// Copyright by Barry G. Becker, 2011. Licensed under MIT License: http://www.opensource.org/licenses/MIT
package com.barrybecker4.game.twoplayer.go.board.move;
import com.barrybecker4.game.common.Move;
import com.barrybecker4.game.common.MoveList;
import com.barrybecker4.game.twoplayer.common.TwoPlayerMove;
import com.barrybecker4.game.twoplayer.go.board.GoBoard;
import com.barrybecker4.game.twoplayer.go.board.elements.position.GoBoardPosition;
import java.util.Iterator;
/**
* Responsible for determining a set of reasonable next moves.
*
* @author Barry Becker
*/
public final class UrgentMoveGenerator {
/**
* Size of group that needs to be in atari before we consider a group urgent.
* Perhaps this should be one.
*/
private static final int CRITICAL_GROUP_SIZE = 3;
private final GoBoard board_;
/**
* Constructor.
*/
public UrgentMoveGenerator(GoBoard board) {
board_ = board;
}
/**
* @param moves all possible moves from the current board state for player to move next.
* @param lastMove last stone placed on board
* @return urgent moves from this position.
*/
public final MoveList generateUrgentMoves( MoveList moves, TwoPlayerMove lastMove) {
GoMove lastMovePlayed = (GoMove) lastMove;
// just keep the moves that take captures
Iterator<Move> it = moves.iterator();
while ( it.hasNext() ) {
GoMove move = (GoMove) it.next();
// urgent if we capture or atari other stones.
boolean isUrgent = move.getNumCaptures() > 0 || putsGroupInAtari(lastMovePlayed);
if (isUrgent) {
move.setUrgent(true);
}
else {
it.remove();
}
}
return moves;
}
/**
* @return true if move is in danger (jeopardy).
*/
public static boolean inJeopardy(GoMove move, GoBoard board) {
return (move.numStonesAtaried(board) >= CRITICAL_GROUP_SIZE);
}
/**
* Determine if the last move caused atari on another group (without putting ourselves in atari).
* @param lastMovePlayed last position just played.
* @return true if the lastMovePlayed puts the lastPositions string in atari.
*/
private boolean putsGroupInAtari(GoMove lastMovePlayed) {
GoBoardPosition lastPos = (GoBoardPosition) board_.getPosition(lastMovePlayed.getToLocation());
return (lastMovePlayed.numStonesAtaried(board_) >= CRITICAL_GROUP_SIZE
&& lastPos.getString().getNumLiberties(board_) > 1);
}
}