refactor(checkout): simplify direct item handling in checkout process

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

@@ -17,36 +17,13 @@ export interface DirectCheckoutItem {
   cantidad: number;
 }
 
-export interface UnavailableCheckoutItem {
-  index: number;
-  catalog_item_id: number;
-  variant_id: number | null;
-  requested_quantity: number;
-  available_quantity: number;
-  message: string;
-}
-
-export interface InsufficientStockResponse {
-  code: 'purchase.insufficient_stock';
-  message: string;
-  errors: Record<string, string[]>;
-  unavailable_items: UnavailableCheckoutItem[];
-}
-
-export function isInsufficientStockResponse(value: unknown): value is InsufficientStockResponse {
-  if (typeof value !== 'object' || value === null) return false;
-
-  const response = value as Partial<InsufficientStockResponse>;
-
-  return (
-    response.code === 'purchase.insufficient_stock' && Array.isArray(response.unavailable_items)
-  );
-}
-
 export type StartCheckoutPayload =
   | {
       cart_id: number;
     }
+  | {
+      direct_item: DirectCheckoutItem;
+    }
   | {
       direct_items: DirectCheckoutItem[];
     };

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

@@ -10,7 +10,7 @@ import {
 } from '@angular/core';
 import { HttpErrorResponse } from '@angular/common/http';
 import { ActivatedRoute, Router } from '@angular/router';
-import { firstValueFrom, Subscription } from 'rxjs';
+import { Subscription } from 'rxjs';
 
 import { CartService } from '../../../../core/services/cart/cart.service';
 import { AuthService } from '../../../../core/services/auth/auth.service';
@@ -225,16 +225,13 @@ export class StoreHomePageComponent implements OnInit, OnDestroy {
     catalogItemId: number,
     variantIds: number[],
   ) {
-    for (const variantId of variantIds) {
-      await firstValueFrom(this.cartService.addItem(catalogItemId, variantId, 1));
-    }
-
-    const cartId = this.cartService.cart()?.id;
-    if (cartId === null || cartId === undefined) {
-      throw new Error('No se pudo crear el carrito para las entradas seleccionadas.');
-    }
-
-    return checkoutService.startCheckout(tenantCode, { cart_id: cartId });
+    return checkoutService.startCheckout(tenantCode, {
+      direct_items: variantIds.map((variantId) => ({
+        catalog_item_id: catalogItemId,
+        variant_id: variantId,
+        cantidad: 1,
+      })),
+    });
   }
 
   protected onAddToCart(event: ProductListCartEvent): void {