Ruby Forum Ruby > IRC Teams (#221)

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## IRC Teams (#221)

Tashi dele Rubyists,

This week's quiz was suggested by [Martin DeMello][1]

A common feature in IRC-based games is the ability to create and join
teams. The game bot sits in the channel and watches for messages in a
certain format, which it interprets as commands. Write a small gamebot
that accepts the following commands:

create team <teamname>
join <teamname>
leave team
show teams
show team <teamname>
show my team
delete team <teamname>
reset

Here's a typical transcript

<foo> create team ruby
<bot> - created team ruby -
<bar> create team python
<bot> - created team python -
<foo> show teams
<bot> teams: ruby, python
<foo> show team ruby
<bot> team ruby: foo
<bar> show my team
<bot> bar is in team python
<baz> join ruby
<bot> baz is now in team ruby
<bar> show team ruby
<bot> team ruby: foo, baz

Think up some useful extensions, such as the ability to join a user
rather than a team, and restricting some commands like reset to ops.
There are plenty of IRC bot libraries out there, go explore! If one
already does team formation, that's cheating, though :)

Have fun!

[1]: http://zem.novylen.net

The main idea behind this quiz was to show how easy it is to get an
irc bot up and running in ruby, especially given the number of bot
frameworks out there. I chose to base my bot on rif
[http://gitorious.org/ruby-irc], a nice lightweight library with
everything I needed to get started immediately.

The code consists of a Teams class, which does all the actual work of
maintaining teams, and a TeamBot, which inherits from RIF::Bot and
handles the IRC part of it. For the sake of simplicity, the bot
frontend does no real validation; it just unpacks an incoming message
into a command and arguments, and blindly sends those arguments to the
Teams  object. All public methods on the Teams object accept a player
name as a first argument, whether they need it or not, and return
either a string or an array of strings, or raise an exception. The bot
sends the return value to the channel; an array is sent one message at
a time.

-------------------------------------------------------------------------------------

gem 'rif'
require 'rif/bot'

class TeambotError < Exception
end

def TeambotError(foo)
  TeambotError.new(foo)
end

class Teams
  attr_accessor :teams, :members

  def initialize
    @teams = {}
    @members = {}
  end

  def create(player, team)
    raise TeambotError("team #{team} already created") if teams[team]
    teams[team] = true
    "created team #{team}"
  end

  def delete(player, team)
    teams.delete(team)
    members.delete_if {|k,v| v == team}
    "deleted team #{team}"
  end

  def join(player, team)
    raise TeambotError("no such team: #{team}") if not teams[team]
    members[player] = team
    "#{player} has joined team #{team}"
  end

  def leave(player, *args)
    team = members.delete(player)
    "#{player} has left team #{team}"
  end

  def reset(*args)
    @members = {}
    @teams = {}
    "deleted all teams"
  end

  def show(player, *args)
    if args[0] == 'my'
      members[player]
    elsif args[0] == 'teams'
      teams.map {|team, _| "#{team}: #{show_players(team)}"}
    elsif args[0] == 'team'
      show_players(team)
    end
  end

  private
  def players(team)
    members.select {|k,v| v == team}.keys
  end

  def show_players(team)
    players(team).join(" ")
  end
end

class TeamBot < RIF::Bot
  attr_reader :teams, :channel
  def initialize(channel, nick, server, port, username)
    @teams = Teams.new
    @channel = channel
    super(nick, server, port, username)
  end

  def on_endofmotd(event)
    join(channel)
  end

  def on_message(event)
    return unless event.channel == channel
    msg, *args = event.message.split(" ")
    player = event.nick
    begin
      *ret = teams.send(msg, player, *args)
    rescue NameError
      ret = nil
    rescue TeambotError => e
      ret = [e.message]
    end
    ret.each {|m| send_message(channel, m)} if ret
  end
end

if __FILE__ == $0
  channel = "##{ARGV[0]}"
  bot = TeamBot.new(channel, "teambot", "irc.freenode.net", 6667, "RIF 
Bot")
  bot.connect
end

martin

This week's quiz was solved by Martin DeMello.

Martin uses the [rif gem][1] to handle the nitty gritty details of
IRC, like establishing a connection and sending and receiving
messages.

The `TeamBot#on_message` method receives the messages from the users
and dispatches them to an instance of the Teams class. This is
accomplished by simply splitting the the message that was sent and
using the first part as the method to invoke. The first argument is
always the player, which is taken from the message event's `nick`
field. The rest of the message, if any, is passed as the remaining
arguments.

Let's look at a full pass through of the following sample message from 
user Bob:

    <Bob> create ruby

This will land in the bot's `on_message` method. The `event` will have
"Bob" as the nick and "create ruby" as the message. That is parsed
into the method to call and the arguments like so:

    msg, *args = event.message.split(" ")

The `teams` object is then sent the parsed message arguments with the
specified method as follows:

    *ret = teams.send(msg, player, *args)

This takes us into the create method and the team is created (if all
goes according to plan):

    def create(player, team)
      raise TeambotError("team #{team} already created") if teams[team]
      teams[team] = true
      "created team #{team}"
    end

The other actions that users may wish to perform are taken care of in
the same way. This simple and flexible solution allows for easy
modification and extension.

Thank you Martin for your solution (and also for the quiz suggestion)!

[IRC Teams (#221) - Solutions][2]

[1]: http://gitorious.org/ruby-irc
[2]: http://rubyquiz.strd6.com/quizzes/221.tar.gz