From: Ruby Quiz <james@...>
Date: 2005-12-09T22:27:31+09:00
Subject: [QUIZ] Kalah (#58)

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by Mark Van Holstyn

For my Computer Science class this month, we had to program a Kalah Player.
Sadly, we had to do our project in Java, but I ported the game code and the
sample players to ruby for this quiz though.

A good explanation of the game can be found at:

	http://rubyurl.com/SqU

Your task is to create the best Kalah player you can. The player should look
like the following:

	class HumanPlayer < Player
		def choose_move
			print 'Enter your move choice: '
			gets.chomp.to_i
		end
	end

The 'choose_move' method is what the game will call to request a move from the
player. The Player class which you player should extend looks like so:

	class Player
		attr_accessor :name
		attr_writer :game, :side
	
		def initialize( name )
			@name = name
		end
	  
		def choose_move
			if @side==KalahGame::TOP
				(7..12).each { |i| return i if @game.stones_at?(i) > 0 }
			else
				(0..5).each { |i| return i if @game.stones_at?(i) > 0 }
			end
		end
	end

The 'game' and 'side' attributes will be assigned by KalahGame. The side will
either be the constant KalahGame::TOP or KalahGame::BOTTOM. This is what you
will use to determine if you should be making moves from bowls 0-5 or 7-12 and
whether your Kalah is 6 or 13.

KalahMatch plays two games, one with each player on the each side of the board
and then averages their scores, so you must make you player be able to play both
on the top and the bottom.

Here's a sample game engine to get you started:

	require 'Player'
	require 'HumanPlayer'
	
	class KalahMatch
		def start( p1, p2 )
			puts ''
			puts '========== GAME 1 =========='
			p1_score_1, p2_score_1 = KalahGame.new.play_game( p1, p2 )
	    
			if p1_score_1 > p2_score_1
				puts p1.name+' won game #1: '+p1_score_1.to_s+'-'+p2_score_1.to_s
			elsif p2_score_1 > p1_score_1
				puts p2.name+' won game #1: '+p2_score_1.to_s+'-'+p1_score_1.to_s
			else
				puts 'game #1 was a tie: '+p1_score_1.to_s+'-'+p2_score_1.to_s
			end
	    
			puts ''
			puts '========== GAME 2 =========='		
			p2_score_2, p1_score_2 = KalahGame.new.play_game( p2, p1 )
	    
			if p1_score_2 > p2_score_2
				puts p1.name+' won game #2: '+p1_score_2.to_s+'-'+p2_score_2.to_s
			elsif p2_score_2 > p1_score_2
				puts p2.name+' won game #2: '+p2_score_2.to_s+'-'+p1_score_2.to_s
			else
				puts 'game #2 was a tie: '+p1_score_2.to_s+'-'+p2_score_2.to_s
			end
	    
			puts ''
			puts '========== FINAL =========='
	    
			p1_final = p1_score_1+p1_score_2
			p2_final = p2_score_1+p2_score_2
	    
			if p1_final > p2_final
				puts p1.name+' won the match: '+p1_final.to_s+'-'+p2_final.to_s
			elsif p2_final > p1_final
				puts p2.name+' won the match: '+p2_final.to_s+'-'+p1_final.to_s
			else
				puts 'the match was tied overall : '+p1_final.to_s+'-'+p2_final.to_s
			end
		end	
	end
	
	class KalahGame
		NOBODY = 0
		TOP = 1
		BOTTOM = 2
	  
		def stones_at?( i )
			@board[i]
		end
	  
		def legal_move?( move )
			( ( @player_to_move==TOP and move >= 7 and move <= 12 ) || 
				( @player_to_move==BOTTOM and move >= 0 and move <= 5 ) ) and
			@board[move] != 0
		end
	  
		def game_over?
			top = bottom = true
			(7..12).each { |i| top = false if @board[i] > 0 }
			(0..5).each { |i| bottom = false if @board[i] > 0 }
			top or bottom
		end
	  
		def winner
			top, bottom = top_score, bottom_score
			if top > bottm
				return TOP
			elsif bottom > top
				return BOTTOM
			else
				return NOBODY
			end
		end
	  
		def top_score
			score = 0
			(7..13).each { |i| score += @board[i] }
			score
		end
	  
		def bottom_score
			score = 0
			(0..6).each { |i| score += @board[i] }
			score
		end
	  
		def make_move( move )
			( puts 'Illegal move...' ; return ) unless legal_move?( move )
	    
			stones, @board[move] = @board[move], 0
	    
			pos = move+1
			while stones > 0
				pos+=1 if( (@player_to_move==TOP and pos==6) ||
				           (@player_to_move==BOTTOM and pos==13) )
				pos = 0 if pos==14
				@board[pos]+=1
				stones-=1
				pos+=1 if stones > 0
			end
	    
			if( @player_to_move==TOP and pos>6 and pos<13 and @board[pos]==1 )
				@board[13] += @board[12-pos]+1
				@board[12-pos] = @board[pos] = 0
			elsif( @player_to_move==BOTTOM and pos>=0 and pos<6 and @board[pos]==1 )
				@board[6] += @board[12-pos]+1
				@board[12-pos] = @board[pos] = 0
			end
	    
			if @player_to_move==TOP
				@player_to_move = BOTTOM unless pos == 13
			else
				@player_to_move=TOP unless pos == 6
			end
	    
		end
	  
		def display
			puts ''
			top = '    '
			[12,11,10,9,8,7].each { |i| top += @board[i].to_s+'  ' }
			puts top
			puts @board[13].to_s + '                     ' + @board[6].to_s
			bottom = '    '
			(0..5).each { |i| bottom += @board[i].to_s+'  ' }
			puts bottom
			puts ''
		end
	  
		def reset	
			@board = Array.new( 14, 4 )
			@board[6] = @board[13] = 0	
			@player_to_move = BOTTOM
		end
	  
		def play_game( bottom, top )
			reset
	    
			bottom.side = BOTTOM
			top.side = TOP
			top.game = bottom.game = self
	    
			puts bottom.name+' starts...'
			display
	    
			until game_over?
				puts ''
				if @player_to_move == TOP
					move = top.choose_move
					puts top.name+' choose move '+move.to_s
				else
					move = bottom.choose_move
					puts bottom.name+' choose move '+move.to_s
				end
				make_move( move )
				display		
			end
	    
			[top_score, bottom_score]		
		end
	end
	
	p1 = Player.new( 'Player 1' )
	p2 = Player.new( 'Player 2' )
	KalahMatch.new.start( p1, p2 )