<?php
session_start();
require_once 'db/config.php';

if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['coupon_code'])) {
    $coupon_code = trim($_POST['coupon_code']);
    $pdo = db();

    $stmt = $pdo->prepare("SELECT * FROM coupons WHERE code = :code AND is_active = TRUE");
    $stmt->execute(['code' => $coupon_code]);
    $coupon = $stmt->fetch();

    if ($coupon) {
        $_SESSION['coupon'] = [
            'id' => $coupon['id'],
            'code' => $coupon['code'],
            'discount_percentage' => $coupon['discount_percentage']
        ];
        unset($_SESSION['coupon_error']);
    } else {
        $_SESSION['coupon_error'] = "Invalid or expired coupon code.";
        unset($_SESSION['coupon']);
    }
}

header('Location: cart.php');
exit;