feat: add period selection to the calendar view

There are also some small refactors for the UI of the calendar included

packages/flutter_availability/lib/src/config/availability_options.dart

@@ -111,6 +111,6 @@ typedef BaseScreenBuilder = Widget Function(
 /// Builder definition for providing a button implementation
 typedef ButtonBuilder = Widget Function(
   BuildContext context,
-  FutureOr<void>? Function() onPressed,
+  FutureOr<void>? Function()? onPressed,
   Widget child,
 );

packages/flutter_availability/lib/src/ui/screens/availability_overview.dart

@@ -27,6 +27,7 @@ class AvailabilityOverview extends StatefulWidget {
 
 class _AvailabilityOverviewState extends State<AvailabilityOverview> {
   DateTime _selectedDate = DateTime.now();
+  DateTimeRange? _selectedRange;
 
   @override
   Widget build(BuildContext context) {
@@ -50,6 +51,11 @@ class _AvailabilityOverviewState extends State<AvailabilityOverview> {
           _selectedDate = month;
         });
       },
+      onEditDateRange: (range) {
+        setState(() {
+          _selectedRange = range;
+        });
+      },
     );
 
     const templateLegend = SizedBox(
@@ -57,13 +63,18 @@ class _AvailabilityOverviewState extends State<AvailabilityOverview> {
       child: Placeholder(),
     );
 
+    // if there is no range selected we want to disable the button
+    var onButtonPress = _selectedRange == null
+        ? null
+        : () {
+            widget.onEditDateRange(
+              DateTimeRange(start: DateTime(1), end: DateTime(2)),
+            );
+          };
+
     var startEditButton = options.primaryButtonBuilder(
       context,
-      () {
+      onButtonPress,
-        widget.onEditDateRange(
-          DateTimeRange(start: DateTime(1), end: DateTime(2)),
-        );
-      },
       Text(translations.editAvailabilityButton),
     );
 

packages/flutter_availability/lib/src/ui/widgets/calendar.dart

@@ -1,13 +1,15 @@
 import "package:flutter/material.dart";
+import "package:flutter_availability/src/config/availability_translations.dart";
 import "package:flutter_availability/src/ui/widgets/calendar_grid.dart";
 import "package:flutter_availability/src/util/scope.dart";
 
 ///
-class CalendarView extends StatelessWidget {
+class CalendarView extends StatefulWidget {
   ///
   const CalendarView({
     required this.month,
     required this.onMonthChanged,
+    required this.onEditDateRange,
     super.key,
   });
 
@@ -17,6 +19,51 @@ class CalendarView extends StatelessWidget {
   ///
   final void Function(DateTime month) onMonthChanged;
 
