import { describe, it, expect } from 'vitest';
import { DuplicateGame } from './game';

const START = 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR';

function placement(fen: string) {
  return fen.split(' ')[0];
}

describe('DuplicateGame', () => {
  it('starts with four boards in the standard position, North to move', () => {
    const g = new DuplicateGame();
    expect(g.ply).toBe(0);
    expect(g.currentPlayer).toBe('N');
    for (const id of ['NW', 'NE', 'SW', 'SE'] as const) {
      expect(placement(g.boards[id].fen())).toBe(START);
    }
  });

  it("applies a synchronized move to the current player's two boards only", () => {
    const g = new DuplicateGame();
    g.applyMove({ from: 'e2', to: 'e4' }); // North
    expect(g.ply).toBe(1);
    expect(g.currentPlayer).toBe('S');
    expect(placement(g.boards.NW.fen())).toContain('4P3'); // pawn advanced
    expect(placement(g.boards.NE.fen())).toContain('4P3');
    expect(placement(g.boards.SW.fen())).toBe(START); // untouched
    expect(placement(g.boards.SE.fen())).toBe(START);
  });

  it('cycles the current player N -> S -> E -> W -> N', () => {
    const g = new DuplicateGame();
    g.applyMove({ from: 'e2', to: 'e4' }); // N
    g.applyMove({ from: 'e2', to: 'e4' }); // S
    g.applyMove({ from: 'e7', to: 'e5' }); // E
    g.applyMove({ from: 'e7', to: 'e5' }); // W
    expect(g.currentPlayer).toBe('N');
    expect(g.ply).toBe(4);
  });

  it("throws on a move not legal on both of the player's boards", () => {
    const g = new DuplicateGame();
    expect(() => g.applyMove({ from: 'e2', to: 'e5' })).toThrow();
  });

  it('undo removes the last move and restores the position', () => {
    const g = new DuplicateGame();
    g.applyMove({ from: 'e2', to: 'e4' });
    g.undo();
    expect(g.ply).toBe(0);
    expect(g.currentPlayer).toBe('N');
    expect(placement(g.boards.NW.fen())).toBe(START);
  });

  it('rebuilds from a history array passed to the constructor', () => {
    const g = new DuplicateGame([
      { player: 'N', from: 'e2', to: 'e4' },
      { player: 'S', from: 'e2', to: 'e4' },
    ]);
    expect(g.ply).toBe(2);
    expect(g.currentPlayer).toBe('E');
  });

  it('resets the progress clock on a pawn move or capture', () => {
    const g = new DuplicateGame();
    g.applyMove({ from: 'e2', to: 'e4' }); // pawn move -> clock stays 0
    expect(g.pliesSinceProgress).toBe(0);
    g.applyMove({ from: 'e2', to: 'e4' }); // pawn move
    expect(g.pliesSinceProgress).toBe(0);
    g.applyMove({ from: 'g8', to: 'f6' }); // knight move -> clock increments
    expect(g.pliesSinceProgress).toBe(1);
  });
});