blind_chess/packages/server/test/unit/commit-fsm.test.ts

import { describe, it, expect, beforeEach } from 'vitest';
import { Chess } from 'chess.js';
import { handleCommit } from '../../src/commit.js';
import type { Game } from '../../src/state.js';
import { RATE_LIMIT } from '../../src/state.js';

function makeGame(fen?: string): Game {
  const chess = fen ? new Chess(fen) : new Chess();
  return {
    id: 'testtest',
    mode: 'blind',
    highlightingEnabled: false,
    status: 'active',
    createdAt: Date.now(),
    chess,
    moveHistory: [],
    announcements: [],
    players: {
      w: { token: 'w'.repeat(24), socket: null, joinedAt: 0,
            rateBucket: { tokens: RATE_LIMIT.capacity, last: 0 } },
      b: { token: 'b'.repeat(24), socket: null, joinedAt: 0,
            rateBucket: { tokens: RATE_LIMIT.capacity, last: 0 } },
    },
    armed: null,
    drawOffer: null,
    disconnectAt: {},
  };
}

describe('hierarchy decision table', () => {
  let game: Game;
  beforeEach(() => { game = makeGame(); });

  it('row 1: no_such_piece — empty square', () => {
    const r = handleCommit(game, 'w', { from: 'e4' });
    expect(r.kind).toBe('announce');
    if (r.kind === 'announce') expect(r.announcements[0]!.text).toBe('no_such_piece');
  });

  it('row 1b: no_such_piece — opponent piece', () => {
    const r = handleCommit(game, 'w', { from: 'e7' }); // black pawn
    expect(r.kind).toBe('announce');
    if (r.kind === 'announce') expect(r.announcements[0]!.text).toBe('no_such_piece');
  });

  it('row 2: no_legal_moves — knight in starting position is OK; use a contrived fen', () => {
    // White knight surrounded by own pieces. Place a knight at b1 with own
    // pieces blocking a3, c3, d2.
    const g = makeGame('4k3/8/8/8/8/P1P5/3P4/1N2K3 w - - 0 1');
    // Knight at b1: jumps a3, c3, d2. All blocked by own pawns.
    const r = handleCommit(g, 'w', { from: 'b1' });
    expect(r.kind).toBe('announce');
    if (r.kind === 'announce') expect(r.announcements[0]!.text).toBe('no_legal_moves');
  });

  it('row 3: wont_help — pinned bishop, not in check', () => {
    // White king on e1, white bishop on e2 pinned by black rook on e8.
    const g = makeGame('4r2k/8/8/8/8/8/4B3/4K3 w - - 0 1');
    const r = handleCommit(g, 'w', { from: 'e2' });
    expect(r.kind).toBe('announce');
    if (r.kind === 'announce') expect(r.announcements[0]!.text).toBe('wont_help');
  });

  it('row 5: silent on first commit when piece has legal moves', () => {
    const r = handleCommit(game, 'w', { from: 'e2' });
    expect(r.kind).toBe('silent');
    expect(game.armed).toEqual({ color: 'w', from: 'e2' });
  });

  it('row 6: applied move when legal commit completes', () => {
    const r = handleCommit(game, 'w', { from: 'e2', to: 'e4' });
    expect(r.kind).toBe('applied');
    expect(game.armed).toBeNull();
    expect(game.chess.history()).toContain('e4');
  });
});

describe('touch-move enforcement', () => {
  it('after silent arm, commit with different from yields must_move_touched_piece', () => {
    const game = makeGame();
    handleCommit(game, 'w', { from: 'e2' });        // arm
    const r = handleCommit(game, 'w', { from: 'd2', to: 'd4' });
    expect(r.kind).toBe('error');
    if (r.kind === 'error') expect(r.code).toBe('must_move_touched_piece');
  });

  it('after silent arm, illegal destination returns illegal_move and KEEPS touch', () => {
    const game = makeGame();
    handleCommit(game, 'w', { from: 'e2' });
    const r = handleCommit(game, 'w', { from: 'e2', to: 'e5' }); // pawn can't go e2→e5
    expect(r.kind).toBe('announce');
    if (r.kind === 'announce') expect(r.announcements[0]!.text).toBe('illegal_move');
    expect(game.armed).toEqual({ color: 'w', from: 'e2' });
  });

  it('not your turn returns error', () => {
    const game = makeGame();
    const r = handleCommit(game, 'b', { from: 'e7' });
    expect(r.kind).toBe('error');
    if (r.kind === 'error') expect(r.code).toBe('not_your_turn');
  });
});

describe('promotion', () => {
  it('promotion required: pawn on 7th to 8th without promotion field', () => {
    const g = makeGame('7k/4P3/8/8/8/8/8/4K3 w - - 0 1');
    const r = handleCommit(g, 'w', { from: 'e7', to: 'e8' });
    expect(r.kind).toBe('error');
    if (r.kind === 'error') expect(r.code).toBe('promotion_required');
  });

  it('promotion succeeds with field', () => {
    const g = makeGame('7k/4P3/8/8/8/8/8/4K3 w - - 0 1');
    const r = handleCommit(g, 'w', { from: 'e7', to: 'e8', promotion: 'q' });
    expect(r.kind).toBe('applied');
    if (r.kind === 'applied') {
      const promo = r.announcements.find((a) => a.text === 'white_promoted');
      expect(promo).toBeDefined();
      expect(promo?.payload?.promotedTo).toBe('q');
    }
  });
});