<?php
// cart.php - Shopping Cart and Checkout handler
require_once 'db_connect.php';

// Enforce login
if (!isLoggedIn()) {
    header("Location: login.php?redirect=cart.php&error=" . urlencode("Please log in to view your shopping cart."));
    exit();
}

$user = getLoggedInUser();
$action = $_GET['action'] ?? '';

// Handle Actions
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    
    // ACTION: ADD TO CART
    if ($action === 'add') {
        $productId = intval($_POST['product_id'] ?? 0);
        $quantity = intval($_POST['quantity'] ?? 1);
        $size = trim($_POST['size'] ?? 'Standard');
        $color = trim($_POST['color'] ?? 'Standard');

        if (empty($size)) $size = 'Standard';
        if (empty($color)) $color = 'Standard';

        if ($productId <= 0 || $quantity <= 0) {
            header("Location: index.php?error=" . urlencode("Invalid product options selected."));
            exit();
        }

        // Validate stock
        $stmt = $pdo->prepare("SELECT stock, title FROM products WHERE id = ?");
        $stmt->execute([$productId]);
        $product = $stmt->fetch();

        if (!$product) {
            header("Location: index.php?error=" . urlencode("Product not found."));
            exit();
        }

        if ($product['stock'] < $quantity) {
            header("Location: index.php?error=" . urlencode("Insufficient stock. Only {$product['stock']} item(s) left."));
            exit();
        }

        // Check if item is already in the cart with the same parameters
        $stmt = $pdo->prepare("SELECT id, quantity FROM cart WHERE user_id = ? AND product_id = ? AND size = ? AND color = ?");
        $stmt->execute([$user['id'], $productId, $size, $color]);
        $existing = $stmt->fetch();

        if ($existing) {
            $newQty = $existing['quantity'] + $quantity;
            if ($product['stock'] < $newQty) {
                header("Location: index.php?error=" . urlencode("Cannot add more. Combined cart quantity exceeds stock."));
                exit();
            }
            $update = $pdo->prepare("UPDATE cart SET quantity = ? WHERE id = ?");
            $update->execute([$newQty, $existing['id']]);
        } else {
            $insert = $pdo->prepare("INSERT INTO cart (user_id, product_id, quantity, size, color) VALUES (?, ?, ?, ?, ?)");
            $insert->execute([$user['id'], $productId, $quantity, $size, $color]);
        }

        header("Location: cart.php?success=" . urlencode("Added to shopping cart successfully."));
        exit();
    }

    // ACTION: UPDATE QUANTITY
    if ($action === 'update') {
        $cartId = intval($_POST['cart_id'] ?? 0);
        $quantity = intval($_POST['quantity'] ?? 0);

        if ($cartId > 0 && $quantity > 0) {
            // Verify ownership and check stock
            $stmt = $pdo->prepare("
                SELECT c.id, c.user_id, p.stock 
                FROM cart c
                JOIN products p ON c.product_id = p.id
                WHERE c.id = ?
            ");
            $stmt->execute([$cartId]);
            $item = $stmt->fetch();

            if ($item && intval($item['user_id']) === intval($user['id'])) {
                if ($item['stock'] >= $quantity) {
                    $update = $pdo->prepare("UPDATE cart SET quantity = ? WHERE id = ?");
                    $update->execute([$quantity, $cartId]);
                } else {
                    header("Location: cart.php?error=" . urlencode("Cannot update. Only {$item['stock']} items available."));
                    exit();
                }
            }
        }
        header("Location: cart.php");
        exit();
    }

    // ACTION: SIMULATED CHECKOUT TRANSACTION
    if ($action === 'checkout') {
        $shipping_address = trim($_POST['shipping_address'] ?? '');
        $payment_method = $_POST['payment_method'] ?? 'COD';

        if (empty($shipping_address)) {
            header("Location: cart.php?error=" . urlencode("Shipping address is required for checkout."));
            exit();
        }

        // Get cart items to checkout
        $stmt = $pdo->prepare("
            SELECT c.*, p.title, p.price, p.stock 
            FROM cart c
            JOIN products p ON c.product_id = p.id
            WHERE c.user_id = ?
        ");
        $stmt->execute([$user['id']]);
        $items = $stmt->fetchAll();

        if (empty($items)) {
            header("Location: cart.php?error=" . urlencode("Your cart is empty."));
            exit();
        }

        try {
            $pdo->beginTransaction();

