feat: Add stock management features including stock reservations and updates to cart and checkout processes

tienda/migrations/0004_product_stock_stockreservation_stockreservationitem.py

@@ -0,0 +1,45 @@
+# Generated by Django 6.0.1 on 2026-04-09 06:55
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('tienda', '0003_order_transaction_code'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='product',
+            name='stock',
+            field=models.PositiveIntegerField(default=0),
+        ),
+        migrations.CreateModel(
+            name='StockReservation',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('session_key', models.CharField(blank=True, max_length=40, null=True)),
+                ('status', models.CharField(choices=[('active', 'Activa'), ('completed', 'Completada'), ('cancelled', 'Cancelada'), ('expired', 'Expirada')], default='active', max_length=20)),
+                ('payment_method', models.CharField(choices=[('stripe', 'Stripe'), ('paypal', 'PayPal')], max_length=20)),
+                ('expires_at', models.DateTimeField(db_index=True)),
+                ('created_at', models.DateTimeField(auto_now_add=True)),
+                ('updated_at', models.DateTimeField(auto_now=True)),
+                ('user', models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='stock_reservations', to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+        migrations.CreateModel(
+            name='StockReservationItem',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('quantity', models.PositiveIntegerField(default=1)),
+                ('product', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='stock_reservation_items', to='tienda.product')),
+                ('reservation', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='items', to='tienda.stockreservation')),
+            ],
+            options={
+                'unique_together': {('reservation', 'product')},
+            },
+        ),
+    ]

tienda/templates/tienda/cart.html

@@ -12,6 +12,17 @@
 {% if cart_items %}
 <div class="row mt-4">
   <div class="col-md-8">
+    {% if stock_issues %}
+    <div class="alert alert-warning">
+      <strong>Hay productos con stock insuficiente:</strong>
+      <ul class="mb-0 mt-2">
+        {% for issue in stock_issues %}
+        <li>{{ issue.product_name }} - disponible: {{ issue.available }}, en carrito: {{ issue.requested }}</li>
+        {% endfor %}
+      </ul>
+      <div class="mt-2">Actualiza las cantidades antes de continuar al pago.</div>
+    </div>
+    {% endif %}
     <div class="card">
       <div class="card-body">
         <table class="table">
@@ -20,6 +31,7 @@
               <th>Producto</th>
               <th>Precio (sin IVA)</th>
               <th>Cantidad</th>
+              <th>Stock</th>
               <th>Subtotal (con IVA)</th>
               <th>Acciones</th>
             </tr>
@@ -39,10 +51,17 @@
               <td>
                 <form method="post" action="{% url 'update_cart_item' item.id %}" class="d-flex align-items-center" style="max-width: 150px;">
                   {% csrf_token %}
-                  <input type="number" name="quantity" value="{{ item.quantity }}" min="1" class="form-control form-control-sm me-2" style="width: 70px;">
+                  <input type="number" name="quantity" value="{{ item.quantity }}" min="1" max="{{ item.product.stock }}" class="form-control form-control-sm me-2" style="width: 70px;">
                   <button type="submit" class="btn btn-sm btn-primary">Actualizar</button>
                 </form>
               </td>
+              <td>
+                {% if item.product.stock > 0 %}
+                {{ item.product.stock }}
+                {% else %}
+                <span class="text-danger">0</span>
+                {% endif %}
+              </td>
               <td class="price">{{ item.get_subtotal_with_vat|format_price }} €</td>
               <td>
                 <form method="post" action="{% url 'remove_from_cart' item.id %}" style="display: inline;">
@@ -82,7 +101,7 @@
           <strong class="price">{{ cart.get_total_with_vat|format_price }} €</strong>
         </div>
         <div class="d-grid gap-2">
-          <a href="{% url 'checkout' %}" class="btn btn-primary btn-lg">Proceder al Pago</a>
+          <a href="{% url 'checkout' %}" class="btn btn-primary btn-lg {% if stock_issues %}disabled{% endif %}" {% if stock_issues %}aria-disabled="true"{% endif %}>Proceder al Pago</a>
           <a href="{% url 'index' %}" class="btn btn-outline-secondary">Continuar Comprando</a>
           <form method="post" action="{% url 'clear_cart' %}">
             {% csrf_token %}

