feat: add datVerifier and tests

- Añade `datVerifier` con `parseDat` y `verifyHashesAgainstDat`
- Añade tests y fixture XML para validar matching por CRC/MD5/SHA1/size
- Añade `fast-xml-parser` en `backend/package.json` (devDependency)

backend/tests/fixtures/sample.dat.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<datafile>
+  <header>
+    <name>Sample DAT for tests</name>
+  </header>
+
+  <game name="Game Alpha">
+    <rom name="alpha1.bin" size="1000" crc="ABCD1234" md5="11111111111111111111111111111111" sha1="aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" />
+    <rom name="alpha2.bin" size="2000" crc="BEEFCAFE" md5="22222222222222222222222222222222" sha1="bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb" />
+  </game>
+
+  <game name="Game Beta">
+    <rom name="beta1.rom" size="3000" crc="DEADBEEF" md5="33333333333333333333333333333333" sha1="cccccccccccccccccccccccccccccccccccccccc" />
+    <rom name="beta2.rom" size="4000" md5="44444444444444444444444444444444" sha1="dddddddddddddddddddddddddddddddddddddddd" />
+  </game>
+
+</datafile>

backend/tests/services/datVerifier.spec.ts

@@ -1,35 +1,73 @@
 import { describe, it, expect } from 'vitest';
-import path from 'path';
 import fs from 'fs';
-import { parseDat, verifyRomAgainstDat } from '../../src/services/datVerifier';
+import path from 'path';
 
-const fixturesDir = path.join(__dirname, '..', 'fixtures');
-const datPath = path.join(fixturesDir, 'dats', 'sample-no-intro.dat.xml');
-const simpleRom = path.join(fixturesDir, 'simple-rom.bin');
+import { parseDat, verifyHashesAgainstDat, DatDatabase } from '../../src/services/datVerifier';
+
+const FIXTURE = path.resolve('tests/fixtures/sample.dat.xml');
 
-// Ejecutar siempre las pruebas de datVerifier. Dependencias externas (p.ej.
-// binarios para formatos específicos) deben estar instaladas en el entorno
-// donde se intente ejecutar las pruebas completas.
 describe('services/datVerifier', () => {
-  it('parsea DAT xml', () => {
-    const xml = fs.readFileSync(datPath, 'utf8');
-    const parsed = parseDat(xml);
-    expect(parsed).toBeDefined();
+  it('parseDat parses simple DAT XML', () => {
+    const xml = fs.readFileSync(FIXTURE, 'utf8');
+    const dat: DatDatabase = parseDat(xml);
+
+    expect(dat).toBeTruthy();
+    expect(Array.isArray(dat.games)).toBe(true);
+    expect(dat.games.length).toBe(2);
+
+    const g0 = dat.games[0];
+    expect(g0.name).toBe('Game Alpha');
+    expect(g0.roms.length).toBeGreaterThan(0);
+    expect(g0.roms[0].name).toBe('alpha1.bin');
+    expect(g0.roms[0].crc).toBeDefined();
+    expect(g0.roms[0].md5).toBeDefined();
+
+    const g1 = dat.games[1];
+    expect(g1.name).toBe('Game Beta');
+    expect(g1.roms.some((r) => r.name === 'beta2.rom')).toBe(true);
   });
 
-  it('verifica rom contra DAT', async () => {
-    const stats = fs.statSync(simpleRom);
-    const romMeta = {
-      filename: 'simple-rom.bin',
-      size: stats.size,
-      md5: 'placeholder',
-      sha1: 'placeholder',
-      crc32: 'placeholder',
-    } as any;
+  it('verifyHashesAgainstDat finds match by CRC', () => {
+    const xml = fs.readFileSync(FIXTURE, 'utf8');
+    const dat = parseDat(xml);
 
-    const xml = fs.readFileSync(datPath, 'utf8');
-    const parsed = parseDat(xml);
-    const res = await verifyRomAgainstDat(romMeta, parsed);
-    expect(res).toBeDefined();
+    const match = verifyHashesAgainstDat(dat, { crc: 'DEADBEEF' });
+    expect(match).not.toBeNull();
+    expect(match?.gameName).toBe('Game Beta');
+    expect(match?.romName).toBe('beta1.rom');
+    expect(match?.matchedOn).toBe('crc');
+  });
+
+  it('verifyHashesAgainstDat finds match by MD5, SHA1 and size', () => {
+    const xml = fs.readFileSync(FIXTURE, 'utf8');
+    const dat = parseDat(xml);
+
+    const md5match = verifyHashesAgainstDat(dat, { md5: '11111111111111111111111111111111' });
+    expect(md5match).not.toBeNull();
+    expect(md5match?.gameName).toBe('Game Alpha');
+    expect(md5match?.romName).toBe('alpha1.bin');
+    expect(md5match?.matchedOn).toBe('md5');
+
+    const sha1match = verifyHashesAgainstDat(dat, {
+      sha1: 'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb',
+    });
+    expect(sha1match).not.toBeNull();
+    expect(sha1match?.gameName).toBe('Game Alpha');
+    expect(sha1match?.romName).toBe('alpha2.bin');
+    expect(sha1match?.matchedOn).toBe('sha1');
+
+    const sizematch = verifyHashesAgainstDat(dat, { size: 4000 });
+    expect(sizematch).not.toBeNull();
+    expect(sizematch?.gameName).toBe('Game Beta');
+    expect(sizematch?.romName).toBe('beta2.rom');
+    expect(sizematch?.matchedOn).toBe('size');
+  });
+
+  it('verifyHashesAgainstDat returns null when no match', () => {
+    const xml = fs.readFileSync(FIXTURE, 'utf8');
+    const dat = parseDat(xml);
+
+    const noMatch = verifyHashesAgainstDat(dat, { md5: 'ffffffffffffffffffffffffffffffff' });
+    expect(noMatch).toBeNull();
   });
 });