ChatApp/packages/shared/src/chat/games.test.ts

import { describe, expect, it } from 'vitest';

import {
  c4DropRow,
  c4WinningCells,
  emptyC4Board,
  emptyTttBoard,
  isBoardFull,
  tttWinningLine,
  type Cell,
} from './games';

describe('tttWinningLine', () => {
  it('detects a row win', () => {
    const b: Cell[] = [0, 0, 0, null, null, null, null, null, null];
    expect(tttWinningLine(b)).toEqual([0, 1, 2]);
  });

  it('detects a diagonal win', () => {
    const b: Cell[] = [1, null, null, null, 1, null, null, null, 1];
    expect(tttWinningLine(b)).toEqual([0, 4, 8]);
  });

  it('returns null when no winner', () => {
    expect(tttWinningLine(emptyTttBoard())).toBeNull();
    const mixed: Cell[] = [0, 1, 0, 1, 0, 1, 1, 0, 1];
    expect(tttWinningLine(mixed)).toBeNull();
  });
});

describe('c4WinningCells', () => {
  it('detects a horizontal win', () => {
    const b = emptyC4Board();
    b[35] = 1; b[36] = 1; b[37] = 1; b[38] = 1;
    expect(c4WinningCells(b)).toEqual([35, 36, 37, 38]);
  });

  it('detects a vertical win', () => {
    const b = emptyC4Board();
    b[14] = 0; b[21] = 0; b[28] = 0; b[35] = 0;
    expect(c4WinningCells(b)).toEqual([14, 21, 28, 35]);
  });

  it('detects a diagonal ↘ win', () => {
    const b = emptyC4Board();
    b[14] = 1; b[22] = 1; b[30] = 1; b[38] = 1;
    expect(c4WinningCells(b)).toEqual([14, 22, 30, 38]);
  });

  it('returns null when no winner', () => {
    expect(c4WinningCells(emptyC4Board())).toBeNull();
  });
});

describe('c4DropRow', () => {
  it('returns the bottom row on an empty column', () => {
    expect(c4DropRow(emptyC4Board(), 0)).toBe(5);
  });

  it('stacks on top of an existing piece', () => {
    const b = emptyC4Board();
    b[35] = 0;
    expect(c4DropRow(b, 0)).toBe(4);
  });

  it('returns -1 when the column is full', () => {
    const b = emptyC4Board();
    for (let r = 0; r < 6; r++) b[r * 7 + 3] = 0;
    expect(c4DropRow(b, 3)).toBe(-1);
  });
});

describe('isBoardFull', () => {
  it('true for a fully filled board, false otherwise', () => {
    expect(isBoardFull(emptyTttBoard())).toBe(false);
    const filled: Cell[] = [0, 1, 0, 1, 0, 1, 1, 0, 1];
    expect(isBoardFull(filled)).toBe(true);
  });
});