Can change group membership levels

lib/helpers/groups_helper.dart

@@ -306,6 +306,17 @@ class GroupsHelper {
           .addInt("userID", userID)
           .execWithThrow();
 
+  /// Change the membership level of a member of a group
+  ///
+  /// Throws an exception in case of failure
+  static Future<void> setNewLevel(
+          int groupID, int userID, GroupMembershipLevel level) async =>
+      await APIRequest.withLogin("groups/update_membership_level")
+          .addInt("groupID", groupID)
+          .addInt("userID", userID)
+          .addString("level", invertMap(_APIGroupsMembershipLevelsMap)[level])
+          .execWithThrow();
+
   /// Turn an API entry into a group object
   Group _getGroupFromAPI(Map<String, dynamic> map) {
     return Group(

lib/ui/dialogs/multi_choices_dialog.dart

@@ -19,6 +19,8 @@ class MultiChoiceEntry<T> {
     this.subtitle,
   })  : assert(id != null),
         assert(title != null);
+
+  bool get hasSubtitle => subtitle != null;
 }
 
 /// Show multiple choices dialog
@@ -81,7 +83,7 @@ class __MultiChoicesEntryDialogState<T>
                       onChanged: (v) => setState(() => _currChoice = v),
                     ),
                     title: Text(f.title),
-                    subtitle: Text(f.subtitle),
+                    subtitle: f.hasSubtitle ? Text(f.subtitle) : null,
                   ))
               .toList(),
         ),

lib/ui/screens/group_members_screen.dart

@@ -31,13 +31,16 @@ class GroupMembersScreen extends StatefulWidget {
 
 class _GroupMembersScreenState extends State<GroupMembersScreen> {
   final _key = GlobalKey<AsyncScreenWidgetState>();
+  Group _group;
   GroupMembersList _members;
   UsersList _users;
 
   Future<void> _refresh() async {
+    final group = await GroupsHelper().getSingle(widget.groupID, force: true);
     final members = await GroupsHelper.getMembersList(widget.groupID);
     final users = await UsersHelper().getListWithThrow(members.usersID);
 
+    _group = group;
     _members = members;
     _users = users;
   }
@@ -74,6 +77,7 @@ class _GroupMembersScreenState extends State<GroupMembersScreen> {
     final user = _users.getUser(membership.userID);
 
     return _GroupMembershipTile(
+      group: _group,
       membership: membership,
       user: user,
       onUpdated: () => _key.currentState.refresh(),
@@ -110,8 +114,7 @@ List<MultiChoiceEntry<GroupMembershipLevel>> get _membershipLevels => [
       MultiChoiceEntry(
           id: GroupMembershipLevel.ADMINISTRATOR,
           title: tr("Administrator"),
-          subtitle:
-              tr("Can change members privileges and change group settings")),
+          subtitle: tr("Can change members privileges and group settings")),
       MultiChoiceEntry(
           id: GroupMembershipLevel.MODERATOR,
           title: tr("Moderator"),
@@ -128,16 +131,19 @@ List<MultiChoiceEntry<GroupMembershipLevel>> get _membershipLevels => [
     ];
 
 class _GroupMembershipTile extends StatefulWidget {
+  final Group group;
   final GroupMembership membership;
   final User user;
   final void Function() onUpdated;
 
   const _GroupMembershipTile({
     Key key,
+    @required this.group,
     @required this.membership,
     @required this.user,
     @required this.onUpdated,
-  })  : assert(membership != null),
+  })  : assert(group != null),
+        assert(membership != null),
         assert(user != null),
         assert(onUpdated != null),
         super(key: key);
@@ -146,7 +152,7 @@ class _GroupMembershipTile extends StatefulWidget {
   __GroupMembershipTileState createState() => __GroupMembershipTileState();
 }
 
-enum _MemberMenuOptions { DELETE }
+enum _MemberMenuOptions { CHANGE_LEVEL, DELETE }
 
 class __GroupMembershipTileState extends State<_GroupMembershipTile> {
   int get groupID => widget.membership.groupID;
@@ -194,6 +200,13 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
   Widget _buildMemberCase() {
     return PopupMenuButton<_MemberMenuOptions>(
       itemBuilder: (c) => [
+        // Change membership level
+        PopupMenuItem(
+          child: Text(tr("Change level")),
+          enabled: widget.group.isAdmin,
+          value: _MemberMenuOptions.CHANGE_LEVEL,
+        ),
+
         // Remove membership
         PopupMenuItem(
           child: Text(tr("Remove")),
@@ -206,12 +219,36 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
 
   void _handleMenu(_MemberMenuOptions value) {
     switch (value) {
+      case _MemberMenuOptions.CHANGE_LEVEL:
+        _changeLevel();
+        break;
+
       case _MemberMenuOptions.DELETE:
         _removeMembership();
         break;
     }
   }
 
+  void _changeLevel() async {
+    try {
+      final newLevel = await showMultiChoicesDialog(
+        context: context,
+        choices: _membershipLevels,
+        defaultChoice: widget.membership.level,
+        title: tr("New membership level"),
+      );
+
+      if (newLevel == null) return;
+
+      await GroupsHelper.setNewLevel(groupID, userID, newLevel);
+    } catch (e, s) {
+      print("Could not change group membership level! $e\n$s");
+      showSimpleSnack(context, tr("Could not change group membership level!"));
+    }
+
+    widget.onUpdated();
+  }
+
   void _removeMembership() async {
     try {
       if (!await showConfirmDialog(