그룹 스터디 공개/비공개 기능 추가

그룹을 공개로 만들면 "공개 그룹" 목록에 뜨고, 학생이 참여 신청을
보내면 그룹장이 허용/거절할 수 있다. 그룹 상세 화면에 그룹장 전용
공개/비공개 전환 버튼과 대기 중인 참여 신청 목록을 추가.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/function/group_controller.dart

@@ -14,12 +14,14 @@ class GroupController extends ChangeNotifier {
   bool _isBusy = false;
   List<dynamic> _groups = [];
   List<dynamic> _invites = [];
+  List<dynamic> _publicGroups = [];
   bool _disposed = false;
 
   bool get isLoading => _isLoading;
   bool get isBusy => _isBusy;
   List<dynamic> get groups => _groups;
   List<dynamic> get invites => _invites;
+  List<dynamic> get publicGroups => _publicGroups;
 
   void _safeNotify() {
     if (!_disposed) notifyListeners();
@@ -36,7 +38,7 @@ class GroupController extends ChangeNotifier {
   Future<void> refresh() async {
     _isLoading = true;
     _safeNotify();
-    await Future.wait([_fetchGroups(), _fetchInvites()]);
+    await Future.wait([_fetchGroups(), _fetchInvites(), _fetchPublicGroups()]);
     _isLoading = false;
     _safeNotify();
   }
@@ -69,7 +71,24 @@ class GroupController extends ChangeNotifier {
     }
   }
 
-  Future<(bool success, String message)> createGroup(String name) async {
+  Future<void> _fetchPublicGroups() async {
+    try {
+      final response = await http.get(
+        Uri.parse('$baseUrl/api/groups/public?studentId=$studentId'),
+      );
+      if (response.statusCode == 200) {
+        final data = jsonDecode(utf8.decode(response.bodyBytes));
+        _publicGroups = data['groups'] ?? [];
+      }
+    } catch (_) {
+      // 조용히 무시
+    }
+  }
+
+  Future<(bool success, String message)> createGroup(
+    String name, {
+    bool isPublic = false,
+  }) async {
     _isBusy = true;
     _safeNotify();
     try {
@@ -80,6 +99,7 @@ class GroupController extends ChangeNotifier {
           "ownerId": studentId,
           "ownerName": studentName,
           "name": name.trim(),
+          "isPublic": isPublic,
         }),
       );
       final result = jsonDecode(utf8.decode(response.bodyBytes));
@@ -121,4 +141,27 @@ class GroupController extends ChangeNotifier {
       _safeNotify();
     }
   }
+
+  Future<(bool success, String message)> requestJoin(int groupId) async {
+    _isBusy = true;
+    _safeNotify();
+    try {
+      final response = await http.post(
+        Uri.parse('$baseUrl/api/groups/$groupId/join-request'),
+        headers: {"Content-Type": "application/json"},
+        body: jsonEncode({"studentId": studentId, "studentName": studentName}),
+      );
+      final result = jsonDecode(utf8.decode(response.bodyBytes));
+      if (response.statusCode == 200 && result['status'] == 'success') {
+        await _fetchPublicGroups();
+        return (true, '${result['message'] ?? '참여 신청을 보냈습니다.'}');
+      }
+      return (false, '${result['message'] ?? '참여 신청 실패'}');
+    } catch (e) {
+      return (false, '네트워크 에러: $e');
+    } finally {
+      _isBusy = false;
+      _safeNotify();
+    }
+  }
 }

lib/function/group_detail_controller.dart

@@ -13,11 +13,17 @@ class GroupDetailController extends ChangeNotifier {
   bool _isLoading = true;
   bool _isBusy = false;
   List<dynamic> _members = [];
+  List<dynamic> _joinRequests = [];
+  bool _isPublic = false;
   bool _disposed = false;
 
   bool get isLoading => _isLoading;
   bool get isBusy => _isBusy;
   List<dynamic> get members => _members;
+  List<dynamic> get joinRequests => _joinRequests;
+  bool get isPublic => _isPublic;
+  bool get isOwner =>
+      _members.any((m) => m['studentId'] == studentId && m['role'] == 'owner');
 
