Simple IRC bot

#!/usr/bin/ruby
%w(rubygems socket yaml).each { |lib| require lib }

class Bot
  attr_reader :nick, :server, :port, :options, :server_info, :server_message
  
  def initialize(nick, server, port, options = {}, &block)
    @nick = nick
    @server = server
    @port = port
    @options = options
    @event_handlers = []
    @socket = TCPsocket.open(server, port)

    install_exit_handler
    on("PING") { write "PONG #{server_message}" }

    instance_eval(&block)

    nick @nick
    user @nick

    while true
      line = @socket.readline; puts line
      fire_events(line)
      sleep 0.1
    end
  end

  def on(event, &block)
    code = lookup_event_code(event)

    handler = if code == 0
                lambda { |line| instance_eval(&block) if line =~ /#{event}/i }
              else
                lambda { |line| instance_eval(&block) }
              end

    (@event_handlers[code] ||= []) << handler
  end

  def fire_events(line)
    @server_info, @server_message = line.sub(/^:/, "").split(":")
    @server_info =~ /(\d{3})/

    if handlers = @event_handlers[$1.to_i]
      handlers.each { |h| h.call(line) }
    end
  end

  def write(string)
    @socket.write(string + "\n")
  end

  def quit 
    write "QUIT"
  end

  def nick(nick)
    write "NICK #{nick}"
  end

  def user(nick, realname = nil)
    write "USER #{nick} 8 * :#{realname || nick}"
  end

  def join(channel)
    write "JOIN #{channel}"
  end

  def say(to, message)
    write "PRIVMSG #{to} #{message}"
  end

  private

  def install_exit_handler
    exit_handler = lambda { quit; @socket.close }
    %w(INT TRAP).each { |signal| trap(signal, exit_handler) }
  end

  def lookup_event_code(event)
    @event_codes ||= YAML.load_file("irc-events.yml")
    @event_codes.find { |k, v| v == event.to_s }.first rescue 0
  end

end

# Usage

Bot.new("mybot", "irc.freenode.net", "6667") do
  on :endofmotd do
    join "#mychannel"
    say "#mychannel", "hello"
  end
end