<?php
require_once 'db/config.php';
require_once 'stripe/init.php';
require_once 'stripe/config.php'; // for $subscriptions

session_start();

if (!isset($_SESSION['user_id']) || $_SESSION['user_type'] !== 'client') {
    header('Location: login.php');
    exit;
}

if (!isset($_GET['plan_id'])) {
    header('Location: subscription-plans.php?error=missing_plan');
    exit;
}

$plan_id = $_GET['plan_id'];
$client_id = $_SESSION['user_id'];
$coupon_code = $_GET['coupon'] ?? null;

global $subscriptions;
if (!isset($subscriptions[$plan_id])) {
    header('Location: subscription-plans.php?error=invalid_plan');
    exit;
}
$plan = $subscriptions[$plan_id];

$final_price = $plan['price'];
$stripe_coupon_id = null;

if ($coupon_code) {
    // We need to create a coupon in Stripe to apply it to a subscription
    $stmt = db()->prepare('SELECT * FROM discounts WHERE code = ? AND is_active = 1');
    $stmt->execute([$coupon_code]);
    $coupon = $stmt->fetch();

    if ($coupon) {
        // Check date validity and usage limit (already done in previous step, but good to double check)
        // ...

        try {
            $stripe_coupon_params = [];
            if ($coupon['type'] === 'percentage') {
                $stripe_coupon_params['percent_off'] = $coupon['value'];
            } else { // fixed
                $stripe_coupon_params['amount_off'] = $coupon['value'] * 100;
                $stripe_coupon_params['currency'] = 'usd';
            }
            $stripe_coupon_params['duration'] = 'once'; // Or 'repeating', 'forever'
            $stripe_coupon_params['name'] = $coupon['code'];

            $stripe_coupon = \Stripe\Coupon::create($stripe_coupon_params);
            $stripe_coupon_id = $stripe_coupon->id;
        } catch (\Stripe\Exception\ApiErrorException $e) {
            // Coupon creation failed, proceed without discount
        }
    }
}

// Get client's stripe customer id or create a new one
$stmt = db()->prepare("SELECT stripe_customer_id, email, name FROM clients WHERE id = ?");
$stmt->execute([$client_id]);
$client = $stmt->fetch();

$stripe_customer_id = $client['stripe_customer_id'];
if (!$stripe_customer_id) {
    $customer = \Stripe\Customer::create([
        'email' => $client['email'],
        'name' => $client['name'],
    ]);
    $stripe_customer_id = $customer->id;
    $update_stmt = db()->prepare("UPDATE clients SET stripe_customer_id = ? WHERE id = ?");
    $update_stmt->execute([$stripe_customer_id, $client_id]);
}

// Create a Stripe Checkout Session
try {
    $checkout_params = [
        'payment_method_types' => ['card'],
        'line_items' => [[
            'price_data' => [
                'currency' => $plan['currency'],
                'product_data' => [
                    'name' => $plan['name'],
                ],
                'unit_amount' => $plan['price'],
                'recurring' => [
                    'interval' => $plan['interval'],
                ],
            ],
            'quantity' => 1,
        ]],
        'mode' => 'subscription',
        'success_url' => 'http://' . $_SERVER['HTTP_HOST'] . '/subscription-success.php?session_id={CHECKOUT_SESSION_ID}',
        'cancel_url' => 'http://' . $_SERVER['HTTP_HOST'] . '/subscription-cancel.php',
        'client_reference_id' => $client_id,
        'customer' => $stripe_customer_id,
    ];

    if ($stripe_coupon_id) {
        $checkout_params['discounts'] = [['coupon' => $stripe_coupon_id]];
    }

    $checkout_session = \Stripe\Checkout\Session::create($checkout_params);

    header("HTTP/1.1 303 See Other");
    header("Location: " . $checkout_session->url);
    exit;

} catch (\Stripe\Exception\ApiErrorException $e) {
    header('Location: subscribe-checkout.php?plan_id='. $plan_id .'&error=stripe_error&message=' . urlencode($e->getMessage()));
    exit;
} catch (Exception $e) {
    header('Location: subscribe-checkout.php?plan_id=' . $plan_id .'&error=generic_error&message=' . urlencode($e->getMessage()));
    exit;
}