# Supybot plugin author example

## Introduction

Ok, so you want to write a callback for supybot. Good, then this is the place to be. We're going to start from the top (the highest level, where supybot code does the most work for you) and move lower after that.

So have you used supybot? If not, you need to go use it, get a feel for it, see how the various commands work and such.

So now that we know you've used supybot, we'll start getting into details.

## Creating your own plugin

### Using

First, the easiest way to start writing a module is to use the wizard provided,
. Here's an example session:

    functor% scripts/newplugin.py
    What should the name of the plugin be? Random
    Supybot offers two major types of plugins: command-based and regexp-
    based.  Command-based plugins are the kind of plugins you've seen most
    when you've used supybot.  They're also the most featureful and
    easiest to write.  Commands can be nested,  for instance, whereas
    regexp-based callbacks can't do nesting.  That doesn't mean that
    you'll never want regexp-based callbacks. They offer a flexibility
    that command-based callbacks don't offer; however, they don't tie into
    the whole system as well.  If you need to combine a command-based
    callback with some regexp-based methods, you can do so by subclassing
    callbacks.PrivmsgCommandAndRegexp and then adding a class-level
    attribute "regexps" that is a sets.Set of methods that are regexp-
    based.  But you'll have to do that yourself after this wizard is
    finished :)
    Do you want a command-based plugin or a regexp-based plugin? [command/
                                                                  regexp] command
    Sometimes you'll want a callback to be threaded.  If its methods
    (command or regexp-based, either one) will take a signficant amount
    of time to run, you'll want to thread them so they don't block
    the entire bot.

    Does your plugin need to be threaded? [y/n] n
    Your new plugin template is in plugins/Random.py
    functor%

So that's what it looks like. Now let's look at the source code (if you'd like to look at it in your programming editor, the whole plugin is available as `examples/Random.py`):

    #!/usr/bin/env python

    ###
    # Copyright (c) 2002, Jeremiah Fincher
    # All rights reserved.
    #
    # Redistribution and use in source and binary forms, with or without
    # modification, are permitted provided that the following conditions are met:
    #
    #   * Redistributions of source code must retain the above copyright notice,
    #     this list of conditions, and the following disclaimer.
    #   * Redistributions in binary form must reproduce the above copyright notice,
    #     this list of conditions, and the following disclaimer in the
    #     documentation and/or other materials provided with the distribution.
    #   * Neither the name of the author of this software nor the name of
    #     contributors to this software may be used to endorse or promote products
    #     derived from this software without specific prior written consent.
    #
    # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    # ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
    # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    # POSSIBILITY OF SUCH DAMAGE.
    ###

    """
    Add the module docstring here.  This will be used by the setup.py script.
    """

    from baseplugin import *

    import utils
    import privmsgs
    import callbacks

    def configure(onStart, afterConnect, advanced):
        # This will be called by setup.py to configure this module.  onStart and
        # afterConnect are both lists.  Append to onStart the commands you would
        # like to be run when the bot is started; append to afterConnect the
        # commands you would like to be run when the bot has finished connecting.
        from questions import expect, anything, something, yn
        onStart.append('load Random')

    class Random(callbacks.Privmsg):
        pass

    Class = Random

    # vim:set shiftwidth=4 tabstop=8 expandtab textwidth=78:

### Customizing the boilerplate code

So a few notes, before we customize it.

You'll probably want to change the copyright notice to be your name. It wouldn't stick even if you kept my name, so you might as well :)

Describe what you want the plugin to do in the docstring. This is used in
in order to explain to the user the purpose of the module. It's also returned when someone asks the bot for help for a given module (instead of help for a certain command). We'll change this one to `"Lots of stuff relating to random numbers."`

Then there are the imports. The callbacks module is used (the class you're given subclasses `callbacks.Privmsg`) but the privmsgs module isn't used. That's alright; we can almost guarantee you'll use it, so we go ahead and add the import to the template.