tienda/templates/tienda/checkout.html

@@ -49,6 +49,23 @@
         </div>
 
         {% if cart_items %}
+        {% if stock_issues %}
+        <div class="alert alert-warning">
+            <strong>No hay stock suficiente para algunos productos:</strong>
+            <ul class="mb-0 mt-2">
+                {% for issue in stock_issues %}
+                <li>{{ issue.product_name }} - disponible: {{ issue.available }}, en carrito: {{ issue.requested }}</li>
+                {% endfor %}
+            </ul>
+            <div class="mt-2">Vuelve al carrito y ajusta las cantidades antes de pagar.</div>
+        </div>
+        {% endif %}
+
+        <div class="alert alert-info">
+            Al pulsar en pagar se reservará tu stock durante <strong>{{ reservation_minutes }} minutos</strong>.
+            Si el pago no se completa en ese tiempo, la reserva se cancelará automáticamente.
+        </div>
+
         <div class="card mb-4">
             <div class="card-body">
                 <h5 class="card-title mb-3">1) Selecciona la dirección de envío</h5>
@@ -80,6 +97,7 @@
                         <th>Producto</th>
                         <th class="text-end">Precio (sin IVA)</th>
                         <th class="text-end">Cantidad</th>
+                        <th class="text-end">Stock actual</th>
                         <th class="text-end">Subtotal (con IVA)</th>
                     </tr>
                 </thead>
@@ -89,6 +107,7 @@
                         <td>{{ item.product.name }}</td>
                         <td class="text-end">{{ item.product.price|format_price }}€</td>
                         <td class="text-end">{{ item.quantity }}</td>
+                        <td class="text-end">{{ item.product.stock }}</td>
                         <td class="text-end">{{ item.get_subtotal_with_vat|format_price }}€</td>
                     </tr>
                     {% endfor %}
@@ -118,7 +137,7 @@
                     class="btn btn-primary payment-btn"
                     data-config-url="/tienda/config/"
                     data-session-url="/tienda/create-checkout-session/"
-                    {% if not addresses %}disabled{% endif %}>
+                    {% if not addresses or stock_issues %}disabled{% endif %}>
                     💳 Pagar con Stripe
                 </button>
                 
@@ -126,7 +145,7 @@
                     id="paypal-button"
                     class="btn btn-warning payment-btn"
                     data-payment-url="{% url 'create_paypal_payment' %}"
-                    {% if not addresses %}disabled{% endif %}>
+                    {% if not addresses or stock_issues %}disabled{% endif %}>
                     🅿️ Pagar con PayPal
                 </button>
             </div>
@@ -139,7 +158,9 @@
 
 <script>
     // Manejo del botón de PayPal
-    document.getElementById('paypal-button').addEventListener('click', async function(e) {
+    const paypalButton = document.getElementById('paypal-button');
+    if (paypalButton) {
+    paypalButton.addEventListener('click', async function(e) {
         e.preventDefault();
 
         const shippingAddressSelect = document.getElementById('shipping-address');
@@ -202,5 +223,6 @@
             button.innerHTML = originalText;
         }
     });
+    }
 </script>
 {% endblock %}

tienda/templates/tienda/crear_producto.html

@@ -46,6 +46,14 @@
                         </div>
                     </div>
 
+                    <!-- Stock -->
+                    <div class="mb-3">
+                        <label for="stock" class="form-label">Stock disponible <span class="text-danger">*</span></label>
+                        <input type="number" class="form-control" id="stock" name="stock" required
+                               min="0" step="1" placeholder="0">
+                        <div class="form-text">Cantidad máxima que podrán comprar los clientes.</div>
+                    </div>
+
                     <!-- Categoría -->
                     <div class="mb-3">
                         <label for="category" class="form-label">Categoría <span class="text-danger">*</span></label>

