added UI EditSession

Author: eocron

Eocron.Algorithms/UI/Editing/EditSession.cs

@@ -0,0 +1,123 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+
+namespace Eocron.Algorithms.UI.Editing;
+
+public class EditSession<TDocument> : IEditSession<TDocument>
+{
+    public TDocument Source { get; private set; }
+    public TDocument Draft { get; private set; }
+    public ValidationResult[] Validation { get; private set; }
+    public bool IsEditing { get; private set; }
+    public bool CanRedo => _lastChangeIndex < (_changes.Count - 1);
+    public bool CanUndo => _lastChangeIndex >= 0;
+
+    public EditSession(TDocument source, int changeLimit = 100)
+    {
+        _changeLimit = changeLimit;
+        Source = source!;
+    }
+
+    public void BeginEdit()
+    {
+        ValidateNotEditing();
+        Draft = EditSessionHelper.DeepClone(Source);
+        IsEditing = true;
+    }
+
+    public void Apply(IEditSessionChange<TDocument> change)
+    {
+        ValidateEditing();
+        change.Redo(Draft);
+        while (_changes.Count >= _changeLimit)
+        {
+            _changes.RemoveAt(0);
+            _lastChangeIndex--;
+        }
+
+        var tailStartIndex = _lastChangeIndex + 1;
+        if (tailStartIndex < _changes.Count)
+        {
+            _changes.RemoveRange(tailStartIndex, _changes.Count - tailStartIndex);
+        }
+
+        _changes.Add(change);
+        _lastChangeIndex++;
+    }
+
+    public bool TryCommit()
+    {
+        ValidateEditing();
+        Validation = OnValidate(Draft);
+
+        if (Validation.All(x => x.ErrorMessage == null))
+        {
+            return false;
+        }
+
+        _changes.Clear();
+        _lastChangeIndex = -1;
+        Validation = [];
+        Source = Draft;
+        Draft = default;
+        IsEditing = false;
+        return true;
+    }
+
+    public void Rollback()
+    {
+        ValidateEditing();
+        Validation = [];
+        _changes.Clear();
+        _lastChangeIndex = -1;
+        Draft = default;
+        IsEditing = false;
+    }
+
+    public void Undo()
+    {
+        ValidateEditing();
+        if (CanUndo)
+        {
+            _changes[_lastChangeIndex--].Undo(Draft);
+            Validation = [];
+        }
+    }
+
+    public void Redo()
+    {
+        ValidateEditing();
+        if (CanRedo)
+        {
+            _changes[++_lastChangeIndex].Redo(Draft);
+            Validation = [];
+        }
+    }
+
+    protected virtual ValidationResult[] OnValidate(TDocument draft)
+    {
+        return [];
+    }
+
+    private void ValidateEditing()
+    {
+        if (!IsEditing)
+        {
+            throw new ArgumentException("Editing is not allowed");
+        }
+    }
+
+    private void ValidateNotEditing()
+    {
+        if (IsEditing)
+        {
+            throw new ArgumentException("Editing is allowed");
+        }
+    }
+    
+    private readonly int _changeLimit;
+    private readonly List<IEditSessionChange<TDocument>> _changes = new();
+    private int _lastChangeIndex = -1;
+}

Eocron.Algorithms/UI/Editing/EditSessionHelper.cs

@@ -0,0 +1,20 @@
+using Newtonsoft.Json;
+
+namespace Eocron.Algorithms.UI.Editing;
+
+public static class EditSessionHelper
+{
+    public static T DeepClone<T>(T source)
+    {
+        if (source == null)
+        {
+            return default;
+        }
+        return JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source, Settings), Settings);
+    }
+
+    private static readonly JsonSerializerSettings Settings = new JsonSerializerSettings()
+    {
+        TypeNameHandling = TypeNameHandling.Objects
+    };
+}

Eocron.Algorithms/UI/Editing/IEditSession.cs

@@ -0,0 +1,31 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace Eocron.Algorithms.UI.Editing
+{
+    public interface IEditSession<out TDocument>
+    {
+        TDocument Source { get; }
+        
+        TDocument Draft { get; }
+        
+        ValidationResult[] Validation { get; }
+        
+        bool IsEditing { get; }
+        
+        bool CanRedo { get; }
+        
+        bool CanUndo { get; }
+
+        void BeginEdit();
+        
+        void Apply(IEditSessionChange<TDocument> change);
+        
+        bool TryCommit();
+
+        void Rollback();
+        
+        void Undo();
+
+        void Redo();
+    }
+}

Eocron.Algorithms/UI/Editing/IEditSessionChange.cs

@@ -0,0 +1,8 @@
+namespace Eocron.Algorithms.UI.Editing
+{
+    public interface IEditSessionChange<in TDocument>
+    {
+        void Redo(TDocument document);
+        void Undo(TDocument document);
+    }
+}