lib/interaction/undo_manager.rb

   1 # Copyright (c) 2009 Paolo Capriotti <p.capriotti@gmail.com>
   2 #
   3 # This program is free software; you can redistribute it and/or modify
   4 # it under the terms of the GNU General Public License as published by
   5 # the Free Software Foundation; either version 2 of the License, or
   6 # (at your option) any later version.
   7
   8 require 'observer_utils'
   9
  10 class UndoManager
  11   include Observable
  12   DuplicateUndoInformation = Class.new(Exception)
  13   NoSuchPlayer = Class.new(Exception)
  14
  15   def initialize(players)
  16     @players = { }
  17     players.each do |player|
  18       @players[player] = nil
  19     end
  20   end
  21
  22   def undo(player, moves, opts = { })
  23     unless @cancelled
  24       raise NoSuchPlayer unless @players.has_key?(player)
  25       unless @players[player].nil?
  26         raise DuplicateUndoInformation.new(
  27           "player #{player.inspect} already specified undo information")
  28       end
  29       @players[player] = {
  30         :moves => moves,
  31         :more => opts[:allow_more] }
  32       if @players.all?{|p, info| info }
  33         common = find_common
  34         fire :complete => common
  35         fire :execute => common
  36       end
  37     end
  38   end
  39
  40   def cancel
  41     @cancelled = true
  42     fire :complete => nil
  43   end
  44
  45   private
  46
  47   def find_common
  48     common = 1
  49     common_more = true
  50
  51     @players.each do |player, data|
  52       if data
  53         return nil unless data[:moves]
  54         if common.nil? || data[:moves] > common
  55           return nil unless common_more
  56           common = data[:moves]
  57           common_more = data[:more]
  58         elsif data[:moves] < common
  59           return nil unless data[:more]
  60         end
  61       end
  62     end
  63
  64     common
  65   end
  66 end