replace StringUtils::slugify by a proper instance

Previous implementation had a flaw when using a different separating character. New implementation should be well tested.

lib/Alchemy/Phrasea/SearchEngine/Elastic/StringUtils.php

@@ -1,9 +1,8 @@
 <?php
-
-/*
+/**
  * This file is part of Phraseanet
  *
- * (c) 2005-2014 Alchemy
+ * (c) 2005-2016 Alchemy
  *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
@@ -11,28 +10,46 @@
 
 namespace Alchemy\Phrasea\SearchEngine\Elastic;
 
+use Cocur\Slugify\Slugify;
+use Cocur\Slugify\SlugifyInterface;
 use Transliterator;
 
 class StringUtils
 {
+    /**
+     * @var SlugifyInterface|null
+     */
+    private static $slugifier;
+
     private static $transliterator;
 
+    /**
+     * Prevent instantiation of the class
+     */
+    private function __construct()
+    {
+    }
+
+    public static function setSlugify(SlugifyInterface $slugify = null)
+    {
+        self::$slugifier = $slugify;
+    }
+
+    /**
+     * @return SlugifyInterface
+     */
+    private static function getSlugifier()
+    {
+        if (null === self::$slugifier) {
+            self::$slugifier = new Slugify();
+        }
+
+        return self::$slugifier;
+    }
+
     public static function slugify($string, $separator = '-')
     {
-        // Replace non letter or digits by _
-        $string = preg_replace('/[^\\pL\d]+/u', $separator, $string);
-        $string = trim($string, $separator);
-
-        // Transliterate
-        if (function_exists('iconv')) {
-            $string = iconv('UTF-8', 'ASCII//TRANSLIT', $string);
-        }
-
-        // Remove non wording characters
-        $string = preg_replace('/[^-\w]+/', '', $string);
-        $string = strtolower($string);
-
-        return $string;
+        return self::getSlugifier()->slugify($string, $separator);
     }
 
     public static function asciiLowerFold($string)