import NanoEvents from 'nanoevents'

import OP from './op'
import { logger } from '../util'
const log = logger({ name: 'ws', color: 'green' })

export default class StreamingClient extends NanoEvents {
  constructor (url, metrics) {
    super()

    this.url = url
    this.metrics = metrics
    this.ws = null
    this.delay = 1000
  }

  send (packet) {
    this.ws.send(JSON.stringify(packet))
  }

  subscribe () {
    if (!this.metrics) {
      log('not subscribing to channels -- no initial metrics')
      return
    }

    log('subscribing to channels')

    const { status } = this.metrics
    const channels = Object.keys(status).reduce(
      (channels, name) => [...channels, `latency:${name}`, `status:${name}`],
      []
    )

    log(`subscribing to ${channels.length} channels: ${channels.join(', ')}`)
    this.send({ op: OP.SUBSCRIBE, channels })
  }

  handle (packet) {
    const { op, c: channel, d: data } = packet

    if (op !== OP.DATA) {
      return
    }

    const [type, name] = channel.split(':')

    this.emit(type, name, data)
  }

  connect () {
    const begin = Date.now()
    log('connecting')

    const ws = this.ws = new WebSocket(this.url)
    window.ws = ws

    ws.onopen = () => {
      const took = Date.now() - begin
      log(`connected (took ${took}ms)`)
      this.subscribe()
    }

    ws.onclose = ({ code, reason }) => {
      log(
        `ws closed with code ${code} (reason: ${reason || '<none>'}); ` +
        `attempting to reconnect in ${this.delay}ms`
      )

      setTimeout(() => this.connect(), this.delay)
      this.delay *= 2
    }

    ws.onmessage = ({ data }) => {
      const packet = JSON.parse(data)
      log('recv:', packet)

      this.emit('packet', packet)
      this.handle(packet)
    }

    ws.onerror = (err) => {
      log('error:', err)
    }
  }
}