CollectionManager for Tunes, Files and Books

- models and domain code

src/Application/UseCases/ExtractTuneFromCollection.php

@@ -32,4 +32,17 @@ class ExtractTuneFromCollection
             })
             ;
     }
+
+    /**
+     * @return \XaiCorp\AbcParser\Domain\Core\Tune
+     */
+    public function extractTuneFromPreparedCollection() : Tune
+    {
+        return $this->tunes
+            ->unique()
+            ->reduce(new Tune([]), function (Tune $carry, Tune $tune) {
+                return $carry->merge($tune);
+            })
+            ;
+    }
 }

src/Application/UseCases/ImportAbcFile.php

@@ -50,7 +50,7 @@ class ImportAbcFile
      * @param array $abcs
      * @return \XaiCorp\AbcParser\Domain\Core\TuneCollection
      */
-    public function importMultiple(array $abcs)
+    public function importMultiple(array $abcs) : TuneCollection
     {
         $result = Collection::make($abcs)
             ->map(function (string $abc) {