refactor(app_configuration): implement single ExpansionTile open functionality

- Convert AdvertisementsConfigurationTab to StatefulWidget
- Add ValueNotifier to track expanded tile index
- Modify ExpansionTiles to collapse when others are opened
- Ensure only one top-level ExpansionTile can be open at a time

Author: fulleni

lib/app_configuration/view/tabs/advertisements_configuration_tab.dart

@@ -4,14 +4,15 @@ import 'package:flutter_news_app_web_dashboard_full_source_code/app_configuratio
 import 'package:flutter_news_app_web_dashboard_full_source_code/app_configuration/widgets/article_ad_settings_form.dart';
 import 'package:flutter_news_app_web_dashboard_full_source_code/app_configuration/widgets/feed_ad_settings_form.dart';
 import 'package:flutter_news_app_web_dashboard_full_source_code/l10n/l10n.dart';
+import 'package:flutter/foundation.dart';
 import 'package:ui_kit/ui_kit.dart';
 
 /// {@template advertisements_configuration_tab}
 /// A widget representing the "Advertisements" tab in the App Configuration page.
 ///
 /// This tab allows configuration of various ad settings.
 /// {@endtemplate}
-class AdvertisementsConfigurationTab extends StatelessWidget {
+class AdvertisementsConfigurationTab extends StatefulWidget {
   /// {@macro advertisements_configuration_tab}
   const AdvertisementsConfigurationTab({
     required this.remoteConfig,
@@ -25,6 +26,24 @@ class AdvertisementsConfigurationTab extends StatelessWidget {
   /// Callback to notify parent of changes to the [RemoteConfig].
   final ValueChanged<RemoteConfig> onConfigChanged;
 
+  @override
+  State<AdvertisementsConfigurationTab> createState() =>
+      _AdvertisementsConfigurationTabState();
+}
+
+class _AdvertisementsConfigurationTabState
+    extends State<AdvertisementsConfigurationTab> {
+  /// Notifier for the index of the currently expanded top-level ExpansionTile.
+  ///
+  /// A value of `null` means no tile is expanded.
+  final ValueNotifier<int?> _expandedTileIndex = ValueNotifier<int?>(null);
+
+  @override
+  void dispose() {
+    _expandedTileIndex.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     final l10n = AppLocalizationsX(context).l10n;
@@ -33,54 +52,87 @@ class AdvertisementsConfigurationTab extends StatelessWidget {
       padding: const EdgeInsets.all(AppSpacing.lg),
       children: [
         // Top-level ExpansionTile for Ad Platform Configuration
-        ExpansionTile(
-          title: Text(l10n.adPlatformConfigurationTitle),
-          childrenPadding: const EdgeInsetsDirectional.only(
-            start: AppSpacing.lg, // Adjusted padding for hierarchy
-            top: AppSpacing.md,
-            bottom: AppSpacing.md,
-          ),
-          expandedCrossAxisAlignment: CrossAxisAlignment.start, // Align content to start
-          children: [
-            AdPlatformConfigForm(
-              remoteConfig: remoteConfig,
-              onConfigChanged: onConfigChanged,
-            ),
-          ],
+        ValueListenableBuilder<int?>(
+          valueListenable: _expandedTileIndex,
+          builder: (context, expandedIndex, child) {
+            const tileIndex = 0;
+            return ExpansionTile(
+              key: ValueKey('adPlatformConfigTile_$expandedIndex'),
+              title: Text(l10n.adPlatformConfigurationTitle),
+              childrenPadding: const EdgeInsetsDirectional.only(
+                start: AppSpacing.lg,
+                top: AppSpacing.md,
+                bottom: AppSpacing.md,
+              ),
+              expandedCrossAxisAlignment: CrossAxisAlignment.start,
+              onExpansionChanged: (isExpanded) {
+                _expandedTileIndex.value = isExpanded ? tileIndex : null;
+              },
+              initiallyExpanded: expandedIndex == tileIndex,
+              children: [
+                AdPlatformConfigForm(
+                  remoteConfig: widget.remoteConfig,
+                  onConfigChanged: widget.onConfigChanged,
+                ),
+              ],
+            );
+          },
         ),
         const SizedBox(height: AppSpacing.lg),
         // Top-level ExpansionTile for Feed Ad Settings
-        ExpansionTile(
-          title: Text(l10n.feedAdSettingsTitle),
-          childrenPadding: const EdgeInsetsDirectional.only(
-            start: AppSpacing.lg, // Adjusted padding for hierarchy
-            top: AppSpacing.md,
-            bottom: AppSpacing.md,
-          ),
-          expandedCrossAxisAlignment: CrossAxisAlignment.start, // Align content to start
-          children: [
-            FeedAdSettingsForm(
-              remoteConfig: remoteConfig,
-              onConfigChanged: onConfigChanged,
-            ),
-          ],
+        ValueListenableBuilder<int?>(
+          valueListenable: _expandedTileIndex,
+          builder: (context, expandedIndex, child) {
+            const tileIndex = 1;
+            return ExpansionTile(
+              key: ValueKey('feedAdSettingsTile_$expandedIndex'),
+              title: Text(l10n.feedAdSettingsTitle),
+              childrenPadding: const EdgeInsetsDirectional.only(
+                start: AppSpacing.lg,
+                top: AppSpacing.md,
+                bottom: AppSpacing.md,
+              ),
+              expandedCrossAxisAlignment: CrossAxisAlignment.start,
+              onExpansionChanged: (isExpanded) {
+                _expandedTileIndex.value = isExpanded ? tileIndex : null;
+              },
+              initiallyExpanded: expandedIndex == tileIndex,
+              children: [
+                FeedAdSettingsForm(
+                  remoteConfig: widget.remoteConfig,
+                  onConfigChanged: widget.onConfigChanged,
+                ),
+              ],
+            );
+          },
         ),
         const SizedBox(height: AppSpacing.lg),
         // Top-level ExpansionTile for Article Ad Settings
-        ExpansionTile(
-          title: Text(l10n.articleAdSettingsTitle),
-          childrenPadding: const EdgeInsetsDirectional.only(
-            start: AppSpacing.lg, // Adjusted padding for hierarchy
-            top: AppSpacing.md,
-            bottom: AppSpacing.md,
-          ),
-          expandedCrossAxisAlignment: CrossAxisAlignment.start, // Align content to start
-          children: [
-            ArticleAdSettingsForm(
-              remoteConfig: remoteConfig,
-              onConfigChanged: onConfigChanged,
-            ),
-          ],
+        ValueListenableBuilder<int?>(
+          valueListenable: _expandedTileIndex,
+          builder: (context, expandedIndex, child) {
+            const tileIndex = 2;
+            return ExpansionTile(
+              key: ValueKey('articleAdSettingsTile_$expandedIndex'),
+              title: Text(l10n.articleAdSettingsTitle),
+              childrenPadding: const EdgeInsetsDirectional.only(
+                start: AppSpacing.lg,
+                top: AppSpacing.md,
+                bottom: AppSpacing.md,
+              ),
+              expandedCrossAxisAlignment: CrossAxisAlignment.start,
+              onExpansionChanged: (isExpanded) {
+                _expandedTileIndex.value = isExpanded ? tileIndex : null;
+              },
+              initiallyExpanded: expandedIndex == tileIndex,
+              children: [
+                ArticleAdSettingsForm(
+                  remoteConfig: widget.remoteConfig,
+                  onConfigChanged: widget.onConfigChanged,
+                ),
+              ],
+            );
+          },
         ),
       ],
     );