implement Snowflake coffee class (issue #5)

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.
 ###
 
+Query =
+  ###
+  Parse a URL query string or application/x-www-form-urlencoded body. The
+  return type is an object mapping string keys to string values. By design,
+  this function doesn't support multiple values for the same named parameter,
+  for example "a=1&a=2&a=3"; the first definition always wins. Returns null on
+  error.
+
+  Always decodes from UTF-8, not any other encoding.
+  http://dev.w3.org/html5/spec/Overview.html#url-encoded-form-data
+  ###
+  parse: (qs) ->
+    result = {}
+    strings = []
+    strings = qs.split '&' if qs
+    return result if 0 == strings.length
+    for i in [1..strings.length]
+      string = strings[i]
+      j = string.indexOf '='
+      if j == -1
+        name = string
+        value = ''
+      else
+        name = string.substr(0, j)
+        value = string.substr(j + 1)
+      name = decodeURIComponent(name.replace(/\+/g, ' '))
+      value = decodeURIComponent(value.replace(/\+/g, ' '))
+      result[name] = value if !(name in result)
+    result
+
+Params =
+  getBool: (query, param, defaultValue) ->
+    val = query[param]
+    return defaultValue if undefined == val
+    return true if "true" == val || "1" == val || "" == val
+    return false if "false" == val || "0" == val
+    return null
+
+# HEADLESS is true if we are running not in a browser with a DOM.
+query = Query.parse(window.location.search.substr(1))
+HEADLESS = "undefined" == typeof(document)
+DEBUG = Params.getBool(query, "debug", false)
+
 # Janky state machine
 MODE =
   INIT:       0
@@ -10,6 +58,8 @@ MODE =
   CHAT:       2
 currentMode = MODE.INIT
 
+
+# TODO: Different ICE servers.
 config = {
   iceServers: [
     { urls: ["stun:stun.l.google.com:19302"] }
@@ -21,22 +71,96 @@ $chatlog = null
 $send = null
 $input = null
 
-
 window.PeerConnection = window.RTCPeerConnection ||
-                        window.mozRTCPeerConnection || window.webkitRTCPeerConnection
+                        window.mozRTCPeerConnection ||
+                        window.webkitRTCPeerConnection
 window.RTCIceCandidate = window.RTCIceCandidate || window.mozRTCIceCandidate;
-window.RTCSessionDescription = window.RTCSessionDescription || window.mozRTCSessionDescription
+window.RTCSessionDescription = window.RTCSessionDescription ||
+                               window.mozRTCSessionDescription
+
+# TODO: Implement
+class Badge
 
+# Minimum viable snowflake for now - just 1 client.
 class Snowflake
 
+  rateLimit: 0
+  proxyPairs: null
+  badge: null
+  $badge: null
+  MAX_NUM_CLIENTS = 1
+
+  constructor: ->
+    if HEADLESS
+      # No badge
+    else if DEBUG
+      @$badge = debug_div
+    else
+      @badge = new Badge()
+      @$badgem = @badge.elem
+    if (@$badge)
+      @$badge.setAttribute("id", "snowflake-badge")
+
+  start: ->
+    log "Starting up Snowflake..."
+
+  # 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"]
+
+  beginProxy = (client, relay) ->
+    for i in [0..CONNECTIONS_PER_CLIENT]
+      makeProxyPair(client, relay)
+
+  makeProxyPair = (client, relay) ->
+    pair = new ProxyPair(client, relay, @rate_limit);
+    @proxyPairs.push pair
+    pair.onCleanup = (event) =>
+      # Delete from the list of active proxy pairs.
+      @proxyPairs.splice(@proxy_pairs.indexOf(pair), 1)
+      @badge.endProxy() if @badge
+    try
+      proxy_pair.connect()
+    catch err
+      log "ProxyPair: exception while connecting: " + safe_repr(err.message) + "."
+      return
+    @badge.beginProxy if @badge
+
+  cease = ->
+    # @start = null
+    # @proxyMain = null
+    # @make_proxy_pair = function(client_addr, relay_addr) { };
+    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
+
+
+# TODO: Implement
 class ProxyPair
 
+
 #
 ## -- DOM & Input Functionality -- ##
 #
+snowflake = new Snowflake()
 
 welcome = ->
-  log "== snowflake JS proxy =="
+  log "== snowflake browser proxy =="
   log "Input offer from the snowflake client:"
 
 # Log to the message window.
@@ -82,7 +206,7 @@ Signalling =
       log "Invalid JSON."
       return
     # Begin as answerer if peerconnection doesn't exist yet.
-    start false if !pc
+    snowflake.start false if !pc
     desc = recv['sdp']
     ice = recv['candidate']
     if !desc && ! ice