<?php
/************************************************************************
 * This file is part of EspoCRM.
 *
 * EspoCRM – Open Source CRM application.
 * Copyright (C) 2014-2026 EspoCRM, Inc.
 * Website: https://www.espocrm.com
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <https://www.gnu.org/licenses/>.
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License version 3.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License version 3,
 * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
 ************************************************************************/

namespace Espo\Core\Authentication\Oidc;

class PkceUtil
{
    private const string CHARACTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~';
    private const int CODE_LENGTH = 64;

    public static function generateCodeVerifier(): string
    {
        $output = '';

        for ($i = 0; $i < self::CODE_LENGTH; $i++) {
            $output .= self::CHARACTERS[random_int(0, strlen(self::CHARACTERS) - 1)];
        }

        return $output;
    }

    public static function hashAndEncodeCodeVerifier(string $codeVerifier): string
    {
        $code = hash('sha256', $codeVerifier, true);

        return rtrim(strtr(base64_encode($code), '+/', '-_'), '=');
    }
}