feat(core,desktop): implement module duplication and parent auto-sync

src/TextForge.Core/Documents/Document.cs

@@ -106,6 +106,16 @@ public void SelectModule(Module? module)
         NotifyChanged();
     }
 
+    public Module? DuplicateModule(Module module)
+    {
+        var clone = DocumentOperations.Duplicate(Modules, module);
+        if (clone is not null)
+        {
+            NotifyChanged(); // Same notification Move and Remove use internally
+        }
+        return clone;
+    }
+
     private static void SetSelectionRecursive(IEnumerable<Module> modules, bool isSelected)
     {
         foreach (var mod in modules)

src/TextForge.Core/Documents/DocumentOperations.cs

@@ -0,0 +1,41 @@
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using TextForge.Core.Modules;
+
+namespace TextForge.Core;
+
+public static class DocumentOperations
+{
+    /// <summary>
+    /// Duplicates the target module and inserts it directly after the target in its parent collection
+    /// or in the root collection if it is a root module.
+    /// </summary>
+    public static Module Duplicate(IList<Module> rootModules, Module target)
+    {
+        var clone = target.Clone();
+
+        if (target.Parent is not null)
+        {
+            var parentCollection = target.Parent.SubModules;
+            int index = parentCollection.IndexOf(target);
+            if (index >= 0)
+            {
+                parentCollection.Insert(index + 1, clone);
+                return clone;
+            }
+        }
+
+        // Target is a root-level module
+        int rootIndex = rootModules.IndexOf(target);
+        if (rootIndex >= 0)
+        {
+            rootModules.Insert(rootIndex + 1, clone);
+        }
+        else
+        {
+            rootModules.Add(clone);
+        }
+
+        return clone;
+    }
+}

src/TextForge.Core/Modules/Module.cs

@@ -1,20 +1,17 @@
-using System;
-using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
+using System.Text.Json.Serialization;
 
 namespace TextForge.Core.Modules;
 
-/// <summary>
-/// Represents an independent content element within a document.
-/// Modules can be nested hierarchically to form compound structures.
-/// </summary>
 public class Module : INotifyPropertyChanged
 {
     private string _content = string.Empty;
     private bool _isSelected;
     private bool _isExpanded;
+    private Module? _parent;
 
     public event PropertyChangedEventHandler? PropertyChanged;
 
@@ -26,6 +23,24 @@ public class Module : INotifyPropertyChanged
 
     public ModuleType Type { get; init; } = ModuleType.Text;
 
+    /// <summary>
+    /// Reference to the containing parent module. Null if this is a root-level module.
+    /// Ignored during serialization to avoid cyclic object graphs.
+    /// </summary>
+    [JsonIgnore]
+    public Module? Parent
+    {
+        get => _parent;
+        internal set
+        {
+            if (_parent != value)
+            {
+                _parent = value;
+                OnPropertyChanged();
+            }
+        }
+    }
+
     public string Content
     {
         get => _content;
@@ -41,7 +56,7 @@ public string Content
 
     public ModuleFeatures Features { get; set; } = ModuleFeatures.Default;
 
-    public ObservableCollection<Module> SubModules { get; set; } = [];
+    public ObservableCollection<Module> SubModules { get; } = [];
 
     public bool IsSelected
     {
@@ -69,7 +84,10 @@ public bool IsExpanded
         }
     }
 
-    public Module() { }
+    public Module()
+    {
+        WireSubModulesCollection();
+    }
 
     public Module(
         string content,
@@ -83,6 +101,57 @@ public Module(
         StyleKey = styleKey;
         Features = features ?? ModuleFeatures.Default;
         Name = name;
+        WireSubModulesCollection();
+    }
+
+    private void WireSubModulesCollection()
+    {
+        SubModules.CollectionChanged += OnSubModulesChanged;
+    }
+
+    private void OnSubModulesChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        if (e.NewItems != null)
+        {
+            foreach (Module child in e.NewItems)
+            {
+                child.Parent = this;
+            }
+        }
+
+        if (e.OldItems != null)
+        {
+            foreach (Module child in e.OldItems)
+            {
+                if (child.Parent == this)
+                {
+                    child.Parent = null;
+                }
+            }
+        }
+    }
+
+    public Module Clone()
+    {
+        var clone = new Module
+        {
+            Id = Guid.NewGuid(),
+            Name = Name,
+            Type = Type,
+            StyleKey = StyleKey,
+            Content = Content,
+            Features = Features with { },
+            IsExpanded = IsExpanded,
+            IsSelected = false
+        };
+
+        foreach (var subModule in SubModules)
+        {
+            // Adding automatically assigns clone as the Parent
+            clone.SubModules.Add(subModule.Clone());
+        }
+
+        return clone;
     }
 
     protected void OnPropertyChanged([CallerMemberName] string? propertyName = null)

