<?php

/**
 * webtrees: online genealogy
 * Copyright (C) 2019 webtrees development team
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

declare(strict_types=1);

namespace Fisharebest\Webtrees\Http\Middleware;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;

/**
 * Middleware to set security-related HTTP headers.
 */
class SecurityHeaders implements MiddlewareInterface
{
    private const SECURITY_HEADERS = [
        'Referrer-Policy'        => 'same-origin',
        'X-Content-Type-Options' => 'nosniff',
        'X-Frame-Options'        => 'SAMEORIGIN',
        'X-XSS-Protection'       => '1; mode=block',
    ];

    /**
     * @param ServerRequestInterface  $request
     * @param RequestHandlerInterface $handler
     *
     * @return ResponseInterface
     */
    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
    {
        $response = $handler->handle($request);

        foreach (self::SECURITY_HEADERS as $header_name => $header_value) {
            // Don't overwrite existing headers.
            if ($response->getHeader($header_name) === []) {
                $response = $response->withHeader($header_name, $header_value);
            }
        }

        return $response;
    }
}