client.js

module.exports = Client

var Buffer = require('safe-buffer').Buffer
var debug = require('debug')('bittorrent-tracker:client')
var EventEmitter = require('events').EventEmitter
var extend = require('xtend')
var inherits = require('inherits')
var once = require('once')
var parallel = require('run-parallel')
var Peer = require('simple-peer')
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 {Object} opts                          options object
 * @param {string|Buffer} opts.infoHash          torrent info hash
 * @param {string|Buffer} opts.peerId            peer id
 * @param {string|Array.<string>} opts.announce  announce
 * @param {number} opts.port                     torrent client listening port
 * @param {function} opts.getAnnounceOpts        callback to provide data to tracker
 * @param {number} opts.rtcConfig                RTCPeerConnection configuration object
 * @param {number} opts.userAgent                User-Agent header for http requests
 * @param {number} opts.wrtc                     custom webrtc impl (useful in node.js)
 */
function Client (opts) {
  var self = this
  if (!(self instanceof Client)) return new Client(opts)
  EventEmitter.call(self)
  if (!opts) opts = {}

  if (!opts.peerId) throw new Error('Option `peerId` is required')
  if (!opts.infoHash) throw new Error('Option `infoHash` is required')
  if (!opts.announce) throw new Error('Option `announce` is required')
  if (!process.browser && !opts.port) throw new Error('Option `port` is required')

  self.peerId = typeof opts.peerId === 'string'
    ? opts.peerId
    : opts.peerId.toString('hex')
  self._peerIdBuffer = Buffer.from(self.peerId, 'hex')
  self._peerIdBinary = self._peerIdBuffer.toString('binary')

  self.infoHash = typeof opts.infoHash === 'string'
    ? opts.infoHash
    : opts.infoHash.toString('hex')
  self._infoHashBuffer = Buffer.from(self.infoHash, 'hex')
  self._infoHashBinary = self._infoHashBuffer.toString('binary')

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

  self.destroyed = false

  self._port = opts.port
  self._getAnnounceOpts = opts.getAnnounceOpts
  self._rtcConfig = opts.rtcConfig
  self._userAgent = opts.userAgent

  // Support lazy 'wrtc' module initialization
  // See: https://github.com/webtorrent/webtorrent-hybrid/issues/46
  self._wrtc = typeof opts.wrtc === 'function' ? opts.wrtc() : opts.wrtc

  var announce = typeof opts.announce === 'string'
    ? [ opts.announce ]
    : opts.announce == null ? [] : opts.announce

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

  var webrtcSupport = self._wrtc !== false && (!!self._wrtc || Peer.WEBRTC_SUPPORT)

  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) {
        // Skip ws:// trackers on https:// sites because they throw SecurityError
        if (protocol === 'ws:' && typeof window !== 'undefined' &&
            window.location.protocol === 'https:') {
          nextTickWarn(new Error('Unsupported tracker protocol: ' + announceUrl))
          return null
        }
        return new WebSocketTracker(self, announceUrl)
      } else {
        nextTickWarn(new Error('Unsupported tracker protocol: ' + announceUrl))
        return null
      }
    })
    .filter(Boolean)

  function nextTickWarn (err) {
    process.nextTick(function () {
      self.emit('warning', err)
    })
  }
}

/**
 * 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.
 * @params {Object} opts
 * @param  {string|Array.<string>} opts.infoHash
 * @param  {string} opts.announce
 * @param  {function} cb
 */
Client.scrape = function (opts, cb) {
  cb = once(cb)

  if (!opts.infoHash) throw new Error('Option `infoHash` is required')
  if (!opts.announce) throw new Error('Option `announce` is required')

  var clientOpts = extend(opts, {
    infoHash: Array.isArray(opts.infoHash) ? opts.infoHash[0] : opts.infoHash,
    peerId: Buffer.from('01234567890123456789'), // dummy value
    port: 6881 // dummy value
  })

  var client = new Client(clientOpts)
  client.once('error', cb)
  client.once('warning', cb)

  var len = Array.isArray(opts.infoHash) ? opts.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)
      }
    }
  })

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

/**
 * 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 = {}
  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 = []
  self._getAnnounceOpts = null
}

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

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

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

  if (self._getAnnounceOpts) opts = extend(opts, self._getAnnounceOpts())
  return opts
}