<?php
/**
 * AuthMiddleware - Handles authentication via Authelia forward auth headers
 */
require_once dirname(__DIR__) . '/models/UserModel.php';

class AuthMiddleware {
    private $userModel;
    private $conn;

    public function __construct($conn) {
        $this->conn = $conn;
        $this->userModel = new UserModel($conn);
    }

    /**
     * Authenticate user from Authelia forward auth headers
     *
     * @return array User data array
     * @throws Exception if authentication fails
     */
    public function authenticate() {
        // Start session if not already started with secure settings
        if (session_status() === PHP_SESSION_NONE) {
            // Configure secure session settings
            ini_set('session.cookie_httponly', 1);
            ini_set('session.cookie_secure', 1); // Requires HTTPS
            ini_set('session.cookie_samesite', 'Lax'); // Lax allows redirects from Authelia
            ini_set('session.use_strict_mode', 1);
            ini_set('session.gc_maxlifetime', 18000); // 5 hours
            ini_set('session.cookie_lifetime', 0); // Until browser closes

            session_start();
        }

        // Check if user is already authenticated in session
        if (isset($_SESSION['user']) && isset($_SESSION['user']['user_id'])) {
            // Verify session hasn't expired (5 hour timeout)
            if (isset($_SESSION['last_activity']) && (time() - $_SESSION['last_activity'] > 18000)) {
                // Session expired, clear it
                session_unset();
                session_destroy();
                session_start();
            } else {
                // Update last activity time
                $_SESSION['last_activity'] = time();
                return $_SESSION['user'];
            }
        }

        // Read Authelia forward auth headers
        $username = $this->getHeader('HTTP_REMOTE_USER');
        $displayName = $this->getHeader('HTTP_REMOTE_NAME');
        $email = $this->getHeader('HTTP_REMOTE_EMAIL');
        $groups = $this->getHeader('HTTP_REMOTE_GROUPS');

        // Check if authentication headers are present
        if (empty($username)) {
            // No auth headers - user not authenticated
            $this->redirectToAuth();
            exit;
        }

        // Check if user has required group membership
        if (!$this->checkGroupAccess($groups)) {
            $this->showAccessDenied($username, $groups);
            exit;
        }

        // Sync user to database (create or update)
        $user = $this->userModel->syncUserFromAuthelia($username, $displayName, $email, $groups);

        if (!$user) {
            throw new Exception("Failed to sync user from Authelia");
        }

        // Regenerate session ID to prevent session fixation attacks
        session_regenerate_id(true);

        // Store user in session
        $_SESSION['user'] = $user;
        $_SESSION['last_activity'] = time();

        // Generate new CSRF token on login
        require_once __DIR__ . '/CsrfMiddleware.php';
        CsrfMiddleware::generateToken();

        return $user;
    }

    /**
     * Get header value from server variables
     *
     * @param string $header Header name
     * @return string|null Header value or null if not set
     */
    private function getHeader($header) {
        if (isset($_SERVER[$header])) {
            return $_SERVER[$header];
        }
        return null;
    }

    /**
     * Check if user has required group membership
     *
     * @param string $groups Comma-separated group names
     * @return bool True if user has access
     */
    private function checkGroupAccess($groups) {
        if (empty($groups)) {
            return false;
        }

        // Check for admin or employee group membership
        $userGroups = array_map('trim', explode(',', strtolower($groups)));
        $requiredGroups = ['admin', 'employee'];

        return !empty(array_intersect($userGroups, $requiredGroups));
    }

    /**
     * Redirect to Authelia login
     */
    private function redirectToAuth() {
        // Redirect to the auth endpoint (Authelia will handle the redirect back)
        header('HTTP/1.1 401 Unauthorized');
        echo '<!DOCTYPE html>
<html>
<head>
    <title>Authentication Required</title>
    <style>
        body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            margin: 0;
            background: #f5f5f5;
        }
        .auth-container {
            background: white;
            padding: 2rem;
            border-radius: 8px;
            box-shadow: 0 2px 10px rgba(0,0,0,0.1);
            text-align: center;
            max-width: 400px;
        }
        .auth-container h1 {
            color: #333;
            margin-bottom: 1rem;
        }
        .auth-container p {
            color: #666;
            margin-bottom: 1.5rem;
        }
        .auth-container a {
            display: inline-block;
            background: #4285f4;
            color: white;
            padding: 0.75rem 2rem;
            border-radius: 4px;
            text-decoration: none;
            transition: background 0.2s;
        }
        .auth-container a:hover {
            background: #357ae8;
        }
    </style>
</head>
<body>
    <div class="auth-container">
        <h1>Authentication Required</h1>
        <p>You need to be logged in to access Tinker Tickets.</p>
        <a href="/">Continue to Login</a>
    </div>
</body>
</html>';
        exit;
    }

    /**
     * Show access denied page
     *
     * @param string $username Username
     * @param string $groups User groups
     */
    private function showAccessDenied($username, $groups) {
        header('HTTP/1.1 403 Forbidden');
        echo '<!DOCTYPE html>
<html>
<head>
    <title>Access Denied</title>
    <style>
        body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            margin: 0;
            background: #f5f5f5;
        }
        .denied-container {
            background: white;
            padding: 2rem;
            border-radius: 8px;
            box-shadow: 0 2px 10px rgba(0,0,0,0.1);
            text-align: center;
            max-width: 500px;
        }
        .denied-container h1 {
            color: #d32f2f;
            margin-bottom: 1rem;
        }
        .denied-container p {
            color: #666;
            margin-bottom: 0.5rem;
        }
        .denied-container .user-info {
            background: #f5f5f5;
            padding: 1rem;
            border-radius: 4px;
            margin: 1rem 0;
            font-family: monospace;
            font-size: 0.9rem;
        }
    </style>
</head>
<body>
    <div class="denied-container">
        <h1>Access Denied</h1>
        <p>You do not have permission to access Tinker Tickets.</p>
        <p>Required groups: <strong>admin</strong> or <strong>employee</strong></p>
        <div class="user-info">
            <div>Username: ' . htmlspecialchars($username) . '</div>
            <div>Groups: ' . htmlspecialchars($groups ?: 'none') . '</div>
        </div>
        <p>Please contact your administrator if you believe this is an error.</p>
    </div>
</body>
</html>';
        exit;
    }

    /**
     * Get current authenticated user from session
     *
     * @return array|null User data or null if not authenticated
     */
    public static function getCurrentUser() {
        if (session_status() === PHP_SESSION_NONE) {
            session_start();
        }

        return $_SESSION['user'] ?? null;
    }

    /**
     * Logout current user
     */
    public static function logout() {
        if (session_status() === PHP_SESSION_NONE) {
            session_start();
        }

        session_unset();
        session_destroy();
    }
}