+  /// Callback for when the date range is edited by the user
+  final void Function(DateTimeRange? range) onEditDateRange;
+
+  @override
+  State<CalendarView> createState() => _CalendarViewState();
+}
+
+class _CalendarViewState extends State<CalendarView> {
+  DateTimeRange? _selectedRange;
+
+  void onTapDate(DateTime day) {
+    // if there is already a range selected, with a single date and the date
+    //that is selected is after it we extend the range
+    if (_selectedRange != null &&
+        day.isAfter(_selectedRange!.start) &&
+        _selectedRange!.start == _selectedRange!.end) {
+      setState(() {
+        _selectedRange = DateTimeRange(
+          start: _selectedRange!.start,
+          end: day,
+        );
+      });
+      widget.onEditDateRange(_selectedRange);
+      return;
+    }
+
+    // if select the already selected date we want to clear the range
+    if (_selectedRange != null &&
+        day.isAtSameMomentAs(_selectedRange!.start) &&
+        day.isAtSameMomentAs(_selectedRange!.end)) {
+      setState(() {
+        _selectedRange = null;
+      });
+      widget.onEditDateRange(_selectedRange);
+      return;
+    }
+
+    // if there is already a range selected we want to clear
+    //it and start a new one
+    setState(() {
+      _selectedRange = DateTimeRange(start: day, end: day);
+    });
+    widget.onEditDateRange(_selectedRange);
+  }
+
   @override
   Widget build(BuildContext context) {
     var theme = Theme.of(context);
@@ -28,80 +75,74 @@ class CalendarView extends StatelessWidget {
       mainAxisAlignment: MainAxisAlignment.center,
       children: [
         IconButton(
+          padding: EdgeInsets.zero,
           icon: const Icon(Icons.chevron_left),
           onPressed: () {
-            onMonthChanged(DateTime(month.year, month.month - 1));
+            widget.onMonthChanged(
+              DateTime(widget.month.year, widget.month.month - 1),
+            );
           },
         ),
         const SizedBox(width: 44),
-        Text(
+        SizedBox(
-          translations.monthYearFormatter(context, month),
+          width: _calculateTextWidthOfLongestMonth(context, translations),
-          style: theme.textTheme.bodyLarge,
+          child: Text(
+            translations.monthYearFormatter(context, widget.month),
+            style: theme.textTheme.titleMedium,
+            textAlign: TextAlign.center,
+          ),
         ),
         const SizedBox(width: 44),
         IconButton(
+          padding: EdgeInsets.zero,
           icon: const Icon(Icons.chevron_right),
           onPressed: () {
-            onMonthChanged(DateTime(month.year, month.month + 1));
+            widget.onMonthChanged(
+              DateTime(widget.month.year, widget.month.month + 1),
+            );
           },
         ),
       ],
     );
 
     var calendarGrid = CalendarGrid(
-      month: month,
+      month: widget.month,
-      days: [
+      days: const [],
-        CalendarDay(
+      onDayTap: onTapDate,
-          date: DateTime(month.year, month.month, 3),
+      selectedRange: _selectedRange,
-          isSelected: false,
-          color: Colors.red,
-          templateDeviation: false,
-        ),
-        CalendarDay(
-          date: DateTime(month.year, month.month, 4),
-          isSelected: false,
-          color: Colors.red,
-          templateDeviation: true,
-        ),
-        CalendarDay(
-          date: DateTime(month.year, month.month, 10),
-          isSelected: false,
-          color: Colors.blue,
-          templateDeviation: false,
-        ),
-        CalendarDay(
-          date: DateTime(month.year, month.month, 11),
-          isSelected: false,
-          color: Colors.black,
-          templateDeviation: true,
-        ),
-        CalendarDay(
-          date: DateTime(month.year, month.month, 12),
-          isSelected: false,
-          color: Colors.white,
-          templateDeviation: true,
-        ),
-        CalendarDay(
-          date: DateTime(month.year, month.month, 13),
-          isSelected: true,
-          color: Colors.green,
-          templateDeviation: false,
-        ),
-        CalendarDay(
-          date: DateTime(month.year, month.month, 14),
-          isSelected: true,
-          color: Colors.green,
-          templateDeviation: true,
-        ),
-      ],
     );
 
     return Column(
       children: [
         monthDateSelector,
         const Divider(),
+        const SizedBox(height: 20),
         calendarGrid,
       ],
     );
   }
 }
+
+/// loops through all the months of a year and get the width of the
+/// longest month,
+/// this is used to make sure the month selector is always the same width
+double _calculateTextWidthOfLongestMonth(
+  BuildContext context,
+  AvailabilityTranslations translations,
+) {
+  var longestMonth = List.generate(12, (index) {
+    var month = DateTime(2024, index + 1);
+    return translations.monthYearFormatter(context, month);
+  }).reduce(
+    (value, element) => value.length > element.length ? value : element,
+  );
+  // now we calculate the width of the longest month
+  var textPainter = TextPainter(
+    text: TextSpan(
+      text: longestMonth,
+      style: Theme.of(context).textTheme.titleMedium,
+    ),
+    textDirection: TextDirection.ltr,
+  )..layout();
+  return textPainter.width;
+}

packages/flutter_availability/lib/src/ui/widgets/calendar_grid.dart

@@ -8,6 +8,8 @@ class CalendarGrid extends StatelessWidget {
   const CalendarGrid({
     required this.month,
     required this.days,
+    required this.onDayTap,
+    required this.selectedRange,
     super.key,
   });
 
