feat: implement shopping cart feature with user authentication support

- Added `Cart` and `CartItem` models with migrations for managing user-specific carts and items
- Developed services for cart-related operations: adding, removing, and updating cart items
- Built specialized templates (`cart.html`) and styled them with new CSS assets (`cart.css`)
- Enabled real-time UI updates via AJAX in shopping cart interactions (`cart.js`)
- Modified header to dynamically display cart link with user authentication awareness
- Added Leaflet-based interactive map to the contacts page and integrated CSS/JS dependencies
- Expanded tests for cart functionality, item detail page cart integration, and contacts page maps

orders/admin.py

@@ -1,3 +1,22 @@
 from django.contrib import admin
 
-# Register your models here.
+from orders.models import Cart, CartItem
+
+
+class CartItemInline(admin.TabularInline):
+    model = CartItem
+    extra = 0
+
+
+@admin.register(Cart)
+class CartAdmin(admin.ModelAdmin):
+    list_display = ("user", "updated_at", "created_at")
+    search_fields = ("user__username", "user__email")
+    inlines = [CartItemInline]
+
+
+@admin.register(CartItem)
+class CartItemAdmin(admin.ModelAdmin):
+    list_display = ("item", "cart", "quantity", "updated_at")
+    list_select_related = ("cart", "item", "cart__user")
+    search_fields = ("item__name", "cart__user__username", "cart__user__email")

orders/migrations/0001_initial.py

@@ -0,0 +1,49 @@
+# Generated by Django 6.0.4 on 2026-05-15 20:26
+
+import django.core.validators
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ('items', '0003_subcategory_item_subcategory_and_more'),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Cart',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('created_at', models.DateTimeField(auto_now_add=True, verbose_name='Дата создания')),
+                ('updated_at', models.DateTimeField(auto_now=True, verbose_name='Дата обновления')),
+                ('user', models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, related_name='cart', to=settings.AUTH_USER_MODEL, verbose_name='Пользователь')),
+            ],
+            options={
+                'verbose_name': 'Корзина',
+                'verbose_name_plural': 'Корзины',
+            },
+        ),
+        migrations.CreateModel(
+            name='CartItem',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('quantity', models.PositiveIntegerField(validators=[django.core.validators.MinValueValidator(1)], verbose_name='Количество')),
+                ('created_at', models.DateTimeField(auto_now_add=True, verbose_name='Дата создания')),
+                ('updated_at', models.DateTimeField(auto_now=True, verbose_name='Дата обновления')),
+                ('cart', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='items', to='orders.cart', verbose_name='Корзина')),
+                ('item', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='cart_entries', to='items.item', verbose_name='Товар')),
+            ],
+            options={
+                'verbose_name': 'Позиция корзины',
+                'verbose_name_plural': 'Позиции корзины',
+                'ordering': ('created_at', 'id'),
+                'constraints': [models.UniqueConstraint(fields=('cart', 'item'), name='unique_cart_item_per_cart')],
+            },
+        ),
+    ]

orders/models.py

@@ -1,3 +1,59 @@
+from django.conf import settings
+from django.core.validators import MinValueValidator
 from django.db import models
 