   void _safeNotify() {
     if (!_disposed) notifyListeners();
@@ -41,13 +47,79 @@ class GroupDetailController extends ChangeNotifier {
       if (response.statusCode == 200) {
         final data = jsonDecode(utf8.decode(response.bodyBytes));
         _members = data['members'] ?? [];
+        _isPublic = data['isPublic'] == true;
       }
     } catch (_) {
       // 조용히 무시
-    } finally {
+    }
+    if (isOwner) await _fetchJoinRequests();
     _isLoading = false;
     _safeNotify();
   }
+
+  Future<void> _fetchJoinRequests() async {
+    try {
+      final response = await http.get(
+        Uri.parse(
+          '$baseUrl/api/groups/$groupId/join-requests?ownerId=$studentId',
+        ),
+      );
+      if (response.statusCode == 200) {
+        final data = jsonDecode(utf8.decode(response.bodyBytes));
+        _joinRequests = data['requests'] ?? [];
+      }
+    } catch (_) {
+      // 조용히 무시
+    }
+  }
+
+  Future<(bool success, String message)> respondJoinRequest(
+    int requestId,
+    bool accept,
+  ) async {
+    _isBusy = true;
+    _safeNotify();
+    try {
+      final response = await http.post(
+        Uri.parse('$baseUrl/api/groups/join-requests/$requestId/respond'),
+        headers: {"Content-Type": "application/json"},
+        body: jsonEncode({"responderId": studentId, "accept": accept}),
+      );
+      final result = jsonDecode(utf8.decode(response.bodyBytes));
+      if (response.statusCode == 200 && result['status'] == 'success') {
+        await refresh();
+        return (true, '${result['message'] ?? '처리했습니다.'}');
+      }
+      return (false, '${result['message'] ?? '처리 실패'}');
+    } catch (e) {
+      return (false, '네트워크 에러: $e');
+    } finally {
+      _isBusy = false;
+      _safeNotify();
+    }
+  }
+
+  Future<(bool success, String message)> setVisibility(bool isPublic) async {
+    _isBusy = true;
+    _safeNotify();
+    try {
+      final response = await http.post(
+        Uri.parse('$baseUrl/api/groups/$groupId/visibility'),
+        headers: {"Content-Type": "application/json"},
+        body: jsonEncode({"ownerId": studentId, "isPublic": isPublic}),
+      );
+      final result = jsonDecode(utf8.decode(response.bodyBytes));
+      if (response.statusCode == 200 && result['status'] == 'success') {
+        await refresh();
+        return (true, '${result['message'] ?? '변경했습니다.'}');
+      }
+      return (false, '${result['message'] ?? '변경 실패'}');
+    } catch (e) {
+      return (false, '네트워크 에러: $e');
+    } finally {
+      _isBusy = false;
+      _safeNotify();
+    }
   }
 
   Future<(bool success, String message)> invite(

lib/ui/group_detail_screen.dart

@@ -135,6 +135,48 @@ class _GroupDetailScreenState extends State<GroupDetailScreen> {
     friendController.dispose();
   }
 
