Functional cart and balance display

src/app/api/cart/route.ts

@@ -0,0 +1,83 @@
+import { NextResponse } from "next/server";
+import { auth } from "~/server/auth";
+import { db } from "~/server/db";
+
+export async function PATCH(request: Request) {
+  const session = await auth();
+
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
+  type CartItem = {
+    id: string;
+    quantity: number;
+  };
+
+  const userId = session.user.id;
+  const body = (await request.json()) as CartItem;
+  const { id: itemId, quantity } = body;
+
+  if (!itemId || !quantity || quantity == 0) {
+    return NextResponse.json(
+      { error: "Invalid request data" },
+      { status: 400 },
+    );
+  }
+
+  try {
+    // Find or create the user's cart
+    let cart = await db.cart.findFirst({
+      where: { userId },
+      include: { cartItems: true },
+    });
+
+    // Use nullish coalescing assignment
+    cart ??= await db.cart.create({
+      data: { userId },
+      include: { cartItems: true },
+    });
+
+    // Check if the item already exists in the cart
+    const existingCartItem = await db.cartItem.findUnique({
+      where: { itemId },
+    });
+
+    if (existingCartItem) {
+      if (quantity <= 0 && quantity * -1 >= existingCartItem.quantity) {
+        await db.cartItem.delete({
+          where: { itemId },
+        });
+      } else {
+        // Update quantity
+        await db.cartItem.update({
+          where: { itemId },
+          data: { quantity: existingCartItem.quantity + quantity },
+        });
+      }
+    } else {
+      // Add new item
+      await db.cartItem.create({
+        data: {
+          itemId,
+          quantity,
+          cartId: userId,
+        },
+      });
+    }
+
+    // Fetch the updated cart
+    const updatedCart = await db.cart.findUnique({
+      where: { userId: userId },
+      include: { cartItems: { include: { sellable: true } } },
+    });
+
+    return NextResponse.json(updatedCart);
+  } catch (error) {
+    console.error(error);
+    return NextResponse.json(
+      { error: "Failed to add item to cart" },
+      { status: 500 },
+    );
+  }
+}

src/app/api/items/route.ts

@@ -16,6 +16,9 @@ export async function GET() {
       item: { select: { stock: true } },
     },
   });
+  // and cache no store header
 
-  return NextResponse.json(sellables);
+  return NextResponse.json(sellables, {
+    headers: { "Cache-Control": "no-store" },
+  });
 }

src/app/api/user/route.ts

@@ -45,6 +45,12 @@ export async function GET() {
       shops: {
         select: { id: true, label: true, sellables: true },
       },
+      carts: {
+        select: {
+          cartItems: { select: { itemId: true, quantity: true } },
+        },
+      },
+      balance: true,
     },
   });