Add ability to listen for topic changes

Adapters must specifically implement receiving TopicMessage when they handle a
changing topic.

Closes hubotio#349

index.coffee

@@ -1,10 +1,10 @@
-User                                                    = require './src/user'
-Brain                                                   = require './src/brain'
-Robot                                                   = require './src/robot'
-Adapter                                                 = require './src/adapter'
-Response                                                = require './src/response'
-{Listener,TextListener}                                 = require './src/listener'
-{TextMessage,EnterMessage,LeaveMessage,CatchAllMessage} = require './src/message'
+User                                                                 = require './src/user'
+Brain                                                                = require './src/brain'
+Robot                                                                = require './src/robot'
+Adapter                                                              = require './src/adapter'
+Response                                                             = require './src/response'
+{Listener,TextListener}                                              = require './src/listener'
+{TextMessage,EnterMessage,LeaveMessage,TopicMessage,CatchAllMessage} = require './src/message'
 
 module.exports = {
   User
@@ -17,6 +17,7 @@ module.exports = {
   TextMessage
   EnterMessage
   LeaveMessage
+  TopicMessage
   CatchAllMessage
 }
 

src/adapters/campfire.coffee

@@ -1,9 +1,9 @@
 HTTPS          = require 'https'
 {EventEmitter} = require 'events'
 
-Robot                                   = require '../robot'
-Adapter                                 = require '../adapter'
-{TextMessage,EnterMessage,LeaveMessage} = require '../message'
+Robot                                                = require '../robot'
+Adapter                                              = require '../adapter'
+{TextMessage,EnterMessage,LeaveMessage,TopicMessage} = require '../message'
 
 class Campfire extends Adapter
   send: (envelope, strings...) ->
@@ -55,6 +55,10 @@ class Campfire extends Adapter
       unless bot.info.id == author.id
         self.receive new LeaveMessage(author, null, id)
 
+    bot.on "TopicChangeMessage", withAuthor (id, created, room, user, body, author) ->
+      unless bot.info.id == author.id
+        self.receive new TopicMessage(author, body, id)
+
     bot.Me (err, data) ->
       bot.info = data.user
       bot.name = bot.info.name

src/message.coffee

@@ -42,6 +42,13 @@ class EnterMessage extends Message
 # id   - A String of the message ID.
 class LeaveMessage extends Message
 
+# Represents an incoming topic change notification.
+#
+# user - A User instance for the user who changed the topic.
+# text - A String of the new topic
+# id   - A String of the message ID.
+class TopicMessage extends Message
+
 class CatchAllMessage extends Message
   # Represents a message that no matchers matched.
   #
@@ -53,5 +60,6 @@ module.exports = {
   TextMessage
   EnterMessage
   LeaveMessage
+  TopicMessage
   CatchAllMessage
 }

src/robot.coffee

@@ -102,13 +102,25 @@ class Robot
   leave: (callback) ->
     @listeners.push new Listener(@, ((msg) -> msg instanceof LeaveMessage), callback)
 
+  # Public: Adds a Listener that triggers when anyone changes the topic.
+  #
+  # callback - A Function that is called with a Response object.
+  #
+  # Returns nothing.
+  topic: (callback) ->
+    @listeners.push new Listener(@, ((msg) -> msg instanceof TopicMessage), callback)
+
   # Public: Adds a Listener that triggers when no other text matchers match.
   #
   # callback - A Function that is called with a Response object.
   #
   # Returns nothing.
   catchAll: (callback) ->
-    @listeners.push new Listener(@, ((msg) -> msg instanceof CatchAllMessage), ((msg) -> msg.message = msg.message.message; callback msg))
+    @listeners.push new Listener(
+      @,
+      ((msg) -> msg instanceof CatchAllMessage),
+      ((msg) -> msg.message = msg.message.message; callback msg)
+    )
 
   # Public: Passes the given message to any interested Listeners.
   #