feat(saleor): Phase 4 - Checkout Flow

- Create checkout page with form validation
- Implement shipping/billing address forms
- Add Cash on Delivery (COD) payment method
- Integrate Saleor checkout completion mutation
- Add order success page with confirmation
- Handle checkout errors gracefully
- Display order summary with line items

src/app/checkout/page.tsx

@@ -0,0 +1,464 @@
+"use client";
+
+import { useState, useEffect } from "react";
+import { useRouter } from "next/navigation";
+import Link from "next/link";
+import Image from "next/image";
+import Header from "@/components/layout/Header";
+import Footer from "@/components/layout/Footer";
+import { useSaleorCheckoutStore } from "@/stores/saleorCheckoutStore";
+import { formatPrice } from "@/lib/saleor";
+import { saleorClient } from "@/lib/saleor/client";
+import {
+  CHECKOUT_SHIPPING_ADDRESS_UPDATE,
+  CHECKOUT_BILLING_ADDRESS_UPDATE,
+  CHECKOUT_COMPLETE,
+} from "@/lib/saleor/mutations/Checkout";
+
+interface AddressForm {
+  firstName: string;
+  lastName: string;
+  streetAddress1: string;
+  streetAddress2: string;
+  city: string;
+  postalCode: string;
+  phone: string;
+}
+
+export default function CheckoutPage() {
+  const router = useRouter();
+  const { checkout, refreshCheckout, getLines, getTotal } = useSaleorCheckoutStore();
+  const [isLoading, setIsLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+  const [orderComplete, setOrderComplete] = useState(false);
+  const [orderNumber, setOrderNumber] = useState<string | null>(null);
+  
+  const [sameAsShipping, setSameAsShipping] = useState(true);
+  const [shippingAddress, setShippingAddress] = useState<AddressForm>({
+    firstName: "",
+    lastName: "",
+    streetAddress1: "",
+    streetAddress2: "",
+    city: "",
+    postalCode: "",
+    phone: "",
+  });
+  const [billingAddress, setBillingAddress] = useState<AddressForm>({
+    firstName: "",
+    lastName: "",
+    streetAddress1: "",
+    streetAddress2: "",
+    city: "",
+    postalCode: "",
+    phone: "",
+  });
+
+  const lines = getLines();
+  const total = getTotal();
+
+  useEffect(() => {
+    if (!checkout) {
+      refreshCheckout();
+    }
+  }, [checkout, refreshCheckout]);
+
+  // Redirect if cart is empty
+  useEffect(() => {
+    if (lines.length === 0 && !orderComplete) {
+      // Optionally redirect to cart or products
+      // router.push("/products");
+    }
+  }, [lines, orderComplete, router]);
+
+  const handleShippingChange = (field: keyof AddressForm, value: string) => {
+    setShippingAddress((prev) => ({ ...prev, [field]: value }));
+    if (sameAsShipping) {
+      setBillingAddress((prev) => ({ ...prev, [field]: value }));
+    }
+  };
+
+  const handleBillingChange = (field: keyof AddressForm, value: string) => {
+    setBillingAddress((prev) => ({ ...prev, [field]: value }));
+  };
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    
+    if (!checkout) {
+      setError("No active checkout. Please try again.");
+      return;
+    }
+
+    setIsLoading(true);
+    setError(null);
+
+    try {
+      // Update shipping address
+      const shippingResult = await saleorClient.mutate({
+        mutation: CHECKOUT_SHIPPING_ADDRESS_UPDATE,
+        variables: {
+          checkoutId: checkout.id,
+          shippingAddress: {
+            ...shippingAddress,
+            country: "RS", // Serbia
+          },
+        },
+      });
+
+      if (shippingResult.data?.checkoutShippingAddressUpdate?.errors?.length > 0) {
+        throw new Error(shippingResult.data.checkoutShippingAddressUpdate.errors[0].message);
+      }
+
+      // Update billing address
+      const billingResult = await saleorClient.mutate({
+        mutation: CHECKOUT_BILLING_ADDRESS_UPDATE,
+        variables: {
+          checkoutId: checkout.id,
+          billingAddress: {
+            ...billingAddress,
+            country: "RS",
+          },
+        },
+      });
+
+      if (billingResult.data?.checkoutBillingAddressUpdate?.errors?.length > 0) {
+        throw new Error(billingResult.data.checkoutBillingAddressUpdate.errors[0].message);
+      }
+
+      // Complete checkout (creates order)
+      const completeResult = await saleorClient.mutate({
+        mutation: CHECKOUT_COMPLETE,
+        variables: {
+          checkoutId: checkout.id,
+        },
+      });
+
+      if (completeResult.data?.checkoutComplete?.errors?.length > 0) {
+        throw new Error(completeResult.data.checkoutComplete.errors[0].message);
+      }
+
+      const order = completeResult.data?.checkoutComplete?.order;
+      if (order) {
+        setOrderNumber(order.number);
+        setOrderComplete(true);
+      } else {
+        throw new Error("Failed to create order");
+      }
+    } catch (err: any) {
