<?php
/**
 * @see       https://github.com/zendframework/zend-hydrator for the canonical source repository
 * @copyright Copyright (c) 2018 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   https://github.com/zendframework/zend-hydrator/blob/master/LICENSE.md New BSD License
 */

declare(strict_types=1);

namespace Zend\Hydrator\NamingStrategy\UnderscoreNamingStrategy;

use function mb_strtolower;
use function mb_strtoupper;
use function preg_quote;
use function preg_replace_callback;
use function strtoupper;
use function substr;

/**
 * @internal
 */
final class UnderscoreToCamelCaseFilter
{
    use StringSupportTrait;

    public function filter(string $value) : string
    {
        $pcreInfo = $this->getPatternAndReplacement(
            // a unicode safe way of converting characters to \x00\x00 notation
            preg_quote('_', '#')
        );

        $filtered = preg_replace_callback(
            $pcreInfo->pattern,
            $pcreInfo->replacement,
            $value
        );

        $lcFirstFunction = $this->getLcFirstFunction();
        return $lcFirstFunction($filtered);
    }

    private function getPatternAndReplacement(string $pregQuotedSeparator) : PcreReplacement
    {
        return $this->hasPcreUnicodeSupport()
            ? $this->getUnicodePatternAndReplacement($pregQuotedSeparator)
            : new PcreReplacement(
                '#(' . $pregQuotedSeparator . ')([\S]{1})#',
                function ($matches) {
                    return strtoupper($matches[2]);
                }
            );
    }

    private function getUnicodePatternAndReplacement(string $pregQuotedSeparator) : PcreReplacement
    {
        return $this->hasMbStringSupport()
            ? new PcreReplacement(
                '#(' . $pregQuotedSeparator . ')(\P{Z}{1})#u',
                function ($matches) {
                    return mb_strtoupper($matches[2], 'UTF-8');
                }
            )
            : new PcreReplacement(
                '#(' . $pregQuotedSeparator . ')'
                    . '([^\p{Z}\p{Ll}]{1}|[a-zA-Z]{1})#u',
                function ($matches) {
                    return strtoupper($matches[2]);
                }
            );
    }

    private function getLcFirstFunction() : callable
    {
        return $this->hasMbStringSupport()
            ? function ($value) {
                return mb_strtolower($value[0], 'UTF-8') . substr($value, 1);
            }
            : 'lcfirst';
    }
}