Refactor all of the unit conversion code

app/Interfaces/Unit.php

@@ -0,0 +1,87 @@
+<?php
+
+namespace App\Interfaces;
+
+use ArrayAccess;
+
+/**
+ * Class Unit
+ * @package App\Interfaces
+ * @property mixed  $instance
+ * @property string $unit
+ * @property array  $units
+ */
+class Unit implements ArrayAccess
+{
+    /**
+     * The unit this is kept as
+     */
+    public $unit;
+
+    /**
+     * All of the units of this class
+     * @var array
+     */
+    public $units;
+
+    /**
+     * Holds an instance of the PhpUnit type
+     * @var
+     */
+    protected $instance;
+
+    /**
+     * @return mixed
+     */
+    public function value()
+    {
+        return $this->__toString();
+    }
+
+    /**
+     * Implements ArrayAccess
+     * @param $offset
+     * @return bool
+     */
+    public function offsetExists($offset)
+    {
+        return array_key_exists($offset, $this->units);
+    }
+
+    /**
+     * Implements ArrayAccess
+     * @param $offset
+     * @return mixed
+     */
+    public function offsetGet($offset)
+    {
+        return $this->units[$offset];
+    }
+
+    /**
+     * Implements ArrayAccess
+     * @param $offset
+     * @param $value
+     */
+    public function offsetSet($offset, $value)
+    {
+        $this->units[$offset] = $value;
+    }
+
+    /**
+     * Implements ArrayAccess
+     * @param $offset
+     */
+    public function offsetUnset($offset)
+    {
+        $this->units[$offset] = null;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function __toString()
+    {
+        return (string) $this->units[$this->unit];
+    }
+}