source: branches/HeuristicLab.Problems.GrammaticalOptimization/DynamicDataDisplay/Common/UndoSystem/UndoProvider.cs @ 13792

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Windows;

namespace Microsoft.Research.DynamicDataDisplay.Common.UndoSystem
{
  public class UndoProvider : INotifyPropertyChanged
  {
    private readonly ActionStack undoStack = new ActionStack();
    private readonly ActionStack redoStack = new ActionStack();

    public UndoProvider()
    {
      undoStack.IsEmptyChanged += OnUndoStackIsEmptyChanged;
      redoStack.IsEmptyChanged += OnRedoStackIsEmptyChanged;
    }

    private bool isEnabled = true;
    public bool IsEnabled
    {
      get { return isEnabled; }
      set { isEnabled = value; }
    }

    private void OnUndoStackIsEmptyChanged(object sender, EventArgs e)
    {
      PropertyChanged.Raise(this, "CanUndo");
    }

    private void OnRedoStackIsEmptyChanged(object sender, EventArgs e)
    {
      PropertyChanged.Raise(this, "CanRedo");
    }

    public void AddAction(UndoAction action)
    {
      if (!isEnabled)
        return;

      if (state != UndoState.None)
        return;

      undoStack.Push(action);
      redoStack.Clear();
    }

    public void Undo()
    {
      var action = undoStack.Pop();
      redoStack.Push(action);

      state = UndoState.Undoing;
      try
      {
        action.Undo();
      }
      finally
      {
        state = UndoState.None;
      }
    }

    public void Redo()
    {
      var action = redoStack.Pop();
      undoStack.Push(action);

      state = UndoState.Redoing;
      try
      {
        action.Do();
      }
      finally
      {
        state = UndoState.None;
      }
    }

    public bool CanUndo
    {
      get { return !undoStack.IsEmpty; }
    }

    public bool CanRedo
    {
      get { return !redoStack.IsEmpty; }
    }

    private UndoState state = UndoState.None;
    public UndoState State
    {
      get { return state; }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion

    private readonly Dictionary<CaptureKeyHolder, object> captureHolders = new Dictionary<CaptureKeyHolder, object>();
    public void CaptureOldValue(DependencyObject target, DependencyProperty property, object oldValue)
    {
      captureHolders[new CaptureKeyHolder { Target = target, Property = property }] = oldValue;
    }

    public void CaptureNewValue(DependencyObject target, DependencyProperty property, object newValue)
    {
      var holder = new CaptureKeyHolder { Target = target, Property = property };
      if (captureHolders.ContainsKey(holder))
      {
        object oldValue = captureHolders[holder];
        captureHolders.Remove(holder);

        if (!Object.Equals(oldValue, newValue))
        {
          var action = new DependencyPropertyChangedUndoAction(target, property, oldValue, newValue);
          AddAction(action);
        }
      }
    }

    private sealed class CaptureKeyHolder
    {
      public DependencyObject Target { get; set; }
      public DependencyProperty Property { get; set; }

      public override int GetHashCode()
      {
        return Target.GetHashCode() ^ Property.GetHashCode();
      }

      public override bool Equals(object obj)
      {
        if (obj == null) return false;

        CaptureKeyHolder other = obj as CaptureKeyHolder;
        if (other == null) return false;

        return Target == other.Target && Property == other.Property;
      }
    }
  }

  public enum UndoState
  {
    None,
    Undoing,
    Redoing
  }
}