snowflake/proxy/snowflake.coffee

###
A Coffeescript WebRTC snowflake proxy
Using Copy-paste signaling for now.

Uses WebRTC from the client, and websocket to the server.

Assume that the webrtc client plugin is always the offerer, in which case
this must always act as the answerer.
###
DEFAULT_WEBSOCKET = '192.81.135.242:9901'
DEFAULT_PORTS =
  http:  80
  https: 443

DEBUG = false
if window && window.location
  query = Query.parse(window.location.search.substr(1))
  DEBUG = Params.getBool(query, 'debug', false)
# HEADLESS is true if we are running not in a browser with a DOM.
HEADLESS = 'undefined' == typeof(document)

# Bytes per second. Set to undefined to disable limit.
DEFAULT_RATE_LIMIT = DEFAULT_RATE_LIMIT || undefined
MIN_RATE_LIMIT = 10 * 1024
RATE_LIMIT_HISTORY = 5.0

MAX_NUM_CLIENTS = 1
CONNECTIONS_PER_CLIENT = 1

# TODO: Different ICE servers.
config = {
  iceServers: [
    { urls: ['stun:stun.l.google.com:19302'] }
  ]
}

# TODO: Implement
class Badge

# Janky state machine
MODE =
  INIT:              0
  WEBRTC_CONNECTING: 1
  WEBRTC_READY:      2

# Minimum viable snowflake for now - just 1 client.
class Snowflake

  relayAddr: null
  # TODO: Actually support multiple ProxyPairs. (makes more sense once meek-
  # signalling is ready)
  proxyPairs: []
  proxyPair: null

  rateLimit: null
  badge: null
  $badge: null
  state: MODE.INIT

  constructor: ->
    if HEADLESS
      # No badge
    else if DEBUG
      @$badge = debug_div
    else
      @badge = new Badge()
      @$badgem = @badge.elem
    @$badge.setAttribute('id', 'snowflake-badge') if (@$badge)

    rateLimitBytes = undefined
    if 'off' != query['ratelimit']
      rateLimitBytes = Params.getByteCount(query, 'ratelimit',
                                           DEFAULT_RATE_LIMIT)
    if undefined == rateLimitBytes
      @rateLimit = new DummyRateLimit()
    else
      @rateLimit = new BucketRateLimit(rateLimitBytes * RATE_LIMIT_HISTORY,
                                       RATE_LIMIT_HISTORY)

  # TODO: Should fetch from facilitator later.
  setRelayAddr: (relayAddr) ->
    addr = Parse.address relayAddr
    if !addr
      log 'Invalid address spec.'
      return false
    @relayAddr = addr
    log 'Using ' + relayAddr + ' as Relay.'
    @beginWebRTC()
    log 'Input offer from the snowflake client:'
    return true

  # Initialize WebRTC PeerConnection
  beginWebRTC: ->
    log 'Starting up Snowflake...\n'
    @state = MODE.WEBRTC_CONNECTING
    for i in [1..CONNECTIONS_PER_CLIENT]
      @makeProxyPair @relayAddr
    @proxyPair = @proxyPairs[0]

  # Receive an SDP offer from client plugin.
  receiveOffer: (desc) =>
    sdp = new RTCSessionDescription desc
    try
      err = @proxyPair.pc.setRemoteDescription sdp
    catch e
      log 'Invalid SDP message.'
      return false
    log 'SDP ' + sdp.type + ' successfully received.'
    @sendAnswer() if 'offer' == sdp.type
    true

  sendAnswer: =>
    next = (sdp) =>
      log 'webrtc: Answer ready.'
      @proxyPair.pc.setLocalDescription sdp
    promise = @proxyPair.pc.createAnswer next
    promise.then next if promise

  # Poll facilitator when this snowflake can support more clients.
  proxyMain: ->
    if @proxyPairs.length >= MAX_NUM_CLIENTS * CONNECTIONS_PER_CLIENT
      setTimeout(@proxyMain, @facilitator_poll_interval * 1000)
      return
    params = [['r', '1']]
    params.push ['transport', 'websocket']
    params.push ['transport', 'webrtc']

  makeProxyPair: (relay) ->
    pair = new ProxyPair null, relay, @rateLimit
    @proxyPairs.push pair
    pair.onCleanup = (event) =>
      # Delete from the list of active proxy pairs.
      @proxyPairs.splice(@proxyPairs.indexOf(pair), 1)
      @badge.endProxy() if @badge
    try
      pair.connectClient()
    catch err
      log 'ERROR: ProxyPair exception while connecting.'
      log err
      return
    @badge.beginProxy if @badge

  cease: ->
    while @proxyPairs.length > 0
      @proxyPairs.pop().close()

  disable: ->
    log 'Disabling Snowflake.'
    @cease()
    @badge.disable() if @badge

  die: ->
    log 'Snowflake died.'
    @cease()
    @badge.die() if @badge

snowflake = null

#
## -- DOM & Inputs -- #
#

# DOM elements references.
$msglog = null
$send = null
$input = null

Interface =
  # Local input from keyboard into message window.
  acceptInput: ->
    msg = $input.value
    switch snowflake.state
      when MODE.INIT
        # Set target relay.
        if !(snowflake.setRelayAddr msg)
          log 'Defaulting to websocket relay at ' + DEFAULT_WEBSOCKET
          snowflake.setRelayAddr DEFAULT_WEBSOCKET
      when MODE.WEBRTC_CONNECTING
        Signalling.receive msg
      when MODE.WEBRTC_READY
        log 'No input expected - WebRTC connected.'
      else
        log 'ERROR: ' + msg
    $input.value = ''
    $input.focus()

# Signalling channel - just tells user to copy paste to the peer.
# Eventually this should go over the facilitator.
Signalling =
  send: (msg) ->
    log '---- Please copy the below to peer ----\n'
    log JSON.stringify msg
    log '\n'

  receive: (msg) ->
    recv = ''
    try
      recv = JSON.parse msg
    catch e
      log 'Invalid JSON.'
      return
    desc = recv['sdp']
    if !desc
      log 'Invalid SDP.'
      return false
    snowflake.receiveOffer recv if desc

log = (msg) ->  # Log to the message window.
  console.log msg
  # Scroll to latest
  if $msglog
    $msglog.value += msg + '\n'
    $msglog.scrollTop = $msglog.scrollHeight

welcome = ->
  log '== snowflake browser proxy =='
  log 'Input desired relay address:'

init = ->
  $msglog = document.getElementById('msglog')
  $msglog.value = ''

  $send = document.getElementById('send')
  $send.onclick = Interface.acceptInput

  $input = document.getElementById('input')
  $input.focus()
  $input.onkeydown = (e) -> $send.onclick() if 13 == e.keyCode  # enter

  snowflake = new Snowflake()
  window.snowflake = snowflake
  welcome()

window.onload = init if window