tienda/templates/tienda/editar_producto.html

@@ -46,6 +46,14 @@
                         </div>
                     </div>
 
+                    <!-- Stock -->
+                    <div class="mb-3">
+                        <label for="stock" class="form-label">Stock disponible <span class="text-danger">*</span></label>
+                        <input type="number" class="form-control" id="stock" name="stock" required
+                               min="0" step="1" value="{{ producto.stock }}" placeholder="0">
+                        <div class="form-text">Cantidad máxima que podrán comprar los clientes.</div>
+                    </div>
+
                     <!-- Categoría -->
                     <div class="mb-3">
                         <label for="category" class="form-label">Categoría <span class="text-danger">*</span></label>

tienda/templates/tienda/mis_productos.html

@@ -31,6 +31,7 @@
                 <th>Categoría</th>
                 <th class="text-end">Precio (sin IVA)</th>
                 <th class="text-end">Precio (con IVA)</th>
+                <th class="text-end">Stock</th>
                 <th class="text-end">Acciones</th>
             </tr>
         </thead>
@@ -53,6 +54,7 @@
                 <td>{{ producto.category.name }}</td>
                 <td class="text-end">{{ producto.price|format_price }}€</td>
                 <td class="text-end text-success"><strong>{{ producto.get_price_with_vat|format_price }}€</strong></td>
+                <td class="text-end">{{ producto.stock }}</td>
                 <td class="text-end">
                     <div class="d-flex justify-content-end gap-2">
                         <a href="{% url 'editar_producto' producto.id %}" class="btn btn-outline-primary btn-sm">Editar</a>

tienda/templates/tienda/producto.html

@@ -39,14 +39,21 @@
         <div id="descripcion">
             {{ product.briefdesc }}
         </div>
+        <div class="mt-3">
+            {% if product.stock > 0 %}
+            <span class="badge bg-success">Stock disponible: {{ product.stock }}</span>
+            {% else %}
+            <span class="badge bg-danger">Sin stock</span>
+            {% endif %}
+        </div>
         
         <form method="post" action="{% url 'add_to_cart' product.id %}" class="mt-4">
             {% csrf_token %}
             <div class="mb-3">
                 <label for="quantity" class="form-label">Cantidad:</label>
-                <input type="number" name="quantity" id="quantity" value="1" min="1" class="form-control" style="max-width: 100px;">
+                <input type="number" name="quantity" id="quantity" value="1" min="1" max="{{ product.stock }}" class="form-control" style="max-width: 100px;" {% if product.stock == 0 %}disabled{% endif %}>
             </div>
-            <button type="submit" class="btn btn-primary btn-lg">🛒 Agregar al Carrito</button>
+            <button type="submit" class="btn btn-primary btn-lg" {% if product.stock == 0 %}disabled{% endif %}>🛒 Agregar al Carrito</button>
         </form>
     </div>
 </div>

tienda/views.py

@@ -335,7 +335,7 @@ def _cancel_active_stock_reservations_for_request(request: HttpRequest):
     ).update(status=StockReservation.STATUS_CANCELLED)
 
 
-def _get_reserved_quantities_by_product(product_ids, exclude_reservation_id=None):
+def _get_reserved_quantities_by_product(product_ids, exclude_reservation_ids=None):
     if not product_ids:
         return {}
 
@@ -344,27 +344,38 @@ def _get_reserved_quantities_by_product(product_ids, exclude_reservation_id=None
         reservation__status=StockReservation.STATUS_ACTIVE,
         reservation__expires_at__gt=timezone.now(),
     )
-    if exclude_reservation_id:
-        reserved_qs = reserved_qs.exclude(reservation_id=exclude_reservation_id)
+    if exclude_reservation_ids:
+        reserved_qs = reserved_qs.exclude(reservation_id__in=exclude_reservation_ids)
 
     reserved_totals = reserved_qs.values("product_id").annotate(total_reserved=models.Sum("quantity"))
     return {row["product_id"]: row["total_reserved"] for row in reserved_totals}
 
