added form widget for fixed time alarm

lib/widgets/alarm_widgets/fixed_time_alarm_form.dart

@@ -1,19 +1,160 @@
 import 'package:flutter/material.dart';
 
-import '../../model/requests/create_alarm_request.dart';
+import '../../app_theme.dart' show AppTheme;
 import '../../model/requests/create_fixed_time_alarm_request.dart';
+import '../../service/tools.dart';
+import '../../service/validators.dart';
 
-class FixedTimeAlarmForm extends StatelessWidget {
+class FixedTimeAlarmForm extends StatefulWidget {
   const FixedTimeAlarmForm({
     super.key,
     required this.request,
     required this.onChanged,
   });
   final CreateFixedTimeAlarmRequest request;
-  final ValueChanged<CreateAlarmRequest> onChanged;
+  final ValueChanged<CreateFixedTimeAlarmRequest> onChanged;
+
+  @override
+  State<FixedTimeAlarmForm> createState() => _FixedTimeAlarmFormState();
+}
+
+class _FixedTimeAlarmFormState extends State<FixedTimeAlarmForm> {
+  final dueDateController = TextEditingController();
+  final dueTimeController = TextEditingController();
+  final dueDateFocusNode = FocusNode();
+  final dueTimeFocusNode = FocusNode();
+  bool isDueTimeEnabled = false;
+
+  @override
+  void initState() {
+    dueDateController.addListener(onDueDateChanged);
+    dueTimeController.addListener(onDueTimeChanged);
+
+    super.initState();
+  }
 
   @override
   Widget build(BuildContext context) {
-    return const Placeholder();
+    return Flex(
+      direction: Axis.horizontal,
+      children: [
+        Flexible(
+          flex: 3,
+          child: TextFormField(
+            focusNode: dueDateFocusNode,
+            controller: dueDateController,
+            onFieldSubmitted: (_) {
+              isDueTimeEnabled ? dueDateFocusNode.nextFocus() : null;
+            },
+            decoration: InputDecoration(
+              label: Text('Due Date'),
+              suffixIcon: IconButton(
+                onPressed: () async {
+                  final result = await onOpenCalendarPickerPressed();
+                  if (result != null) {
+                    final dateString = getIsoDateString(result);
+                    dueDateController.text = dateString;
+                    maybeEnableDueTime(dateString);
+                    dueTimeFocusNode.requestFocus();
+                  }
+                },
+                icon: Icon(Icons.calendar_month),
+              ),
+            ),
+            validator: dateTimeValidator,
+            keyboardType: TextInputType.datetime,
+            textInputAction: TextInputAction.next,
+          ),
+        ),
+        Padding(
+          padding: EdgeInsetsGeometry.only(left: AppTheme.formColumnSpacing),
+        ),
+        Flexible(
+          flex: 2,
+          child: TextFormField(
+            focusNode: dueTimeFocusNode,
+            onFieldSubmitted: (_) => dueTimeFocusNode.nextFocus(),
+            controller: dueTimeController,
+            enabled: isDueTimeEnabled,
+            onChanged: (value) {},
+            decoration: InputDecoration(
+              label: Text('Due Time'),
+              suffixIcon: IconButton(
+                onPressed: () async {
+                  final result = await onOpenTimePickerPressed();
+                  if (result != null && context.mounted) {
+                    dueTimeController.text = result.format(context);
+                  }
+                },
+                icon: Icon(Icons.schedule),
+              ),
+            ),
+            validator: timeValidator,
+            keyboardType: TextInputType.text,
+            textInputAction: TextInputAction.next,
+          ),
+        ),
+      ],
+    );
+  }
+
+  Future<DateTime?> onOpenCalendarPickerPressed() {
+    return showDialog<DateTime?>(
+      context: context,
+      builder: (context) => DatePickerDialog(
+        firstDate: DateTime(DateTime.now().year - 100),
+        lastDate: DateTime(DateTime.now().year + 100),
+        initialDate:
+            DateTime.tryParse(dueDateController.text) ?? DateTime.now(),
+      ),
+    );
+  }
+
+  Future<TimeOfDay?> onOpenTimePickerPressed() {
+    return showDialog<TimeOfDay?>(
+      context: context,
+      builder: (context) => TimePickerDialog(
+        initialTime: TimeOfDay.fromDateTime(
+          widget.request.triggerAt ?? DateTime.now(),
+        ),
+      ),
+    );
+  }
+
+  void maybeEnableDueTime(String value) {
+    if (value.isNotEmpty && dateTimeValidator(value) == null) {
+      setState(() {
+        isDueTimeEnabled = true;
+      });
+    } else if (isDueTimeEnabled) {
+      setState(() {
+        isDueTimeEnabled = false;
+      });
+    }
+  }
+
+  void onDueDateChanged() {
+    final String value = dueDateController.text;
+    maybeEnableDueTime(value);
+    if (dateTimeValidator(value) == null) {
+      final dateTime = DateTime.tryParse(
+        '$value ${dueTimeController.text}'.trim(),
+      );
+      if (dateTime != null) {
+        widget.onChanged(CreateFixedTimeAlarmRequest(triggerAt: dateTime));
+      }
+    }
+  }
+
+  void onDueTimeChanged() {
+    final String value = dueTimeController.text;
+    if (timeValidator(value) == null) {
+      final dateTime = DateTime.tryParse(
+        '${dueDateController.text} $value'.trim(),
+      );
+      if (dateTime != null) {
+        widget.onChanged(CreateFixedTimeAlarmRequest(triggerAt: dateTime));
+      }
+    }
   }
 }