Add hash tag extract

Author: yooper

src/Extracts/HashTag.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace TextAnalysis\Extracts;
+use TextAnalysis\Interfaces\IExtractStrategy;
+
+/**
+ * check if the given token is a hash tag
+ * @author yooper
+ */
+class HashTag implements IExtractStrategy
+{
+    /**
+     *
+     * @var int
+     */
+    protected $minLength = 3;
+        
+    public function __construct(int $minLength = 3) 
+    {
+        $this->minLength = $minLength;
+    }
+    
+    /**
+     * 
+     * @param string $token
+     * @return false|string
+     */
+    public function filter($token) 
+    {
+        // don't count the hash tag sign -1
+        if($token[0] === '#' && strlen($token)-1 >= $this->getMinLength()) {
+            return $token;
+        }
+        return false;
+    }
+    
+    public function getMinLength() : int
+    {
+        return $this->minLength;
+    }
+
+}

tests/TextAnalysis/Extracts/HashTagTest.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace Tests\TextAnalysis\Extracts;
+
+use TextAnalysis\Extracts\HashTag;
+
+/**
+ * Test if hashtag extraction is working
+ * @author yooper
+ */
+class HashTagTest extends \PHPUnit_Framework_TestCase
+{
+    public function testHashTag()
+    {
+        $extract = new HashTag();
+        $this->assertFalse($extract->filter("testing"));
+        $this->assertEquals('#holiday', $extract->filter('#holiday'));
+        $this->assertFalse($extract->filter('#DA'));
+    }
+    
+    public function testMinLengthHashTag()
+    {
+        $extract = new HashTag(2);
+        $this->assertEquals('#DA', $extract->filter('#DA'));
+        $this->assertFalse($extract->filter('#1'));
+    }
+    
+}