-# Create your models here.
+from items.models import Item
+
+
+class Cart(models.Model):
+    user = models.OneToOneField(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE,
+        related_name="cart",
+        verbose_name="Пользователь",
+    )
+    created_at = models.DateTimeField(auto_now_add=True, verbose_name="Дата создания")
+    updated_at = models.DateTimeField(auto_now=True, verbose_name="Дата обновления")
+
+    class Meta:
+        verbose_name = "Корзина"
+        verbose_name_plural = "Корзины"
+
+    def __str__(self):
+        return f"Корзина пользователя {self.user}"
+
+
+class CartItem(models.Model):
+    cart = models.ForeignKey(
+        Cart,
+        on_delete=models.CASCADE,
+        related_name="items",
+        verbose_name="Корзина",
+    )
+    item = models.ForeignKey(
+        Item,
+        on_delete=models.CASCADE,
+        related_name="cart_entries",
+        verbose_name="Товар",
+    )
+    quantity = models.PositiveIntegerField(
+        validators=[MinValueValidator(1)],
+        verbose_name="Количество",
+    )
+    created_at = models.DateTimeField(auto_now_add=True, verbose_name="Дата создания")
+    updated_at = models.DateTimeField(auto_now=True, verbose_name="Дата обновления")
+
+    class Meta:
+        ordering = ("created_at", "id")
+        constraints = [
+            models.UniqueConstraint(fields=("cart", "item"), name="unique_cart_item_per_cart"),
+        ]
+        verbose_name = "Позиция корзины"
+        verbose_name_plural = "Позиции корзины"
+
+    def __str__(self):
+        return f"{self.item} x {self.quantity}"
+
+    @property
+    def subtotal(self):
+        return self.item.price * self.quantity

orders/services.py

@@ -0,0 +1,69 @@
+from decimal import Decimal
+from typing import Any
+
+from django.core.exceptions import ValidationError
+from django.utils import formats
+
+from items.models import Item
+from orders.models import Cart, CartItem
+
+
+def format_currency(value: Decimal) -> str:
+    return f"{formats.number_format(value, 2)} руб."
+
+
+def get_or_create_cart(user: Any) -> Cart:
+    cart, _ = Cart.objects.get_or_create(user=user)
+    return cart
+
+
+def get_user_cart_item_ids(user: Any) -> set[int]:
+    if not getattr(user, "is_authenticated", False):
+        return set()
+
+    return set(
+        CartItem.objects.filter(cart__user=user).values_list("item_id", flat=True)
+    )
+
+
+def get_user_cart(user: Any) -> Cart | None:
+    if not getattr(user, "is_authenticated", False):
+        return None
+
+    return (
+        Cart.objects.filter(user=user)
+        .prefetch_related("items__item__images")
+        .select_related("user")
+        .first()
+    )
+
+
+def add_item_to_cart(user: Any, item: Item, quantity: int = 1) -> tuple[CartItem, bool]:
+    if quantity < 1:
+        raise ValidationError("Количество товара должно быть не меньше 1.")
+
+    if not item.is_available:
+        raise ValidationError("Недоступный товар нельзя добавить в корзину.")
+
+    cart = get_or_create_cart(user)
+    cart_item, created = CartItem.objects.get_or_create(
+        cart=cart,
+        item=item,
+        defaults={"quantity": quantity},
+    )
+    return cart_item, created
+
+
+def remove_item_from_cart(user: Any, item_id: int) -> bool:
+    deleted, _ = CartItem.objects.filter(cart__user=user, item_id=item_id).delete()
+    return bool(deleted)
+
+
+def update_cart_item_quantity(user: Any, item_id: int, quantity: int) -> CartItem:
+    if quantity < 1:
+        raise ValidationError("Количество товара должно быть не меньше 1.")
+
+    cart_item = CartItem.objects.select_related("item").get(cart__user=user, item_id=item_id)
+    cart_item.quantity = quantity
+    cart_item.save(update_fields=["quantity", "updated_at"])
+    return cart_item

orders/tests.py

@@ -1,3 +1,110 @@
-from django.test import TestCase
+from django.contrib.auth import get_user_model
+from django.db import IntegrityError
+from django.test import TestCase, override_settings
+from django.urls import reverse
 
