Update photo when it was updated on remote

lib/db/photo_db.dart

@@ -149,6 +149,20 @@ class PhotoDB {
     }
   }
 
+  Future<Photo> getMatchingRemotePhoto(int uploadedFileId) async {
+    final db = await instance.database;
+    final rows = await db.query(
+      table,
+      where: '$columnUploadedFileId=?',
+      whereArgs: [uploadedFileId],
+    );
+    if (rows.isNotEmpty) {
+      return _getPhotoFromRow(rows[0]);
+    } else {
+      throw ("No matching photo found");
+    }
+  }
+
   Future<int> updatePhoto(
       int generatedId, int uploadedId, String remotePath, int updateTimestamp,
       [String thumbnailPath]) async {

lib/folder_service.dart

@@ -57,9 +57,22 @@ class FolderSharingService {
     } catch (e) {
       // Folder has never been synced
     }
-    var photos = await getDiff(folder.id, lastSyncTimestamp, _diffLimit);
-    await PhotoDB.instance.insertPhotos(photos);
-    if (photos.length == _diffLimit) {
+    var diff = await getDiff(folder.id, lastSyncTimestamp, _diffLimit);
+    for (Photo photo in diff) {
+      try {
+        var existingPhoto =
+            await PhotoDB.instance.getMatchingRemotePhoto(photo.uploadedFileId);
+        await PhotoDB.instance.updatePhoto(
+            existingPhoto.generatedId,
+            photo.uploadedFileId,
+            photo.remotePath,
+            photo.updateTimestamp,
+            photo.thumbnailPath);
+      } catch (e) {
+        await PhotoDB.instance.insertPhoto(photo);
+      }
+    }
+    if (diff.length == _diffLimit) {
       await syncDiff(folder);
     }
   }