Word game IRC bot, as a Cinch plugin

word_game.rb

require 'cinch'

class Cinch::Plugins::WordGame
  include Cinch::Plugin

  match(/word start/, method: :start)
  def start(m)
    @word = DictionaryWord.new("/etc/dictionaries-common/words")
    @guesses = 0
    m.reply "Starting a new word game. Make a guess."
  end

  match(/word cheat/, method: :cheat)
  def cheat(m)
    if @word
      m.reply "You want to cheat after #{@guesses} guesses? Fine. The word is #{@word.word}. #{m.user}: you suck."
    end
  end

  match(/guess (\S+)/, method: :guess)
  def guess(m, word)
    if @word
      @guesses += 1
      if @word == word
        m.reply("Yes, that's the word! Congratulations, #{m.user} wins! You had #{@guesses} guesses.")
      else
        m.reply("My word comes #{@word.before_or_after(word)} \"#{word}\". You've had #{@guesses} guesses.")
      end
    else
      m.reply("I haven't started a word game yet. Use !word to start one.")
    end
  end

  class DictionaryWord
    attr_accessor :word

    def initialize(filename)
      begin
        word = random_line(filename)
      end until word[0] == word[0].downcase # remove proper nouns

      @word = word.gsub(/'.*/, '') # Remove apostrophes
    end

    def before?(word)
      @word < word.downcase
    end

    def before_or_after(word)
      before?(word) ? "before" : "after"
    end

    def ==(word)
      @word == word
    end

  private
    def random_line(filename)
      blocksize, line = 1024, ""
      File.open(filename) do |file|
        initial_position = rand(File.size(filename) - 1) + 1 # random pointer position. Not a line number!
        pos = Array.new(2, initial_position) # array [prev_position, current_position]

        # Find beginning of current line
        begin
          pos.push([pos[1] - blocksize, 0].max).shift # calc new position
          file.pos = pos[1] # move pointer backward within file
          offset = (n = file.read(pos[0] - pos[1]).rindex(/\n/) ) ? n+1 : nil
        end until pos[1] == 0 || offset
        file.pos = pos[1] + offset.to_i

        # Collect line text till the end
        begin
          data = file.read(blocksize)
          line.concat((p = data.index(/\n/)) ? data[0,p.to_i] : data)
        end until file.eof? or p
      end
      line
    end
  end

end