+  Future<void> _toggleVisibility() async {
+    final makePublic = !_controller.isPublic;
+    final confirmed = await showDialog<bool>(
+      context: context,
+      builder: (dialogContext) => AlertDialog(
+        title: Text(makePublic ? '공개 그룹으로 전환' : '비공개 그룹으로 전환'),
+        content: Text(
+          makePublic
+              ? '이제 누구나 이 그룹을 찾아서 참여 신청을 보낼 수 있어요. 참여는 그룹장이 허용해야 완료됩니다.'
+              : '더 이상 공개 목록에 뜨지 않고, 대기 중인 참여 신청은 모두 거절 처리됩니다.',
+        ),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(dialogContext, false),
+            child: const Text('취소', style: TextStyle(color: Colors.grey)),
+          ),
+          ElevatedButton(
+            style: ElevatedButton.styleFrom(
+              backgroundColor: AppPalette.ink,
+              foregroundColor: AppPalette.paper,
+            ),
+            onPressed: () => Navigator.pop(dialogContext, true),
+            child: const Text('전환'),
+          ),
+        ],
+      ),
+    );
+    if (confirmed != true) return;
+    final (_, message) = await _controller.setVisibility(makePublic);
+    if (!mounted) return;
+    AppNotice.show(context, message);
+  }
+
+  Future<void> _respondJoinRequest(int requestId, bool accept) async {
+    final (_, message) = await _controller.respondJoinRequest(
+      requestId,
+      accept,
+    );
+    if (!mounted) return;
+    AppNotice.show(context, message);
+  }
+
   Future<void> _leave() async {
     final confirmed = await showDialog<bool>(
       context: context,
@@ -183,6 +225,16 @@ class _GroupDetailScreenState extends State<GroupDetailScreen> {
             foregroundColor: AppPalette.ink,
             elevation: 0,
             actions: [
+              if (_controller.isOwner)
+                IconButton(
+                  icon: Icon(
+                    _controller.isPublic
+                        ? Icons.public_rounded
+                        : Icons.lock_rounded,
+                  ),
+                  tooltip: _controller.isPublic ? '공개 그룹' : '비공개 그룹',
+                  onPressed: _toggleVisibility,
+                ),
               IconButton(
                 icon: const Icon(Icons.exit_to_app_rounded),
                 tooltip: '그룹 나가기',
@@ -213,6 +265,86 @@ class _GroupDetailScreenState extends State<GroupDetailScreen> {
                           Expanded(child: _statPill('오늘 공부함', attendedCount)),
                         ],
                       ),
+                      if (_controller.isOwner &&
+                          _controller.joinRequests.isNotEmpty) ...[
+                        const SizedBox(height: 20),
+                        Row(
+                          children: [
+                            Container(
+                              width: 4,
+                              height: 16,
+                              decoration: BoxDecoration(
+                                color: AppPalette.ink,
+                                borderRadius: BorderRadius.circular(2),
+                              ),
+                            ),
+                            const SizedBox(width: 8),
+                            const Text(
+                              '대기 중인 참여 신청',
+                              style: TextStyle(
+                                fontSize: 16,
+                                fontWeight: FontWeight.bold,
+                                color: AppPalette.ink,
+                              ),
+                            ),
+                            const SizedBox(width: 6),
+                            Text(
+                              '${_controller.joinRequests.length}명',
+                              style: TextStyle(
+                                fontSize: 13,
+                                color: Colors.grey[500],
+                              ),
+                            ),
+                          ],
+                        ),
+                        const SizedBox(height: 10),
+                        for (final r in _controller.joinRequests)
+                          Container(
+                            margin: const EdgeInsets.only(bottom: 8),
+                            padding: const EdgeInsets.symmetric(
+                              horizontal: 16,
+                              vertical: 12,
+                            ),
+                            decoration: BoxDecoration(
+                              color: AppPalette.paper,
+                              borderRadius: BorderRadius.circular(16),
+                              border: Border.all(color: AppPalette.sage),
+                            ),
+                            child: Row(
+                              children: [
+                                Expanded(
+                                  child: Text(
+                                    '${r['name']} (${r['studentId']})',
+                                    style: const TextStyle(
+                                      fontWeight: FontWeight.bold,
+                                    ),
+                                  ),
+                                ),
+                                TextButton(
+                                  onPressed: () => _respondJoinRequest(
+                                    r['requestId'] as int,
+                                    false,
+                                  ),
+                                  child: const Text(
+                                    '거절',
+                                    style: TextStyle(color: Colors.grey),
+                                  ),
+                                ),
+                                ElevatedButton(
+                                  style: ElevatedButton.styleFrom(
+                                    backgroundColor: AppPalette.ink,
+                                    foregroundColor: AppPalette.paper,
+                                  ),
+                                  onPressed: () => _respondJoinRequest(
+                                    r['requestId'] as int,
+                                    true,
+                                  ),
+                                  child: const Text('허용'),
+                                ),
+                              ],
+                            ),
+                          ),
+                      ],
                       const SizedBox(height: 20),
                       Row(
                         children: [

lib/ui/group_list_screen.dart

@@ -43,11 +43,17 @@ class _GroupListScreenState extends State<GroupListScreen> {
 
   Future<void> _showCreateGroupDialog() async {
     final nameController = TextEditingController();
+    bool isPublic = false;
     final result = await showDialog<bool>(
       context: context,
-      builder: (dialogContext) => AlertDialog(
+      builder: (dialogContext) => StatefulBuilder(
+        builder: (dialogContext, setDialogState) => AlertDialog(
           title: const Text('그룹 만들기'),
-        content: TextField(
+          content: Column(
+            mainAxisSize: MainAxisSize.min,
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              TextField(
                 controller: nameController,
                 maxLength: 20,
                 decoration: const InputDecoration(
@@ -55,6 +61,19 @@ class _GroupListScreenState extends State<GroupListScreen> {
                   border: OutlineInputBorder(),
                 ),
               ),
+              SwitchListTile(
+                contentPadding: EdgeInsets.zero,
+                title: const Text('공개 그룹으로 만들기'),
+                subtitle: const Text(
+                  '누구나 목록에서 보고 참여 신청할 수 있어요\n(그룹장이 허용해야 들어옵니다)',
+                  style: TextStyle(fontSize: 12),
+                ),
+                value: isPublic,
+                activeThumbColor: AppPalette.ink,
+                onChanged: (v) => setDialogState(() => isPublic = v),
+              ),
+            ],
+          ),
           actions: [
             TextButton(
               onPressed: () => Navigator.pop(dialogContext, false),
@@ -70,10 +89,12 @@ class _GroupListScreenState extends State<GroupListScreen> {
             ),
           ],
         ),
+      ),
     );
     if (result != true || nameController.text.trim().isEmpty) return;
     final (success, message) = await _controller.createGroup(
       nameController.text.trim(),
+      isPublic: isPublic,
     );
     if (!mounted) return;
     AppNotice.show(
@@ -89,6 +110,16 @@ class _GroupListScreenState extends State<GroupListScreen> {
     AppNotice.show(context, message);
   }
 
