merge decks

lib/screens/deck_edit_screen.dart

@@ -1,4 +1,7 @@
+import 'dart:convert';
+
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import '../utils/top_snackbar.dart';
 import 'package:practice_engine/practice_engine.dart';
 import '../services/deck_storage.dart';
@@ -149,6 +152,27 @@ class _DeckEditScreenState extends State<DeckEditScreen> {
     Navigator.pop(context, updatedDeck);
   }
 
+  void _copyQuestionsJson() {
+    if (_questionEditors.isEmpty) {
+      showTopSnackBar(context, message: 'No questions to copy');
+      return;
+    }
+    final questions = _questionEditors.map((e) => e.toQuestion()).toList();
+    final list = questions.map((q) => {
+      'id': q.id,
+      'prompt': q.prompt,
+      'answers': q.answers,
+      'correctAnswerIndices': q.correctAnswerIndices,
+    }).toList();
+    final jsonString = const JsonEncoder.withIndent('  ').convert(list);
+    Clipboard.setData(ClipboardData(text: jsonString));
+    showTopSnackBar(
+      context,
+      message: '${questions.length} question(s) copied as JSON',
+      backgroundColor: Colors.green,
+    );
+  }
+
   @override
   Widget build(BuildContext context) {
     if (_deck == null) {
@@ -161,6 +185,11 @@ class _DeckEditScreenState extends State<DeckEditScreen> {
       appBar: AppBar(
         title: const Text('Edit Deck'),
         actions: [
+          IconButton(
+            icon: const Icon(Icons.copy),
+            onPressed: _copyQuestionsJson,
+            tooltip: 'Copy questions as JSON',
+          ),
           IconButton(
             icon: const Icon(Icons.add),
             onPressed: _addQuestion,

lib/screens/deck_import_screen.dart

@@ -586,7 +586,7 @@ class _DeckImportScreenState extends State<DeckImportScreen> {
                             child: CircularProgressIndicator(strokeWidth: 2),
                           )
                         : const Icon(Icons.merge_type, size: 20),
-                    label: Text(_isLoading ? '...' : 'Merge with existing deck'),
+                    label: Text(_isLoading ? '...' : 'Merge with deck'),
                     style: OutlinedButton.styleFrom(
                       padding: const EdgeInsets.symmetric(vertical: 16),
                     ),

lib/screens/deck_list_screen.dart

@@ -102,6 +102,68 @@ class _DeckListScreenState extends State<DeckListScreen> {
     });
   }
 
+  void _mergeDeck(Deck sourceDeck) async {
+    final otherDecks = _decks.where((d) => d.id != sourceDeck.id).toList();
+    if (otherDecks.isEmpty) {
+      showTopSnackBar(
+        context,
+        message: 'No other deck to merge with',
+        backgroundColor: Colors.orange,
+      );
+      return;
+    }
+
+    final targetDeck = await showDialog<Deck>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Merge with deck'),
+        content: SizedBox(
+          width: double.maxFinite,
+          child: ListView.builder(
+            shrinkWrap: true,
+            itemCount: otherDecks.length,
+            itemBuilder: (context, index) {
+              final deck = otherDecks[index];
+              return ListTile(
+                title: Text(deck.title),
+                subtitle: Text('${deck.questions.length} questions'),
+                onTap: () => Navigator.pop(context, deck),
+              );
+            },
+          ),
+        ),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context),
+            child: const Text('Cancel'),
+          ),
+        ],
+      ),
+    );
+
+    if (targetDeck == null || !mounted) return;
+
+    final timestamp = DateTime.now().millisecondsSinceEpoch;
+    final mergedQuestions = [
+      ...targetDeck.questions,
+      ...sourceDeck.questions.asMap().entries.map((e) {
+        final q = e.value;
+        final i = e.key;
+        return q.copyWith(id: '${q.id}_merged_${timestamp}_$i');
+      }),
+    ];
+    final mergedDeck = targetDeck.copyWith(questions: mergedQuestions);
+    _deckStorage.saveDeckSync(mergedDeck);
+    _loadDecks();
+    if (mounted) {
+      showTopSnackBar(
+        context,
+        message: 'Merged ${sourceDeck.questions.length} question(s) into "${targetDeck.title}"',
+        backgroundColor: Colors.green,
+      );
+    }
+  }
+
   void _cloneDeck(Deck deck) {
     // Create a copy of the deck with a new ID and reset progress
     final clonedDeck = deck.copyWith(
@@ -452,6 +514,21 @@ class _DeckListScreenState extends State<DeckListScreen> {
                                         );
                                       },
                                     ),
+                                    PopupMenuItem(
+                                      child: const Row(
+                                        children: [
+                                          Icon(Icons.merge_type, color: Colors.teal),
+                                          SizedBox(width: 8),
+                                          Text('Merge'),
+                                        ],
+                                      ),
+                                      onTap: () {
+                                        Future.delayed(
+                                          const Duration(milliseconds: 100),
+                                          () => _mergeDeck(deck),
+                                        );
+                                      },
+                                    ),
                                     PopupMenuItem(
                                       child: const Row(
                                         children: [