 
-def _get_available_stock_by_product(product_ids, exclude_reservation_id=None):
+def _get_active_reservation_ids_for_request(request: HttpRequest):
+    _release_expired_stock_reservations()
+    return list(
+        StockReservation.objects.filter(
+            **_get_reservation_owner_filters(request),
+            status=StockReservation.STATUS_ACTIVE,
+            expires_at__gt=timezone.now(),
+        ).values_list("id", flat=True)
+    )
+
+
+def _get_available_stock_by_product(product_ids, exclude_reservation_ids=None):
     _release_expired_stock_reservations()
     products = Product.objects.filter(id__in=product_ids)
     stocks = {product.id: product.stock for product in products}
-    reserved = _get_reserved_quantities_by_product(product_ids, exclude_reservation_id=exclude_reservation_id)
+    reserved = _get_reserved_quantities_by_product(product_ids, exclude_reservation_ids=exclude_reservation_ids)
     return {
         product_id: max(stocks.get(product_id, 0) - reserved.get(product_id, 0), 0)
         for product_id in product_ids
     }
 
 
-def _get_cart_stock_issues(cart_items, exclude_reservation_id=None):
+def _get_cart_stock_issues(cart_items, exclude_reservation_ids=None):
     product_ids = [item.product_id for item in cart_items]
-    available_by_product = _get_available_stock_by_product(product_ids, exclude_reservation_id=exclude_reservation_id)
+    available_by_product = _get_available_stock_by_product(product_ids, exclude_reservation_ids=exclude_reservation_ids)
 
     issues = []
     for item in cart_items:
@@ -527,7 +538,7 @@ def create_order_from_cart(request, payment_method, payment_reference="", shippi
 
         reserved_from_others = _get_reserved_quantities_by_product(
             product_ids,
-            exclude_reservation_id=locked_reservation.id if locked_reservation else None,
+            exclude_reservation_ids=[locked_reservation.id] if locked_reservation else None,
         )
 
         for item in cart_items:
@@ -604,9 +615,25 @@ def add_to_cart(request: HttpRequest, product_id: int):
     try:
         product = Product.objects.get(id=product_id)
         cart = get_or_create_cart(request)
+
+        _cancel_active_stock_reservations_for_request(request)
+        _clear_stock_reservation_session(request)
         
         # Obtener cantidad del POST o por defecto 1
         quantity = int(request.POST.get('quantity', 1))
+        if quantity <= 0:
+            messages.error(request, "La cantidad debe ser mayor que cero.")
+            return redirect('producto', id=product_id)
+
+        existing_item = CartItem.objects.filter(cart=cart, product=product).first()
+        desired_quantity = quantity if existing_item is None else existing_item.quantity + quantity
+        available = _get_available_stock_by_product([product.id]).get(product.id, 0)
+        if desired_quantity > available:
+            messages.error(
+                request,
+                f"No hay stock suficiente de '{product.name}'. Disponible: {available}, solicitado: {desired_quantity}.",
+            )
+            return redirect('producto', id=product_id)
         
         # Buscar si ya existe el producto en el carrito
         cart_item, created = CartItem.objects.get_or_create(
@@ -632,6 +659,10 @@ def add_to_cart(request: HttpRequest, product_id: int):
             })
         
         return redirect('view_cart')
+
+    except ValueError:
+        messages.error(request, "Cantidad no válida.")
+        return redirect('producto', id=product_id)
     
     except Product.DoesNotExist:
         messages.error(request, "Producto no encontrado.")
@@ -641,9 +672,13 @@ def add_to_cart(request: HttpRequest, product_id: int):
 def view_cart(request: HttpRequest):
     """Muestra el contenido del carrito"""
     cart = get_or_create_cart(request)
+    cart_items = list(cart.items.select_related("product"))
+    active_reservation_ids = _get_active_reservation_ids_for_request(request)
+    stock_issues = _get_cart_stock_issues(cart_items, exclude_reservation_ids=active_reservation_ids)
     return render(request, "tienda/cart.html", {
         "cart": cart,
-        "cart_items": cart.items.all()
+        "cart_items": cart_items,
+        "stock_issues": stock_issues,
     })
 
