package backend;

import java.util.ArrayList;
import java.util.Random;

public class AutoPlayer {

    public Move computeBestMove(Board board) {
        boolean isWhite = board.isTurnWhite();
        ArrayList<Move> allMoves = new ArrayList<>();
        ArrayList<Piece> pieces = board.getPieces();

        for (int i = 0; i < pieces.size(); i++) {
            Piece piece = pieces.get(i);

            if (piece.isWhite() == isWhite) {
                ArrayList<int[]> moves = board.getValidMoves(piece);

                for (int j = 0; j < moves.size(); j++) {
                    int[] moveCoords = moves.get(j);
                    int toX = moveCoords[0];
                    int toY = moveCoords[1];
                    
                    int fromX = piece.getX();
                    int fromY = piece.getY(); 
                    
                    Piece captured = board.getPieceAt(toX, toY);

                 // Detect en passant
                    if (piece.getType() == PieceType.Pawn && board.isEnPassant() && toX == board.getXCoordinatePawn() &&
                     toY == (piece.isWhite() ? board.getYCoordinatePawn() - 1 : board.getYCoordinatePawn() + 1)) {

                     captured = board.getPieceAt(board.getXCoordinatePawn(), board.getYCoordinatePawn());
                 }
                 
                 // --- Castling detection ---
                    if (piece.getType() == PieceType.King && Math.abs(toX - fromX) == 2 && toY == fromY) {
                     System.out.println("AI considering castling move.");
                     // No need to set captured, just allow the move
                 }

                 Move move = new Move(piece, piece.getX(), piece.getY(), toX, toY, captured);
                    allMoves.add(move);
                }
            }
        }

        if (allMoves.isEmpty()) {
            return null; // no legal moves → maybe stalemate or checkmate
        }

        // === Basic Evaluation: Prefer capturing higher-value pieces ===
        Move bestMove = allMoves.get(0);
        int bestScore = evaluateCapture(bestMove.getCaptured());

        for (int i = 1; i < allMoves.size(); i++) {
            Move move = allMoves.get(i);
            int score = evaluateCapture(move.getCaptured());

            if (score > bestScore) {
                bestMove = move;
                bestScore = score;
            }
        }

        return bestMove;
    }

    // Simple evaluation: return value of captured piece, or 0 if no capture
    private int evaluateCapture(Piece captured) {
        if (captured == null) return 0;

        PieceType type = captured.getType();

        if (type == PieceType.Pawn) return 1;
        if (type == PieceType.Knight || type == PieceType.Bishop) return 3;
        if (type == PieceType.Rook) return 5;
        if (type == PieceType.Queen) return 9;
        return 0; // king shouldn't be captured anyway
    }
}