src/TextForge.Core/Modules/ModuleFeatures.cs

@@ -39,4 +39,5 @@ public ModuleFeatures MergeWith(ModuleFeatures? fallback)
             LineSpacing = LineSpacing ?? fallback.LineSpacing
         };
     }
+
 }

src/TextForge.Core/model/IModule.cs

@@ -0,0 +1,7 @@
+namespace TextForge.Core.Models;
+
+public interface IModule
+{
+    Guid Id { get; }
+    IModule Clone();
+}

src/TextForge.Desktop/Views/Components/ModuleEditorView.axaml

@@ -1,7 +1,7 @@
 <UserControl xmlns="https://github.com/avaloniaui"
-             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             xmlns:mod="using:TextForge.Core.Modules"
-             x:Class="TextForge.Desktop.Views.Components.ModuleEditorView">
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:mod="using:TextForge.Core.Modules"
+    x:Class="TextForge.Desktop.Views.Components.ModuleEditorView">
 
     <UserControl.Styles>
         <Style Selector="ListBoxItem">
@@ -39,75 +39,91 @@
         <!-- Self-Referencing Recursive Template for Modules & Submodules at any depth -->
         <DataTemplate x:Key="RecursiveModuleTemplate" x:DataType="mod:Module">
             <Border Classes="module-card"
-                    Tag="{Binding}"
-                    Margin="0,1"
-                    Padding="2">
+                Tag="{Binding}"
+                Margin="0,1"
+                Padding="2">
                 <Expander IsExpanded="{Binding IsExpanded, Mode=TwoWay, FallbackValue=False}"
-                          HorizontalAlignment="Stretch"
-                          Background="Transparent">
+                    HorizontalAlignment="Stretch"
+                    Background="Transparent">
                     <Expander.Header>
                         <Grid ColumnDefinitions="Auto,*,Auto"
-                              VerticalAlignment="Center"
-                              Background="Transparent">
+                            VerticalAlignment="Center"
+                            Background="Transparent">
                             <!-- Archetype Tag -->
                             <Border Grid.Column="0"
-                                    Background="#E5E7EB"
-                                    CornerRadius="4"
-                                    Padding="6,2"
-                                    Margin="0,0,8,0">
+                                Background="#E5E7EB"
+                                CornerRadius="4"
+                                Padding="6,2"
+                                Margin="0,0,8,0">
                                 <TextBlock Text="{Binding Name}"
-                                           FontSize="11"
-                                           FontWeight="SemiBold"
-                                           Foreground="#374151" />
+                                    FontSize="11"
+                                    FontWeight="SemiBold"
+                                    Foreground="#374151" />
                             </Border>
 
                             <!-- Content Preview -->
                             <TextBlock Grid.Column="1"
-                                       Text="{Binding Content}"
-                                       TextTrimming="CharacterEllipsis"
-                                       VerticalAlignment="Center"
-                                       FontSize="12"
-                                       Foreground="#1F2937" />
+                                Text="{Binding Content}"
+                                TextTrimming="CharacterEllipsis"
+                                VerticalAlignment="Center"
+                                FontSize="12"
+                                Foreground="#1F2937" />
 
                             <!-- Action Buttons -->
-                            <StackPanel Grid.Column="2" Orientation="Horizontal" Spacing="2" Margin="4,0,0,0">
+                            <StackPanel Grid.Column="2" Orientation="Horizontal" Spacing="2"
+                                Margin="4,0,0,0">
                                 <Button Content="▲" FontSize="10" Width="22" Height="22" Padding="0"
-                                        HorizontalContentAlignment="Center" VerticalContentAlignment="Center"
-                                        Background="Transparent" Foreground="#6B7280" ToolTip.Tip="Move Up"
-                                        Tag="{Binding}" Click="MoveUpButton_Click" />
+                                    HorizontalContentAlignment="Center"
+                                    VerticalContentAlignment="Center"
+                                    Background="Transparent" Foreground="#6B7280"
+                                    ToolTip.Tip="Move Up"
+                                    Tag="{Binding}" Click="MoveUpButton_Click" />
                                 <Button Content="▼" FontSize="10" Width="22" Height="22" Padding="0"
-                                        HorizontalContentAlignment="Center" VerticalContentAlignment="Center"
-                                        Background="Transparent" Foreground="#6B7280" ToolTip.Tip="Move Down"
-                                        Tag="{Binding}" Click="MoveDownButton_Click" />
+                                    HorizontalContentAlignment="Center"
+                                    VerticalContentAlignment="Center"
+                                    Background="Transparent" Foreground="#6B7280"
+                                    ToolTip.Tip="Move Down"
+                                    Tag="{Binding}" Click="MoveDownButton_Click" />
                                 <Button Content="✕" FontSize="11" Width="22" Height="22" Padding="0"
-                                        HorizontalContentAlignment="Center" VerticalContentAlignment="Center"
-                                        Background="Transparent" Foreground="#EF4444" ToolTip.Tip="Delete Module"
-                                        Tag="{Binding}" Click="DeleteModuleButton_Click" />
+                                    HorizontalContentAlignment="Center"
+                                    VerticalContentAlignment="Center"
+                                    Background="Transparent" Foreground="#EF4444"
+                                    ToolTip.Tip="Delete Module"
+                                    Tag="{Binding}" Click="DeleteModuleButton_Click" />
+                                <Button Content="+" FontSize="14" FontWeight="Bold" Width="22"
+                                    Height="22" Padding="0"
+                                    HorizontalContentAlignment="Center"
+                                    VerticalContentAlignment="Center"
+                                    Background="Transparent" Foreground="#10B981"
+                                    ToolTip.Tip="Duplicate Module"
+                                    Tag="{Binding}" Click="DuplicateModuleButton_Click" />
+
                             </StackPanel>
                         </Grid>
                     </Expander.Header>
 