-# Create your tests here.
+from items.models import Category, Item, ItemImage, Subcategory
+from orders.models import Cart, CartItem
+
+
+User = get_user_model()
+
+
+@override_settings(MEDIA_URL="/media/")
+class CartFlowTests(TestCase):
+    def setUp(self):
+        self.user = User.objects.create_user(
+            username="cart-user",
+            email="cart@example.com",
+            password="StrongPassword123",
+            is_active=True,
+        )
+        self.category = Category.objects.create(name="Сантехника", slug="plumbing")
+        self.subcategory = Subcategory.objects.create(name="Мойки", slug="sinks", category=self.category)
+        self.item = Item.objects.create(
+            name="Кухонная мойка",
+            slug="kitchen-sink",
+            category=self.category,
+            subcategory=self.subcategory,
+            description="Искусственный камень",
+            price="1600.00",
+            is_available=True,
+        )
+        self.unavailable_item = Item.objects.create(
+            name="Смеситель",
+            slug="tap",
+            category=self.category,
+            subcategory=self.subcategory,
+            description="Недоступный товар",
+            price="400.00",
+            is_available=False,
+        )
+
+    def test_cart_item_is_unique_per_cart(self):
+        cart = Cart.objects.create(user=self.user)
+        CartItem.objects.create(cart=cart, item=self.item, quantity=1)
+
+        with self.assertRaises(IntegrityError):
+            CartItem.objects.create(cart=cart, item=self.item, quantity=2)
+
+    def test_add_remove_and_update_quantity_for_authenticated_user(self):
+        self.client.force_login(self.user)
+
+        add_response = self.client.post(
+            reverse("orders:add"),
+            data={"item_id": self.item.id, "next": reverse("orders:cart")},
+        )
+        self.assertRedirects(add_response, reverse("orders:cart"))
+        self.assertTrue(CartItem.objects.filter(cart__user=self.user, item=self.item, quantity=1).exists())
+
+        update_response = self.client.post(
+            reverse("orders:update_quantity"),
+            data={"item_id": self.item.id, "quantity": 3, "next": reverse("orders:cart")},
+        )
+        self.assertRedirects(update_response, reverse("orders:cart"))
+        self.assertTrue(CartItem.objects.filter(cart__user=self.user, item=self.item, quantity=3).exists())
+
+        remove_response = self.client.post(
+            reverse("orders:remove"),
+            data={"item_id": self.item.id, "next": reverse("orders:cart")},
+        )
+        self.assertRedirects(remove_response, reverse("orders:cart"))
+        self.assertFalse(CartItem.objects.filter(cart__user=self.user, item=self.item).exists())
+
+    def test_add_endpoint_rejects_unavailable_item(self):
+        self.client.force_login(self.user)
+
+        response = self.client.post(
+            reverse("orders:add"),
+            data={"item_id": self.unavailable_item.id, "next": reverse("orders:cart")},
+            follow=True,
+        )
+
+        self.assertEqual(response.status_code, 200)
+        self.assertFalse(CartItem.objects.filter(cart__user=self.user, item=self.unavailable_item).exists())
+        self.assertContains(response, "Недоступный товар нельзя добавить в корзину.")
+
+    def test_cart_page_shows_authenticated_user_items(self):
+        cart = Cart.objects.create(user=self.user)
+        CartItem.objects.create(cart=cart, item=self.item, quantity=2)
+        ItemImage.objects.create(
+            item=self.item,
+            image="items/cart-item.jpg",
+            alt="Фото мойки",
+            is_primary=True,
+        )
+        self.client.force_login(self.user)
+
+        response = self.client.get(reverse("orders:cart"))
+
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(response, "Кухонная мойка")
+        self.assertContains(response, "1600,00 руб.")
+        self.assertContains(response, "3200,00 руб.")
+        self.assertContains(response, "/media/items/cart-item.jpg")
+
+    def test_cart_page_redirects_guest_to_login(self):
+        response = self.client.get(reverse("orders:cart"))
+
+        self.assertEqual(response.status_code, 302)
+        self.assertIn(reverse("users:login"), response["Location"])

orders/urls.py

@@ -1,3 +1,13 @@
 
+from django.urls import path
 
-urlpatterns = []
+from orders import views
+
+app_name = "orders"
+
+urlpatterns = [
+    path("cart/", views.cart, name="cart"),
+    path("cart/add/", views.add, name="add"),
+    path("cart/remove/", views.remove, name="remove"),
+    path("cart/update-quantity/", views.update_quantity, name="update_quantity"),
+]

orders/views.py

@@ -1,3 +1,106 @@
-from django.shortcuts import render
+from decimal import Decimal
 
