Ably connection setup

ably.js

// @flow
import * as Ably from 'ably'
import type Channel from 'ably/common/lib/client/channel'
import type ConnectionStateChange from 'ably/common/lib/client/connectionstatechange'
// import type ErrorInfo from 'ably/common/lib/types/errorinfo'
import winston from 'winston'
import EventEmitter from 'events'

type AuthHeaders = {[string]: string}

export type AblyEvent = {
  type: string,
  payload: any,
}

class AblyConnection extends EventEmitter {
  channel: string
  ably: Ably.Realtime
  ablyChannel: ?Channel

  constructor(channel: string, authUrl: string, authHeaders: AuthHeaders = {}) {
    super()
    this.channel = channel
    this.ably = new Ably.Realtime({
      transports: ['web_socket'],
      authUrl,
      authHeaders,
    })
  }

  start(): Promise<void> {
    return new Promise((resolve, reject) => {
      const check = (event: ConnectionStateChange) => {
        if (event.current === 'disconnected') {
          winston.warn('Ably connection attempt failed, will keep retrtying')
        } else if (event.current === 'suspended') {
          // We failed for 2 minutes - just abort
          winston.error('Ably connection failed')
          this.ably.close()
          reject()
          return
        } else if (event.current === 'failed') {
          winston.error(`Ably connection failed: ${event.reason.message}`)
          reject()
        } else if (event.current === 'connected') {
          winston.info('Ably connection established')
          resolve()
          return
        }
        this.ably.connection.once(check)
      }

      this.ably.connection.once(check)
    })
      .then(() => {
        return new Promise((resolve, reject) => {
          this.ablyChannel = this.ably.channels.get(this.channel)
          this.ablyChannel.subscribe(this.onMessage.bind(this))
          // flow-disable-next-line
          this.ablyChannel.attach((err) => {
            if (err) {
              winston.error('Ably channel attach failed')
              reject()
            } else {
              winston.info('Ably channel attach succeeded')
              resolve()
            }
          })
        })
      })
  }

  stop(): Promise<void> {
    if (this.ably.connected.state === 'connecting'
      || this.ably.connected.state === 'connected'
      || this.ably.connected.state === 'disconnected'
      || this.ably.connected.state === 'suspended'
    ) {
      if (this.ablyChannel) {
        this.ablyChannel.unsunscribe()
      }
      this.ably.close()
    }
    return Promise.resolve()
  }

  onMessage(msg: any): void {
    winston.verbose(`Received ably message ${msg.name}`)
    const event: AblyEvent = {
      type: msg.name,
      payload: msg.data,
    }
    this.emit('message', event)
  }
}


export default AblyConnection