import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class CheckerGame extends JFrame {
    private static final int BOARD_SIZE = 8;
    private static final int CELL_SIZE = 80;
    private static final int PIECE_RADIUS = 30;

    private Cell[][] board;
    private Piece selectedPiece;
    private boolean isWhiteTurn;

    public CheckerGame() {
        setTitle("Checker Game");
        setSize(CELL_SIZE * BOARD_SIZE, CELL_SIZE * BOARD_SIZE);
        setResizable(false);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        board = new Cell[BOARD_SIZE][BOARD_SIZE];
        selectedPiece = null;
        isWhiteTurn = true;

        addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent e) {
                int row = e.getY() / CELL_SIZE;
                int col = e.getX() / CELL_SIZE;
                handleCellClick(row, col);
            }
        });

        setFocusable(true);
        requestFocusInWindow();
    }

    public void startGame() {
        initializeBoard();
        repaint();
    }

    private void initializeBoard() {
        for (int row = 0; row < BOARD_SIZE; row++) {
            for (int col = 0; col < BOARD_SIZE; col++) {
                if ((row + col) % 2 == 0) {
                    board[row][col] = new Cell(row, col, null, Color.LIGHT_GRAY);
                } else {
                    if (row < 3) {
                        board[row][col] = new Cell(row, col, new Piece(row, col, true), Color.LIGHT_GRAY);
                    } else if (row > 4) {
                        board[row][col] = new Cell(row, col, new Piece(row, col, false), Color.LIGHT_GRAY);
                    } else {
                        board[row][col] = new Cell(row, col, null, Color.LIGHT_GRAY);
                    }
                }
            }
        }
    }

    private void handleCellClick(int row, int col) {
        if (selectedPiece == null) {
            Piece piece = board[row][col].getPiece();
            if (piece != null && piece.isWhite() == isWhiteTurn) {
                selectedPiece = piece;
            }
        } else {
            if (selectedPiece.isValidMove(row, col) && isMoveValid(row, col)) {
                movePiece(selectedPiece, row, col);
                selectedPiece = null;
                isWhiteTurn = !isWhiteTurn;
            }
        }
        repaint();
    }

    private boolean isMoveValid(int row, int col) {
        int selectedRow = selectedPiece.getRow();
        int selectedCol = selectedPiece.getCol();

        if (row < 0 || row >= BOARD_SIZE || col < 0 || col >= BOARD_SIZE) {
            return false;
        }

        if (board[row][col].getPiece() != null) {
            return false;
        }

        int rowDiff = Math.abs(row - selectedRow);
        int colDiff = Math.abs(col - selectedCol);

        if (rowDiff == 1 && colDiff == 1) {
            return true;
        } else if (rowDiff == 2 && colDiff == 2) {
            int jumpRow = (row + selectedRow) / 2;
            int jumpCol = (col + selectedCol) / 2;
            Piece jumpedPiece = board[jumpRow][jumpCol].getPiece();
            return jumpedPiece != null && jumpedPiece.isWhite() != selectedPiece.isWhite();
        }

        return false;
    }

    private void movePiece(Piece piece, int row, int col) {
        int selectedRow = piece.getRow();
        int selectedCol = piece.getCol();

        board[selectedRow][selectedCol].setPiece(null);
        board[row][col].setPiece(piece);
        piece.setRow(row);
        piece.setCol(col);
    }

    public void paint(Graphics g) {
        super.paint(g);

        for (int row = 0; row < BOARD_SIZE; row++) {
            for (int col = 0; col < BOARD_SIZE; col++) {
                Cell cell = board[row][col];
                g.setColor(cell.getColor());
                g.fillRect(col * CELL_SIZE, row * CELL_SIZE, CELL_SIZE, CELL_SIZE);

                Piece piece = cell.getPiece();
                if (piece != null) {
                    g.setColor(piece.isWhite() ? Color.WHITE : Color.BLACK);
                    g.fillOval(col * CELL_SIZE + (CELL_SIZE - PIECE_RADIUS * 2) / 2,
                            row * CELL_SIZE + (CELL_SIZE - PIECE_RADIUS * 2) / 2,
                            PIECE_RADIUS * 2, PIECE_RADIUS * 2);
                }
            }
        }
    }

    private class Cell {
        private int row;
        private int col;
        private Piece piece;
        private Color color;

        public Cell(int row, int col, Piece piece, Color color) {
            this.row = row;
            this.col = col;
            this.piece = piece;
            this.color = color;
        }

        public int getRow() {
            return row;
        }

        public int getCol() {
            return col;
        }

        public Piece getPiece() {
            return piece;
        }

        public Color getColor() {
            return color;
        }

        public void setPiece(Piece piece) {
            this.piece = piece;
        }
    }

    private class Piece {
        private int row;
        private int col;
        private boolean isWhite;

        public Piece(int row, int col, boolean isWhite) {
            this.row = row;
            this.col = col;
            this.isWhite = isWhite;
        }

        public int getRow() {
            return row;
        }

        public void setRow(int row) {
            this.row = row;
        }

        public int getCol() {
            return col;
        }

        public void setCol(int col) {
            this.col = col;
        }

        public boolean isWhite() {
            return isWhite;
        }

        public boolean isValidMove(int row, int col) {
            int rowDiff = Math.abs(row - this.row);
            int colDiff = Math.abs(col - this.col);
            return (rowDiff == 1 && colDiff == 1) || (rowDiff == 2 && colDiff == 2);
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                CheckerGame game = new CheckerGame();
                game.setVisible(true);
                game.startGame();
            }
        });
    }
}