Create GallerySections model for holding data about a gallery

mobile/lib/models/gallery/gallery_sections.dart

@@ -0,0 +1,61 @@
+import "dart:core";
+
+import "package:photos/models/file/file.dart";
+import "package:photos/ui/viewer/gallery/component/group/type.dart";
+import "package:uuid/uuid.dart";
+
+class GallerySections {
+  final List<EnteFile> allFiles;
+  final GroupType groupType;
+  final bool sortOrderAsc;
+  GallerySections({
+    required this.allFiles,
+    required this.groupType,
+    this.sortOrderAsc = true,
+  });
+
+  late final List<String> _groupIDs;
+  late final Map<String, List<EnteFile>> _groupIDToFilesMap;
+  late Map<String, GroupHeaderData> _groupIdToheaderDataMap;
+
+  List<String> get groupIDs => _groupIDs;
+  Map<String, List<EnteFile>> get groupIDToFilesMap => _groupIDToFilesMap;
+  Map<String, GroupHeaderData> get groupIdToheaderDataMap =>
+      _groupIdToheaderDataMap;
+
+  final _uuid = const Uuid();
+
+  void init() {
+    List<EnteFile> dailyFiles = [];
+    for (int index = 0; index < allFiles.length; index++) {
+      if (index > 0 &&
+          groupType.areFromSameGroup(allFiles[index - 1], allFiles[index])) {
+        _createNewGroup(dailyFiles);
+        dailyFiles = [];
+      }
+      dailyFiles.add(allFiles[index]);
+    }
+    if (dailyFiles.isNotEmpty) {
+      _createNewGroup(dailyFiles);
+    }
+  }
+
+  void _createNewGroup(
+    List<EnteFile> dailyFiles,
+  ) {
+    final uuid = _uuid.v1();
+    _groupIDs.add(uuid);
+    _groupIDToFilesMap[uuid] = dailyFiles;
+    _groupIdToheaderDataMap[uuid] = GroupHeaderData(
+      title: dailyFiles.first.creationTime!.toString(),
+    );
+  }
+}
+
+class GroupHeaderData {
+  final String title;
+
+  GroupHeaderData({
+    required this.title,
+  });
+}

mobile/lib/ui/viewer/gallery/gallery.dart

@@ -379,6 +379,7 @@ class GalleryState extends State<Gallery> {
       sortOrderAsc: _sortOrderAsc,
       inSelectionMode: widget.inSelectionMode,
       type: widget.groupType,
+      // Replace this with the new gallery and use `_allGalleryFiles`
       child: MultipleGroupsGalleryView(
         itemScroller: _itemScroller,
         groupedFiles: currentGroupedFiles,