+      setError(err.message || "An error occurred during checkout");
+    } finally {
+      setIsLoading(false);
+    }
+  };
+
+  // Order Success Page
+  if (orderComplete) {
+    return (
+      <main className="min-h-screen">
+        <Header />
+        <section className="pt-24 pb-20 px-4">
+          <div className="max-w-2xl mx-auto text-center">
+            <div className="mb-6">
+              <div className="w-16 h-16 bg-green-100 rounded-full flex items-center justify-center mx-auto mb-4">
+                <svg className="w-8 h-8 text-green-600" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M5 13l4 4L19 7" />
+                </svg>
+              </div>
+              <h1 className="text-3xl font-serif mb-2">Order Confirmed!</h1>
+              <p className="text-foreground-muted">Thank you for your purchase.</p>
+            </div>
+            
+            {orderNumber && (
+              <div className="bg-background-ice p-6 rounded-lg mb-6">
+                <p className="text-sm text-foreground-muted mb-1">Order Number</p>
+                <p className="text-2xl font-serif">#{orderNumber}</p>
+              </div>
+            )}
+            
+            <p className="text-foreground-muted mb-8">
+              You will receive a confirmation email shortly. We will contact you to arrange Cash on Delivery.
+            </p>
+            
+            <Link
+              href="/products"
+              className="inline-block px-8 py-3 bg-foreground text-white hover:bg-accent-dark transition-colors"
+            >
+              Continue Shopping
+            </Link>
+          </div>
+        </section>
+        <Footer />
+      </main>
+    );
+  }
+
+  return (
+    <main className="min-h-screen">
+      <Header />
+      
+      <section className="pt-24 pb-20 px-4">
+        <div className="max-w-7xl mx-auto">
+          <h1 className="text-3xl font-serif mb-8">Checkout</h1>
+          
+          {error && (
+            <div className="bg-red-50 border border-red-200 text-red-600 p-4 mb-6 rounded">
+              {error}
+            </div>
+          )}
+          
+          <div className="grid grid-cols-1 lg:grid-cols-2 gap-12">
+            {/* Checkout Form */}
+            <div>
+              <form onSubmit={handleSubmit} className="space-y-6">
+                {/* Shipping Address */}
+                <div className="border-b border-border pb-6">
+                  <h2 className="text-xl font-serif mb-4">Shipping Address</h2>
+                  <div className="grid grid-cols-2 gap-4">
+                    <div>
+                      <label className="block text-sm font-medium mb-1">First Name</label>
+                      <input
+                        type="text"
+                        required
+                        value={shippingAddress.firstName}
+                        onChange={(e) => handleShippingChange("firstName", e.target.value)}
+                        className="w-full border border-border px-4 py-2 rounded"
+                      />
+                    </div>
+                    <div>
+                      <label className="block text-sm font-medium mb-1">Last Name</label>
+                      <input
+                        type="text"
+                        required
+                        value={shippingAddress.lastName}
+                        onChange={(e) => handleShippingChange("lastName", e.target.value)}
+                        className="w-full border border-border px-4 py-2 rounded"
+                      />
+                    </div>
+                    <div className="col-span-2">
+                      <label className="block text-sm font-medium mb-1">Street Address</label>
+                      <input
+                        type="text"
+                        required
+                        value={shippingAddress.streetAddress1}
+                        onChange={(e) => handleShippingChange("streetAddress1", e.target.value)}
+                        className="w-full border border-border px-4 py-2 rounded"
+                      />
+                    </div>
+                    <div className="col-span-2">
+                      <input
+                        type="text"
+                        value={shippingAddress.streetAddress2}
+                        onChange={(e) => handleShippingChange("streetAddress2", e.target.value)}
+                        placeholder="Apartment, suite, etc. (optional)"
+                        className="w-full border border-border px-4 py-2 rounded"
+                      />
+                    </div>
+                    <div>
+                      <label className="block text-sm font-medium mb-1">City</label>
+                      <input
+                        type="text"
+                        required
