feat(checkout): enhance countdown synchronization and cleanup logic

src/app/core/services/checkout-countdown.service.spec.ts

@@ -54,4 +54,16 @@ describe('CheckoutCountdownService', () => {
 
     expect(service.remainingSeconds()).toBeNull();
   });
+
+  it('keeps the active countdown when a partial checkout response omits timing fields', () => {
+    service.synchronize({
+      expires_at: null,
+      expires_in_seconds: 10,
+      server_time: '2026-08-27T15:00:00.000Z',
+    });
+
+    service.synchronize({});
+
+    expect(service.remainingSeconds()).toBe(10);
+  });
 });

src/app/core/services/checkout-countdown.service.ts

@@ -16,9 +16,13 @@ export class CheckoutCountdownService implements OnDestroy {
 
   readonly remainingSeconds = this.remainingSecondsState.asReadonly();
 
-  synchronize(timing: CheckoutTiming): void {
+  synchronize(timing: Partial<CheckoutTiming>): void {
     const remainingSeconds = this.resolveRemainingSeconds(timing);
 
+    if (remainingSeconds === undefined) {
+      return;
+    }
+
     if (remainingSeconds === null) {
       this.clear();
       return;
@@ -43,9 +47,15 @@ export class CheckoutCountdownService implements OnDestroy {
     this.clear();
   }
 
-  private resolveRemainingSeconds(timing: CheckoutTiming): number | null {
-    const expiresAt = timing.expires_at ? Date.parse(timing.expires_at) : Number.NaN;
-    const serverTime = Date.parse(timing.server_time);
+  private resolveRemainingSeconds(timing: Partial<CheckoutTiming>): number | null | undefined {
+    if (timing.expires_at === null && timing.expires_in_seconds === null) {
+      return null;
+    }
+
+    const expiresAt =
+      typeof timing.expires_at === 'string' ? Date.parse(timing.expires_at) : Number.NaN;
+    const serverTime =
+      typeof timing.server_time === 'string' ? Date.parse(timing.server_time) : Number.NaN;
 
     if (Number.isFinite(expiresAt) && Number.isFinite(serverTime)) {
       return Math.max(0, Math.ceil((expiresAt - serverTime) / 1_000));
@@ -62,7 +72,7 @@ export class CheckoutCountdownService implements OnDestroy {
       return Math.max(0, Math.ceil((expiresAt - Date.now()) / 1_000));
     }
 
-    return null;
+    return undefined;
   }
 
   private updateRemainingSeconds(): void {

src/app/features/store/pages/checkout-page/checkout-page.component.ts

@@ -177,7 +177,6 @@ export class CheckoutPageComponent implements OnInit, OnDestroy {
   ngOnDestroy(): void {
     this.stopQrPolling();
     this.stopTransferPolling();
-    this.checkoutCountdownService.clear();
   }
 
   private mapPurchaseItemToMock(item: PurchaseDetailItemResponse): CartItemMock {
@@ -287,6 +286,7 @@ export class CheckoutPageComponent implements OnInit, OnDestroy {
     const tenant = this.tenantService.tenant();
     const purchaseId = this.createdPurchaseId();
     if (!tenant || !purchaseId) {
+      this.checkoutCountdownService.clear();
       return true;
     }
 
@@ -297,6 +297,7 @@ export class CheckoutPageComponent implements OnInit, OnDestroy {
       await firstValueFrom(this.cartService.loadCart());
       this.createdPurchaseId.set(null);
       this.createdPurchase.set(null);
+      this.checkoutCountdownService.clear();
 
       this.navigationStarted = true;
       return true;
@@ -310,6 +311,7 @@ export class CheckoutPageComponent implements OnInit, OnDestroy {
         });
         this.createdPurchaseId.set(null);
         this.createdPurchase.set(null);
+        this.checkoutCountdownService.clear();
         this.navigationStarted = true;
         return true;
       }
@@ -671,6 +673,7 @@ export class CheckoutPageComponent implements OnInit, OnDestroy {
     this.navigationStarted = true;
     this.stopQrPolling();
     this.stopTransferPolling();
+    this.checkoutCountdownService.clear();
 
     void this.router.navigate(['/checkout/status', purchaseId]);
   }
@@ -792,6 +795,7 @@ export class CheckoutPageComponent implements OnInit, OnDestroy {
       this.navigationStarted = true;
       this.stopQrPolling();
       this.stopTransferPolling();
+      this.checkoutCountdownService.clear();
       void this.router.navigate(['/checkout/status', purchaseId], {
         queryParams: { status: 'expired' },
       });