feat(caa upload): retain source format for Apple Music images

When the source image on Apple Music is JPEG, return the maximised image as JPEG. If it's not JPEG, always use PNG. See #80 for discussion.
ROpdebee · Oct 20, 2021 · c830f6e · c830f6e
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diff --git a/src/mb_enhanced_cover_art_uploads/maximise.ts b/src/mb_enhanced_cover_art_uploads/maximise.ts
@@ -67,6 +67,10 @@ async function maximiseExceptions(smallurl: URL): Promise<MaximisedImage[] | und
         return maximiseDiscogs(smallurl);
     }
 
+    if (smallurl.hostname.endsWith('.mzstatic.com')) {
+        return maximiseAppleMusic(smallurl);
+    }
+
     return;
 }
 
@@ -79,3 +83,31 @@ async function maximiseDiscogs(smallurl: URL): Promise<MaximisedImage[]> {
         headers: {},
     }];
 }
+
+async function maximiseAppleMusic(smallurl: URL): Promise<MaximisedImage[]> {
+    // For Apple Music, IMU always returns a PNG, regardless of whether the
+    // original source image was PNG or JPEG. When the original image is a JPEG,
+    // we want to fetch a JPEG version. Although the PNG is of slightly better
+    // quality due to generational loss when a JPEG is re-encoded, the quality
+    // loss is so minor that the additional costs of downloading, uploading,
+    // and storing the PNG are unjustifiable. See #80.
+
+    const results: MaximisedImage[] = [];
+    for await (const imgGeneric of maximiseGeneric(smallurl)) {
+        // Assume original file name is penultimate component of pathname, e.g.
+        // https://is5-ssl.mzstatic.com/image/thumb/Music124/v4/58/34/98/58349857-55bb-62ae-81d4-4a2726e33528/5060786561909.png/999999999x0w-999.png
+        // We're still conservative though, if it's not a JPEG, we won't
+        // return the JPEG version
+        if (/\.jpe?g$/i.test(imgGeneric.url.pathname.split('/').at(-2))) {
+            results.push({
+                ...imgGeneric,
+                url: new URL(imgGeneric.url.href.replace(/\.png$/i, '.jpg'))
+            });
+        }
+
+        // Always return the original maximised URL as a backup
+        results.push(imgGeneric);
+    }
+
+    return results;
+}
diff --git a/tests/mb_enhanced_cover_art_uploads/maximise.test.ts b/tests/mb_enhanced_cover_art_uploads/maximise.test.ts
@@ -10,6 +10,10 @@ beforeAll(() => {
     __set__('maxurl', fakeImu);
 });
 