                     <StackPanel Spacing="6" Margin="4,6,4,4">
                         <TextBox Text="{Binding Content, Mode=TwoWay}"
-                                 AcceptsReturn="True"
-                                 TextWrapping="Wrap"
-                                 MinHeight="45" />
+                            AcceptsReturn="True"
+                            TextWrapping="Wrap"
+                            MinHeight="45" />
 
-                        <!-- Recursive ItemsControl: uses the exact same template for child submodules -->
+                        <!-- Recursive ItemsControl: uses the exact same template for child
+                        submodules -->
                         <ItemsControl ItemsSource="{Binding SubModules}"
-                                      ItemTemplate="{StaticResource RecursiveModuleTemplate}"
-                                      Margin="14,2,0,0" />
+                            ItemTemplate="{StaticResource RecursiveModuleTemplate}"
+                            Margin="14,2,0,0" />
                     </StackPanel>
                 </Expander>
             </Border>
         </DataTemplate>
     </UserControl.Resources>
 
     <ScrollViewer VerticalScrollBarVisibility="Auto"
-                  HorizontalScrollBarVisibility="Disabled">
+        HorizontalScrollBarVisibility="Disabled">
         <ListBox Name="ModuleListBox"
-                 Background="Transparent"
-                 SelectionMode="Single"
-                 ItemTemplate="{StaticResource RecursiveModuleTemplate}" />
+            Background="Transparent"
+            SelectionMode="Single"
+            ItemTemplate="{StaticResource RecursiveModuleTemplate}" />
     </ScrollViewer>
 </UserControl>

src/TextForge.Desktop/Views/Components/ModuleEditorView.axaml.cs

@@ -1,6 +1,7 @@
 using System;
 using Avalonia.Controls;
 using Avalonia.Interactivity;
+using TextForge.Core;
 using TextForge.Core.Documents;
 using TextForge.Core.Modules;
 
@@ -12,6 +13,7 @@ public partial class ModuleEditorView : UserControl
     public event EventHandler<Module>? ModuleMoveUpRequested;
     public event EventHandler<Module>? ModuleMoveDownRequested;
     public event EventHandler<Module>? ModuleDeleteRequested;
+    public event EventHandler<Module>? ModuleDuplicateRequested;
 
     public ModuleEditorView()
     {
@@ -41,6 +43,15 @@ private void DeleteModuleButton_Click(object? sender, RoutedEventArgs e)
             ModuleDeleteRequested?.Invoke(this, module);
         }
     }
+
+    private void DuplicateModuleButton_Click(object? sender, RoutedEventArgs e)
+    {
+        if (sender is Button { Tag: Module module })
+        {
+            ModuleDuplicateRequested?.Invoke(this, module);
+        }
+    }
+
     /// <summary>
     /// Binds the editor to a document instance.
     /// Done once per document load.

src/TextForge.Desktop/Views/MainWindow.axaml.cs

@@ -95,6 +95,8 @@ private void BindModuleList()
         moduleEditor.ModuleMoveUpRequested += ModuleEditor_ModuleMoveUpRequested;
         moduleEditor.ModuleMoveDownRequested += ModuleEditor_ModuleMoveDownRequested;
         moduleEditor.ModuleDeleteRequested += ModuleEditor_ModuleDeleteRequested;
+        moduleEditor.ModuleDuplicateRequested += ModuleEditor_ModuleDuplicateRequested;
+
 
         var moduleListBox = moduleEditor.FindControl<ListBox>("ModuleListBox");
         if (moduleListBox is not null)
@@ -196,6 +198,14 @@ private void ModuleEditor_ModuleDeleteRequested(object? sender, Module module)
         RefreshModuleEditorList();
     }
 
+    private void ModuleEditor_ModuleDuplicateRequested(object? sender, Module module)
+    {
+        if (_currentDocument?.DuplicateModule(module) is not null)
+        {
+            RefreshModuleEditorList();
+        }
+    }
+
     #endregion
 
     #region Document & Preview Synchronization