import WebSocket from 'ws'
import * as diff from 'diff'
import { readFileSync } from 'fs'

const getSocketUrl = async () => {
  const tchRand = Math.floor(100000 + Math.random() * 900000) // They're surely using 6 digit random number for ws url.
  const socketUrl = `wss://tch${tchRand}.tch.quora.com`
  const credentials = JSON.parse(readFileSync('config.json', 'utf8'))
  const appSettings = credentials.app_settings.tchannelData
  const boxName = appSettings.boxName
  const minSeq = appSettings.minSeq
  const channel = appSettings.channel
  const hash = appSettings.channelHash
  return `${socketUrl}/up/${boxName}/updates?min_seq=${minSeq}&channel=${channel}&hash=${hash}`
}

export const connectWs = async () => {
  const url = await getSocketUrl()
  const ws = new WebSocket(url)
  return new Promise((resolve, reject) => {
    ws.on('open', function open () {
      console.log('Connected to websocket')
      return resolve(ws)
    })
  })
}

export const disconnectWs = async (ws) => {
  return new Promise((resolve, reject) => {
    ws.on('close', function close () {
      return resolve(true)
    })
    ws.close()
  })
}

export const listenWs = async (ws) => {
  let previousText = ''
  return new Promise((resolve, reject) => {
    const onMessage = function incoming (data) {
      let jsonData = JSON.parse(data)
      if (jsonData.messages && jsonData.messages.length > 0) {
        const messages = JSON.parse(jsonData.messages[0])
        const dataPayload = messages.payload.data
        const text = dataPayload.messageAdded.text
        const state = dataPayload.messageAdded.state
        if (state !== 'complete') {
          const differences = diff.diffChars(previousText, text)
          let result = ''
          differences.forEach((part) => {
            if (part.added) {
              result += part.value
            }
          })
          previousText = text
          process.stdout.write(result)
        } else {
          ws.removeListener('message', onMessage)
          return resolve(true)
        }
      }
    }
    ws.on('message', onMessage)
  })
}