<?php
declare(strict_types=1);

require_once __DIR__ . '/Config.php';
require_once __DIR__ . '/Db.php';

final class Auth {
    public static function startSession(): void {
        if (session_status() === PHP_SESSION_ACTIVE) return;

        $secure = ($_SERVER['HTTP_X_FORWARDED_PROTO'] ?? '') === 'https'
               || (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off');

        session_name('donna_session');
        session_set_cookie_params([
            'lifetime' => Config::int('SESSION_LIFETIME', 28800),
            'path'     => '/',
            'secure'   => $secure,
            'httponly' => true,
            'samesite' => 'Lax',
        ]);
        session_start();
    }

    public static function isAuthenticated(): bool {
        self::startSession();
        return !empty($_SESSION['authenticated'])
            && !empty($_SESSION['auth_time'])
            && (time() - (int)$_SESSION['auth_time']) < Config::int('SESSION_LIFETIME', 28800);
    }

    public static function user(): array {
        self::startSession();
        return [
            'email' => $_SESSION['user_email'] ?? '',
            'name'  => $_SESSION['user_name']  ?? '',
        ];
    }

    public static function buildLoginUrl(?string $returnTo = null): string {
        self::startSession();
        $state = bin2hex(random_bytes(16));
        $_SESSION['oauth_state']     = $state;
        $_SESSION['oauth_return_to'] = $returnTo ?: ($_SERVER['REQUEST_URI'] ?? '/');

        $params = http_build_query([
            'response_type' => 'code',
            'client_id'     => Config::get('OAUTH_CLIENT_ID'),
            'redirect_uri'  => Config::get('OAUTH_REDIRECT_URI'),
            'scope'         => Config::get('OAUTH_SCOPE', 'profile'),
            'state'         => $state,
        ]);
        return Config::get('OAUTH_AUTH_URL') . '?' . $params;
    }

    public static function requireAuth(): void {
        if (self::isAuthenticated()) return;
        $loginUrl = self::buildLoginUrl();
        $accepts  = $_SERVER['HTTP_ACCEPT'] ?? '';
        $isAjax   = !empty($_SERVER['HTTP_X_REQUESTED_WITH'])
                 || str_contains($accepts, 'application/json');
        if ($isAjax) {
            header('Content-Type: application/json; charset=utf-8');
            http_response_code(401);
            echo json_encode(['ok' => false, 'auth_required' => true, 'login_url' => $loginUrl]);
            exit;
        }
        header('Location: ' . $loginUrl);
        exit;
    }

    public static function emailDomainAllowed(string $email): bool {
        $allowed = Config::list('ALLOWED_EMAIL_DOMAINS');
        if (!$allowed) return true;
        $parts = explode('@', strtolower(trim($email)));
        if (count($parts) !== 2) return false;
        return in_array($parts[1], array_map('strtolower', $allowed), true);
    }

    public static function completeLogin(string $email, string $name): void {
        self::startSession();
        session_regenerate_id(true);
        $_SESSION['authenticated'] = true;
        $_SESSION['user_email']    = $email;
        $_SESSION['user_name']     = $name ?: $email;
        $_SESSION['auth_time']     = time();

        try {
            $pdo = Db::pdo();
            $stmt = $pdo->prepare(
                'INSERT INTO users (email, name, first_seen_at, last_login_at)
                 VALUES (:email, :name, NOW(), NOW())
                 ON DUPLICATE KEY UPDATE name = VALUES(name), last_login_at = NOW()'
            );
            $stmt->execute([':email' => $email, ':name' => $name]);
        } catch (Throwable $e) {
            error_log('users upsert failed: ' . $e->getMessage());
        }
    }

    public static function logout(): void {
        self::startSession();
        $_SESSION = [];
        if (ini_get('session.use_cookies')) {
            $p = session_get_cookie_params();
            setcookie(session_name(), '', time() - 42000, $p['path'], $p['domain'] ?? '', $p['secure'], $p['httponly']);
        }
        session_destroy();
    }

    public static function popReturnTo(): string {
        self::startSession();
        $to = $_SESSION['oauth_return_to'] ?? '/';
        unset($_SESSION['oauth_return_to']);
        return $to;
    }

    public static function checkState(string $state): bool {
        self::startSession();
        $expected = $_SESSION['oauth_state'] ?? '';
        unset($_SESSION['oauth_state']);
        return $state !== '' && hash_equals((string)$expected, $state);
    }
}