 
@@ -652,10 +687,21 @@ def update_cart_item(request: HttpRequest, item_id: int):
     try:
         cart = get_or_create_cart(request)
         cart_item = CartItem.objects.get(id=item_id, cart=cart)
+
+        _cancel_active_stock_reservations_for_request(request)
+        _clear_stock_reservation_session(request)
         
         quantity = int(request.POST.get('quantity', 1))
         
         if quantity > 0:
+            available = _get_available_stock_by_product([cart_item.product_id]).get(cart_item.product_id, 0)
+            if quantity > available:
+                messages.error(
+                    request,
+                    f"No hay stock suficiente de '{cart_item.product.name}'. Disponible: {available}, solicitado: {quantity}.",
+                )
+                return redirect('view_cart')
+
             cart_item.quantity = quantity
             cart_item.save()
             messages.success(request, "Cantidad actualizada.")
@@ -668,12 +714,17 @@ def update_cart_item(request: HttpRequest, item_id: int):
     except CartItem.DoesNotExist:
         messages.error(request, "Producto no encontrado en el carrito.")
         return redirect('view_cart')
+    except ValueError:
+        messages.error(request, "Cantidad no válida.")
+        return redirect('view_cart')
 
 
 def remove_from_cart(request: HttpRequest, item_id: int):
     """Elimina un producto del carrito"""
     try:
         cart = get_or_create_cart(request)
+        _cancel_active_stock_reservations_for_request(request)
+        _clear_stock_reservation_session(request)
         cart_item = CartItem.objects.get(id=item_id, cart=cart)
         product_name = cart_item.product.name
         cart_item.delete()
@@ -688,6 +739,8 @@ def remove_from_cart(request: HttpRequest, item_id: int):
 def clear_cart(request: HttpRequest):
     """Vacía todo el carrito"""
     cart = get_or_create_cart(request)
+    _cancel_active_stock_reservations_for_request(request)
+    _clear_stock_reservation_session(request)
     cart.items.all().delete()
     messages.success(request, "Carrito vaciado.")
     return redirect('view_cart')
@@ -769,12 +822,13 @@ def crear_producto(request: HttpRequest):
         briefdesc = request.POST.get("briefdesc")
         description = request.POST.get("description")
         price = request.POST.get("price")
+        stock = request.POST.get("stock")
         category_id = request.POST.get("category")
         primary_image_file = request.FILES.get("primary_image")
         secondary_images_files = request.FILES.getlist("secondary_images")
         
         # Validaciones
-        if not all([name, description, price, category_id]):
+        if not all([name, description, price, stock, category_id]):
             messages.error(request, "Por favor completa todos los campos obligatorios.")
             categories = Category.objects.all()
             return render(request, "tienda/crear_producto.html", {"categories": categories})
@@ -787,6 +841,15 @@ def crear_producto(request: HttpRequest):
             messages.error(request, "El precio debe ser un número válido.")
             categories = Category.objects.all()
             return render(request, "tienda/crear_producto.html", {"categories": categories})
+
+        try:
+            stock = int(stock)
+            if stock < 0:
+                raise ValueError("El stock no puede ser negativo")
+        except ValueError:
+            messages.error(request, "El stock debe ser un número entero válido.")
+            categories = Category.objects.all()
+            return render(request, "tienda/crear_producto.html", {"categories": categories})
         
         try:
             category = Category.objects.get(id=category_id)
@@ -809,6 +872,7 @@ def crear_producto(request: HttpRequest):
             briefdesc=briefdesc or "",
             description=description,
             price=price,
+            stock=stock,
             category=category,
             primary_image=primary_image,
             creator=request.user
@@ -841,11 +905,12 @@ def editar_producto(request: HttpRequest, id: int):
         briefdesc = request.POST.get("briefdesc")
         description = request.POST.get("description")
         price = request.POST.get("price")
+        stock = request.POST.get("stock")
         category_id = request.POST.get("category")
         primary_image_file = request.FILES.get("primary_image")
         secondary_images_files = request.FILES.getlist("secondary_images")
 
-        if not all([name, description, price, category_id]):
+        if not all([name, description, price, stock, category_id]):
             messages.error(request, "Por favor completa todos los campos obligatorios.")
             categories = Category.objects.all()
             return render(request, "tienda/editar_producto.html", {
@@ -865,6 +930,18 @@ def editar_producto(request: HttpRequest, id: int):
                 "producto": producto
             })
 
