// adpated from https://github.com/sebastianseilund/node-json-socket

// native
import { StringDecoder } from 'string_decoder'
import EventEmitter from 'events'

// import to from 'await-to-js'

const decoder = new StringDecoder()

/**
 * JsonStream - Description
 * @extends EventEmitter
 */
class JsonStream extends EventEmitter {
  // private fields
  #contentLength = null
  #buffer =''
  #delimiter='#'
  #state='online'
  #queue=[]
  #stream

  constructor (opts = {}) {
    super()
    this.#delimiter = opts.delimiter || this.#delimiter
    this.onData = this.onData.bind(this)
    this.serialize = this.serialize.bind(this)
  }

  get state () { return this.#state }

  get queue () { return this.#queue }

  offline () { this.#state = 'offline' }

  pause () { this.#state = 'paused' } // queue messages in handler

  resume () {
    // emit FIFO
    for (let index = 0; index < this.#queue.length; index++) {
      this.emit('message', this.#queue[index])
    }
    this.#queue = []
    this.#state = 'online'
  }

  online () { this.#state = 'online' }

  onData (data) {
    data = decoder.write(data)
    try {
      this.#handleData(data)
    } catch (err) {
      // emit an error
      this.emit('error', err)
    }
  }

  async serialize (message) {
    return new Promise((resolve, reject) => {
      let messageData; let length
      try { messageData = JSON.stringify(message) } catch (err) { reject(err) }
      try { length = Buffer.byteLength(messageData, 'utf8') } catch (err) { reject(err) }
      const data = length + this.#delimiter + messageData
      resolve(data)
    })
  }

  #handleData (data) {
    this.#buffer += data
    if (this.#contentLength == null) {
      const i = this.#buffer.indexOf(this.#delimiter)
      // Check if the buffer has a this.#opts.delimeter or "#", if not, the end of the buffer string might be in the middle of a content length string
      if (i !== -1) {
        const rawContentLength = this.#buffer.substring(0, i)
        this.#contentLength = parseInt(rawContentLength)
        if (isNaN(this.#contentLength)) {
          this.#contentLength = null
          this.#buffer = ''
          const err = new Error(
            'Invalid content length supplied (' +
              rawContentLength +
              ') in: ' +
              this.#buffer
          )
          err.code = 'E#INVALID#CONTENT#LENGTH'
          throw err
        }
        this.#buffer = this.#buffer.substring(i + 1)
      }
    }
    if (this.#contentLength != null) {
      const length = Buffer.byteLength(this.#buffer, 'utf8')
      if (length === this.#contentLength) {
        this.#handleMessage(this.#buffer)
      } else if (length > this.#contentLength) {
        const message = this.#buffer.substring(0, this.#contentLength)
        const rest = this.#buffer.substring(this.#contentLength)
        this.#handleMessage(message)
        this.onData(rest)
      }
    }
  }

  // private methods

  #handleMessage (data) {
    this.#contentLength = null
    this.#buffer = ''
    let message
    try {
      message = JSON.parse(data)
    } catch (e) {
      const err = new Error(
        'Could not parse JSON: ' + e.message + '\nRequest data: ' + data
      )
      err.code = 'E#INVALID#JSON'
      throw err
    }
    message = message || {}
    // console.log('stream message', message, this.#state)
    if (this.#state === 'paused') {
      this.#queue.push(message)
    }
    if (this.#state === 'online') {
      this.#queue = []
      this.emit('message', message)
    }
  }
}

export { JsonStream }
export default JsonStream