<?php
require_once '../db/config.php';
require_once 'init.php';
require_once '../mail/MailService.php';

// Function to log messages
function log_webhook_event($message) {
    $log_file = __DIR__ . '/webhook_events.log';
    file_put_contents($log_file, date('[Y-m-d H:i:s] ') . $message . "\n", FILE_APPEND);
}

$payload = @file_get_contents('php://input');
$sig_header = $_SERVER['HTTP_STRIPE_SIGNATURE'];
$event = null;

try {
    $event = \Stripe\Webhook::constructEvent(
        $payload, $sig_header, STRIPE_WEBHOOK_SECRET
    );
} catch(\UnexpectedValueException $e) {
    // Invalid payload
    log_webhook_event("Error: Invalid payload. " . $e->getMessage());
    http_response_code(400);
    exit();
} catch(\Stripe\Exception\SignatureVerificationException $e) {
    // Invalid signature
    log_webhook_event("Error: Invalid signature. " . $e->getMessage());
    http_response_code(400);
    exit();
}

log_webhook_event("Received event: " . $event->type);
log_webhook_event(json_encode($event->data->object));


// Handle the event
switch ($event->type) {
    case 'checkout.session.completed':
        $session = $event->data->object;
        $metadata = $session->metadata;

        // --- Idempotency Check ---
        // Check if we have already processed this session for a package or gift
        $stmt_check = db()->prepare("SELECT id FROM client_packages WHERE stripe_session_id = ? UNION SELECT id FROM gift_codes WHERE stripe_session_id = ?");
        $stmt_check->execute([$session->id, $session->id]);
        if ($stmt_check->fetch()) {
            log_webhook_event("Event {$session->id} already processed. Exiting.");
            http_response_code(200);
            exit();
        }

        // --- Validate Metadata ---
        $client_id = $metadata->client_id ?? null;
        $package_id = $metadata->package_id ?? null;
        $payment_option = $metadata->payment_option ?? 'full_price'; // e.g., 'full_price', 'deposit'
        $is_gift = $metadata->is_gift === 'true';

        if (!$client_id || !$package_id) {
            log_webhook_event("Webhook Error: Missing client_id or package_id in session metadata for session {$session->id}.");
            http_response_code(400);
            exit();
        }

        // --- Get Package and Client Details ---
        $stmt_pkg = db()->prepare("SELECT * FROM service_packages WHERE id = ?");
        $stmt_pkg->execute([$package_id]);
        $package = $stmt_pkg->fetch(PDO::FETCH_ASSOC);

        $stmt_client = db()->prepare("SELECT * FROM clients WHERE id = ?");
        $stmt_client->execute([$client_id]);
        $client = $stmt_client->fetch(PDO::FETCH_ASSOC);

        if (!$package || !$client) {
            log_webhook_event("Webhook Error: Package or Client not found for session {$session->id}.");
            http_response_code(404);
            exit();
        }

        // --- Update Client with Stripe Customer ID ---
        $stripe_customer_id = $session->customer ?? $client['stripe_customer_id'];
        if ($stripe_customer_id && empty($client['stripe_customer_id'])) {
            $update_stmt = db()->prepare("UPDATE clients SET stripe_customer_id = ? WHERE id = ?");
            $update_stmt->execute([$stripe_customer_id, $client_id]);
            log_webhook_event("Updated stripe_customer_id for client {$client_id}.");
        }
        
        // --- Handle Purchase based on Type ---
        if ($is_gift) {
            // --- Handle Gift Purchase ---
            $gift_code = 'GIFT' . strtoupper(bin2hex(random_bytes(8)));
            $stmt_gift = db()->prepare("INSERT INTO gift_codes (code, package_id, purchaser_client_id, stripe_session_id, is_redeemed, created_at) VALUES (?, ?, ?, ?, 0, NOW())");
            $stmt_gift->execute([$gift_code, $package_id, $client_id, $session->id]);
            log_webhook_event("Created gift code {$gift_code} for package {$package_id} purchased by client {$client_id}.");
        } else {
            // --- Handle Regular Purchase (Package for Self) ---

            // 1. Create the client package record
            $sessions_to_add = $package['sessions_per_package'] ?? 0;
            if ($package['payment_type'] === 'subscription') {
                $sessions_to_add = 0; // Sessions are added on invoice payment for subscriptions
            }
            
            $stmt_cp = db()->prepare("INSERT INTO client_packages (client_id, package_id, stripe_session_id, purchase_date, sessions_remaining) VALUES (?, ?, ?, NOW(), ?)");
            $stmt_cp->execute([$client_id, $package_id, $session->id, $sessions_to_add]);
            log_webhook_event("Created client_packages record for client {$client_id}, package {$package_id}.");

            // 2. Handle Subscription Creation
            if ($session->mode === 'subscription') {
                // This was a recurring package from the start
                $stmt_sub = db()->prepare("INSERT INTO client_subscriptions (client_id, package_id, stripe_subscription_id, status, start_date) VALUES (?, ?, ?, 'active', NOW())");
                $stmt_sub->execute([$client_id, $package_id, $session->subscription]);
                log_webhook_event("Created client_subscriptions record for Stripe subscription {$session->subscription}.");

