Improve update message dialog

lib/ui/screens/conversation_screen.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:comunic/helpers/conversations_helper.dart';
 import 'package:comunic/helpers/events_helper.dart';
+import 'package:comunic/helpers/server_config_helper.dart';
 import 'package:comunic/helpers/users_helper.dart';
 import 'package:comunic/lists/conversation_messages_list.dart';
 import 'package:comunic/lists/users_list.dart';
@@ -440,7 +441,12 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
       title: tr("Update message"),
       message: tr("Please enter new message content:"),
       defaultValue: message.message.content,
-        hint: tr("New message"));
+      hint: tr("New message"),
+      minLength:
+          ServerConfigurationHelper.config.conversationsPolicy.minMessageLen,
+      maxLength:
+          ServerConfigurationHelper.config.conversationsPolicy.maxMessageLen,
+    );
 
     if (newContent == null) return;
 

lib/utils/ui_utils.dart

@@ -93,6 +93,7 @@ Future<String> askUserString({
   @required String defaultValue,
   @required String hint,
   int maxLength = 200,
+  int minLength = 1,
 }) async {
   assert(context != null);
   assert(title != null);
@@ -105,19 +106,58 @@ Future<String> askUserString({
 
   final confirm = await showDialog<bool>(
       context: context,
-      builder: (c) => AlertDialog(
-            title: Text(title),
+      builder: (c) => _InputTextDialog(
+            title: title,
+            message: message,
+            controller: controller,
+            maxLength: maxLength,
+            minLength: minLength,
+            hint: hint,
+          ));
+
+  if (confirm == null || !confirm) return null;
+
+  return controller.text;
+}
+
+class _InputTextDialog extends StatefulWidget {
+  final String title;
+  final String message;
+  final TextEditingController controller;
+  final int maxLength;
+  final int minLength;
+  final String hint;
+
+  const _InputTextDialog({
+    Key key,
+    @required this.title,
+    @required this.message,
+    @required this.controller,
+    @required this.maxLength,
+    @required this.minLength,
+    @required this.hint,
+  }) : super(key: key);
+
+  @override
+  __InputTextDialogState createState() => __InputTextDialogState();
+}
+
+class __InputTextDialogState extends State<_InputTextDialog> {
+  @override
+  Widget build(BuildContext c) => AlertDialog(
+        title: Text(widget.title),
         content: AutoSizeDialogContentWidget(
           child: Column(
             children: <Widget>[
-                  Text(message),
+              Text(widget.message),
               TextField(
-                    controller: controller,
+                controller: widget.controller,
                 maxLines: null,
-                    maxLength: maxLength,
+                maxLength: widget.maxLength,
                 keyboardType: TextInputType.text,
+                onChanged: (s) => setState(() {}),
                 decoration: InputDecoration(
-                      labelText: hint,
+                  labelText: widget.hint,
                   alignLabelWithHint: true,
                 ),
               )
@@ -131,14 +171,12 @@ Future<String> askUserString({
           ),
           FlatButton(
             child: Text(tr("OK")),
-                onPressed: () => Navigator.pop(c, true),
+            onPressed: widget.controller.text.length >= widget.minLength
+                ? () => Navigator.pop(c, true)
+                : null,
           ),
         ],
-          ));
-
-  if (confirm == null || !confirm) return null;
-
-  return controller.text;
+      );
 }
 
 /// Show an alert dialog to get user confirmation for something