Then you see a `configure` function. This the function that's called when users decide to add your module in
. You'll note that by default it simply adds `"load Example"` (where 'Example' is the name you provided as the name of your plugin, so in our case it is `"load Random"`) at the bottom. For many plugins this is all you need; for more complex plugins, you might need to ask questions and add commands based on the answers.

### Digging in: customizing the plugin class

Now comes the meat of the plugin: the plugin class.

What you're given is a skeleton: a simple subclass of `callbacks.Privmsg` for you to start with. Now let's add a command.

I don't know what you know about random number generators, but the short of it is that they start at a certain number (a seed) and they continue (via some somewhat complicated/unpredictable algorithm) from there. This seed (and the rest of the sequence, really) is all nice and packaged up in Python's random module, the `Random` object. So the first thing we're going to have to do is give our plugin a `Random` object.

Normally, when we want to give instances of a class an object, we'll do so in the `__init__` method. And that works great for plugins, too. The one thing you have to be careful of is that you call the superclass `__init__` method at the end of your own `__init__`. So to add this `random.Random` object to our plugin, we can replace the pass statement with this:

    def __init__(self):
            self.rng = random.Random()
            callbacks.Privmsg.__init__(self)

(`rng`is an abbreviation for "random number generator," in case you were curious)

Do be careful not to give your `__init__` any arguments (other than `self`, of course). There's no way anything will ever get to them! If you have some sort of initial values you need to get to your plugin before it can do anything interesting, add a command that gets those values. By convention, those commands begin with "start" -- check out the Relay and Enforcer plugins for examples of such commands.

There's an easier way to get our plugin to have its own rng than to define an `__init__`. Plugins are unique among classes because we're always certain that there will only be one instance -- supybot doesn't allow us to load multiple instances of a single plugin. So instead of adding the rng in `__init__`, we can just add it as a attribute to the class itself. Like so (replacing the `pass` statement again):

        rng = random.Random()

And we save two lines of code and make our code a little more clear :)

Now that we have an RNG, we need some way to get random numbers. So first, we'll add a command that simply gets the next random number and gives it back to the user. It takes no arguments, of course (what would you give it?). Here's the command, and I'll follow that with the explanation of what each part means.

        def random(self, irc, msg, args):
            """takes no arguments

            Returns the next random number generated by the random number
            generator.
            """
            irc.reply(msg, str(self.rng.random()))

And that's it! Pretty simple, huh? Anyway, you're probably wondering what all that means. We'll start with the def statement:

        def random(self, irc, msg, args):

What that does is define a command `random`. You can call it by saying "@random" (or whatever prefix character your specific bot uses). The arguments are a bit less obvious. `self` is self-evident (hah!). `irc` is the `Irc` object passed to the command; `msg` is the original `IrcMsg` object. But you're really not going to have to deal with either of these too much (with the exception of calling `irc.reply` or `irc.error`). What you're really interested in is the `args` arg. That if a list of all the arguments passed to your command, pre-parsed and already evaluated (i.e., you never have to worry about nested commands, or handling double quoted strings, or splitting on whitespace -- the work has already been done for you). You can read about the `Irc` object in `irclib.py` (you won't find `.reply` or `.error` there, though, because you're actually getting an `IrcObjectProxy`, but that's beyond the level we want to describe here :)). You can read about the `msg` object in `ircmsgs.py`. But again, aside from calling `irc.reply` or `irc.error`, you'll very rarely be using these objects.

(In case you're curious, the answer is yes, you must name your arguments `(self, irc, msg, args)`. The names of those arguments is one of the ways that supybot uses to determine which methods in a plugin class are commands and which aren't. And while we're talking about naming restrictions, all your commands should be named in all-lowercase with no underscores. Before calling a command, supybot always converts the command name to lowercase and removes all dashes and underscores. On the other hand, you now know an easy way to make sure a method is never called (even if its arguments are `(self, irc, msg, args)`, however unlikely that may be). Just name it with an underscore or an uppercase letter in it :))

You'll also note that the docstring is odd. The wonderful thing about the supybot framework is that it's easy to write complete commands with help and everything: the docstring is the help! Given the above docstring, this is what a supybot does:

<angryman> jemfinch: random takes no arguments (for more help use the morehelp command) <jemfinch> $morehelp random <angryman> jemfinch: Returns the next random number from the current random number generator.

