Initial broker registration of browser proxies

- broker.coffee contains the xhr stuff
- COR enabled on the go broker
- POST body reflection works

proxy/broker.coffee

@@ -0,0 +1,49 @@
+###
+Communication with the snowflake broker.
+
+Browser snowflakes must register with the broker in order
+to get assigned to clients.
+###
+
+# Represents a broker running remotely.
+class Broker
+  # When interacting with the Broker, snowflake must generate a unique session
+  # ID so the Broker can keep track of which signalling channel it's speaking
+  # to.
+  constructor: (@url) ->
+    log 'Using Broker at ' + @url
+
+  # Snowflake registers with the broker using an HTTP POST request, and expects
+  # a response from the broker containing some client offer
+  register: ->
+    # base_url = this.fac_url.replace(/\?.*/, "");
+    # url = base_url + "?" + build_query_string(params);
+    xhr = new XMLHttpRequest()
+    try
+      xhr.open 'POST', @url
+      xhr
+    catch err
+      ###
+      An exception happens here when, for example, NoScript allows the domain on
+      which the proxy badge runs, but not the domain to which it's trying to
+      make the HTTP request. The exception message is like "Component returned
+      failure code: 0x805e0006 [nsIXMLHttpRequest.open]" on Firefox.
+      ###
+      log 'Broker: exception while connecting: ' + err.message
+      return
+
+    # xhr.responseType = 'text'
+    xhr.onreadystatechange = ->
+      if xhr.DONE == xhr.readyState
+        if 200 == xhr.status
+          log 'Broker: success'
+          log 'Response: ' + xhr.responseText
+          # @fac_complete xhr.responseText
+        else
+          log 'Broker error ' + xhr.status + ' - ' + xhr.statusText
+
+    xhr.send 'snowflake-testing'
+
+  sendAnswer: (answer) ->
+    log 'Sending answer to broker.'
+    log answer