+  Future<void> _requestJoin(int groupId) async {
+    final (success, message) = await _controller.requestJoin(groupId);
+    if (!mounted) return;
+    AppNotice.show(
+      context,
+      message,
+      icon: success ? Icons.check_circle_rounded : Icons.error_outline_rounded,
+    );
+  }
+
   Future<void> _openGroup(dynamic group) async {
     await pushLaunchpad(
       context,
@@ -268,13 +299,55 @@ class _GroupListScreenState extends State<GroupListScreen> {
                                       crossAxisAlignment:
                                           CrossAxisAlignment.start,
                                       children: [
-                                        Text(
+                                        Row(
+                                          children: [
+                                            Flexible(
+                                              child: Text(
                                                 '${g['name']}',
+                                                overflow: TextOverflow.ellipsis,
                                                 style: const TextStyle(
                                                   fontWeight: FontWeight.bold,
                                                   fontSize: 15,
                                                 ),
                                               ),
+                                            ),
+                                            if (g['isPublic'] == true) ...[
+                                              const SizedBox(width: 6),
+                                              const Icon(
+                                                Icons.public_rounded,
+                                                size: 14,
+                                                color: Colors.grey,
+                                              ),
+                                            ],
+                                            if ((g['pendingRequestCount'] ??
+                                                    0) >
+                                                0) ...[
+                                              const SizedBox(width: 6),
+                                              Container(
+                                                padding:
+                                                    const EdgeInsets.symmetric(
+                                                      horizontal: 6,
+                                                      vertical: 1,
+                                                    ),
+                                                decoration: BoxDecoration(
+                                                  color: Colors.red[50],
+                                                  borderRadius:
+                                                      BorderRadius.circular(20),
+                                                  border: Border.all(
+                                                    color: Colors.red,
+                                                  ),
+                                                ),
+                                                child: Text(
+                                                  '대기 ${g['pendingRequestCount']}',
+                                                  style: const TextStyle(
+                                                    fontSize: 10,
+                                                    color: Colors.red,
+                                                  ),
+                                                ),
+                                              ),
+                                            ],
+                                          ],
+                                        ),
                                         Text(
                                           '멤버 ${g['memberCount']}명'
                                           '${g['isOwner'] == true ? ' · 그룹장' : ''}',
@@ -294,6 +367,73 @@ class _GroupListScreenState extends State<GroupListScreen> {
                               ),
                             ),
                           ),
+                      if (_controller.publicGroups.isNotEmpty) ...[
+                        const SizedBox(height: 20),
+                        _sectionHeader(
+                          '공개 그룹',
+                          count: _controller.publicGroups.length,
+                        ),
+                        const SizedBox(height: 10),
+                        for (final g in _controller.publicGroups)
+                          Container(
+                            margin: const EdgeInsets.only(bottom: 8),
+                            padding: const EdgeInsets.symmetric(
+                              horizontal: 16,
+                              vertical: 12,
+                            ),
+                            decoration: BoxDecoration(
+                              color: AppPalette.paper,
+                              borderRadius: BorderRadius.circular(16),
+                              border: Border.all(color: AppPalette.sage),
+                            ),
+                            child: Row(
+                              children: [
+                                const Icon(
+                                  Icons.public_rounded,
+                                  color: AppPalette.ink,
+                                  size: 18,
+                                ),
+                                const SizedBox(width: 10),
+                                Expanded(
+                                  child: Column(
+                                    crossAxisAlignment:
+                                        CrossAxisAlignment.start,
+                                    children: [
+                                      Text(
+                                        '${g['name']}',
+                                        style: const TextStyle(
+                                          fontWeight: FontWeight.bold,
+                                        ),
+                                      ),
+                                      Text(
+                                        '${g['ownerName']} · 멤버 ${g['memberCount']}명',
+                                        style: TextStyle(
+                                          fontSize: 12,
+                                          color: Colors.grey[500],
+                                        ),
+                                      ),
+                                    ],
+                                  ),
+                                ),
+                                if (g['requested'] == true)
+                                  Text(
+                                    '신청됨',
+                                    style: TextStyle(color: Colors.grey[500]),
+                                  )
+                                else
+                                  ElevatedButton(
+                                    style: ElevatedButton.styleFrom(
+                                      backgroundColor: AppPalette.ink,
+                                      foregroundColor: AppPalette.paper,
+                                    ),
+                                    onPressed: () =>
+                                        _requestJoin(g['groupId'] as int),
+                                    child: const Text('참여 신청'),
+                                  ),
+                              ],
+                            ),
+                          ),
+                      ],
                     ],
                   ),
                 ),