            $subtotal = 0;
            // Validate stock levels
            foreach ($items as $item) {
                if ($item['stock'] < $item['quantity']) {
                    throw new Exception("Product '{$item['title']}' has insufficient stock. Only {$item['stock']} remaining.");
                }
                $subtotal += floatval($item['price']) * intval($item['quantity']);
            }

            $shippingFee = 5.00;
            $grandTotal = $subtotal + $shippingFee;

            // 1. Create order
            $orderStmt = $pdo->prepare("
                INSERT INTO orders (buyer_id, total_amount, shipping_address, payment_method, status) 
                VALUES (?, ?, ?, ?, 'Pending')
            ");
            $orderStmt->execute([$user['id'], $grandTotal, $shipping_address, $payment_method]);
            $orderId = $pdo->lastInsertId();

            // 2. Insert items, deduct stock, remove from cart
            $itemInsert = $pdo->prepare("
                INSERT INTO order_items (order_id, product_id, quantity, price, size, color) 
                VALUES (?, ?, ?, ?, ?, ?)
            ");
            
            $stockDeduct = $pdo->prepare("UPDATE products SET stock = stock - ? WHERE id = ?");
            $cartClear = $pdo->prepare("DELETE FROM cart WHERE id = ?");

            foreach ($items as $item) {
                $itemInsert->execute([
                    $orderId, 
                    $item['product_id'], 
                    $item['quantity'], 
                    $item['price'], 
                    $item['size'], 
                    $item['color']
                ]);

                $stockDeduct->execute([$item['quantity'], $item['product_id']]);
                $cartClear->execute([$item['id']]);
            }

            // Save default shipping address if not set
            if (empty($user['shipping_address'])) {
                $addrUpdate = $pdo->prepare("UPDATE users SET shipping_address = ? WHERE id = ?");
                $addrUpdate->execute([$shipping_address, $user['id']]);
            }

            $pdo->commit();
            header("Location: index.php?success=" . urlencode("Checkout successful! Order placed. Order ID is TV-{$orderId}."));
            exit();

        } catch (Exception $e) {
            if ($pdo->inTransaction()) {
                $pdo->rollBack();
            }
            header("Location: cart.php?error=" . urlencode($e->getMessage()));
            exit();
        }
    }
}

// Handle GET Action (Removal)
if ($action === 'remove') {
    $cartId = intval($_GET['cart_id'] ?? 0);
    if ($cartId > 0) {
        $stmt = $pdo->prepare("SELECT user_id FROM cart WHERE id = ?");
        $stmt->execute([$cartId]);
        $item = $stmt->fetch();

        if ($item && intval($item['user_id']) === intval($user['id'])) {
            $delete = $pdo->prepare("DELETE FROM cart WHERE id = ?");
            $delete->execute([$cartId]);
        }
    }
    header("Location: cart.php?success=" . urlencode("Item removed from cart."));
    exit();
}

// Fetch Cart items to display
$stmt = $pdo->prepare("
    SELECT c.*, p.title, p.price, p.stock, p.images, u.username as seller_name 
    FROM cart c
    JOIN products p ON c.product_id = p.id
    JOIN users u ON p.seller_id = u.id
    WHERE c.user_id = ?
");
$stmt->execute([$user['id']]);
$cartItems = $stmt->fetchAll();

// Calculate subtotal
$subtotal = 0;
foreach ($cartItems as $item) {
    $subtotal += floatval($item['price']) * intval($item['quantity']);
}
$shippingFee = count($cartItems) > 0 ? 5.00 : 0.00;
$grandTotal = $subtotal + $shippingFee;

renderHeader(__('cart_page_title'));
?>

<div class="grid grid-cols-1 lg:grid-cols-12 gap-8 items-start">
    
    <!-- Left Side: Cart Items list -->
    <div class="lg:col-span-8 space-y-4">
        <h2 class="text-2xl font-extrabold text-gray-900 tracking-tight mb-6"><?php echo __('cart_heading'); ?></h2>

