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src/Artemis.UI.Shared/Services/NodeEditor/NodeEditorHistory.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reactive;
+using System.Reactive.Linq;
+using System.Reactive.Subjects;
+using Artemis.Core;
+using ReactiveUI;
+
+namespace Artemis.UI.Shared.Services.NodeEditor;
+
+public class NodeEditorHistory
+{
+    private readonly Subject<bool> _canRedo = new();
+    private readonly Subject<bool> _canUndo = new();
+    private readonly Stack<INodeEditorCommand> _redoCommands = new();
+    private readonly Stack<INodeEditorCommand> _undoCommands = new();
+
+    public NodeEditorHistory(INodeScript nodeScript)
+    {
+        NodeScript = nodeScript;
+
+        Execute = ReactiveCommand.Create<INodeEditorCommand>(ExecuteEditorCommand);
+        Undo = ReactiveCommand.Create(ExecuteUndo, CanUndo);
+        Redo = ReactiveCommand.Create(ExecuteRedo, CanRedo);
+    }
+
+    public INodeScript NodeScript { get; }
+    public IObservable<bool> CanUndo => _canUndo.AsObservable().DistinctUntilChanged();
+    public IObservable<bool> CanRedo => _canRedo.AsObservable().DistinctUntilChanged();
+
+    public ReactiveCommand<INodeEditorCommand, Unit> Execute { get; }
+    public ReactiveCommand<Unit, INodeEditorCommand?> Undo { get; }
+    public ReactiveCommand<Unit, INodeEditorCommand?> Redo { get; }
+
+    public void Clear()
+    {
+        ClearRedo();
+        ClearUndo();
+        UpdateSubjects();
+    }
+
+    public void ExecuteEditorCommand(INodeEditorCommand command)
+    {
+        command.Execute();
+
+        _undoCommands.Push(command);
+        ClearRedo();
+        UpdateSubjects();
+    }
+
+    private void ClearRedo()
+    {
+        foreach (INodeEditorCommand nodeEditorCommand in _redoCommands)
+            if (nodeEditorCommand is IDisposable disposable)
+                disposable.Dispose();
+
+        _redoCommands.Clear();
+    }
+
+    private void ClearUndo()
+    {
+        foreach (INodeEditorCommand nodeEditorCommand in _undoCommands)
+            if (nodeEditorCommand is IDisposable disposable)
+                disposable.Dispose();
+
+        _undoCommands.Clear();
+    }
+
+    private INodeEditorCommand? ExecuteUndo()
+    {
+        if (!_undoCommands.TryPop(out INodeEditorCommand? command))
+            return null;
+
+        command.Undo();
+        _redoCommands.Push(command);
+        UpdateSubjects();
+
+        return command;
+    }
+
+    private INodeEditorCommand? ExecuteRedo()
+    {
+        if (!_redoCommands.TryPop(out INodeEditorCommand? command))
+            return null;
+
+        command.Execute();
+        _undoCommands.Push(command);
+        UpdateSubjects();
+
+        return command;
+    }
+
+    private void UpdateSubjects()
+    {
+        _canUndo.OnNext(_undoCommands.Any());
+        _canRedo.OnNext(_redoCommands.Any());
+    }
+}