No gemini (#45)

* Update IslandoraServiceProvider.php

* Just using EntityMapper instead of Gemini

* Updates from testing

* Coding standards and tests

EntityMapper/EntityMapper.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Islandora\Crayfish\Commons\EntityMapper;
+
+class EntityMapper implements EntityMapperInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getFedoraPath($uuid)
+    {
+        if (strlen($uuid) < 8) {
+            throw new \InvalidArgumentException(
+                "Provided UUID must be at least of length 8 to account for pair-trees",
+                400
+            );
+        }
+
+        $segments = str_split(substr($uuid, 0, 8), 2);
+        return implode("/", $segments) . "/$uuid";
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getDrupalUuid($fedora_path)
+    {
+        if (empty($fedora_path)) {
+            throw new \InvalidArgumentException(
+                "Empty string provided fedora path",
+                400
+            );
+        }
+        $segments = explode("/", $fedora_path);
+        return end($segments);
+    }
+}

EntityMapper/EntityMapperInterface.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Islandora\Crayfish\Commons\EntityMapper;
+
+interface EntityMapperInterface
+{
+    /**
+     * Gets a fedora path given a uuid.
+     *
+     * @param string $uuid
+     * @return string
+     */
+    public function getFedoraPath($uuid);
+
+    /**
+     * Gets a drupal uuid from a fedora path.
+     *
+     * @param string $fedora_path
+     * @return string
+     */
+    public function getDrupalUuid($fedora_path);
+}