--- a/rollbot.py	Sat May 14 14:05:49 2016 +0800
+++ b/rollbot.py	Sat May 14 14:07:31 2016 +0800
@@ -1,5 +1,7 @@
 #!/usr/bin/env python
 import logging
+import random
+import re
 import sys
 from argparse import ArgumentParser, FileType, SUPPRESS
 
@@ -24,6 +26,38 @@
         return '(no help available, try experimenting)'
 
 
+class Roll(Command):
+    name = 'roll'
+    regex = re.compile('^(?P<times>\d+)?d(?P<sides>\d+)$', re.IGNORECASE)
+
+    def usage(self):
+        return '%s <X>D<Y> means roll Y-sided die X times, if X is 1 it can be omitted' % self.name
+
+    def respond(self, words, message):
+        if len(words) == 2:
+            match = self.regex.match(words[1])
+            if match is not None:
+                times = match.group('times')
+                if times is None:
+                    times = 1
+                sides = match.group('sides')
+                rolls, total = self.roll(int(times), int(sides))
+                return self.format(rolls, total)
+
+        return '%s usage: %s' % (self.name, self.usage())
+
+    def roll(self, times, sides):
+        results = [random.randint(1, sides) for i in range(times)]
+        total = sum(results)
+        return results, total
+
+    def format(self, rolls, total):
+        if len(rolls) == 1:
+            return '%d' % total
+        else:
+            return '(%s) = %d' % (' + '.join('%d' % r for r in rolls), total)
+
+
 class Help(Command):
     name = 'help'
 
@@ -53,6 +87,7 @@
         self.prefix = prefix
 
         self.commands = {}
+        self.add_command(Roll)
         self.add_command(Help)
 
         self.add_event_handler('session_start', self.start)