+        try:
+            stock = int(stock)
+            if stock < 0:
+                raise ValueError("El stock no puede ser negativo")
+        except ValueError:
+            messages.error(request, "El stock debe ser un número entero válido.")
+            categories = Category.objects.all()
+            return render(request, "tienda/editar_producto.html", {
+                "categories": categories,
+                "producto": producto
+            })
+
         try:
             category = Category.objects.get(id=category_id)
         except Category.DoesNotExist:
@@ -879,6 +956,7 @@ def editar_producto(request: HttpRequest, id: int):
         producto.briefdesc = briefdesc or ""
         producto.description = description
         producto.price = price
+        producto.stock = stock
         producto.category = category
 
         if primary_image_file:
@@ -925,12 +1003,16 @@ def borrar_producto(request: HttpRequest, id: int):
 @login_required
 def checkout(request: HttpRequest):
     cart = get_or_create_cart(request)
-    cart_items = cart.items.select_related("product")
+    cart_items = list(cart.items.select_related("product"))
+    active_reservation_ids = _get_active_reservation_ids_for_request(request)
+    stock_issues = _get_cart_stock_issues(cart_items, exclude_reservation_ids=active_reservation_ids)
     addresses = ShippingAddress.objects.filter(user=request.user)
     return render(request, "tienda/checkout.html", {
         "cart": cart,
         "cart_items": cart_items,
         "addresses": addresses,
+        "stock_issues": stock_issues,
+        "reservation_minutes": STOCK_RESERVATION_MINUTES,
     })
 
 @csrf_exempt
@@ -954,11 +1036,24 @@ def create_checkout_session(request: HttpRequest):
             return JsonResponse({"error": "Debes seleccionar una dirección de envío válida."}, status=400)
 
         cart = get_or_create_cart(request)
-        cart_items = cart.items.select_related("product")
+        cart_items = list(cart.items.select_related("product"))
 
-        if not cart_items.exists():
+        if not cart_items:
             return JsonResponse({"error": "El carrito está vacío"}, status=400)
 
+        active_reservation_ids = _get_active_reservation_ids_for_request(request)
+        stock_issues = _get_cart_stock_issues(cart_items, exclude_reservation_ids=active_reservation_ids)
+        if stock_issues:
+            return JsonResponse({"error": _build_stock_issue_message(stock_issues[0])}, status=400)
+
+        reservation, reservation_issues = _create_stock_reservation_for_cart(
+            request,
+            cart_items,
+            StockReservation.PAYMENT_STRIPE,
+        )
+        if reservation is None:
+            return JsonResponse({"error": reservation_issues[0]}, status=400)
+
         stripe.api_key = settings.STRIPE_SECRET_KEY
 
         line_items = []
@@ -995,6 +1090,8 @@ def create_checkout_session(request: HttpRequest):
 
         request.session['stripe_session_id'] = session.id
         request.session['selected_shipping_address_id'] = shipping_address.id
+        request.session[STOCK_RESERVATION_SESSION_KEY] = reservation.id
+        request.session[STOCK_RESERVATION_PAYMENT_SESSION_KEY] = StockReservation.PAYMENT_STRIPE
 
         return JsonResponse({"sessionId": session.id})
     except Exception as e:
@@ -1002,20 +1099,37 @@ def create_checkout_session(request: HttpRequest):
         return JsonResponse({"error": f"Error al crear sesión de pago: {str(e)}"}, status=500)
 
 
+@login_required
 def checkout_success(request: HttpRequest):
     payment_reference = request.session.get('stripe_session_id', "")
     shipping_address_id = request.session.get('selected_shipping_address_id')
     shipping_address = ShippingAddress.objects.filter(id=shipping_address_id, user=request.user).first()
-    order = create_order_from_cart(request, Order.PAYMENT_STRIPE, payment_reference, shipping_address)
+    reservation = _get_session_stock_reservation(request, StockReservation.PAYMENT_STRIPE)
+    order, order_error = create_order_from_cart(
+        request,
+        Order.PAYMENT_STRIPE,
+        payment_reference,
+        shipping_address,
+        stock_reservation=reservation,
+    )
+
+    if order is None:
+        messages.error(request, order_error)
+        return redirect("checkout")
+
     if 'stripe_session_id' in request.session:
         del request.session['stripe_session_id']
     if 'selected_shipping_address_id' in request.session:
         del request.session['selected_shipping_address_id']
+    _clear_stock_reservation_session(request)
     messages.success(request, "Pago realizado correctamente. ¡Gracias por tu compra!")
     return render(request, "tienda/checkout_success.html", {"order": order})
 
