/* finin@Umbc.edu, 2001

  a simple minimax algorithm for playing two person games.  To define
  the game, provide definitions for

   start(S) -- true if S is the initial game state.
   move(S1,S2) - true if there is a legal move from state S1 to S2.
   win(P,S) -- true if state S is a win for player P.
   draw(S) -- true of state S is a draw
   eval(S,V) -- true if the static evaluator for state S is V
     (with positive being good for player 1 and negative for player 2).
   printBoard(S) -- prints the curent board

  We assume that a state is of the form s(P,B) where P is the player
  whose turn is next (1 or 2) and B represents the "board position".

*/


:- use_module(mm).

play :- play(2).

% play(N) uses a lookahed depth of N for both players.
play(N) :- play(N,N).

% play(N1,N2) plays a game with a look ahead depth of N! for player 1
% and N2 for player2.

play(N1,N2) :-
  start(S),
  showState(S),
  play(N1,N2,S).

play(_,_,S) :-
  % the game is over if someone has won.
  win(P,S),
  format("Player ~p has won.\n",[P]).

play(_,_,S) :-
  % the game is over if it's a draw
  draw(S),
  format("The game has ended in a draw.\n",[]).

play(N1,N2,S) :-
  % chose the best move and continue playing from there.
  mm(N1,S,S2,_),
  showState(S2),
  play(N2,N1,S2).
	
showState(s(Player,Board)) :-
  format("~p's move.\n",[Player]),
  printBoard(Board) -> true | defaultPrintBoard(Board).

defaultPrintBoard(B) :-  format(" ~p\n",[B]).