--- a/rollbot.py	Tue May 10 17:17:47 2016 +0800
+++ b/rollbot.py	Wed May 11 00:04:29 2016 +0800
@@ -19,8 +19,12 @@
         sleekxmpp.ClientXMPP.__init__(self, jid, password)
 
         self.nick = nick
+        self.prefix = '!'
+        self.commands = []
 
         self.add_event_handler('session_start', self.start)
+        self.add_event_handler('message', self.message)
+        self.add_event_handler('groupchat_message', self.muc_message)
         self.add_event_handler('groupchat_invite', self.muc_invite)
         self.add_event_handler('groupchat_direct_invite', self.muc_direct_invite)
 
@@ -28,6 +32,34 @@
         self.get_roster()
         self.send_presence()
 
+    def message(self, msg):
+        if msg['type'] not in ('chat', 'normal'):
+            return
+
+        rbody = self.respond(msg['body'].strip())
+        if rbody:
+            msg.reply(rbody)
+            msg.send()
+
+    def muc_message(self, msg):
+        if msg['mucnick'] == self.nick:
+            return
+
+        mbody = msg['body'].lstrip()
+        if mbody.startswith(self.nick):
+            mbody = mbody[len(self.nick):]
+        elif mbody.startswith(self.prefix):
+            mbody = mbody[len(self.prefix):]
+        else:
+            return
+
+        mbody = mbody.lstrip(':, \t')
+        rbody = self.respond(mbody)
+        if rbody:
+            rbody = '%s: %s' % (msg['mucnick'], rbody)
+            msg.reply(rbody)
+            msg.send()
+
     def muc_invite(self, invite):
         room = invite['from']
         password = '' # https://github.com/fritzy/SleekXMPP/issues/409
@@ -38,6 +70,14 @@
         password = invite['groupchat_invite']['password']
         self.plugin['xep_0045'].joinMUC(room, self.nick, password=password, wait=True)
 
+    def respond(self, message, prefix=None):
+        response = ''
+        for command in self.commands:
+            response = command.parse(message)
+            if response:
+                break
+        return response
+
 
 def lookup(key, args, config, default=None):
     if hasattr(args, key):