--- a/rollbot.py	Wed May 11 14:43:23 2016 +0800
+++ b/rollbot.py	Sat May 14 14:05:49 2016 +0800
@@ -14,13 +14,46 @@
     raw_input = input
 
 
+class Command(object):
+    name = 'command'
+
+    def __init__(self, rollbot):
+        self.rollbot = rollbot
+
+    def usage(self):
+        return '(no help available, try experimenting)'
+
+
+class Help(Command):
+    name = 'help'
+
+    def usage(self):
+        return '%s or %s <command>' % (self.name, self.name)
+
+    def respond(self, words, message):
+        if len(words) == 2:
+            cmdname = words[1]
+            if cmdname in self.rollbot.commands:
+                command = self.rollbot.commands[cmdname]
+                return '%s usage: %s' % (command.name, command.usage())
+            else:
+                return 'no such command: %s' % cmdname
+        elif len(words) == 1:
+            cmds = ' '.join(sorted(self.rollbot.commands.keys()))
+            return 'available commands: %s' % cmds
+        else:
+            return '%s usage: %s' % (self.name, self.usage())
+
+
 class RollBot(sleekxmpp.ClientXMPP):
     def __init__(self, jid, password, nick, prefix):
         sleekxmpp.ClientXMPP.__init__(self, jid, password)
 
         self.nick = nick
         self.prefix = prefix
-        self.commands = []
+
+        self.commands = {}
+        self.add_command(Help)
 
         self.add_event_handler('session_start', self.start)
         self.add_event_handler('message', self.message)
@@ -28,6 +61,9 @@
         self.add_event_handler('groupchat_invite', self.muc_invite)
         self.add_event_handler('groupchat_direct_invite', self.muc_direct_invite)
 
+    def add_command(self, commandcls):
+        self.commands[commandcls.name] = commandcls(self)
+
     def start(self, event):
         self.get_roster()
         self.send_presence()
@@ -77,10 +113,12 @@
 
     def respond(self, message, prefix=None):
         response = ''
-        for command in self.commands:
-            response = command.parse(message)
-            if response:
-                break
+        words = message.split()
+        if words:
+            cmdname = words[0].lower()
+            if cmdname in self.commands:
+                command = self.commands[cmdname]
+                response = command.respond(words, message)
         return response