fix(spoiler): keep collapse state in document

This commit allows to save and load spoiler card collapse state in delta
document. A new field `collapsed` indicates the spoiler area is
collapsed or not. Fixed the spoiler collapse state not persist when
rebuilds where user added new line above the spoiler card.

The new field `collapsed` is optional to keep compatible with documents
generated by former versions. Default value is `true`.

lib/src/tags/spoiler/spoiler_builder.dart

@@ -174,7 +174,7 @@ class _SpoilerCardState extends State<_SpoilerCard> {
   late BBCodeSpoilerInfo data;
 
   /// Flag indicating body is visible or not.
-  bool _visible = false;
+  late bool _visible;
 
   Future<void> editSpoiler() async {
     final data = await Navigator.push<BBCodeSpoilerInfo>(
@@ -198,7 +198,8 @@ class _SpoilerCardState extends State<_SpoilerCard> {
     );
     if (data != null) {
       setState(() {
-        this.data = data;
+        // Keep collapsed state.
+        this.data = data.copyWith(collapsed: !_visible);
         bodyController.setDocumentFromJson(
           jsonDecode(data.body) as List<dynamic>,
         );
@@ -315,6 +316,8 @@ class _SpoilerCardState extends State<_SpoilerCard> {
         });
       });
     }
+    // Restore the spoiler body visibility.
+    _visible = !data.collapsed;
   }
 
   @override
@@ -350,9 +353,12 @@ class _SpoilerCardState extends State<_SpoilerCard> {
                     : const Icon(Icons.expand_more_outlined),
                 label: Text(data.title),
                 onPressed: () {
+                  widget.onTap.call();
                   setState(() {
                     _visible = !_visible;
                   });
+                  data = data.copyWith(collapsed: !_visible);
+                  widget.onEdited(data);
                 },
               ),
               if (_visible) ...[
@@ -459,6 +465,7 @@ class _SpoilerEditPageState extends State<_SpoilerEditPage> {
               BBCodeSpoilerInfo(
                 title: titleController.text,
                 body: bodyController.toQuillDelta(),
+                collapsed: widget.initialData?.collapsed ?? true,
               ),
             ),
           ),

lib/src/tags/spoiler/spoiler_embed.dart

@@ -25,6 +25,7 @@ final class BBCodeSpoilerInfo {
   const BBCodeSpoilerInfo({
     required this.title,
     required this.body,
+    required this.collapsed,
   });
 
   /// Construct from [json] string.
@@ -38,10 +39,15 @@ final class BBCodeSpoilerInfo {
       {BBCodeSpoilerKeys.body: final String data} => data,
       _ => throw Exception('bbcode spoiler body not found'),
     };
+    final collapsed = switch (data) {
+      {BBCodeSpoilerKeys.collapsed: final bool data} => data,
+      _ => true,
+    };
 
     return BBCodeSpoilerInfo(
       title: title,
       body: body,
+      collapsed: collapsed,
     );
   }
 
@@ -52,7 +58,7 @@ final class BBCodeSpoilerInfo {
   /// The [title] should be constructed according to current locale and built to
   /// be a default value, usually injected with l10n on build context.
   factory BBCodeSpoilerInfo.buildEmpty(String title) =>
-      BBCodeSpoilerInfo(title: title, body: '');
+      BBCodeSpoilerInfo(title: title, body: '', collapsed: true);
 
   /// Parse a current type [embed] and add bbcode to [out].
   static void toBBCode(Embed embed, StringSink out) {
@@ -68,13 +74,39 @@ final class BBCodeSpoilerInfo {
   /// Raw bbcode body in the spoiler area
   final String body;
 
+  /// Spoiler is collapsed or not
+  ///
+  /// Only a flag indicating should expand the spoiler card or not when
+  /// rendering into an editor. Not be into the generated bbcode.
+  ///
+  /// This field is optional, meaning it's a field added later in release, make
+  /// it optional to keep compatible with old version documents.
+  ///
+  /// Default value is true.
+  final bool collapsed;
+
   /// Convert to json map string.
   String toJson() => jsonEncode(<String, dynamic>{
         BBCodeSpoilerKeys.title: title,
         BBCodeSpoilerKeys.body: body,
+        BBCodeSpoilerKeys.collapsed: collapsed,
       });
 
+  /// The copy with method.
+  BBCodeSpoilerInfo copyWith({
+    String? title,
+    String? body,
+    bool? collapsed,
+  }) {
+    return BBCodeSpoilerInfo(
+      title: title ?? this.title,
+      body: body ?? this.body,
+      collapsed: collapsed ?? this.collapsed,
+    );
+  }
+
   @override
   String toString() => '${BBCodeSpoilerKeys.title}=$title, '
-      '${BBCodeSpoilerKeys.body}=$body';
+      '${BBCodeSpoilerKeys.body}=$body, '
+      '${BBCodeSpoilerKeys.collapsed}=$collapsed';
 }

lib/src/tags/spoiler/spoiler_keys.dart

@@ -10,4 +10,7 @@ final class BBCodeSpoilerKeys {
 
   /// Raw bbcode body inside the spoiler block.
   static const String body = 'data';
+
+  /// Spoiler should be rendered in collapsed state or not.
+  static const String collapsed = 'collapsed';
 }