use a 'sensible range' for headline weight/measurements charts

this allows user to focus on their recent progress on the initial chart.
if they want to see the full history, that's only a tap away

Author: Dieterbe

lib/widgets/dashboard/widgets.dart

@@ -42,6 +42,7 @@ import 'package:wger/widgets/core/core.dart';
 import 'package:wger/widgets/measurements/categories_card.dart';
 import 'package:wger/widgets/measurements/charts.dart';
 import 'package:wger/widgets/measurements/forms.dart';
+import 'package:wger/widgets/measurements/helpers.dart';
 import 'package:wger/widgets/nutrition/charts.dart';
 import 'package:wger/widgets/nutrition/forms.dart';
 import 'package:wger/widgets/weight/forms.dart';
@@ -161,9 +162,9 @@ class _DashboardWeightWidgetState extends State<DashboardWeightWidget> {
     final profile = context.read<UserProvider>().profile;
     final weightProvider = context.read<BodyWeightProvider>();
 
-    final entriesAll =
-        weightProvider.items.map((e) => MeasurementChartEntry(e.weight, e.date)).toList();
-    final entries7dAvg = moving7dAverage(entriesAll);
+    final (entriesAll, entries7dAvg) = sensibleRange(
+      weightProvider.items.map((e) => MeasurementChartEntry(e.weight, e.date)).toList(),
+    );
 
     return Consumer<BodyWeightProvider>(
       builder: (context, workoutProvider, child) => Card(

lib/widgets/measurements/categories_card.dart

@@ -4,6 +4,7 @@ import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 import 'package:wger/models/measurements/measurement_category.dart';
 import 'package:wger/screens/form_screen.dart';
 import 'package:wger/screens/measurement_entries_screen.dart';
+import 'package:wger/widgets/measurements/helpers.dart';
 import 'charts.dart';
 import 'forms.dart';
 
@@ -15,9 +16,9 @@ class CategoriesCard extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final entriesAll =
-        currentCategory.entries.map((e) => MeasurementChartEntry(e.value, e.date)).toList();
-    final entries7dAvg = moving7dAverage(entriesAll);
+    final (entriesAll, entries7dAvg) = sensibleRange(
+      currentCategory.entries.map((e) => MeasurementChartEntry(e.value, e.date)).toList(),
+    );
 
     return Card(
       elevation: elevation,

lib/widgets/measurements/helpers.dart

@@ -77,3 +77,30 @@ List<Widget> getOverviewWidgetsSeries(
     ),
   ];
 }
+
+// return the raw and average meaasurements for a "sensible range"
+// a sensible range is something relatively recent, which is most relevant
+// for the user to track their progress, but a range should always include
+// at least 5 points, and if not we chose a bigger one.
+// we return a range of the last 2 months, 4 months, or the full history
+(List<MeasurementChartEntry>, List<MeasurementChartEntry>) sensibleRange(
+  List<MeasurementChartEntry> entriesAll,
+) {
+  final entries7dAvg = moving7dAverage(entriesAll);
+  final twoMonthsAgo = DateTime.now().subtract(const Duration(days: 61));
+  final fourMonthsAgo = DateTime.now().subtract(const Duration(days: 122));
+
+  if (entriesAll.where((e) => e.date.isAfter(twoMonthsAgo)).length > 4) {
+    return (
+      entriesAll.where((e) => e.date.isAfter(twoMonthsAgo)).toList(),
+      entries7dAvg.where((e) => e.date.isAfter(twoMonthsAgo)).toList(),
+    );
+  }
+  if (entriesAll.where((e) => e.date.isAfter(fourMonthsAgo)).length > 4) {
+    return (
+      entriesAll.where((e) => e.date.isAfter(fourMonthsAgo)).toList(),
+      entries7dAvg.where((e) => e.date.isAfter(fourMonthsAgo)).toList(),
+    );
+  }
+  return (entriesAll, entries7dAvg);
+}