Adding snowball stemmer

Author: yooper

composer.json

@@ -27,7 +27,8 @@
         "php": ">=5.5",
         "yooper/stop-words": "^1.0",
         "symfony/console": ">=2.7",
-        "camspiers/porter-stemmer": "1.0.*"
+        "camspiers/porter-stemmer": "1.0.*",
+        "wamania/php-stemmer": "1.2"
     },
     "require-dev": {
         "phpunit/phpunit": "5.*",

src/Stemmers/SnowballStemmer.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace TextAnalysis\Stemmers;
+
+use TextAnalysis\Interfaces\IStemmer;
+
+/**
+ * A wrapper around PHP native snowball implementation
+ * @author yooper
+ */
+class SnowballStemmer implements IStemmer
+{
+    const BASE_NAMESPACE = '\\Wamania\\Snowball\\';
+    
+    /**
+     *
+     * @var \Wamania\Snowball\Stem
+     */
+    protected $stemmer;
+    
+    public function __construct($stemmerType = 'English') 
+    {
+        $className = self::BASE_NAMESPACE.$stemmerType;
+        if(!class_exists($className)) { 
+            throw new \RuntimeException("Class {$stemmerType} does not exist");
+        }
+        $this->stemmer = new $className();
+    }
+    
+    public function stem($token) 
+    {
+        return $this->stemmer->stem($token);
+    }
+
+}

tests/TextAnalysis/Stemmers/SnowballStemmerTest.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Tests\TextAnalysis\Stemmers;
+
+use TextAnalysis\Stemmers\SnowballStemmer;
+
+/**
+ *
+ * @author yooper
+ */
+class SnowballStemmerTest extends \PHPUnit_Framework_TestCase
+{
+    public function testDefaultEnglish()
+    {       
+        $stemmer = new SnowballStemmer('English');
+        $this->assertEquals("judg", $stemmer->stem("judges"));
+        $this->assertEquals('ski', $stemmer->stem('skis'));
+        $this->assertEquals('univers', $stemmer->stem('universities'));
+        $this->assertEquals('news', $stemmer->stem('news'));                        
+    }
+    
+    public function testSwedish()
+    {       
+        $stemmer = new SnowballStemmer('Swedish');
+        $this->assertEquals("affärschef", $stemmer->stem("affärscheferna"));
+    }    
+    
+    public function testException()
+    {     
+        $this->setExpectedException('Exception');
+        $stemmer = new SnowballStemmer('Wookie');
+    }
+}