-# Create your views here.
+from django.contrib import messages
+from django.contrib.auth.decorators import login_required
+from django.core.exceptions import ValidationError
+from django.http import Http404, HttpRequest, HttpResponse
+from django.shortcuts import get_object_or_404, redirect, render
+from django.urls import reverse
+from django.utils.http import url_has_allowed_host_and_scheme
+from django.views.decorators.http import require_POST
+
+from items.models import Item
+from orders.models import CartItem
+from orders.services import (
+    add_item_to_cart,
+    format_currency,
+    get_user_cart,
+    remove_item_from_cart,
+    update_cart_item_quantity,
+)
+
+
+def resolve_next_url(request: HttpRequest, fallback: str) -> str:
+    next_url = request.POST.get("next") or fallback
+    if not url_has_allowed_host_and_scheme(
+        next_url,
+        allowed_hosts={request.get_host()},
+        require_https=request.is_secure(),
+    ):
+        return fallback
+    return next_url
+
+
+@login_required
+def cart(request: HttpRequest) -> HttpResponse:
+    cart_items: list[CartItem] = []
+    total_quantity = 0
+    total_amount = "0,00 руб."
+
+    cart_obj = get_user_cart(request.user)
+    if cart_obj:
+        cart_items = list(
+            cart_obj.items.select_related("item__category", "item__subcategory").prefetch_related("item__images")
+        )
+        total_quantity = sum(cart_item.quantity for cart_item in cart_items)
+        total_amount_value = sum(
+            (cart_item.item.price * cart_item.quantity for cart_item in cart_items),
+            start=Decimal("0.00"),
+        )
+        total_amount = format_currency(total_amount_value)
+
+    return render(request, "orders/cart.html", {
+        "cart_items": cart_items,
+        "total_quantity": total_quantity,
+        "total_amount": total_amount,
+    })
+
+
+@login_required
+@require_POST
+def add(request: HttpRequest) -> HttpResponse:
+    item = get_object_or_404(Item, pk=request.POST.get("item_id"))
+
+    try:
+        _, created = add_item_to_cart(request.user, item)
+        if created:
+            messages.success(request, f"Товар «{item.name}» добавлен в корзину.")
+        else:
+            messages.info(request, f"Товар «{item.name}» уже есть в корзине.")
+    except ValidationError as error:
+        messages.error(request, error.message)
+
+    return redirect(resolve_next_url(request, reverse("orders:cart")))
+
+
+@login_required
+@require_POST
+def remove(request: HttpRequest) -> HttpResponse:
+    item = get_object_or_404(Item, pk=request.POST.get("item_id"))
+    removed = remove_item_from_cart(request.user, item.id)
+
+    if removed:
+        messages.success(request, f"Товар «{item.name}» удалён из корзины.")
+    else:
+        messages.info(request, f"Товар «{item.name}» уже отсутствует в корзине.")
+
+    return redirect(resolve_next_url(request, reverse("orders:cart")))
+
+
+@login_required
+@require_POST
+def update_quantity(request: HttpRequest) -> HttpResponse:
+    item = get_object_or_404(Item, pk=request.POST.get("item_id"))
+
+    try:
+        quantity = int(request.POST.get("quantity"))
+        update_cart_item_quantity(request.user, item.id, quantity)
+        messages.success(request, f"Количество товара «{item.name}» обновлено.")
+    except (TypeError, ValueError):
+        messages.error(request, "Некорректное количество товара.")
+    except CartItem.DoesNotExist as error:
+        raise Http404() from error
+    except ValidationError as error:
+        messages.error(request, error.message)
+
+    return redirect(resolve_next_url(request, reverse("orders:cart")))