'help <command>' replies with the command name followed by the first line of the command's docstring; there should be a blank line following, and then 'morehelp <command>' will reply with the remainder of the docstring. So that explains the docstring. Now on to the actual body of the function:

        irc.reply(msg, str(self.rng.random()))

`irc.reply` takes two arguments, an `IrcMsg` (like the one passed into your function) and a string. The `IrcMsg` is used to determine who the reply should go to and whether or not it should be sent in private message (commands sent in private are replied to in private). The string is the reply to be sent. Don't worry about length restrictions or anything -- if the string you want to send is too big for an IRC message (and oftentimes that turns out to be the case :)) the supybot framework handles that entirely transparently to you. Do make sure, however, that you give `irc.reply` a string. It doesn't take anything else (sometimes even unicode fails!). That's why we have "str(self.rng.random())" instead of simply "self.rng.random()" -- we had to give `irc.reply` a string.

Anyway, now that we have an RNG, we have a need for seed! Of course, Python gives us a good seed already (it uses the current time as a seed if we don't give it one) but users might want to be able to repeat "random" sequences, so letting them set the seed is a good thing. So we'll add a seed command to give the RNG a specific seed:

        def seed(self, irc, msg, args):
            """<seed>

            Sets the seed of the random number generator.  <seed> must be
            an int or a long.
            """
            seed = privmsgs.getArgs(args)
            try:
                seed = long(seed)
            except ValueError:
                # It wasn't a valid long!
                irc.error(msg, '<seed> must be a valid int or long.')
                return
            self.rng.seed(seed)
            irc.reply(msg, conf.replySuccess)

So this one's a bit more complicated. But it's still pretty simple. The method name is "seed" so that'll be the command name. The arguments are the same, the docstring is of the same form, so we don't need to go over that again. The body of the function, however, is significantly different.

`privmsgs.getArgs` is a function you're going to be seeing a lot of when you write plugins for supybot. What it does is basically give you the right number of arguments for your comamnd. In this case, we want one argument. But we might have been given any number of arguments by the user. So `privmsgs.getArgs` joins them appropriately, leaving us with one single "seed" argument (by default, it returns one argument as a single value; more arguments are returned in a tuple/list). Yes, we could've just said "seed = args[0]" and gotten the first argument, but what if the user didn't pass us an argument at all? Then we've got to catch the `IndexError` from `args[0]` and complain to the user about it. `privmsgs.getArgs`, on the other hand, handles all that for us. If the user didn't give us enough arguments, it'll reply with the help string for the command, thus saving us the effort.

So we have the seed from `privmsgs.getArgs`. But it's a string. The next three lines is pretty darn obvious: we're just converting the string to a int of some sort. But if it's not, that's when we're going to call `irc.error`. It has the same interface as we saw before in `irc.reply`, but it makes sure to remind the user that an error has been encountered (currently, that means it puts "Error: " at the beginning of the message). After erroring, we return. It's important to remember this return here; otherwise, we'll just keep going down through the function and try to use this "seed" variable that never got assigned. A good general rule of thumb is that any time you use `irc.error`, you'll want to return immediately afterwards.

Then we set the seed -- that's a simple function on our rng object. Assuming that succeeds (and doesn't raise an exception, which it shouldn't, because we already read the documentation and know that it should work) we reply to say that everything worked fine. That's what `conf.replySuccess` says. By default, it has the very dry (and appropriately robot-like) "The operation succeeded." but you're perfectly welcome to customize it yourself -- `conf.py` was written to be modified!

