<?php

// phpcs:disable PSR1.Files.SideEffects
defined('SYSPATH') or die('No direct access allowed.');
// phpcs:enable PSR1.Files.SideEffects
/**
 * utf8::substr
 *
 * @package    Core
 * @author     Kohana Team
 * @copyright  (c) 2007 Kohana Team
 * @copyright  (c) 2005 Harry Fuecks
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt
 */
function _substr($str, $offset, $length = null)
{
    if (SERVER_UTF8) {
        return ($length === null) ? mb_substr($str, $offset) : mb_substr($str, $offset, $length);
    }

    if (utf8::is_ascii($str)) {
        return ($length === null) ? substr($str, $offset) : substr($str, $offset, $length);
    }

    // Normalize params
    $str    = (string) $str;
    $strlen = utf8::strlen($str);
    $offset = (int) ($offset < 0) ? max(0, $strlen + $offset) : $offset; // Normalize to positive offset
    $length = ($length === null) ? null : (int) $length;

    // Impossible
    if ($length === 0 or $offset >= $strlen or ($length < 0 and $length <= $offset - $strlen)) {
        return '';
    }

    // Whole string
    if ($offset == 0 and ($length === null or $length >= $strlen)) {
        return $str;
    }

    // Build regex
    $regex = '^';

    // Create an offset expression
    if ($offset > 0) {
        // PCRE repeating quantifiers must be less than 65536, so repeat when necessary
        $x = (int) ($offset / 65535);
        $y = (int) ($offset % 65535);
        $regex .= ($x == 0) ? '' : '(?:.{65535}){' . $x . '}';
        $regex .= ($y == 0) ? '' : '.{' . $y . '}';
    }

    // Create a length expression
    if ($length === null) {
        $regex .= '(.*)'; // No length set, grab it all
    } elseif ($length > 0) {
        // Find length from the left (positive length)
        // Reduce length so that it can't go beyond the end of the string
        $length = min($strlen - $offset, $length);

        $x = (int) ($length / 65535);
        $y = (int) ($length % 65535);
        $regex .= '(';
        $regex .= ($x == 0) ? '' : '(?:.{65535}){' . $x . '}';
        $regex .= '.{' . $y . '})';
    } else {
        // Find length from the right (negative length)
        $x = (int) (-$length / 65535);
        $y = (int) (-$length % 65535);
        $regex .= '(.*)';
        $regex .= ($x == 0) ? '' : '(?:.{65535}){' . $x . '}';
        $regex .= '.{' . $y . '}';
    }

    preg_match('/' . $regex . '/us', $str, $matches);
    return $matches[1];
}