client.js

module.exports = Client

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

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

inherits(Client, EventEmitter)

/**
 * BitTorrent tracker client.
 *
 * Find torrent peers, to help a torrent client participate in a torrent swarm.
 *
 * @param {string|Buffer} peerId   peer id
 * @param {Number} port            torrent client listening port
 * @param {Object} torrent         parsed torrent
 * @param {Object} opts            options object
 * @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._peerIdHex = self._peerId.toString('hex')
  self._peerIdBinary = self._peerId.toString('binary')

  self._infoHash = Buffer.isBuffer(torrent.infoHash)
    ? torrent.infoHash
    : new Buffer(torrent.infoHash, 'hex')
  self._infoHashHex = self._infoHash.toString('hex')
  self._infoHashBinary = self._infoHash.toString('binary')

  self.torrentLength = torrent.length
  self.destroyed = false

  self._port = port

  self._rtcConfig = opts.rtcConfig
  self._wrtc = opts.wrtc
  self._userAgent = opts.userAgent
  self._key = opts.key
  self._statsForAnnounce = opts.statsForAnnounce

  debug('new client %s', self._infoHashHex)

  var webrtcSupport = !!self._wrtc || typeof window !== 'undefined'

  var announce = (typeof torrent.announce === 'string')
    ? [ torrent.announce ]
    : torrent.announce == null
      ? []
      : torrent.announce

  announce = announce.map(function (announceUrl) {
    announceUrl = announceUrl.toString()
    if (announceUrl[announceUrl.length - 1] === '/') {
      // remove trailing slash from trackers to catch duplicates
      announceUrl = announceUrl.substring(0, announceUrl.length - 1)
    }
    return announceUrl
  })

  announce = uniq(announce)

  self._trackers = announce
    .map(function (announceUrl) {
      var protocol = url.parse(announceUrl).protocol
      if ((protocol === 'http:' || protocol === 'https:') &&
          typeof HTTPTracker === 'function') {
        return new HTTPTracker(self, announceUrl)
      } else if (protocol === 'udp:' && typeof UDPTracker === 'function') {
        return new UDPTracker(self, announceUrl)
      } else if ((protocol === 'ws:' || protocol === 'wss:') && webrtcSupport) {
        return new WebSocketTracker(self, announceUrl)
      } else {
        process.nextTick(function () {
          var err = new Error('unsupported tracker protocol for ' + announceUrl)
          self.emit('warning', err)
        })
      }
      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()
  })
}

/**
 * Send a `stop` announce to the trackers.
 * @param {Object} opts
 * @param {number=} opts.uploaded
 * @param {number=} opts.downloaded
 * @param {number=} opts.numwant
 * @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)
}

/**
 * Send a `complete` announce to the trackers.
 * @param {Object} opts
 * @param {number=} opts.uploaded
 * @param {number=} opts.downloaded
 * @param {number=} opts.numwant
 * @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.numwant
 * @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 should not modify `opts` object, it's passed to all trackers
    tracker.announce(opts)
  })
}

/**
 * Send a scrape request to the trackers.
 * @param {Object} opts
 */
Client.prototype.scrape = function (opts) {
  var self = this
  debug('send `scrape`')
  if (!opts) opts = {}
  self._trackers.forEach(function (tracker) {
    // tracker should not modify `opts` object, it's passed to all trackers
    tracker.scrape(opts)
  })
}

Client.prototype.setInterval = function (intervalMs) {
  var self = this
  debug('setInterval %d', intervalMs)
  self._trackers.forEach(function (tracker) {
    tracker.setInterval(intervalMs)
  })
}

Client.prototype.destroy = function (cb) {
  var self = this
  if (self.destroyed) return
  self.destroyed = true
  debug('destroy')

  var tasks = self._trackers.map(function (tracker) {
    return function (cb) {
      tracker.destroy(cb)
    }
  })

  parallel(tasks, cb)
  self._trackers = []
}

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

  if (opts.numwant == null) opts.numwant = common.DEFAULT_ANNOUNCE_PEERS

  var providedStats = self._statsForAnnounce ? self._statsForAnnounce() : {}

  if (opts.uploaded == null) { opts.uploaded = providedStats.uploaded || 0 }
  if (opts.downloaded == null) { opts.downloaded = providedStats.downloaded || 0 }
  if (self._key) { opts.key = self._key }

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

  return opts
}