So that's a bit more complicated command. But we still haven't dealt with multiple arguments. Let's do that next.

So these random numbers are useful, but they're not the kind of random numbers we usually want in Real Life. In Real Life, we like to tell someone to "pick a number between 1 and 10." So let's write a function that does that. Of course, we won't hardcode the 1 or the 10 into the function, but we'll take them as arguments. First the function:

        def range(self, irc, msg, args):
            """<start> <end>

            Returns a number between <start> and <end>, inclusive (i.e., the number
            can be either of the endpoints.
            """
            (start, end) = privmsgs.getArgs(args, required=2)
            try:
                end = int(end)
                start = int(start)
            except ValueError:
                irc.error(msg, '<start> and <end> must both be integers.')
                return
            # .randrange() doesn't include the endpoint, so we use end+1.
            irc.reply(msg, str(self.rng.randrange(start, end+1)))

Pretty simple. This is becoming old hat by now. The only new thing here is the call to `privmsgs.getArgs`. We have to make sure, since we want two values, to pass a keyword parameter "required" into `privmsgs.getArgs`. Of course, `privmsgs.getArgs` handles all the checking for missing arguments and whatnot so we don't have to.

The `Random` object we're using offers us a "sample" method that takes a sequence and a number (we'll call it `N`) and returns a list of `N` items taken randomly from the sequence. So I'll show you an example that takes advantage of multiple arguments but doesn't use `privmsgs.getArgs` (and thus has to handle its own errors if the number of arguments isn't right). Here's the code:

        def sample(self, irc, msg, args):
            """<number of items> [<text> ...]

            Returns a sample of the <number of items> taken from the remaining
            arguments.  Obviously <number of items> must be less than the number
            of arguments given.
            """
            try:
                n = int(args.pop(0))
            except IndexError: # raised by .pop(0)
                raise callbacks.ArgumentError
            except ValueError:
                irc.error(msg, '<number of items> must be an integer.')
                return
            if n > len(args):
                irc.error(msg, '<number of items> must be less than the number '
                               'of arguments.')
                return
            sample = self.rng.sample(args, n)
            irc.reply(msg, utils.commaAndify(map(repr, sample)))

Most everything here is familiar. The difference between this and the previous examples is that we're dealing with `args` directly, rather than through `getArgs`. Since we already have the arguments in a list, it doesn't make any sense to have `privmsgs.getArgs` smush them all together into a big long string that we'll just have to re-split. But we still want the nice error handling of `privmsgs.getArgs`. So what do we do? We raise `callbacks.ArgumentError`! That's the secret juju that `privmsgs.getArgs` is doing; now we're just doing it ourself. Someone up our callchain knows how to handle it so a neat error message is returned. So in this function, if `.pop(0)` fails, we weren't given enough arguments and thus need to tell the user how to call us.

So we have the args, we have the number, we do a simple call to `random.sample` and then we do this funky `utils.commaAndify` to it. Yeah, so I was running low on useful names :) Anyway, what it does is take a list of strings and return a string with them joined by a comma, the last one being joined with a comma and "and". So the list ['foo', 'bar', 'baz'] becomes "foo, bar, and baz". It's pretty useful for showing the user lists in a useful form. We map the strings with `repr()` first just to surround them with quotes.

So we have one more example. Yes, I hear your groans, but it's pedagogically useful :) This time we're going to write a command that makes the bot roll a die. It'll take one argument (the number of sides on the die) and will respond with the equivalent of "/me rolls a __" where __ is the number the bot rolled. So here's the code:

        def diceroll(self, irc, msg, args):
            """[<number of sides>]

            Rolls a die with <number of sides> sides.  The default number
            of sides is 6.
            """
            try:
                n = privmsgs.getArgs(args, required=0, optional=1)
                if not n:
                    n = 6
                n = int(n)
            except ValueError:
                irc.error(msg, 'Dice have integer numbers of sides.  Use one.')
                return
            s = 'rolls a %s' % self.rng.randrange(1, n+1)
            irc.queueMsg(ircmsgs.action(ircutils.replyTo(msg), s))
            raise callbacks.CannotNest

