/**
 * modified from wss-lite in ts-liveview
 */

import { WSClientMessage, WSServerMessage, Ping, Pong, Send } from './ws-types'

const DefaultReconnectInterval = 250
const MaxReconnectInterval = 10 * 1000

const HeartHeatInterval = 30 * 1000
const HeartHeatTimeout = 45 * 1000
const HeartBeatTimeoutCode = 4013
const HeartBeatTimeoutReason = 'heartbeat timeout'

type Timer = ReturnType<typeof setTimeout>

export type ManagedWebsocket = {
  ws: WebSocket
  send(event: WSClientMessage): void
  close(code?: number, reason?: string): void
}

let reconnectInterval = DefaultReconnectInterval

export function connectWS(options: {
  createWS: (protocol: string) => WebSocket
  attachWS: (ws: ManagedWebsocket) => void
  onMessage: (data: WSServerMessage) => void
}) {
  const ws = options.createWS('ws-lite')

  let pingTimer: Timer
  let pongTimer: Timer
  heartbeat()

  function heartbeat() {
    clearTimeout(pingTimer)
    clearTimeout(pongTimer)
    pingTimer = setTimeout(sendPing, HeartHeatInterval)
    pongTimer = setTimeout(onHeartbeatTimeout, HeartHeatTimeout)
  }

  function sendPing() {
    if (ws.bufferedAmount === 0 && ws.readyState === ws.OPEN) {
      ws.send(Ping)
    }
  }

  function onHeartbeatTimeout() {
    console.debug('onHeartbeatTimeout')
    ws.close(HeartBeatTimeoutCode, HeartBeatTimeoutReason)
  }

  ws.addEventListener('open', () => {
    reconnectInterval = DefaultReconnectInterval
    heartbeat()
  })

  ws.addEventListener('close', event => {
    teardown()
    // reference: https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent
    if (event.code === 1001) {
      // don't auto-reconnect when the browser is navigating away from the page
      return
    }
    console.debug(
      'will reconnect ws after',
      (reconnectInterval / 1000).toFixed(1),
      'seconds',
    )
    setTimeout(() => connectWS(options), reconnectInterval)
    reconnectInterval = Math.min(reconnectInterval * 1.5, MaxReconnectInterval)
  })

  function teardown() {
    clearTimeout(pingTimer)
    clearTimeout(pongTimer)
  }

  function close(code?: number, reason?: string) {
    teardown()
    ws.close(code, reason)
  }

  function send(event: WSClientMessage) {
    clearTimeout(pingTimer)
    let data = Send + JSON.stringify(event)
    ws.send(data)
  }

  ws.addEventListener('message', event => {
    heartbeat()
    let data = String(event.data)
    if (data === Ping) {
      if (ws.bufferedAmount === 0) {
        ws.send(Pong)
      }
      return
    }
    if (data === Pong) {
      return
    }
    if (data[0] === Send) {
      options.onMessage(JSON.parse(data.slice(1)))
      return
    }
    console.debug('received unknown ws message:', event)
  })

  options.attachWS({ ws, send, close })
}