 
+@login_required
 def checkout_cancel(request: HttpRequest):
+    _cancel_active_stock_reservations_for_request(request)
+    _clear_stock_reservation_session(request)
     messages.info(request, "Pago cancelado. Puedes intentarlo de nuevo cuando quieras.")
     return render(request, "tienda/checkout_cancel.html", {})
 
@@ -1057,11 +1171,24 @@ def create_paypal_payment(request: HttpRequest):
         import paypalrestsdk
         
         cart = get_or_create_cart(request)
-        cart_items = cart.items.select_related("product")
+        cart_items = list(cart.items.select_related("product"))
 
-        if not cart_items.exists():
+        if not cart_items:
             return JsonResponse({"error": "El carrito está vacío"}, status=400)
 
+        active_reservation_ids = _get_active_reservation_ids_for_request(request)
+        stock_issues = _get_cart_stock_issues(cart_items, exclude_reservation_ids=active_reservation_ids)
+        if stock_issues:
+            return JsonResponse({"error": _build_stock_issue_message(stock_issues[0])}, status=400)
+
+        reservation, reservation_issues = _create_stock_reservation_for_cart(
+            request,
+            cart_items,
+            StockReservation.PAYMENT_PAYPAL,
+        )
+        if reservation is None:
+            return JsonResponse({"error": reservation_issues[0]}, status=400)
+
         # Configurar PayPal
         paypalrestsdk.configure({
             "mode": settings.PAYPAL_MODE,
@@ -1124,6 +1251,8 @@ def create_paypal_payment(request: HttpRequest):
             # Guardar el payment ID en sesión
             request.session['paypal_payment_id'] = payment.id
             request.session['selected_shipping_address_id'] = shipping_address.id
+            request.session[STOCK_RESERVATION_SESSION_KEY] = reservation.id
+            request.session[STOCK_RESERVATION_PAYMENT_SESSION_KEY] = StockReservation.PAYMENT_PAYPAL
             
             # Encontrar el link de aprobación
             for link in payment.links:
@@ -1178,13 +1307,25 @@ def paypal_execute(request: HttpRequest):
             # Pago exitoso - crear pedido y limpiar el carrito
             shipping_address_id = request.session.get('selected_shipping_address_id')
             shipping_address = ShippingAddress.objects.filter(id=shipping_address_id, user=request.user).first()
-            order = create_order_from_cart(request, Order.PAYMENT_PAYPAL, payment_id, shipping_address)
+            reservation = _get_session_stock_reservation(request, StockReservation.PAYMENT_PAYPAL)
+            order, order_error = create_order_from_cart(
+                request,
+                Order.PAYMENT_PAYPAL,
+                payment_id,
+                shipping_address,
+                stock_reservation=reservation,
+            )
+
+            if order is None:
+                messages.error(request, order_error)
+                return redirect("checkout")
             
             # Limpiar la sesión
             if 'paypal_payment_id' in request.session:
                 del request.session['paypal_payment_id']
             if 'selected_shipping_address_id' in request.session:
                 del request.session['selected_shipping_address_id']
+            _clear_stock_reservation_session(request)
 
             messages.success(request, "¡Pago realizado correctamente con PayPal! Gracias por tu compra.")
             return render(request, "tienda/checkout_success.html", {"order": order})
@@ -1197,6 +1338,8 @@ def paypal_execute(request: HttpRequest):
         logger.exception("PAYPAL_EXECUTE_EXCEPTION user_id=%s error=%s", request.user.id, str(e))
         messages.error(request, f"Error: {str(e)}")
         return redirect("checkout")
+
+
 def search_suggestions(request: HttpRequest):
     """API AJAX que retorna sugerencias de búsqueda en JSON"""
     query = request.GET.get('q', '').strip()