From b09b46607ade798e28b6edda44ba169fc6c7f37c Mon Sep 17 00:00:00 2001
From: PIRANUT_PHLANG <piranutphlong@gmail.com>
Date: Tue, 13 May 2025 14:48:53 +0200
Subject: [PATCH] implement SEF and Negamax

---
 src/backend/AutoPlayer.java | 61 +++++++++++++++++++++++++++++++++++++
 src/backend/Board.java      | 16 ++++++++++
 src/backend/Game.java       |  7 +++--
 3 files changed, 82 insertions(+), 2 deletions(-)

diff --git a/src/backend/AutoPlayer.java b/src/backend/AutoPlayer.java
index 960d406..5510750 100644
--- a/src/backend/AutoPlayer.java
+++ b/src/backend/AutoPlayer.java
@@ -36,6 +36,67 @@ public class AutoPlayer {
     return possibleMoves.get(rand.nextInt(possibleMoves.size()));
 		
 	}
+	// Negamax search
+	public int negamax(Board board, int depth, int color) {
+	    if (depth == 0) {
+	        return color * board.evaluateBoard();
+	    }
+
+	    int bestScore = Integer.MIN_VALUE;
+
+	    for (Move move : getAllPossibleMoves(board)) {
+	        board.playMove(move);
+	        int score = -negamax(board, depth - 1, -color);
+	        board.undoLastMove();
+
+	        if (score > bestScore) {
+	            bestScore = score;
+	        }
+	    }
+
+	    return bestScore;
+	}
+
+	// Get best move using negamax
+	public Move getBestMoveUsingNegamax(Board board, int depth) {
+	    int bestScore = Integer.MIN_VALUE;
+	    Move bestMove = null;
+	    int color = board.isTurnWhite() ? 1 : -1;
+
+	    for (Move move : getAllPossibleMoves(board)) {
+	        board.playMove(move);
+	        int score = -negamax(board, depth - 1, -color);
+	        board.undoLastMove();
+
+	        if (score > bestScore) {
+	            bestScore = score;
+	            bestMove = move;
+	        }
+	    }
+
+	    return bestMove;
+	}
+
+	// Helper to get all legal moves for current player
+	private ArrayList<Move> getAllPossibleMoves(Board board) {
+	    ArrayList<Move> possibleMoves = new ArrayList<>();
+	    boolean isWhiteTurn = board.isTurnWhite();
+
+	    for (Piece piece : board.getPieces()) {
+	        if (piece.isWhite() == isWhiteTurn) {
+	            ArrayList<int[]> legalPositions = board.getLegalMoves(piece);
+	            for (int[] pos : legalPositions) {
+	                Piece target = board.getPieceAt(pos[0], pos[1]);
+	                Move move = new Move(piece, piece.getX(), piece.getY(), pos[0], pos[1], target);
+	                possibleMoves.add(move);
+	            }
+	        }
+	    }
+
+	    return possibleMoves;
+	}
+
+	
 	
 	
 }
diff --git a/src/backend/Board.java b/src/backend/Board.java
index fc7469a..474b9bd 100644
--- a/src/backend/Board.java
+++ b/src/backend/Board.java
@@ -353,5 +353,21 @@ public void undoLastMove() {
 		    selected = null;
 		    highlighted.clear();
 		}
+	public int evaluateBoard() {
+	    int score = 0;
+	    for (Piece piece : pieces) {
+	        int value = 0;
+	        switch (piece.getType()) {
+	            case Pawn: value = 100; break;
+	            case Knight: value = 320; break;
+	            case Bishop: value = 330; break;
+	            case Rook: value = 500; break;
+	            case Queen: value = 900; break;
+	        }
+	        if (piece.isWhite()) score += value;
+	        else score -= value;
+	    }
+	    return score;
+	}
 
 }  
\ No newline at end of file
diff --git a/src/backend/Game.java b/src/backend/Game.java
index 4c64f70..3834699 100644
--- a/src/backend/Game.java
+++ b/src/backend/Game.java
@@ -48,8 +48,11 @@ public class Game extends Thread {
 	}
 
 	private void aiPlayerTurn() {
-		if(isAITurn()) {
-			board.playMove(aiPlayer.computeBestMove(new Board(board)));
+		if (isAITurn()) {
+			Move bestMove = aiPlayer.getBestMoveUsingNegamax(board, 2); // Change depth as needed
+			if (bestMove != null) {
+				board.playMove(bestMove);
+			}
 		}
 	}