tp1/src/main/java/iialib/games/algs/algorithms/MiniMax.java

package iialib.games.algs.algorithms;

import iialib.games.algs.GameAlgorithm;
import iialib.games.algs.IHeuristic;
import iialib.games.model.IBoard;
import iialib.games.model.IMove;
import iialib.games.model.IRole;

public class MiniMax<Move extends IMove,Role extends IRole,Board extends IBoard<Move,Role,Board>> implements GameAlgorithm<Move,Role,Board> {

	// Constants
	/** Defaut value for depth limit 
     */
	private final static int DEPTH_MAX_DEFAUT = 4;

	// Attributes
	/** Role of the max player 
     */
	private final Role playerMaxRole;

	/** Role of the min player 
     */
	private final Role playerMinRole;

	/** Algorithm max depth
     */
	private int depthMax = DEPTH_MAX_DEFAUT;

	
	/** Heuristic used by the max player 
     */
	private IHeuristic<Board, Role> h;

	//
	/** number of internal visited (developed) nodes (for stats)
     */
	private int nbNodes;
	
	/** number of leaves nodes nodes (for stats)

     */
	private int nbLeaves;

	// --------- Constructors ---------

	public MiniMax(Role playerMaxRole, Role playerMinRole, IHeuristic<Board, Role> h) {
		this.playerMaxRole = playerMaxRole;
		this.playerMinRole = playerMinRole;
		this.h = h;
	}

	//
	public MiniMax(Role playerMaxRole, Role playerMinRole, IHeuristic<Board, Role> h, int depthMax) {
		this(playerMaxRole, playerMinRole, h);
		this.depthMax = depthMax;
	}

	/*
	 * IAlgo METHODS =============
	 */

	@Override
	public Move bestMove(Board board, Role playerRole) {
		System.out.println("[MiniMax]");
		nbNodes = 0;
		nbLeaves = 0;

		Move bestMove = null;
		int bestValue = IHeuristic.MIN_VALUE;

		for (Move move : board.possibleMoves(playerMaxRole)) {
			Board successor = board.play(move, playerMaxRole);
			int value = minValue(successor, 1);
			if (value > bestValue) {
				bestValue = value;
				bestMove = move;
			}
		}

		System.out.println("Nodes=" + nbNodes + " Leaves=" + nbLeaves);
		return bestMove;
	}

	/*
	 * PUBLIC METHODS ==============
	 */

	public String toString() {
		return "MiniMax(ProfMax=" + depthMax + ")";
	}

	/*
	 * PRIVATE METHODS ===============
	 */

	private int maxValue(Board board, int depth) {
		nbNodes++;
		if (board.isGameOver() || depth >= depthMax) {
			nbLeaves++;
			return h.eval(board, playerMaxRole);
		}
		int value = IHeuristic.MIN_VALUE;
		for (Move move : board.possibleMoves(playerMaxRole)) {
			Board successor = board.play(move, playerMaxRole);
			value = Math.max(value, minValue(successor, depth + 1));
		}
		return value;
	}

	private int minValue(Board board, int depth) {
		nbNodes++;
		if (board.isGameOver() || depth >= depthMax) {
			nbLeaves++;
			return h.eval(board, playerMaxRole);
		}
		int value = IHeuristic.MAX_VALUE;
		for (Move move : board.possibleMoves(playerMinRole)) {
			Board successor = board.play(move, playerMinRole);
			value = Math.min(value, maxValue(successor, depth + 1));
		}
		return value;
	}
}