fix: separate resource previews from downloads

src/App.test.tsx

@@ -53,12 +53,17 @@ class SuccessfulParserWorker implements WorkerPort {
   onerror: ((event: ErrorEvent) => void) | null = null;
   terminated = false;
   lastMessage: WorkerRequest | undefined;
+  readonly messages: WorkerRequest[] = [];
   lastTransfer: Transferable[] = [];
 
-  constructor(private readonly packageResult?: OneNotePackageDto) {}
+  constructor(
+    private readonly packageResult?: OneNotePackageDto,
+    private readonly resourcePage = false
+  ) {}
 
   postMessage(message: WorkerRequest, transfer: Transferable[] = []): void {
     this.lastMessage = message;
+    this.messages.push(message);
     this.lastTransfer = transfer;
     queueMicrotask(() => {
       if (message.type === 'parse-one') {
@@ -84,27 +89,67 @@ class SuccessfulParserWorker implements WorkerPort {
           page: {
             ...page,
             id: message.pageId,
-            blocks: [
-              {
-                kind: 'text',
-                id: 'text-1',
-                sourceText: page.text,
-                text: page.text,
-                runs: [
+            blocks: this.resourcePage
+              ? [
                   {
-                    start: 0,
-                    end: page.text.length,
+                    kind: 'image',
+                    id: 'image-1',
+                    resourceId: 'resource-image',
+                    filename: 'large.png',
+                    isBackground: false,
+                    layout: {},
+                  },
+                ]
+              : [
+                  {
+                    kind: 'text',
+                    id: 'text-1',
+                    sourceText: page.text,
                     text: page.text,
-                    style: {},
+                    runs: [
+                      {
+                        start: 0,
+                        end: page.text.length,
+                        text: page.text,
+                        style: {},
+                      },
+                    ],
+                    paragraphStyle: {},
+                    layout: {},
                   },
                 ],
-                paragraphStyle: {},
-                layout: {},
-              },
-            ],
             diagnostics: [],
           },
         });
+      } else if (message.type === 'get-resource') {
+        if (message.intent === 'preview') {
+          this.respond({
+            type: 'failure',
+            requestId: message.requestId,
+            error: {
+              code: 'resource-not-available',
+              message:
+                'This image can be downloaded but is not approved for automatic preview.',
+              recoverable: true,
+            },
+          });
+        } else {
+          this.respond({
+            type: 'resource',
+            requestId: message.requestId,
+            sessionId: message.sessionId,
+            resource: {
+              id: message.resourceId,
+              kind: 'image',
+              filename: 'large.png',
+              extension: 'png',
+              mediaType: 'image/png',
+              browserRenderable: false,
+              size: 4,
+              bytes: Uint8Array.of(1, 2, 3, 4).buffer,
+            },
+          });
+        }
       } else if (message.type === 'export-session') {
         this.respond({
           type: 'export-artifact',
@@ -231,6 +276,54 @@ describe('OneNoteApplication', () => {
     expect(click).toHaveBeenCalledOnce();
   });
 
+  it('requests a rejected preview separately from an explicit image download', async () => {
+    const user = userEvent.setup();
+    const worker = new SuccessfulParserWorker(undefined, true);
+    vi.spyOn(URL, 'createObjectURL').mockReturnValue('blob:local-image');
+    const click = vi
+      .spyOn(HTMLAnchorElement.prototype, 'click')
+      .mockImplementation(() => undefined);
+    render(
+      <OneNoteApplication
+        createWorkerClient={() => new OneNoteWorkerClient(() => worker)}
+      />
+    );
+
+    await user.upload(
+      screen.getByLabelText('Choose OneNote files'),
+      new File([new Uint8Array([1, 2, 3])], 'Section.one')
+    );
+
+    expect(
+      await screen.findByText(/not approved for automatic preview/i)
+    ).toBeVisible();
+    expect(worker.messages).toContainEqual(
+      expect.objectContaining({
+        type: 'get-resource',
+        resourceId: 'resource-image',
+        intent: 'preview',
+      })
+    );
+    expect(
+      worker.messages.some(
+        (message) =>
+          message.type === 'get-resource' && message.intent === 'download'
+      )
+    ).toBe(false);
+
+    await user.click(
+      screen.getByRole('button', { name: 'Download original image' })
+    );
+    expect(worker.messages).toContainEqual(
+      expect.objectContaining({
+        type: 'get-resource',
+        resourceId: 'resource-image',
+        intent: 'download',
+      })
+    );
+    expect(click).toHaveBeenCalledOnce();
+  });
+
   it('opens a dropped OneNote package through the local worker', async () => {
     const notebook: OneNotePackageDto = {
       format: 'onepkg',