Update ComposeController, add mediaProcessingCheck method

app/Http/Controllers/ComposeController.php

@@ -513,4 +513,39 @@ class ComposeController extends Controller
 
 		return $status->url();
 	}
+
+	public function mediaProcessingCheck(Request $request)
+	{
+		$this->validate($request, [
+			'id' => 'required|integer|min:1'
+		]);
+
+		$media = Media::whereUserId($request->user()->id)
+			->whereNull('status_id')
+			->findOrFail($request->input('id'));
+
+		if(config('pixelfed.media_fast_process')) {
+			return [
+				'finished' => true
+			];
+		}
+
+		$finished = false;
+
+		switch ($media->mime) {
+			case 'image/jpeg':
+			case 'image/png':
+			case 'video/mp4':
+				$finished = config('pixelfed.cloud_storage') ? (bool) $media->cdn_url : (bool) $media->processed_at;
+				break;
+			
+			default:
+				# code...
+				break;
+		}
+
+		return [
+			'finished' => $finished
+		];
+	}
 }