ext(sw): add preview_totp_from_secret popup handler

extension/src/service-worker/router/__tests__/router.test.ts

@@ -1000,3 +1000,41 @@ describe('list_groups', () => {
     expect(resp.data).toEqual({ groups: [] });
   });
 });
+
+// --- preview_totp_from_secret ---
+
+describe('preview_totp_from_secret', () => {
+  let originalChrome: any;
+  beforeEach(() => { originalChrome = (globalThis as any).chrome; });
+  afterEach(() => { (globalThis as any).chrome = originalChrome; });
+
+  it('returns code for valid base32', async () => {
+    const state = makeState();
+    state.wasm = {
+      totp_compute: vi.fn().mockReturnValue({ code: '123456', expires_at: 9_999_999_999 }),
+    };
+    const resp = await route(
+      { type: 'preview_totp_from_secret', secret_b32: 'JBSWY3DPEHPK3PXP' } as any,
+      state, makePopupSender(),
+    );
+    expect(resp.ok).toBe(true);
+    expect(resp.data).toEqual({ code: '123456', expires_at: 9_999_999_999 });
+    // Verify a transient TotpConfig was passed (sha1, 6 digits, 30s)
+    const cfgArg = JSON.parse(state.wasm.totp_compute.mock.calls[0][0]);
+    expect(cfgArg.algorithm).toBe('sha1');
+    expect(cfgArg.digits).toBe(6);
+    expect(cfgArg.period_seconds).toBe(30);
+  });
+
+  it('rejects invalid base32', async () => {
+    const state = makeState();
+    state.wasm = { totp_compute: vi.fn() };
+    const resp = await route(
+      { type: 'preview_totp_from_secret', secret_b32: 'too-short!!!' } as any,
+      state, makePopupSender(),
+    );
+    expect(resp.ok).toBe(false);
+    expect(resp.error).toMatch(/invalid/i);
+    expect(state.wasm.totp_compute).not.toHaveBeenCalled();
+  });
+});