chess/tests/unit/pieces/Bishop.test.js

/**
 * @jest-environment jsdom
 */

import { Bishop } from '../../../js/pieces/Bishop.js';
import { Board } from '../../../js/game/Board.js';

describe('Bishop', () => {
  let board;

  beforeEach(() => {
    board = new Board();
    board.clear();
  });

  describe('Diagonal Movement', () => {
    test('bishop in center can move to 13 squares', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      board.setPiece(4, 4, bishop);

      const moves = bishop.getValidMoves(board);

      // 4 diagonals: 4+3+3+3 = 13 squares
      expect(moves).toHaveLength(13);
    });

    test('bishop moves only diagonally', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      board.setPiece(4, 4, bishop);

      const moves = bishop.getValidMoves(board);

      moves.forEach(move => {
        const rowDiff = Math.abs(move.row - 4);
        const colDiff = Math.abs(move.col - 4);

        // Diagonal means row and column difference are equal
        expect(rowDiff).toBe(colDiff);
      });
    });

    test('bishop can move to all four diagonal directions', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      board.setPiece(4, 4, bishop);

      const moves = bishop.getValidMoves(board);

      // Check all four diagonals are represented
      const upLeft = moves.some(m => m.row < 4 && m.col < 4);
      const upRight = moves.some(m => m.row < 4 && m.col > 4);
      const downLeft = moves.some(m => m.row > 4 && m.col < 4);
      const downRight = moves.some(m => m.row > 4 && m.col > 4);

      expect(upLeft).toBe(true);
      expect(upRight).toBe(true);
      expect(downLeft).toBe(true);
      expect(downRight).toBe(true);
    });

    test('bishop in corner has 7 moves', () => {
      const bishop = new Bishop('white', { row: 0, col: 0 });
      board.setPiece(0, 0, bishop);

      const moves = bishop.getValidMoves(board);

      expect(moves).toHaveLength(7); // One diagonal from corner
    });

    test('bishop on edge has limited moves', () => {
      const bishop = new Bishop('white', { row: 0, col: 3 });
      board.setPiece(0, 3, bishop);

      const moves = bishop.getValidMoves(board);

      // Can move along two diagonals
      expect(moves.length).toBeGreaterThan(0);
      moves.forEach(move => {
        expect(move.row).toBeGreaterThan(0); // All moves go down from top edge
      });
    });
  });

  describe('Blocking and Obstacles', () => {
    test('bishop blocked by own piece', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      const blockingPawn = { type: 'pawn', color: 'white', position: { row: 2, col: 2 } };

      board.setPiece(4, 4, bishop);
      board.setPiece(2, 2, blockingPawn);

      const moves = bishop.getValidMoves(board);

      // Can move to (3,3) but not (2,2) or beyond
      expect(moves).toContainEqual({ row: 3, col: 3 });
      expect(moves).not.toContainEqual({ row: 2, col: 2 });
      expect(moves).not.toContainEqual({ row: 1, col: 1 });
      expect(moves).not.toContainEqual({ row: 0, col: 0 });
    });

    test('bishop blocked by opponent piece but can capture', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      const opponentPawn = { type: 'pawn', color: 'black', position: { row: 2, col: 2 } };

      board.setPiece(4, 4, bishop);
      board.setPiece(2, 2, opponentPawn);

      const moves = bishop.getValidMoves(board);

      // Can move to (3,3) and capture at (2,2) but not beyond
      expect(moves).toContainEqual({ row: 3, col: 3 });
      expect(moves).toContainEqual({ row: 2, col: 2 }); // Can capture
      expect(moves).not.toContainEqual({ row: 1, col: 1 });
    });

    test('bishop cannot jump over pieces', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });

      board.setPiece(4, 4, bishop);
      board.setPiece(3, 3, { type: 'pawn', color: 'black', position: { row: 3, col: 3 } });
      board.setPiece(3, 5, { type: 'pawn', color: 'white', position: { row: 3, col: 5 } });

      const moves = bishop.getValidMoves(board);

      // Can capture at (3,3) but not beyond
      expect(moves).toContainEqual({ row: 3, col: 3 });
      expect(moves).not.toContainEqual({ row: 2, col: 2 });

      // Cannot move to (3,5) because it's own piece
      expect(moves).not.toContainEqual({ row: 3, col: 5 });
      expect(moves).not.toContainEqual({ row: 2, col: 6 });
    });

    test('multiple pieces blocking different diagonals', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });

      board.setPiece(4, 4, bishop);
      board.setPiece(2, 2, { type: 'pawn', color: 'white', position: { row: 2, col: 2 } });
      board.setPiece(2, 6, { type: 'pawn', color: 'black', position: { row: 2, col: 6 } });
      board.setPiece(6, 2, { type: 'knight', color: 'black', position: { row: 6, col: 2 } });

      const moves = bishop.getValidMoves(board);