There's a lot of stuff you haven't seen before in there. The most important, though, is the first thing you'll notice that's different: the `privmsg.getArgs` call. Here we're offering a default argument in case the user is too lazy to supply one (or just wants a nice, standard six-sided die :)) `privmsgs.getArgs` supports that; we'll just tell it that we don't need any arguments (via `required=0`) and that we might like one argument (`optional=1`). If the user provides an argument, we'll get it -- if they don't, we'll just get an empty string. Hence the "if not n: n = 6", where we provide the default.

Later, though, you'll see something other than `irc.reply`. This is `irc.queueMsg`, the general interface for sending messages to the server. It's what `irc.reply` is using under the covers. It takes an `IrcMsg` object. Fortunately, that's exactly what's returned by `ircmsgs.action`. An action message, just in case you don't know, is a /me kind of message. `ircmsgs.action` is a helper function that takes a target (a place to send the message, either a channel or a person) and a payload (the thing to /me) and returns the appropriate `IrcMsg` object. `ircutils.replyTo` simply takes an `IrcMsg` and returns where we should reply to; if the message was originally sent to a channel, we'll reply to there, if it was originally sent to us privately, we'll reply in private.

At the end, you might be surprised by the "raise callbacks.CannotNest". That's used simply because at the moment you can't nest actions (just like you can't nest anything that doesn't go through `irc.reply`). That raise just makes sure the user finds this out if he tries to nest this like "@rot13 [diceroll]".

So that's our plugin. 5 commands, each building in complexity. You should now be able to write most anything you want to do in Supybot. Except regexp-based plugins, but that's a story for another day (and those aren't nearly as cool as these command-based callbacks anyway :)). Now we need to flesh it out to make it a full-fledged plugin.

### Finishing touches

Let's take a look at that `configure` function
made for us. Here it is, in case you've forgotten:

    def configure(onStart, afterConnect, advanced):
        # This will be called by setup.py to configure this module.  onStart and
        # afterConnect are both lists.  Append to onStart the commands you would
        # like to be run when the bot is started; append to afterConnect the
        # commands you would like to be run when the bot has finished connecting.
        from questions import expect, anything, something, yn
        onStart.append('load Random')

You remember when you first started running supybot and ran
and it asked you all those questions? Well, now's your chance to ask other users some questions of your own. In our case, with our Random plugin, it might be nice to offer the user the ability to specify a seed to use whenever the plugin is loaded. So let's ask him if he wants to do that, and if so, let's ask him what the seed should be.

    def configure(onStart, afterConnect, advanced):
        # This will be called by setup.py to configure this module.  onStart and
        # afterConnect are both lists.  Append to onStart the commands you would
        # like to be run when the bot is started; append to afterConnect the
        # commands you would like to be run when the bot has finished connecting.
        from questions import expect, anything, something, yn
        onStart.append('load Random')
        if yn('Do you want to specify a seed to be used for the RNG')=='y':
            seed = something('What seed?  It must be an int or long.')
            while not seed.isdigit():
                print 'That\'s not a valid seed.'
                seed = something('What seed?')
            onStart.append('seed %s' % seed)

As you can see, what the questions module does is fairly self-evident: `yn` returns either 'y' or 'n'; `something` returns something (but not nothing; for nothing, you'd want `anything`). So basically we ask some questions until we get a good seed. Then we do this "onStart.append('seed %s' % seed)" doohickey. `onStart` is a list of the commands to run when the bot starts; we're just throwing our little piece into it. These commands will then be written into the template
creates for the bot.

We've written our own plugin from scratch (well, from the boilerplate that we got from
:)) and survived! Now go write more plugins for supybot, and send them to me so I can use them too :)