explanation

packages/practice_engine/lib/models/question.dart

@@ -6,6 +6,9 @@ class Question {
   /// The question prompt.
   final String prompt;
 
+  /// Optional explanation shown when viewing question details (e.g. after an attempt).
+  final String? explanation;
+
   /// List of possible answers.
   final List<String> answers;
 
@@ -42,6 +45,7 @@ class Question {
   Question({
     required this.id,
     required this.prompt,
+    this.explanation,
     required this.answers,
     List<int>? correctAnswerIndices,
     @Deprecated('Use correctAnswerIndices instead') int? correctAnswerIndex,
@@ -60,6 +64,7 @@ class Question {
   Question copyWith({
     String? id,
     String? prompt,
+    String? explanation,
     List<String>? answers,
     List<int>? correctAnswerIndices,
     @Deprecated('Use correctAnswerIndices instead') int? correctAnswerIndex,
@@ -74,6 +79,7 @@ class Question {
     return Question(
       id: id ?? this.id,
       prompt: prompt ?? this.prompt,
+      explanation: explanation ?? this.explanation,
       answers: answers ?? this.answers,
       correctAnswerIndices: correctAnswerIndices ?? this.correctAnswerIndices,
       correctAnswerIndex: correctAnswerIndex ?? this.correctAnswerIndex,
@@ -119,6 +125,7 @@ class Question {
           runtimeType == other.runtimeType &&
           id == other.id &&
           prompt == other.prompt &&
+          explanation == other.explanation &&
           answers.toString() == other.answers.toString() &&
           correctAnswerIndices.toString() == other.correctAnswerIndices.toString() &&
           consecutiveCorrect == other.consecutiveCorrect &&
@@ -133,6 +140,7 @@ class Question {
   int get hashCode =>
       id.hashCode ^
       prompt.hashCode ^
+      (explanation?.hashCode ?? 0) ^
       answers.hashCode ^
       correctAnswerIndices.hashCode ^
       consecutiveCorrect.hashCode ^