client.js

module.exports = Client

var debug = require('debug')('bittorrent-tracker')
var EventEmitter = require('events').EventEmitter
var inherits = require('inherits')
var once = require('once')
var url = require('url')

var common = require('./lib/common')
var HTTPTracker = require('./lib/http-tracker') // empty object in browser
var UDPTracker = require('./lib/udp-tracker') // empty object in browser
var WebSocketTracker = require('./lib/websocket-tracker')

inherits(Client, EventEmitter)

/**
 * BitTorrent tracker client.
 *
 * Find torrent peers, to help a torrent client participate in a torrent swarm.
 *
 * @param {string} peerId          peer id
 * @param {Number} port            torrent client listening port
 * @param {Object} torrent         parsed torrent
 * @param {Object} opts            options object
 * @param {Number} opts.numWant    number of peers to request
 * @param {Number} opts.interval   announce interval (in ms)
 * @param {Number} opts.rtcConfig  RTCPeerConnection configuration object
 * @param {Number} opts.wrtc       custom webrtc implementation
 */
function Client (peerId, port, torrent, opts) {
  var self = this
  if (!(self instanceof Client)) return new Client(peerId, port, torrent, opts)
  EventEmitter.call(self)
  if (!opts) opts = {}

  // required
  self._peerId = Buffer.isBuffer(peerId)
    ? peerId
    : new Buffer(peerId, 'hex')
  self._port = port
  self._infoHash = Buffer.isBuffer(torrent.infoHash)
    ? torrent.infoHash
    : new Buffer(torrent.infoHash, 'hex')
  self.torrentLength = torrent.length

  self._rtcConfig = opts.rtcConfig
  self._wrtc = opts.wrtc

  // optional
  self._numWant = opts.numWant || common.DEFAULT_ANNOUNCE_PEERS
  self._intervalMs = opts.interval || common.DEFAULT_ANNOUNCE_INTERVAL

  debug('new client %s', self._infoHash.toString('hex'))

  if (typeof torrent.announce === 'string') torrent.announce = [ torrent.announce ]
  if (torrent.announce == null) torrent.announce = []

  var trackerOpts = { interval: self._intervalMs }
  var webrtcSupport = !!self._wrtc || typeof window !== 'undefined'

  self._trackers = torrent.announce
    .map(function (announceUrl) {
      var protocol = url.parse(announceUrl).protocol

      if ((protocol === 'http:' || protocol === 'https:') &&
          typeof HTTPTracker === 'function') {
        return new HTTPTracker(self, announceUrl, trackerOpts)
      } else if (protocol === 'udp:' && typeof UDPTracker === 'function') {
        return new UDPTracker(self, announceUrl, trackerOpts)
      } else if ((protocol === 'ws:' || protocol === 'wss:') && webrtcSupport) {
        return new WebSocketTracker(self, announceUrl, trackerOpts)
      }
      return null
    })
    .filter(Boolean)
}

/**
 * Simple convenience function to scrape a tracker for an info hash without needing to
 * create a Client, pass it a parsed torrent, etc. Support scraping a tracker for multiple
 * torrents at the same time.
 * @param  {string} announceUrl
 * @param  {string|Array.<string>} infoHash
 * @param  {function} cb
 */
Client.scrape = function (announceUrl, infoHash, cb) {
  cb = once(cb)

  var peerId = new Buffer('01234567890123456789') // dummy value
  var port = 6881 // dummy value
  var torrent = {
    infoHash: Array.isArray(infoHash) ? infoHash[0] : infoHash,
    announce: [ announceUrl ]
  }
  var client = new Client(peerId, port, torrent)
  client.once('error', cb)

  var len = Array.isArray(infoHash) ? infoHash.length : 1
  var results = {}
  client.on('scrape', function (data) {
    len -= 1
    results[data.infoHash] = data
    if (len === 0) {
      client.destroy()
      var keys = Object.keys(results)
      if (keys.length === 1) {
        cb(null, results[keys[0]])
      } else {
        cb(null, results)
      }
    }
  })

  infoHash = Array.isArray(infoHash)
    ? infoHash.map(function (infoHash) { return new Buffer(infoHash, 'hex') })
    : new Buffer(infoHash, 'hex')
  client.scrape({ infoHash: infoHash })
}

