Fetch and persist collections on startup

lib/services/collections_service.dart

@@ -3,18 +3,26 @@ import 'dart:io';
 import 'package:dio/dio.dart';
 import 'package:logging/logging.dart';
 import 'package:photos/core/configuration.dart';
+import 'package:photos/db/collections_db.dart';
 import 'package:photos/models/collection.dart';
 
 class CollectionsService {
   final _logger = Logger("CollectionsService");
 
-  CollectionsService._privateConstructor() {}
+  CollectionsDB _db;
+
+  CollectionsService._privateConstructor() {
+    _db = CollectionsDB.instance;
+  }
 
   static final CollectionsService instance =
       CollectionsService._privateConstructor();
 
   Future<void> sync() async {
-    // TODO
+    final lastCollectionCreationTime =
+        await _db.getLastCollectionCreationTime();
+    final collections = await getCollections(lastCollectionCreationTime ?? 0);
+    await _db.insert(collections);
   }
 
   Future<Collection> getFolder(String path) async {
@@ -37,4 +45,26 @@ class CollectionsService {
       }
     });
   }
+
+  Future<List<Collection>> getCollections(int sinceTime) {
+    return Dio()
+        .get(
+      Configuration.instance.getHttpEndpoint() + "/collections/",
+      queryParameters: {
+        "sinceTime": sinceTime,
+      },
+      options:
+          Options(headers: {"X-Auth-Token": Configuration.instance.getToken()}),
+    )
+        .then((response) {
+      final collections = List<Collection>();
+      if (response != null) {
+        final c = response.data["collections"];
+        for (final collection in c) {
+          collections.add(Collection.fromMap(collection));
+        }
+      }
+      return collections;
+    });
+  }
 }