        <?php if (empty($cartItems)): ?>
            <div class="text-center py-16 bg-white rounded-3xl border border-gray-100 shadow-sm space-y-4">
                <div class="w-16 h-16 bg-orange-50 border border-orange-100 text-orange-500 rounded-2xl flex items-center justify-center mx-auto">
                    <svg class="w-8 h-8" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="1.5" d="M3 3h2l.4 2M7 13h10l4-8H5.4M7 13L5.4 5M7 13l-2.293 2.293c-.63.63-.184 1.707.707 1.707H17m0 0a2 2 0 100 4 2 2 0 000-4zm-8 2a2 2 0 11-4 0 2 2 0 014 0z"/></svg>
                </div>
                <h3 class="text-xl font-bold text-gray-900"><?php echo __('cart_empty_title'); ?></h3>
                <p class="text-sm text-gray-500 max-w-xs mx-auto"><?php echo __('cart_empty_desc'); ?></p>
                <a href="index.php" class="inline-block px-6 py-2.5 bg-gradient-to-r from-orange-500 to-rose-500 text-white font-bold rounded-xl shadow-md hover:shadow-lg transition-all text-sm"><?php echo __('cart_start_shopping'); ?></a>
            </div>
        <?php else: ?>
            <div class="space-y-4">
                <?php foreach ($cartItems as $item): 
                    $price = floatval($item['price']);
                    $itemTotal = ($price * intval($item['quantity']));
                    $img = getProductImgUrl($item['product_id'], $item['images']);
                ?>
                    <div class="bg-white p-5 rounded-2xl border border-gray-100 shadow-sm flex flex-col sm:flex-row items-start sm:items-center justify-between gap-4 relative">
                        <!-- Details -->
                        <div class="flex items-center gap-4 flex-1">
                            <img 
                                src="<?php echo $img; ?>" 
                                alt="<?php echo sanitize($item['title']); ?>" 
                                class="w-16 h-16 rounded-xl object-cover border border-gray-100"
                                onerror="this.onerror=null; this.src='https://images.unsplash.com/photo-1526170375885-4d8ecf77b99f?w=100';"
                            >
                            <div class="space-y-1">
                                <span class="text-[9px] font-bold text-gray-400 uppercase tracking-widest"><?php echo __('cart_store'); ?> <?php echo sanitize($item['seller_name']); ?></span>
                                <h4 class="font-bold text-gray-900 text-sm sm:text-base"><?php echo sanitize($item['title']); ?></h4>
                                <div class="flex items-center gap-3 text-xs font-semibold text-gray-400">
                                    <?php if (!empty($item['size']) && $item['size'] !== 'Standard'): ?>
                                        <span><?php echo __('cart_option'); ?> <strong class="text-gray-700"><?php echo sanitize($item['size']); ?></strong></span>
                                    <?php endif; ?>
                                    <?php if (!empty($item['color']) && $item['color'] !== 'Standard'): ?>
                                        <span><?php echo __('cart_variant'); ?> <strong class="text-gray-700"><?php echo sanitize($item['color']); ?></strong></span>
                                    <?php endif; ?>
                                </div>
                            </div>
                        </div>

                        <!-- Controls -->
                        <div class="flex items-center justify-between w-full sm:w-auto sm:justify-end gap-6 border-t border-gray-100 sm:border-0 pt-3 sm:pt-0">
                            <!-- Qty update form -->
                            <form action="cart.php?action=update" method="POST" class="flex items-center border border-gray-200 rounded-lg overflow-hidden bg-gray-50 text-xs">
                                <input type="hidden" name="cart_id" value="<?php echo $item['id']; ?>">
                                <button type="submit" name="quantity" value="<?php echo $item['quantity'] - 1; ?>" class="px-2.5 py-1 text-gray-500 hover:bg-gray-100 font-bold" <?php echo $item['quantity'] <= 1 ? 'disabled' : ''; ?>>-</button>
                                <span class="px-3.5 py-1 font-bold text-gray-900 bg-white border-x border-gray-100 w-8 text-center"><?php echo $item['quantity']; ?></span>
                                <button type="submit" name="quantity" value="<?php echo $item['quantity'] + 1; ?>" class="px-2.5 py-1 text-gray-500 hover:bg-gray-100 font-bold" <?php echo $item['quantity'] >= $item['stock'] ? 'disabled' : ''; ?>>+</button>
                            </form>

