<?php
/**
 * Zend Framework (http://framework.zend.com/)
 *
 * @link      http://github.com/zendframework/zf2 for the canonical source repository
 * @copyright Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd New BSD License
 * @package   Zend_I18n
 */

namespace Zend\I18n\Filter;

use Locale;

/**
 * @category   Zend
 * @package    Zend_I18n
 * @subpackage Filter
 */
class Alpha extends Alnum
{
    /**
     * Defined by Zend\Filter\FilterInterface
     *
     * Returns the string $value, removing all but alphabetic characters
     *
     * @param  string $value
     * @return string
     */
    public function filter($value)
    {
        $whiteSpace = $this->options['allow_white_space'] ? '\s' : '';
        $language   = Locale::getPrimaryLanguage($this->getLocale());

        if (!static::hasPcreUnicodeSupport()) {
            // POSIX named classes are not supported, use alternative [a-zA-Z] match
            $pattern = '/[^a-zA-Z' . $whiteSpace . ']/';
        } elseif ($language == 'ja' || $language == 'ko' || $language == 'zh') {
            // Use english alphabet
            $pattern = '/[^a-zA-Z'  . $whiteSpace . ']/u';
        } else {
            // Use native language alphabet
            $pattern = '/[^\p{L}' . $whiteSpace . ']/u';
        }

        return preg_replace($pattern, '', (string) $value);
    }
}
