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

session_start();

if (!isset($_SESSION['user_id']) || $_SESSION['user_type'] !== 'client') {
    http_response_code(403);
    echo json_encode(['error' => 'Unauthorized']);
    exit;
}

// --- 1. Get Input Data ---
$package_id = $_POST['package_id'] ?? null;
$coupon_code = $_POST['coupon_code'] ?? null;
$is_gift = isset($_POST['is_gift']) && $_POST['is_gift'] === 'true';
$payment_option = $_POST['payment_option'] ?? 'pay_full';
$client_id = $_SESSION['user_id'];

if (!$package_id) {
    header('Location: coaches.php?error=missing_package');
    exit;
}

// --- 2. Fetch Package Details ---
$stmt = db()->prepare('SELECT * FROM service_packages WHERE id = ?');
$stmt->execute([$package_id]);
$package = $stmt->fetch(PDO::FETCH_ASSOC);

if (!$package) {
    header('Location: coaches.php?error=invalid_package');
    exit;
}

// --- 3. Determine Price, Mode, and Metadata ---
$line_items = [];
$metadata = [
    'package_id' => $package_id,
    'client_id' => $client_id,
    'is_gift' => $is_gift ? 'true' : 'false',
    'payment_option' => $payment_option
];
$mode = 'payment'; // Default to one-time payment

$unit_amount = 0;
$product_name = $package['name'];

if ($package['payment_type'] === 'payment_plan' && $payment_option === 'payment_plan') {
    // --- PAYMENT PLAN ---
    if ($package['deposit_amount'] > 0) {
        // A. Plan with a deposit: Create a one-time payment for the deposit.
        // Webhook will handle creating the subscription for the rest.
        $unit_amount = $package['deposit_amount'] * 100;
        $product_name .= ' - Deposit';
        $metadata['payment_plan_action'] = 'start_subscription_after_deposit';
    } else {
        // B. Plan with no deposit: Create a subscription directly.
        $mode = 'subscription';
        $unit_amount = ($package['price'] * 100) / $package['installments'];
        $line_items[] = [
            'price_data' => [
                'currency' => 'usd',
                'product_data' => ['name' => $product_name],
                'unit_amount' => $unit_amount,
                'recurring' => [
                    'interval' => $package['installment_interval'],
                    'interval_count' => 1,
                ],
            ],
            'quantity' => 1,
        ];
    }
} else {
    // --- PAY IN FULL (or one-time package) ---
    $unit_amount = $package['price'] * 100;
    if ($package['payment_type'] === 'payment_plan' && !empty($package['pay_in_full_discount_percentage'])) {
        $discount = $unit_amount * ($package['pay_in_full_discount_percentage'] / 100);
        $unit_amount -= $discount;
        $metadata['discount_applied'] = 'pay_in_full';
    }
}

// Add the primary line item if not already added (for non-subscription cases)
if (empty($line_items)) {
    $line_items[] = [
        'price_data' => [
            'currency' => 'usd',
            'product_data' => ['name' => $product_name],
            'unit_amount' => round($unit_amount, 0),
        ],
        'quantity' => 1,
    ];
}


// --- 4. Handle Coupon ---
$discounts = [];
if ($coupon_code) {
    $stmt = db()->prepare('SELECT * FROM discounts WHERE code = ? AND is_active = 1');
    $stmt->execute([$coupon_code]);
    $coupon = $stmt->fetch();

    $is_valid = $coupon &&
                (!$coupon['start_date'] || strtotime($coupon['start_date']) <= time()) &&
                (!$coupon['end_date'] || strtotime($coupon['end_date']) >= time()) &&
                ($coupon['uses_limit'] === null || $coupon['times_used'] < $coupon['uses_limit']);

    if ($is_valid) {
        try {
            $stripe_coupon_params = ['duration' => 'once', 'name' => $coupon['code']];
            if ($coupon['type'] === 'percentage') {
                $stripe_coupon_params['percent_off'] = $coupon['value'];
            } else {
                $stripe_coupon_params['amount_off'] = $coupon['value'] * 100;
                $stripe_coupon_params['currency'] = 'usd';
            }
            $stripe_coupon = \Stripe\Coupon::create($stripe_coupon_params);
            $discounts[] = ['coupon' => $stripe_coupon->id];
            $metadata['coupon_code'] = $coupon_code;
        } catch (\Exception $e) { /* Ignore Stripe error, proceed without coupon */ }
    }
}

// --- 5. Define Success/Cancel URLs ---
$success_url = 'http://' . $_SERVER['HTTP_HOST'] . ($is_gift ? '/purchase-gift-success.php' : '/purchase-package-success.php') . '?session_id={CHECKOUT_SESSION_ID}';
$cancel_url = 'http://' . $_SERVER['HTTP_HOST'] . '/purchase-package-cancel.php';

// --- 6. Create and Redirect to Checkout ---
try {
    $checkout_session = \Stripe\Checkout\Session::create([
        'payment_method_types' => ['card'],
        'line_items' => $line_items,
        'mode' => $mode,
        'success_url' => $success_url,
        'cancel_url' => $cancel_url,
        'metadata' => $metadata,
        'discounts' => $discounts,
    ]);

    header("Location: " . $checkout_session->url);
    exit;
} catch (\Exception $e) {
    $error_message = urlencode($e->getMessage());
    header("Location: purchase-package.php?package_id={$package_id}&error=stripe_error&message={$error_message}");
    exit;
}