      // Upper-left diagonal: blocked at (2,2)
      expect(moves).toContainEqual({ row: 3, col: 3 });
      expect(moves).not.toContainEqual({ row: 2, col: 2 });

      // Upper-right diagonal: can capture at (2,6)
      expect(moves).toContainEqual({ row: 3, col: 5 });
      expect(moves).toContainEqual({ row: 2, col: 6 });

      // Lower-left diagonal: can capture at (6,2)
      expect(moves).toContainEqual({ row: 5, col: 3 });
      expect(moves).toContainEqual({ row: 6, col: 2 });

      // Lower-right diagonal: clear
      expect(moves).toContainEqual({ row: 5, col: 5 });
      expect(moves).toContainEqual({ row: 6, col: 6 });
      expect(moves).toContainEqual({ row: 7, col: 7 });
    });
  });

  describe('Capture Mechanics', () => {
    test('bishop can capture opponent pieces', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      const blackPawn1 = { type: 'pawn', color: 'black', position: { row: 2, col: 2 } };
      const blackPawn2 = { type: 'pawn', color: 'black', position: { row: 6, col: 6 } };

      board.setPiece(4, 4, bishop);
      board.setPiece(2, 2, blackPawn1);
      board.setPiece(6, 6, blackPawn2);

      const moves = bishop.getValidMoves(board);

      expect(moves).toContainEqual({ row: 2, col: 2 });
      expect(moves).toContainEqual({ row: 6, col: 6 });
    });

    test('bishop cannot capture own pieces', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      const whitePawn = { type: 'pawn', color: 'white', position: { row: 2, col: 2 } };

      board.setPiece(4, 4, bishop);
      board.setPiece(2, 2, whitePawn);

      const moves = bishop.getValidMoves(board);

      expect(moves).not.toContainEqual({ row: 2, col: 2 });
    });
  });

  describe('Board Boundaries', () => {
    test('bishop respects board edges', () => {
      const bishop = new Bishop('white', { row: 4, col: 4 });
      board.setPiece(4, 4, bishop);

      const moves = bishop.getValidMoves(board);

      moves.forEach(move => {
        expect(move.row).toBeGreaterThanOrEqual(0);
        expect(move.row).toBeLessThan(8);
        expect(move.col).toBeGreaterThanOrEqual(0);
        expect(move.col).toBeLessThan(8);
      });
    });

    test('bishop from all corners reaches opposite corner', () => {
      // Top-left to bottom-right
      const bishop1 = new Bishop('white', { row: 0, col: 0 });
      board.setPiece(0, 0, bishop1);
      expect(bishop1.getValidMoves(board)).toContainEqual({ row: 7, col: 7 });

      // Top-right to bottom-left
      board.clear();
      const bishop2 = new Bishop('white', { row: 0, col: 7 });
      board.setPiece(0, 7, bishop2);
      expect(bishop2.getValidMoves(board)).toContainEqual({ row: 7, col: 0 });
    });
  });

  describe('Color-Bound Movement', () => {
    test('bishop on light square can only reach light squares', () => {
      const bishop = new Bishop('white', { row: 0, col: 2 }); // Light square
      board.setPiece(0, 2, bishop);

      const moves = bishop.getValidMoves(board);

      moves.forEach(move => {
        // Light squares: (row + col) is even
        expect((move.row + move.col) % 2).toBe(0);
      });
    });

    test('bishop on dark square can only reach dark squares', () => {
      const bishop = new Bishop('white', { row: 0, col: 0 }); // Dark square
      board.setPiece(0, 0, bishop);

      const moves = bishop.getValidMoves(board);

      moves.forEach(move => {
        // Dark squares: (row + col) is odd
        expect((move.row + move.col) % 2).toBe(0);
      });
    });
  });

  describe('Initial Position', () => {
    test('bishops on initial board have no moves', () => {
      board = new Board(); // Reset to initial position

      const whiteBishop1 = board.getPiece(7, 2);
      const whiteBishop2 = board.getPiece(7, 5);

      expect(whiteBishop1.type).toBe('bishop');
      expect(whiteBishop2.type).toBe('bishop');

      // Blocked by pawns initially
      expect(whiteBishop1.getValidMoves(board)).toHaveLength(0);
      expect(whiteBishop2.getValidMoves(board)).toHaveLength(0);
    });

    test('bishop can move after pawn advances', () => {
      board = new Board();

      // Move pawn to open diagonal
      board.movePiece(6, 3, 4, 3); // d2 to d4

      const whiteBishop = board.getPiece(7, 2); // c1 bishop
      const moves = whiteBishop.getValidMoves(board);

      // Now has moves available
      expect(moves.length).toBeGreaterThan(0);
    });
  });
});