add merge tune to extract tunes by title

update Tune::merge() and add Tune::equals()

src/Domain/Core/Collection.php

@@ -9,7 +9,7 @@ class Collection extends BaseCollection
 {
     /**
      * @param $initial
-     * @param callable $callback
+     * @param callable($carry, $item) $callback
      * @return mixed
      */
     public function reduce($initial, callable $callback)

src/Domain/Core/Tune.php

@@ -263,11 +263,9 @@ class Tune implements EntityInterface
      */
     public function getSettings()
     {
-        return $this->tuneSettings;
+        return $this->tuneSettings ?: [];
     }
 
-
-
     /**
      * @param $attribute
      * @param $value
@@ -363,8 +361,23 @@ class Tune implements EntityInterface
         $this->titles = array_merge($this->getTitles(), $source->getTitles());
         $this->authors = array_merge($this->getAuthors(), $source->getAuthors());
         $this->composers = array_merge($this->getComposers(), $source->getComposers());
+        $this->groups = array_merge($this->getGroups(), $source->getGroups());
         $this->history = array_merge($this->getHistory(), $source->getHistory());
+        $this->origins = array_merge($this->getOrigins(), $source->getOrigins());
+        $this->rhythms = array_merge($this->getRhythms(), $source->getRhythms());
         $this->tuneSettings = array_merge($this->getSettings(), $source->getSettings());
         return $this;
     }
+
+    /**
+     * @param \XaiCorp\AbcParser\Domain\Core\Tune $otherTune
+     * @return bool
+     */
+    public function equals(Tune $otherTune)
+    {
+        //TODO:
+        return $this->getTitles() === $otherTune->getTitles()
+            && $this->getRhythms() === $otherTune->getRhythms()
+            ;
+    }
 }