/**
 * Send a `start` announce to the trackers.
 * @param {Object} opts
 * @param {number=} opts.uploaded
 * @param {number=} opts.downloaded
 * @param {number=} opts.left (if not set, calculated automatically)
 */
Client.prototype.start = function (opts) {
  var self = this
  debug('send `start`')
  opts = self._defaultAnnounceOpts(opts)
  opts.event = 'started'
  self._announce(opts)

  // start announcing on intervals
  self._trackers.forEach(function (tracker) {
    tracker.setInterval(self._intervalMs)
  })
}

/**
 * Send a `stop` announce to the trackers.
 * @param {Object} opts
 * @param {number=} opts.uploaded
 * @param {number=} opts.downloaded
 * @param {number=} opts.left (if not set, calculated automatically)
 */
Client.prototype.stop = function (opts) {
  var self = this
  debug('send `stop`')
  opts = self._defaultAnnounceOpts(opts)
  opts.event = 'stopped'
  self._announce(opts)

  self.destroy()
}

/**
 * Send a `complete` announce to the trackers.
 * @param {Object} opts
 * @param {number=} opts.uploaded
 * @param {number=} opts.downloaded
 * @param {number=} opts.left (if not set, calculated automatically)
 */
Client.prototype.complete = function (opts) {
  var self = this
  debug('send `complete`')
  if (!opts) opts = {}
  if (opts.downloaded == null && self.torrentLength != null) {
    opts.downloaded = self.torrentLength
  }
  opts = self._defaultAnnounceOpts(opts)
  opts.event = 'completed'
  self._announce(opts)
}

/**
 * Send a `update` announce to the trackers.
 * @param {Object} opts
 * @param {number=} opts.uploaded
 * @param {number=} opts.downloaded
 * @param {number=} opts.left (if not set, calculated automatically)
 */
Client.prototype.update = function (opts) {
  var self = this
  debug('send `update`')
  opts = self._defaultAnnounceOpts(opts)
  if (opts.event) delete opts.event
  self._announce(opts)
}

Client.prototype._announce = function (opts) {
  var self = this
  self._trackers.forEach(function (tracker) {
    tracker.announce(opts)
  })
}

/**
 * Send a scrape request to the trackers.
 * @param {Object} opts
 * @param {number=} opts.uploaded
 * @param {number=} opts.downloaded
 * @param {number=} opts.left (if not set, calculated automatically)
 */
Client.prototype.scrape = function (opts) {
  var self = this
  debug('send `scrape`')
  if (!opts) opts = {}
  self._trackers.forEach(function (tracker) {
    tracker.scrape(opts)
  })
}

Client.prototype.setInterval = function (intervalMs) {
  var self = this
  debug('setInterval')
  self._intervalMs = intervalMs

  self._trackers.forEach(function (tracker) {
    tracker.setInterval(intervalMs)
  })
}

Client.prototype.destroy = function () {
  var self = this
  debug('destroy')

  self._trackers.forEach(function (tracker) {
    if (tracker.destroy) tracker.destroy()
    tracker.setInterval(0) // stop announcing on intervals
  })
}

Client.prototype._defaultAnnounceOpts = function (opts) {
  var self = this
  if (!opts) opts = {}

  if (opts.numWant == null) opts.numWant = self._numWant

  if (opts.uploaded == null) opts.uploaded = 0
  if (opts.downloaded == null) opts.downloaded = 0

  if (opts.left == null && self.torrentLength != null) {
    opts.left = self.torrentLength - opts.downloaded
  }
  return opts
}