+                        value={shippingAddress.city}
+                        onChange={(e) => handleShippingChange("city", e.target.value)}
+                        className="w-full border border-border px-4 py-2 rounded"
+                      />
+                    </div>
+                    <div>
+                      <label className="block text-sm font-medium mb-1">Postal Code</label>
+                      <input
+                        type="text"
+                        required
+                        value={shippingAddress.postalCode}
+                        onChange={(e) => handleShippingChange("postalCode", e.target.value)}
+                        className="w-full border border-border px-4 py-2 rounded"
+                      />
+                    </div>
+                    <div className="col-span-2">
+                      <label className="block text-sm font-medium mb-1">Phone</label>
+                      <input
+                        type="tel"
+                        required
+                        value={shippingAddress.phone}
+                        onChange={(e) => handleShippingChange("phone", e.target.value)}
+                        className="w-full border border-border px-4 py-2 rounded"
+                      />
+                    </div>
+                  </div>
+                </div>
+
+                {/* Billing Address Toggle */}
+                <div className="border-b border-border pb-6">
+                  <label className="flex items-center gap-2 cursor-pointer">
+                    <input
+                      type="checkbox"
+                      checked={sameAsShipping}
+                      onChange={(e) => setSameAsShipping(e.target.checked)}
+                      className="w-4 h-4"
+                    />
+                    <span>Billing address same as shipping</span>
+                  </label>
+                </div>
+
+                {/* Billing Address (if different) */}
+                {!sameAsShipping && (
+                  <div className="border-b border-border pb-6">
+                    <h2 className="text-xl font-serif mb-4">Billing Address</h2>
+                    <div className="grid grid-cols-2 gap-4">
+                      <div>
+                        <label className="block text-sm font-medium mb-1">First Name</label>
+                        <input
+                          type="text"
+                          required
+                          value={billingAddress.firstName}
+                          onChange={(e) => handleBillingChange("firstName", e.target.value)}
+                          className="w-full border border-border px-4 py-2 rounded"
+                        />
+                      </div>
+                      <div>
+                        <label className="block text-sm font-medium mb-1">Last Name</label>
+                        <input
+                          type="text"
+                          required
+                          value={billingAddress.lastName}
+                          onChange={(e) => handleBillingChange("lastName", e.target.value)}
+                          className="w-full border border-border px-4 py-2 rounded"
+                        />
+                      </div>
+                      <div className="col-span-2">
+                        <label className="block text-sm font-medium mb-1">Street Address</label>
+                        <input
+                          type="text"
+                          required
+                          value={billingAddress.streetAddress1}
+                          onChange={(e) => handleBillingChange("streetAddress1", e.target.value)}
+                          className="w-full border border-border px-4 py-2 rounded"
+                        />
+                      </div>
+                      <div>
+                        <label className="block text-sm font-medium mb-1">City</label>
+                        <input
+                          type="text"
+                          required
+                          value={billingAddress.city}
+                          onChange={(e) => handleBillingChange("city", e.target.value)}
+                          className="w-full border border-border px-4 py-2 rounded"
+                        />
+                      </div>
+                      <div>
+                        <label className="block text-sm font-medium mb-1">Postal Code</label>
+                        <input
+                          type="text"
+                          required
+                          value={billingAddress.postalCode}
+                          onChange={(e) => handleBillingChange("postalCode", e.target.value)}
+                          className="w-full border border-border px-4 py-2 rounded"
