.send({ data: 'ping', fail: () => this.handleDisconnect(task) })
    }, 25000)
  }

  handleDisconnect(task) {
    if (task && this.socketTask !== task) return
    this.stopHeartbeat()
    this.socketTask = null
    if (this.manualClose) return
    this.options.onStatus && this.options.onStatus('offline')
    this.scheduleReconnect()
  }

  scheduleReconnect() {
    if (this.manualClose || this.reconnectTimer || !this.connectionParams || !this.networkOnline) return
    const delay = RECONNECT_DELAYS[Math.min(this.reconnectCount, RECONNECT_DELAYS.length - 1)]
    this.reconnectCount += 1
    this.reconnectTimer = setTimeout(() => {
      this.reconnectTimer = null
      this.options.onReconnect && this.options.onReconnect(this.reconnectCount)
      this.connect(this.connectionParams)
    }, delay)
  }

  reconnectNow() {
    if (this.manualClose || this.socketTask || !this.connectionParams || !this.networkOnline) return
    if (this.reconnectTimer) clearTimeout(this.reconnectTimer)
    this.reconnectTimer = null
    this.connect(this.connectionParams)
  }

  handleNetworkChange(status = {}) {
    this.networkOnline = status.isConnected !== false
    if (!this.networkOnline) {
      this.options.onStatus && this.options.onStatus('offline')
      this.stopHeartbeat()
      const task = this.socketTask
      this.socketTask = null
      if (task) {
        try {
          task.close({ code: 1000, reason: 'network offline' })
        } catch (error) {
          // The platform may have disposed the socket before the offline event.
        }
      }
      return
    }
    this.reconnectNow()
  }

  bindNetworkListeners() {
    if (typeof uni.onNetworkStatusChange === 'function') {
      uni.onNetworkStatusChange(this.networkListener)
    }
    if (typeof window !== 'undefined' && window.addEventListener) {
      this.networkOnline = typeof navigator === 'undefined' || navigator.onLine !== false
      window.addEventListener('online', this.browserOnlineListener)
      window.addEventListener('offline', this.browserOfflineListener)
    }
  }

  unbindNetworkListeners() {
    if (typeof uni.offNetworkStatusChange === 'function') {
      uni.offNetworkStatusChange(this.networkListener)
    }
    if (typeof window !== 'undefined' && window.removeEventListener) {
      window.removeEventListener('online', this.browserOnlineListener)
      window.removeEventListener('offline', this.browserOfflineListener)
    }
  }

  stopHeartbeat() {
    if (this.heartbeatTimer) clearInterval(this.heartbeatTimer)
    this.heartbeatTimer = null
  }

  close() {
    this.manualClose = true
    this.stopHeartbeat()
    if (this.reconnectTimer) clearTimeout(this.reconnectTimer)
    this.reconnectTimer = null
    this.connectionParams = null
    this.unbindNetworkListeners()
    const task = this.socketTask
    this.socketTask = null
    if (task) task.close({ code: 1000, reason: 'page hidden' })
    this.options.onStatus && this.options.onStatus('closed')
  }
}