import { describe, it, expect } from 'vitest';
import { Chess } from 'chess.js';
import { legalCandidates } from '../../../src/bot/candidates.js';
import type { Game } from '../../../src/state.js';
import { RATE_LIMIT } from '../../../src/state.js';

function makeGame(mode: 'blind' | 'vanilla', fen?: string): Game {
  return {
    id: 'cand0001',
    mode,
    highlightingEnabled: false,
    status: 'active',
    createdAt: Date.now(),
    chess: fen ? new Chess(fen) : new 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('legalCandidates / vanilla', () => {
  it('starting position: 20 candidates for white', () => {
    const game = makeGame('vanilla');
    const candidates = legalCandidates(game, 'w');
    expect(candidates.length).toBe(20);
  });

  it('returns from/to on each candidate', () => {
    const game = makeGame('vanilla');
    const candidates = legalCandidates(game, 'w');
    expect(candidates.every((c) => c.from && c.to)).toBe(true);
  });

  it('vanilla excludes pinned-piece moves (chess.js filters self-check)', () => {
    // White king e1, white bishop e2, black rook e8. Bishop is pinned.
    const game = makeGame('vanilla', '4r2k/8/8/8/8/8/4B3/4K3 w - - 0 1');
    const candidates = legalCandidates(game, 'w');
    // Bishop on e2 has zero legal moves (any move drops the king to check).
    expect(candidates.find((c) => c.from === 'e2')).toBeUndefined();
  });

  it('vanilla expands all 4 promotion options', () => {
    // White pawn on a7, ready to promote.
    const game = makeGame('vanilla', '4k3/P7/8/8/8/8/8/4K3 w - - 0 1');
    const candidates = legalCandidates(game, 'w').filter((c) => c.from === 'a7');
    expect(candidates.map((c) => c.promotion).sort()).toEqual(['b', 'n', 'q', 'r']);
  });
});

describe('legalCandidates / blind', () => {
  it('starting position: 34 geometric candidates for white', () => {
    // 8 pawns: edge pawns (a2, h2) return 3 moves each (forward 1, forward 2, 1 diagonal),
    // interior pawns (b2-g2) return 4 moves each (forward 1, forward 2, 2 diagonals).
    // Total pawn: 2*3 + 6*4 = 30.
    // 2 knights: 2 moves each = 4.
    // Total: 34.
    const game = makeGame('blind');
    const candidates = legalCandidates(game, 'w');
    expect(candidates.length).toBe(34);
  });

  it('blind INCLUDES pinned-piece moves (geometric does not know about pins)', () => {
    // Same pinned-bishop position. Geometric move-gen sees no own piece blocking;
    // bishop can geometrically reach d3, c4, b5, a6, f3, etc.
    const game = makeGame('blind', '4r2k/8/8/8/8/8/4B3/4K3 w - - 0 1');
    const candidates = legalCandidates(game, 'w');
    expect(candidates.some((c) => c.from === 'e2')).toBe(true);
  });

  it('blind expands all 4 promotion options for own pawn', () => {
    const game = makeGame('blind', '4k3/P7/8/8/8/8/8/4K3 w - - 0 1');
    const candidates = legalCandidates(game, 'w').filter((c) => c.from === 'a7' && c.to === 'a8');
    expect(candidates.map((c) => c.promotion).sort()).toEqual(['b', 'n', 'q', 'r']);
  });

  it('blind ignores whose turn it is (returns moves for either color)', () => {
    // Vanilla path filters by chess.js .moves() which respects toMove. Blind
    // path iterates own pieces directly, so black candidates exist on move 0.
    const game = makeGame('blind');
    const candidates = legalCandidates(game, 'b');
    // Same geometric move count as white: 34.
    expect(candidates.length).toBe(34);
  });

  it('zero own pieces = zero candidates (degenerate)', () => {
    // FEN with only black king + pieces — but FEN must be valid, kings required.
    const game = makeGame('blind', '4k3/8/8/8/8/8/8/4K3 w - - 0 1');
    const black = legalCandidates(game, 'b');
    // Black king on e8 has 5 geometric king moves (d8, f8, d7, e7, f7).
    expect(black.length).toBe(5);
  });
});