confirmation dialog on proxy close (close #23)

proxy/snowflake.coffee

@@ -44,6 +44,8 @@ MODE =
   WEBRTC_CONNECTING: 1
   WEBRTC_READY:      2
 
+CONFIRMATION_MESSAGE = "You're currently serving a Tor user via Snowflake."
+
 # Minimum viable snowflake for now - just 1 client.
 class Snowflake
 
@@ -200,4 +202,11 @@ init = ->
   snowflake.setRelayAddr relayAddr
   snowflake.beginWebRTC()
 
+# Notification of closing tab with active proxy.
+# TODO: Opt-in/out parameter or cookie
+window.onbeforeunload = ->
+  if MODE.WEBRTC_READY == snowflake.state
+    return CONFIRMATION_MESSAGE
+  null
+
 window.onload = init if window

proxy/spec/snowflake.spec.coffee

@@ -23,6 +23,7 @@ snowflake =
   ui: fakeUI
   broker:
     sendAnswer: ->
+  state: MODE.INIT
 
 describe 'Snowflake', ->
 
@@ -58,3 +59,14 @@ describe 'Snowflake', ->
     s = new Snowflake(new FakeBroker(), fakeUI)
     s.makeProxyPair()
     expect(s.proxyPairs.length).toBe 2
+
+  it 'gives a dialog when closing, only while active', ->
+    snowflake.state = MODE.WEBRTC_READY
+    msg = window.onbeforeunload()
+    expect(snowflake.state).toBe MODE.WEBRTC_READY
+    expect(msg).toBe CONFIRMATION_MESSAGE
+
+    snowflake.state = MODE.INIT
+    msg = window.onbeforeunload()
+    expect(snowflake.state).toBe MODE.INIT
+    expect(msg).toBe null