'use strict'

const { Buffer } = require('buffer')
const Transform = require('readable-stream').Transform
const duplexify = require('duplexify')

/* global wx */
let socketTask, proxy, stream

function buildProxy () {
  const proxy = new Transform()
  proxy._write = function (chunk, encoding, next) {
    socketTask.send({
      data: chunk.buffer,
      success: function () {
        next()
      },
      fail: function (errMsg) {
        next(new Error(errMsg))
      }
    })
  }
  proxy._flush = function socketEnd (done) {
    socketTask.close({
      success: function () {
        done()
      }
    })
  }

  return proxy
}

function setDefaultOpts (opts) {
  if (!opts.hostname) {
    opts.hostname = 'localhost'
  }
  if (!opts.path) {
    opts.path = '/'
  }

  if (!opts.wsOptions) {
    opts.wsOptions = {}
  }
}

function buildUrl (opts, client) {
  const protocol = opts.protocol === 'wxs' ? 'wss' : 'ws'
  let url = protocol + '://' + opts.hostname + opts.path
  if (opts.port && opts.port !== 80 && opts.port !== 443) {
    url = protocol + '://' + opts.hostname + ':' + opts.port + opts.path
  }
  if (typeof (opts.transformWsUrl) === 'function') {
    url = opts.transformWsUrl(url, opts, client)
  }
  return url
}

function bindEventHandler () {
  socketTask.onOpen(function () {
    stream.setReadable(proxy)
    stream.setWritable(proxy)
    stream.emit('connect')
  })

  socketTask.onMessage(function (res) {
    let data = res.data

    if (data instanceof ArrayBuffer) data = Buffer.from(data)
    else data = Buffer.from(data, 'utf8')
    proxy.push(data)
  })

  socketTask.onClose(function () {
    stream.end()
    stream.destroy()
  })

  socketTask.onError(function (res) {
    stream.destroy(new Error(res.errMsg))
  })
}

function buildStream (client, opts) {
  opts.hostname = opts.hostname || opts.host

  if (!opts.hostname) {
    throw new Error('Could not determine host. Specify host manually.')
  }

  const websocketSubProtocol =
    (opts.protocolId === 'MQIsdp') && (opts.protocolVersion === 3)
      ? 'mqttv3.1'
      : 'mqtt'

  setDefaultOpts(opts)

  const url = buildUrl(opts, client)
  socketTask = wx.connectSocket({
    url: url,
    protocols: [websocketSubProtocol]
  })

  proxy = buildProxy()
  stream = duplexify.obj()
  stream._destroy = function (err, cb) {
    socketTask.close({
      success: function () {
        cb && cb(err)
      }
    })
  }

  const destroyRef = stream.destroy
  stream.destroy = function () {
    stream.destroy = destroyRef

    const self = this
    setTimeout(function () {
      socketTask.close({
        fail: function () {
          self._destroy(new Error())
        }
      })
    }, 0)
  }.bind(stream)

  bindEventHandler()

  return stream
}

module.exports = buildStream