            } else if ($payment_option === 'deposit' && $package['payment_type'] === 'payment_plan' && $package['installments'] > 1) {
                // This was a deposit, now create the subscription for the rest
                $remaining_amount = $package['price'] - $package['deposit_amount'];
                $installments_count = $package['installments'] - 1; // Already paid one installment (the deposit)

                if ($installments_count > 0 && $remaining_amount > 0) {
                    $installment_amount = round(($remaining_amount / $installments_count) * 100);

                    try {
                        // Create a new Price for the installments
                        $stripe_price = \Stripe\Price::create([
                            'product_data' => ['name' => $package['name'] . ' - Installment Plan'],
                            'unit_amount' => $installment_amount,
                            'currency' => 'usd',
                            'recurring' => ['interval' => $package['installment_interval']],
                        ]);

                        // Create the subscription
                        $subscription = \Stripe\Subscription::create([
                            'customer' => $stripe_customer_id,
                            'items' => [['price' => $stripe_price->id]],
                            'metadata' => [
                                'client_id' => $client_id,
                                'package_id' => $package_id,
                                'is_installment_plan' => 'true'
                            ],
                            'payment_behavior' => 'default_incomplete',
                            'payment_settings' => ['save_default_payment_method' => 'on_subscription'],
                            'proration_behavior' => 'none',
                            'trial_end' => strtotime('+1 ' . $package['installment_interval']), // Start billing after one interval
                        ]);

                        // Save subscription to our DB
                        $stmt_db_sub = db()->prepare("INSERT INTO client_subscriptions (client_id, package_id, stripe_subscription_id, status, start_date) VALUES (?, ?, ?, 'active', NOW())");
                        $stmt_db_sub->execute([$client_id, $package_id, $subscription->id]);
                        log_webhook_event("Created Stripe subscription {$subscription->id} for client {$client_id} after deposit.");

                    } catch(\Exception $e) {
                        log_webhook_event("Webhook Error: Failed to create subscription for client {$client_id} after deposit. Error: " . $e->getMessage());
                    }
                }
            }
        }

        // --- Update Coupon Usage ---
        if (isset($metadata->coupon_code)) {
            $stmt_coupon = db()->prepare('UPDATE discounts SET times_used = times_used + 1 WHERE code = ?');
            $stmt_coupon->execute([$metadata->coupon_code]);
            log_webhook_event("Incremented usage count for coupon {$metadata->coupon_code}.");
        }

        break;
    
    case 'invoice.payment_succeeded':
        $invoice = $event->data->object;
        $subscription_id = $invoice->subscription;

        if (!$subscription_id) break;

        // Retrieve our subscription record
        $stmt = db()->prepare('SELECT * FROM client_subscriptions WHERE stripe_subscription_id = ?');
        $stmt->execute([$subscription_id]);
        $subscription_record = $stmt->fetch(PDO::FETCH_ASSOC);

        if ($subscription_record) {
            $client_id = $subscription_record['client_id'];
            $package_id = $subscription_record['package_id'];

            // Get the package details to find out how many sessions to add
            $stmt_pkg = db()->prepare("SELECT sessions_per_package FROM service_packages WHERE id = ?");
            $stmt_pkg->execute([$package_id]);
            $package = $stmt_pkg->fetch(PDO::FETCH_ASSOC);
            $sessions_to_add = $package['sessions_per_package'] ?? 0;

            if ($sessions_to_add > 0) {
                 // Find the corresponding client_package to update sessions
                $update_stmt = db()->prepare('UPDATE client_packages SET sessions_remaining = sessions_remaining + ? WHERE client_id = ? AND package_id = ?');
                $update_stmt->execute([$sessions_to_add, $client_id, $package_id]);
                log_webhook_event("Added {$sessions_to_add} sessions to client {$client_id} for package {$package_id} after invoice payment.");
            }

            // Ensure subscription status is active
            $update_sub_stmt = db()->prepare('UPDATE client_subscriptions SET status = ? WHERE id = ?');
            $update_sub_stmt->execute(['active', $subscription_record['id']]);
        } else {
             log_webhook_event("Webhook Warning: Received invoice.payment_succeeded for an unknown subscription: {$subscription_id}");
        }
        break;

    case 'invoice.payment_failed':
        $invoice = $event->data->object;
        $customer_id = $invoice->customer;
        $subscription_id = $invoice->subscription;

        if (!$subscription_id) break;

        // Update subscription status in our DB
        $stmt = db()->prepare("UPDATE client_subscriptions SET status = 'past_due' WHERE stripe_subscription_id = ?");
        $stmt->execute([$subscription_id]);
        log_webhook_event("Set subscription status to 'past_due' for {$subscription_id}.");

        // Find client to send email
        $stmt_client = db()->prepare("SELECT * FROM clients WHERE stripe_customer_id = ?");
        $stmt_client->execute([$customer_id]);
        $client = $stmt_client->fetch(PDO::FETCH_ASSOC);

        if ($client) {
            $to = $client['email'];
            $subject = 'Your Subscription Payment Failed';
            $message_html = '<p>Hi ' . htmlspecialchars($client['name']) . ',</p>' .
                            '<p>We were unable to process your recent subscription payment. Please update your payment method to keep your subscription active.</p>' .
                            '<p>You can manage your subscription here: <a href="' . getenv('APP_URL') . '/manage-subscription.php">Manage Subscription</a></p>';
            MailService::sendMail($to, $subject, $message_html, strip_tags($message_html));
            log_webhook_event("Sent payment failed email to {$to}.");
        }
        break;

    case 'customer.subscription.deleted':
        $subscription = $event->data->object;
        $stmt = db()->prepare("UPDATE client_subscriptions SET status = 'canceled' WHERE stripe_subscription_id = ?");
        $stmt->execute([$subscription->id]);
        log_webhook_event("Set subscription status to 'canceled' for {$subscription->id}.");
        break;

    default:
        log_webhook_event("Received unhandled event type: " . $event->type);
}

http_response_code(200);