Added missing file, make extension based implementation also use the …

…reverse lookup.

src/ExtensionLookup.php

@@ -0,0 +1,14 @@
+<?php
+declare(strict_types=1);
+
+namespace League\MimeTypeDetection;
+
+interface ExtensionLookup
+{
+    public function lookupExtension(string $mimetype): ?string;
+
+    /**
+     * @return string[]
+     */
+    public function lookupAllExtensions(string $mimetype): array;
+}

src/ExtensionMimeTypeDetector.php

@@ -6,7 +6,7 @@
 
 use const PATHINFO_EXTENSION;
 
-class ExtensionMimeTypeDetector implements MimeTypeDetector
+class ExtensionMimeTypeDetector implements MimeTypeDetector, ExtensionLookup
 {
     /**
      * @var ExtensionToMimeTypeMap
@@ -39,4 +39,18 @@ public function detectMimeTypeFromBuffer(string $contents): ?string
     {
         return null;
     }
+
+    public function lookupExtension(string $mimetype): ?string
+    {
+        return $this->extensions instanceof ExtensionLookup
+            ? $this->extensions->lookupExtension($mimetype)
+            : null;
+    }
+
+    public function lookupAllExtensions(string $mimetype): array
+    {
+        return $this->extensions instanceof ExtensionLookup
+            ? $this->extensions->lookupAllExtensions($mimetype)
+            : [];
+    }
 }