Added Open Project to Main Menu and implemented dialog interaction fo…

…r opening an existing project.

#27
#28

Horizon/View/Controls/MainMenu.xaml

@@ -17,6 +17,16 @@
                         </MenuItem.Icon>
                     </MenuItem>
                 </MenuItem>
+                <MenuItem Header="Open" InputGestureText="Ctrl+Shift+O">
+                    <MenuItem.Icon>
+                        <Image Source="/Resources/Images/Open Small.png" Width="18" Height="18" />
+                    </MenuItem.Icon>
+                    <MenuItem x:Name="OpenProjectMenuItem" Header="Project...">
+                        <MenuItem.Icon>
+                            <Image Source="/Resources/Images/Open Small.png" Width="18" Height="18" />
+                        </MenuItem.Icon>
+                    </MenuItem>
+                </MenuItem>
             </MenuItem>
         </Menu>
     </StackPanel>

Horizon/View/Controls/MainMenu.xaml.cs

@@ -26,6 +26,12 @@ public MainMenu()
                 .Select(x => new Unit())
                 .InvokeCommand(App.CommandsViewModel, x => x.NewProjectDialog)
                 .DisposeWith(dispose);
+
+            this.OpenProjectMenuItem.Events()
+                .Click
+                .Select(x => new Unit())
+                .InvokeCommand(App.CommandsViewModel, x => x.OpenProjectDialog)
+                .DisposeWith(dispose);
         });
     }
 }

Horizon/View/Windows/Workspace.xaml.cs

@@ -1,5 +1,7 @@
 using AvalonDock;
 using Horizon.Converters;
+using Horizon.ObjectModel;
+using Microsoft.WindowsAPICodePack.Dialogs;
 using ReactiveMarbles.ObservableEvents;
 using ReactiveUI;
 using System.Reactive;
@@ -124,5 +126,35 @@ private void Interactions(CompositeDisposable dispose)
                 }, RxApp.MainThreadScheduler);
             })
         .DisposeWith(dispose);
+
+        App.CommandsViewModel
+            .OpenProjectDialogInteraction
+            .RegisterHandler(interaction =>
+            {
+                CommonOpenFileDialog fileDialog = new() { EnsureFileExists = true, Title = "Select a project file...", Multiselect = false };
+                fileDialog.Filters.Add(new CommonFileDialogFilter("Project Files", "Project.horizon"));
+
+                return Observable.StartAsync(async () =>
+                {
+                    if (fileDialog.ShowDialog() == CommonFileDialogResult.Ok)
+                    {
+                        ProjectFile? project = await JsonFile.FromAbstractFile<ProjectFile>(fileDialog.FileName);
+
+                        if (project is not null)
+                        {
+                            interaction.SetOutput(project);
+                        }
+                        else
+                        {
+                            interaction.SetOutput(null);
+                        }
+                    }
+                    else
+                    {
+                        interaction.SetOutput(null);
+                    }
+                }, RxApp.MainThreadScheduler);
+            })
+            .DisposeWith(dispose);
     }
 }

Horizon/ViewModel/CommandsViewModel.cs

@@ -16,13 +16,24 @@ public sealed class CommandsViewModel : ReactiveObject
     public CommandsViewModel()
     {
         this.NewProjectDialog = ReactiveCommand.CreateFromTask(this.HandleNewProjectDialog);
+        this.OpenProjectDialog = ReactiveCommand.CreateFromTask(this.HandleOpenProjectDialog);
     }
 
     /// <summary>
     /// Command that opens a "new Project" dialog and waits for the interaction to complete.
     /// </summary>
     public ReactiveCommand<Unit, Unit> NewProjectDialog { get; set; }
 
+    /// <summary>
+    /// Command that opens an "Open Project" file picker and waits for the interaction to complete.
+    /// </summary>
+    public ReactiveCommand<Unit, Unit> OpenProjectDialog { get; set; }
+
+    /// <summary>
+    /// Interaction that handles the "Open Project" dialog without blocking the UI.
+    /// </summary>
+    public Interaction<Unit, ProjectFile?> OpenProjectDialogInteraction { get; } = new();
+
     /// <summary>
     /// Interaction that handles the "New Project" dialog without blocking the UI.
     /// </summary>
@@ -74,6 +85,20 @@ private static async Task OpenProject(ProjectFile project)
         await LoadProject(project);
     }
 
+    /// <summary>
+    /// Handles the "Open Project" dialog and opens the selected project if the input is accepted.
+    /// </summary>
+    /// <returns>An awaitable <see cref="Task" />.</returns>
+    private async Task HandleOpenProjectDialog()
+    {
+        ProjectFile? project = await this.OpenProjectDialogInteraction.Handle(Unit.Default);
+
+        if (project is not null)
+        {
+            await OpenProject(project);
+        }
+    }
+
     /// <summary>
     /// handles the "New Project" dialog and creates a new project if the input is accepted.
     /// </summary>