Added ID3v2 support for FLAC files. (Fixes #417) (#418)

* Added ID3v2 support for FLAC files.  (Fixes #417)

* Fix ID3v2 header size calculation, adjust ID3v2 logic for FLAC files

---------

Co-authored-by: Vanilagy <[email protected]>

test/node/flac.test.ts

@@ -1,5 +1,6 @@
 import { expect, test } from 'vitest';
 import path from 'node:path';
+import fs from 'node:fs/promises';
 import { assert, toUint8Array } from '../../src/misc.js';
 import { Input } from '../../src/input.js';
 import { BufferSource, FilePathSource } from '../../src/source.js';
@@ -284,3 +285,59 @@ test('appendOnly writes correct STREAMINFO header', async () => {
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 	]));
 });
+
+test('can read a FLAC file with leading ID3v2 tags', async () => {
+	const createId3V23TitleTag = (title: string) => {
+		const titleBytes = new TextEncoder().encode(title);
+		const frame = new Uint8Array(11 + titleBytes.length);
+		frame.set([0x54, 0x49, 0x54, 0x32]); // TIT2
+		frame[7] = 1 + titleBytes.length;
+		frame[10] = 0; // ISO-8859-1
+		frame.set(titleBytes, 11);
+
+		const tag = new Uint8Array(10 + frame.length);
+		tag.set([0x49, 0x44, 0x33, 0x03, 0x00, 0x00]); // ID3v2.3
+		tag[9] = frame.length;
+		tag.set(frame, 10);
+
+		return tag;
+	};
+
+	const concatenateBytes = (...chunks: Uint8Array[]) => {
+		const result = new Uint8Array(chunks.reduce((sum, chunk) => sum + chunk.byteLength, 0));
+		let offset = 0;
+
+		for (const chunk of chunks) {
+			result.set(chunk, offset);
+			offset += chunk.byteLength;
+		}
+
+		return result;
+	};
+
+	using input = new Input({
+		source: new BufferSource(concatenateBytes(
+			createId3V23TitleTag('First tag'),
+			createId3V23TitleTag('Second tag'),
+			await fs.readFile(new URL('../public/sample.flac', import.meta.url)),
+		)),
+		formats: ALL_FORMATS,
+	});
+
+	expect(await input.canRead()).toBe(true);
+	expect(await input.getFormat()).toBe(FLAC);
+
+	const track = await input.getPrimaryAudioTrack();
+	assert(track);
+	expect(await track.getDurationFromMetadata()).toEqual(19.714285714285715);
+
+	const firstPacket = await new EncodedPacketSink(track).getPacket(0);
+	assert(firstPacket);
+	expect(firstPacket.sequenceNumber).toBe(0);
+	expect(firstPacket.timestamp).toBe(0);
+
+	const metadataTags = await input.getMetadataTags();
+	expect(metadataTags.title).toBe('First tag');
+	expect(metadataTags.raw!['TIT2']).toBe('First tag');
+	expect(metadataTags.raw!['TITLE']).toBe('The Happy Meeting');
+});