+                        />
+                      </div>
+                      <div className="col-span-2">
+                        <label className="block text-sm font-medium mb-1">Phone</label>
+                        <input
+                          type="tel"
+                          required
+                          value={billingAddress.phone}
+                          onChange={(e) => handleBillingChange("phone", e.target.value)}
+                          className="w-full border border-border px-4 py-2 rounded"
+                        />
+                      </div>
+                    </div>
+                  </div>
+                )}
+
+                {/* Payment Method */}
+                <div className="border-b border-border pb-6">
+                  <h2 className="text-xl font-serif mb-4">Payment Method</h2>
+                  <div className="bg-background-ice p-4 rounded">
+                    <div className="flex items-center gap-3">
+                      <input
+                        type="radio"
+                        checked
+                        readOnly
+                        className="w-4 h-4"
+                      />
+                      <span>Cash on Delivery (COD)</span>
+                    </div>
+                    <p className="text-sm text-foreground-muted mt-2 ml-7">
+                      Pay when your order is delivered to your door.
+                    </p>
+                  </div>
+                </div>
+
+                {/* Submit Button */}
+                <button
+                  type="submit"
+                  disabled={isLoading || lines.length === 0}
+                  className="w-full py-4 bg-foreground text-white font-medium hover:bg-accent-dark transition-colors disabled:opacity-50"
+                >
+                  {isLoading ? "Processing..." : `Complete Order - ${formatPrice(total)}`}
+                </button>
+              </form>
+            </div>
+
+            {/* Order Summary */}
+            <div className="bg-background-ice p-6 rounded-lg h-fit">
+              <h2 className="text-xl font-serif mb-6">Order Summary</h2>
+              
+              {lines.length === 0 ? (
+                <p className="text-foreground-muted">Your cart is empty</p>
+              ) : (
+                <>
+                  <div className="space-y-4 mb-6">
+                    {lines.map((line) => (
+                      <div key={line.id} className="flex gap-4">
+                        <div className="w-16 h-16 bg-white relative flex-shrink-0">
+                          {line.variant.product.media[0]?.url && (
+                            <Image
+                              src={line.variant.product.media[0].url}
+                              alt={line.variant.product.name}
+                              fill
+                              className="object-cover"
+                            />
+                          )}
+                        </div>
+                        <div className="flex-1">
+                          <h3 className="font-medium text-sm">{line.variant.product.name}</h3>
+                          <p className="text-foreground-muted text-sm">
+                            Qty: {line.quantity}
+                          </p>
+                          <p className="text-sm">
+                            {formatPrice(line.totalPrice.gross.amount)}
+                          </p>
+                        </div>
+                      </div>
+                    ))}
+                  </div>
+                  
+                  <div className="border-t border-border pt-4 space-y-2">
+                    <div className="flex justify-between">
+                      <span className="text-foreground-muted">Subtotal</span>
+                      <span>{formatPrice(checkout?.subtotalPrice?.gross?.amount || 0)}</span>
+                    </div>
+                    <div className="flex justify-between">
+                      <span className="text-foreground-muted">Shipping</span>
+                      <span>
+                        {checkout?.shippingPrice?.gross?.amount 
+                          ? formatPrice(checkout.shippingPrice.gross.amount)
+                          : "Calculated"
+                        }
+                      </span>
+                    </div>
+                    <div className="flex justify-between font-medium text-lg pt-2 border-t border-border">
+                      <span>Total</span>
+                      <span>{formatPrice(total)}</span>
+                    </div>
+                  </div>
+                </>
+              )}
+            </div>
+          </div>
+        </div>
+      </section>
+      
+      <Footer />
+    </main>
+  );
+}