                            <!-- Price info -->
                            <div class="text-right">
                                <span class="block text-base font-black text-rose-600">$<?php echo number_format($itemTotal, 2); ?></span>
                                <a href="cart.php?action=remove&cart_id=<?php echo $item['id']; ?>" class="text-xs font-semibold text-gray-400 hover:text-red-500 transition-colors"><?php echo __('cart_remove'); ?></a>
                            </div>
                        </div>
                    </div>
                <?php endforeach; ?>
            </div>
        <?php endif; ?>
    </div>

    <!-- Right Side: Order summary & Checkout -->
    <?php if (!empty($cartItems)): ?>
        <div class="lg:col-span-4 bg-white p-6 rounded-3xl border border-gray-100 shadow-sm space-y-6 lg:sticky lg:top-24">
            <h3 class="font-bold text-gray-900 text-lg border-b border-gray-100 pb-4"><?php echo __('cart_checkout_title'); ?></h3>
            
            <form action="cart.php?action=checkout" method="POST" class="space-y-6">
                <!-- Shipping Address -->
                <div class="space-y-2">
                    <label for="shipping_address" class="block text-xs font-bold uppercase tracking-wider text-gray-500"><?php echo __('cart_shipping_label'); ?></label>
                    <textarea 
                        name="shipping_address" 
                        id="shipping_address"
                        rows="3" 
                        required 
                        placeholder="<?php echo __('cart_shipping_ph'); ?>"
                        class="w-full p-3 bg-gray-50 border border-gray-200 rounded-xl text-sm focus:outline-none focus:bg-white focus:ring-2 focus:ring-orange-500/20 focus:border-orange-500 transition-all"
                    ><?php echo sanitize($user['shipping_address']); ?></textarea>
                </div>

                <!-- Payment Method -->
                <div class="space-y-2">
                    <label class="block text-xs font-bold uppercase tracking-wider text-gray-500"><?php echo __('cart_payment_label'); ?></label>
                    <div class="grid grid-cols-1 gap-2.5">
                        <label class="flex items-center gap-3 p-3 rounded-xl border border-gray-200 hover:border-orange-500 cursor-pointer bg-gray-50/50 text-xs">
                            <input type="radio" name="payment_method" value="COD" checked class="text-orange-500 focus:ring-orange-500">
                            <div>
                                <strong class="block text-gray-900"><?php echo __('cart_cod_title'); ?></strong>
                                <span class="text-gray-400"><?php echo __('cart_cod_desc'); ?></span>
                            </div>
                        </label>
                        <label class="flex items-center gap-3 p-3 rounded-xl border border-gray-200 hover:border-orange-500 cursor-pointer bg-gray-50/50 text-xs">
                            <input type="radio" name="payment_method" value="Credit Card" class="text-orange-500 focus:ring-orange-500">
                            <div>
                                <strong class="block text-gray-900"><?php echo __('cart_cc_title'); ?></strong>
                                <span class="text-gray-400"><?php echo __('cart_cc_desc'); ?></span>
                            </div>
                        </label>
                    </div>
                </div>

                <!-- Calculations -->
                <div class="space-y-3 text-xs border-t border-gray-100 pt-4">
                    <div class="flex justify-between text-gray-500">
                        <span><?php echo __('cart_subtotal'); ?></span>
                        <span class="font-bold text-gray-900">$<?php echo number_format($subtotal, 2); ?></span>
                    </div>
                    <div class="flex justify-between text-gray-500">
                        <span><?php echo __('cart_shipping_fee'); ?></span>
                        <span class="font-bold text-gray-900">$<?php echo number_format($shippingFee, 2); ?></span>
                    </div>
                    <div class="border-t border-gray-100 pt-3 flex justify-between text-sm font-black text-gray-900">
                        <span><?php echo __('cart_total'); ?></span>
                        <span class="text-rose-600 text-base">$<?php echo number_format($grandTotal, 2); ?></span>
                    </div>
                </div>

                <button type="submit" class="w-full py-3 bg-gradient-to-r from-orange-500 to-rose-500 text-white font-extrabold rounded-xl shadow-lg hover:shadow-xl transition-all hover:-translate-y-0.5 focus:outline-none">
                    <?php echo __('cart_place_order'); ?>
                </button>
            </form>
        </div>
    <?php endif; ?>

</div>

<?php
renderFooter();
?>