<?php
/**
 * Akeeba Engine
 *
 * @package   akeebaengine
 * @copyright Copyright (c)2006-2021 Nicholas K. Dionysopoulos / Akeeba Ltd
 * @license   GNU General Public License version 3, or later
 */

namespace Akeeba\Engine\Util;

defined('AKEEBAENGINE') || die();

/**
 * Crypto-safe random value generator. Based on the Randval class of the Aura for PHP's Session package.
 * The following is the license file accompanying the original file.
 *
 * ********************************************************************************
 * Copyright (c) 2011-2016, Aura for PHP
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * ********************************************************************************
 *
 * Please note that this is a MODIFIED copy of the Randval class, mainly to allow it to be used on hosts
 * which lack both mbcrypt and OpenSSL PHP modules.
 */
class RandomValue
{
	/**
	 *
	 * Returns a cryptographically secure random value.
	 *
	 * @param   integer  $bytes  How many bytes to return
	 *
	 * @return  string
	 */
	public function generate($bytes = 32)
	{
		return random_bytes($bytes);
	}

	/**
	 * Generates a random string with the specified length. WARNING: You get to specify the number of
	 * random characters in the string, not the number of random bytes. The character pool is 64 characters
	 * (6 bits) long. The entropy of your string is 6 * $characters bits. This means that a random string
	 * of 32 characters has an entropy of 192 bits whereas a random sequence of 32 bytes returned by generate()
	 * has an entropy of 8 * 32 = 256 bits.
	 *
	 * @param   int    $characters    Number of characters
	 * @param   string $characterSet  Characters to pick from
	 *
	 * @return string
	 */
	public function generateString($characters = 32, $characterSet = 'abcdefghijklmnopqrstuvwxyz-ABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789')
	{
		$sourceString = str_split('abcdefghijklmnopqrstuvwxyz-ABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789', 1);
		$ret          = '';

		$bytes     = ceil($characters / 4) * 3;
		$randBytes = $this->generate($bytes);

		for ($i = 0; $i < $bytes; $i += 3)
		{
			$subBytes = substr($randBytes, $i, 3);
			$subBytes = str_split($subBytes, 1);
			$subBytes = ord($subBytes[0]) * 65536 + ord($subBytes[1]) * 256 + ord($subBytes[2]);
			$subBytes = $subBytes & bindec('00000000111111111111111111111111');

			$b    = [];
			$b[0] = $subBytes >> 18;
			$b[1] = ($subBytes >> 12) & bindec('111111');
			$b[2] = ($subBytes >> 6) & bindec('111111');
			$b[3] = $subBytes & bindec('111111');

			$ret .= $sourceString[$b[0]] . $sourceString[$b[1]] . $sourceString[$b[2]] . $sourceString[$b[3]];
		}

		return substr($ret, 0, $characters);
	}
}