+beforeEach(() => {
+    fakeImu.mockClear();
+});
+
 describe('maximising images', () => {
     it('yields the maximised image', async () => {
         fakeImu.mockImplementation((_url, options) => options.cb?.([{ url: 'https://example.com/max' } as unknown as maxurlResult]));
@@ -83,3 +87,94 @@ describe('maximising Discogs images', () => {
         expect(result.done).toBeTrue();
     });
 });
+
+describe('maximising Apple Music images', () => {
+    beforeAll(() => {
+        fakeImu.mockImplementation((url, options) => {
+            options.cb?.([{ url } as unknown as maxurlResult]);
+        });
+    });
+
+    it('retains PNG format if original is PNG', async () => {
+        const it = getMaximisedCandidates(new URL('https://is5-ssl.mzstatic.com/image/thumb/Music124/v4/58/34/98/58349857-55bb-62ae-81d4-4a2726e33528/5060786561909.png/999999999x0w-999.png'));
+        let result = await it.next();
+
+        // expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is5-ssl.mzstatic.com/image/thumb/Music124/v4/58/34/98/58349857-55bb-62ae-81d4-4a2726e33528/5060786561909.png/999999999x0w-999.png');
+
+        result = await it.next();
+
+        expect(result.done).toBeTrue();
+    });
+
+    it('uses JPEG format if original is JPEG', async () => {
+        const it = getMaximisedCandidates(new URL('https://is3-ssl.mzstatic.com/image/thumb/Music124/v4/73/bd/c8/73bdc8dc-9ab2-ce6e-e581-4bb3d9e559fc/190295474089.jpg/999999999x0w-999.png'));
+        const result = await it.next();
+
+        expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is3-ssl.mzstatic.com/image/thumb/Music124/v4/73/bd/c8/73bdc8dc-9ab2-ce6e-e581-4bb3d9e559fc/190295474089.jpg/999999999x0w-999.jpg');
+    });
+
+    it('uses PNG format as backup for JPEG', async () => {
+        const it = getMaximisedCandidates(new URL('https://is3-ssl.mzstatic.com/image/thumb/Music124/v4/73/bd/c8/73bdc8dc-9ab2-ce6e-e581-4bb3d9e559fc/190295474089.jpg/999999999x0w-999.png'));
+        let result = await it.next();
+
+        expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is3-ssl.mzstatic.com/image/thumb/Music124/v4/73/bd/c8/73bdc8dc-9ab2-ce6e-e581-4bb3d9e559fc/190295474089.jpg/999999999x0w-999.jpg');
+
+        result = await it.next();
+
+        expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is3-ssl.mzstatic.com/image/thumb/Music124/v4/73/bd/c8/73bdc8dc-9ab2-ce6e-e581-4bb3d9e559fc/190295474089.jpg/999999999x0w-999.png');
+
+        result = await it.next();
+
+        expect(result.done).toBeTrue();
+    });
+
+    it('keeps original maximised URL if format is unknown', async () => {
+        const it = getMaximisedCandidates(new URL('https://is3-ssl.mzstatic.com/image/thumb/Music124/v4/73/bd/c8/73bdc8dc-9ab2-ce6e-e581-4bb3d9e559fc/190295474089.webp/999999999x0w-999.png'));
+        let result = await it.next();
+
+        expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is3-ssl.mzstatic.com/image/thumb/Music124/v4/73/bd/c8/73bdc8dc-9ab2-ce6e-e581-4bb3d9e559fc/190295474089.webp/999999999x0w-999.png');
+
+        result = await it.next();
+
+        expect(result.done).toBeTrue();
+    });
+
+    it('maximises images', async () => {
+        fakeImu.mockImplementationOnce((_url, options) => {
+            options.cb?.([{ url: 'https://is4-ssl.mzstatic.com/image/thumb/Music115/v4/f1/e6/ad/f1e6adf1-fce1-a7fa-2f9c-e37e32738306/075679767103.jpg/999999999x0w-999.png' } as unknown as maxurlResult]);
+        });
+
+        const it = getMaximisedCandidates(new URL('https://is4-ssl.mzstatic.com/image/thumb/Music115/v4/f1/e6/ad/f1e6adf1-fce1-a7fa-2f9c-e37e32738306/075679767103.jpg/160x160bb-60.jpg'));
+        let result = await it.next();
+
+        expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is4-ssl.mzstatic.com/image/thumb/Music115/v4/f1/e6/ad/f1e6adf1-fce1-a7fa-2f9c-e37e32738306/075679767103.jpg/999999999x0w-999.jpg');
+
+        result = await it.next();
+
+        expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is4-ssl.mzstatic.com/image/thumb/Music115/v4/f1/e6/ad/f1e6adf1-fce1-a7fa-2f9c-e37e32738306/075679767103.jpg/999999999x0w-999.png');
+
+        result = await it.next();
+
+        expect(result.done).toBeTrue();
+        expect(fakeImu).toHaveBeenCalledOnce();
+    });
+
+    it('retains PNG for old-style iTunes URLs', async () => {
+        const it = getMaximisedCandidates(new URL('https://is2-ssl.mzstatic.com/image/thumb/Music114/v4/61/67/d4/6167d478-a353-28be-75fa-0ebbc74808e2/source/999999999x0w-999.png'));
+        let result = await it.next();
+
+        expect(result.done).toBeFalse();
+        expect(result.value.url.href).toBe('https://is2-ssl.mzstatic.com/image/thumb/Music114/v4/61/67/d4/6167d478-a353-28be-75fa-0ebbc74808e2/source/999999999x0w-999.png');
+
+        result = await it.next();
+
+        expect(result.done).toBeTrue();
+    });
+});