import { describe, it, expect } from 'vitest';
import { parseSaveDex } from '../src/lib/savedex.js';

// --- Synthetic Gen 1 (R/B/Y) SRAM -------------------------------------
// 32 KB, with the owned/seen bitfields and the byte checksum the parser
// verifies. Offsets mirror src/lib/savedex.js `G1`.
const G1 = {
  owned: 0x25a3,
  seen: 0x25b6,
  species: 151,
  ckByte: 0x3523,
  ckFrom: 0x2598,
  ckTo: 0x3522,
};

function setBits(bytes, start, ids) {
  for (const n of ids) bytes[start + ((n - 1) >> 3)] |= 1 << ((n - 1) & 7);
}

function makeGen1Save({ caught, seen }) {
  const bytes = new Uint8Array(0x8000);
  setBits(bytes, G1.owned, caught);
  setBits(bytes, G1.seen, seen);
  let sum = 0;
  for (let i = G1.ckFrom; i <= G1.ckTo; i++) sum = (sum + bytes[i]) >>> 0;
  bytes[G1.ckByte] = ~sum & 0xff;
  return bytes.buffer;
}

describe('parseSaveDex — Gen 1', () => {
  it('reads owned/seen and verifies the checksum', () => {
    const caught = [1, 25, 151];
    const seen = [1, 4, 25, 151];
    const dex = parseSaveDex(makeGen1Save({ caught, seen }));

    expect(dex.gen).toBe(1);
    expect(dex.game).toBe('Red / Blue / Yellow');
    expect(dex.versionGroups).toEqual(['red-blue', 'yellow']);
    expect(dex.caught).toEqual(caught);
    expect(dex.seen).toEqual(seen);
    expect(dex.checksumOk).toBe(true);
    expect(dex.nationalUnlocked).toBe(true);
  });

  it('still parses (checksumOk false) when the checksum byte is wrong', () => {
    const buf = makeGen1Save({ caught: [1], seen: [1, 2] });
    new Uint8Array(buf)[G1.ckByte] ^= 0xff;
    const dex = parseSaveDex(buf);
    expect(dex.gen).toBe(1);
    expect(dex.caught).toEqual([1]);
    expect(dex.checksumOk).toBe(false);
  });

  it('rejects a file that is too small', () => {
    expect(() => parseSaveDex(new Uint8Array(1024).buffer)).toThrow(/too small/i);
  });

  it('rejects a large file with no recognisable Pokédex', () => {
    expect(() => parseSaveDex(new Uint8Array(0x20000).buffer)).toThrow();
  });
});