album: group by month

lib/model/image_entry.dart

@@ -79,8 +79,8 @@ class ImageEntry {
     return null;
   }
 
-  DateTime getDayTaken() {
+  DateTime getMonthTaken() {
     final d = getBestDate();
-    return d == null ? null : DateTime(d.year, d.month, d.day);
+    return d == null ? null : DateTime(d.year, d.month);
   }
 }

lib/thumbnail_collection.dart

@@ -16,7 +16,7 @@ class ThumbnailCollection extends StatelessWidget {
   final ScrollController scrollController = ScrollController();
 
   ThumbnailCollection({Key key, this.entries, this.done})
-      : sections = groupBy(entries, (entry) => entry.getDayTaken()),
+      : sections = groupBy(entries, (entry) => entry.getMonthTaken()),
         super(key: key);
 
   @override
@@ -85,7 +85,7 @@ class SectionSliver extends StatelessWidget {
 //    debugPrint('$runtimeType build with sectionKey=$sectionKey');
     final columnCount = 4;
     return SliverStickyHeader(
-      header: DaySectionHeader(date: sectionKey),
+      header: MonthSectionHeader(date: sectionKey),
       sliver: SliverGrid(
         delegate: SliverChildBuilderDelegate(
           (sliverContext, index) {
@@ -146,6 +146,28 @@ class DaySectionHeader extends StatelessWidget {
   }
 }
 
+class MonthSectionHeader extends StatelessWidget {
+  final String text;
+
+  MonthSectionHeader({Key key, DateTime date})
+      : text = formatDate(date),
+        super(key: key);
+
+  static DateFormat m = DateFormat.MMMM();
+  static DateFormat ym = DateFormat.yMMMM();
+
+  static formatDate(DateTime date) {
+    if (isThisMonth(date)) return 'This month';
+    if (isThisYear(date)) return m.format(date);
+    return ym.format(date);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return SectionHeader(text: text);
+  }
+}
+
 class SectionHeader extends StatelessWidget {
   final String text;
 

lib/utils/date_utils.dart

@@ -6,4 +6,6 @@ bool isAtSameDayAs(DateTime d1, DateTime d2) => isAtSameMonthAs(d1, d2) && d1.da
 
 bool isToday(DateTime d) => isAtSameDayAs(d, DateTime.now());
 
+bool isThisMonth(DateTime d) => isAtSameMonthAs(d, DateTime.now());
+
 bool isThisYear(DateTime d) => isAtSameYearAs(d, DateTime.now());