Refactor collection repositories: use one instance per databox

lib/Alchemy/Phrasea/Collection/Repository/ArrayCacheCollectionRepository.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace Alchemy\Phrasea\Collection\Repository;
+
+use Alchemy\Phrasea\Collection\CollectionRepository;
+
+class ArrayCacheCollectionRepository implements CollectionRepository
+{
+    /**
+     * @var CollectionRepository
+     */
+    private $collectionRepository;
+
+    /**
+     * @var \collection[]
+     */
+    private $collectionCache = null;
+
+    public function __construct(CollectionRepository $collectionRepository)
+    {
+        $this->collectionRepository = $collectionRepository;
+    }
+
+    /**
+     * @return \collection[]
+     */
+    public function findAll()
+    {
+        if ($this->collectionCache === null) {
+            $this->collectionCache = $this->collectionRepository->findAll();
+        }
+
+        return $this->collectionCache;
+    }
+
+    /**
+     * @param int $collectionId
+     * @return \collection|null
+     */
+    public function find($collectionId)
+    {
+        $collections = $this->findAll();
+
+        if (isset($collections[$collectionId])) {
+            return $collections[$collectionId];
+        }
+
+        return null;
+    }
+}