@@ -17,6 +19,12 @@ class CalendarGrid extends StatelessWidget {
   /// A list of days that need to be displayed differently
   final List<CalendarDay> days;
 
+  /// A callback that is called when a day is tapped
+  final void Function(DateTime) onDayTap;
+
+  /// The selected range of dates
+  final DateTimeRange? selectedRange;
+
   @override
   Widget build(BuildContext context) {
     var theme = Theme.of(context);
@@ -26,7 +34,8 @@ class CalendarGrid extends StatelessWidget {
     var options = availabilityScope.options;
     var colors = options.colors;
     var translations = options.translations;
-    var calendarDays = _generateCalendarDays(month, days, colors, colorScheme);
+    var calendarDays =
+        _generateCalendarDays(month, days, selectedRange, colors, colorScheme);
 
     // get the names of the days of the week
     var dayNames = List.generate(7, (index) {
@@ -34,25 +43,30 @@ class CalendarGrid extends StatelessWidget {
       return translations.weekDayAbbreviatedFormatter(context, day);
     });
 
+    var calendarDaysRow = GridView.builder(
+      padding: EdgeInsets.zero,
+      shrinkWrap: true,
+      itemCount: 7,
+      gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+        crossAxisCount: 7,
+        crossAxisSpacing: 12,
+        mainAxisSpacing: 0,
+      ),
+      itemBuilder: (context, index) {
+        var day = dayNames[index];
+        return Text(
+          day,
+          style: textTheme.bodyLarge,
+          textAlign: TextAlign.center,
+        );
+      },
+    );
+
     return Column(
       children: [
-        Row(
+        calendarDaysRow,
-          mainAxisAlignment: MainAxisAlignment.spaceAround,
-          children: dayNames
-              .map(
-                (day) => Expanded(
-                  child: Center(
-                    child: Text(
-                      day,
-                      style: textTheme.bodyLarge,
-                    ),
-                  ),
-                ),
-              )
-              .toList(),
-        ),
-        const SizedBox(height: 4.0),
         GridView.builder(
+          padding: EdgeInsets.zero,
           shrinkWrap: true,
           itemCount: calendarDays.length,
           gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
@@ -72,9 +86,7 @@ class CalendarGrid extends StatelessWidget {
             var textStyle = textTheme.bodyLarge?.copyWith(color: textColor);
 
             return GestureDetector(
-              onTap: () {
+              onTap: () => onDayTap(day.date),
-                // Handle day tap here
-              },
               child: DecoratedBox(
                 decoration: BoxDecoration(
                   color: day.outsideMonth ? Colors.transparent : day.color,
@@ -154,6 +166,7 @@ class CalendarDay {
 List<CalendarDay> _generateCalendarDays(
   DateTime month,
   List<CalendarDay> days,
+  DateTimeRange? selectedRange,
   AvailabilityColors colors,
   ColorScheme colorScheme,
 ) {
@@ -195,11 +208,15 @@ List<CalendarDay> _generateCalendarDays(
         templateDeviation: false,
       ),
     );
-    // if the day is selected we need to change the color
+    var dayIsSelected = selectedRange != null &&
+        !day.isBefore(selectedRange.start) &&
+        !day.isAfter(selectedRange.end);
+    // if the day is selected we need to change the color and remove the marking
     specialDay = specialDay.copyWith(
-      color: specialDay.isSelected
+      color: dayIsSelected
           ? colors.selectedDayColor ?? colorScheme.primaryFixedDim
           : null,
+      templateDeviation: dayIsSelected ? false : null,
     );
     calendarDays.add(specialDay);
   }