feat(archive): add MIME types and compound-extension aliases for archive formats

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/mime.js

@@ -31,6 +31,12 @@ const OUTPUT_MIME_TYPES = {
   snb: 'application/octet-stream',
   tcr: 'application/octet-stream',
   azw3: 'application/vnd.amazon.ebook',
+  zip: 'application/zip',
+  tar: 'application/x-tar',
+  'tar.gz': 'application/gzip',
+  'tar.bz2': 'application/x-bzip2',
+  '7z': 'application/x-7z-compressed',
+  'tar.7z': 'application/x-7z-compressed',
 };
 
 export async function detectInputMime(filePath) {
@@ -67,6 +73,9 @@ function normalizeFormat(format) {
   if (format === 'heif') return 'heic';
   if (format === 'azw3') return 'mobi';
   if (format === 'fb2') return 'xml';
+  if (format === 'tar.gz') return 'gz';
+  if (format === 'tar.bz2') return 'bz2';
+  if (format === 'tar.7z') return '7z';
   return format;
 }
 

test/mime.test.js

@@ -242,3 +242,38 @@ describe('resolveInputFormat — dfont', () => {
     await fs.unlink(fixturePath);
   });
 });
+
+describe('outputMimeType — archives', () => {
+  it('returns the correct MIME type for each archive target format', () => {
+    expect(outputMimeType('zip')).toBe('application/zip');
+    expect(outputMimeType('tar')).toBe('application/x-tar');
+    expect(outputMimeType('tar.gz')).toBe('application/gzip');
+    expect(outputMimeType('tar.bz2')).toBe('application/x-bzip2');
+    expect(outputMimeType('7z')).toBe('application/x-7z-compressed');
+    expect(outputMimeType('tar.7z')).toBe('application/x-7z-compressed');
+  });
+});
+
+describe('resolveInputFormat — compound archive extensions', () => {
+  it('accepts a real gzip file declared as tar.gz (file-type sniffs the outer gzip layer only)', async () => {
+    const zlib = await import('node:zlib');
+    const fixturePath = path.join(import.meta.dirname, 'fixtures', 'sample.tar.gz');
+    await fs.writeFile(fixturePath, zlib.gzipSync(Buffer.from('irrelevant payload for this check')));
+
+    const result = await resolveInputFormat(fixturePath, 'tar.gz');
+    expect(result.valid).toBe(true);
+
+    await fs.unlink(fixturePath);
+  });
+
+  it('accepts a real 7z file declared as tar.7z (file-type sniffs the outer 7z layer only)', async () => {
+    const fixturePath = path.join(import.meta.dirname, 'fixtures', 'sample.tar.7z');
+    // Minimal valid 7z signature header (6-byte magic + 2-byte version), enough for file-type to sniff `ext: '7z'`.
+    await fs.writeFile(fixturePath, Buffer.from([0x37, 0x7a, 0xbc, 0xaf, 0x27, 0x1c, 0x00, 0x04]));
+
+    const result = await resolveInputFormat(fixturePath, 'tar.7z');
+    expect(result.valid).toBe(true);
+
+    await fs.unlink(fixturePath);
+  });
+});