UndoableBase.cs

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//-----------------------------------------------------------------------
// <copyright file="UndoableBase.cs" company="Marimer LLC">
//     Copyright (c) Marimer LLC. All rights reserved.
//     Website: https://www.lhotka.net/cslanet/
// </copyright>
// <summary>Implements n-level undo capabilities as</summary>
//-----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.IO;
using System.ComponentModel;
using Csla.Properties;
using Csla.Reflection;
using Csla.Serialization.Mobile;
using Csla.Serialization;
using System.Linq;
 
namespace Csla.Core
{
  [Serializable()]
  public abstract class UndoableBase : Csla.Core.BindableBase,
    Csla.Core.IUndoableObject, IUseApplicationContext
  {
    // keep a stack of object state values.
    [NotUndoable()]
    private readonly Stack<byte[]> _stateStack = new();
    [NotUndoable]
    private bool _bindingEdit;
    [NotUndoable]
    private ApplicationContext _applicationContext;
 
    ApplicationContext IUseApplicationContext.ApplicationContext { get => ApplicationContext; set => ApplicationContext = value; }
 
    protected ApplicationContext ApplicationContext 
    { 
      get => _applicationContext;
      set
      {
        _applicationContext = value;
        OnApplicationContextSet();
      }
    }
 
    protected virtual void OnApplicationContextSet()
    { }
 
    protected UndoableBase()
    {
 
    }
 
    [EditorBrowsable(EditorBrowsableState.Never)]
    protected bool BindingEdit
    {
      get
      {
        return _bindingEdit;
      }
      set
      {
        _bindingEdit = value;
      }
    }
 
    int IUndoableObject.EditLevel
    {
      get { return EditLevel; }
    }
 
    [EditorBrowsable(EditorBrowsableState.Never)]
    protected int EditLevel
    {
      get { return _stateStack.Count; }
    }
 
    void IUndoableObject.CopyState(int parentEditLevel, bool parentBindingEdit)
    {
      if (!parentBindingEdit)
        CopyState(parentEditLevel);
    }
 
    void IUndoableObject.UndoChanges(int parentEditLevel, bool parentBindingEdit)
    {
      if (!parentBindingEdit)
        UndoChanges(parentEditLevel);
    }
 
    void IUndoableObject.AcceptChanges(int parentEditLevel, bool parentBindingEdit)
    {
      if (!parentBindingEdit)
        AcceptChanges(parentEditLevel);
    }
 
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected virtual void CopyingState()
    {
    }
 
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected virtual void CopyStateComplete()
    {
    }
 
    [EditorBrowsable(EditorBrowsableState.Never)]
    protected internal void CopyState(int parentEditLevel)
    {
      CopyingState();
 
      Type currentType = this.GetType();
      var state = new MobileDictionary<string, object>();
 
      if (this.EditLevel + 1 > parentEditLevel)
        throw new UndoException(string.Format(Resources.EditLevelMismatchException, "CopyState"), this.GetType().Name, null, this.EditLevel, parentEditLevel - 1);
 
      do
      {
        var currentTypeName = currentType.FullName;
        // get the list of fields in this type
        List<DynamicMemberHandle> handlers =
          UndoableHandler.GetCachedFieldHandlers(currentType);
        foreach (var h in handlers)
        {
          var value = h.DynamicMemberGet(this);
          var fieldName = GetFieldName(currentTypeName, h.MemberName);
 
          if (typeof(IUndoableObject).IsAssignableFrom(h.MemberType))
          {
            if (value == null)
            {
              // variable has no value - store that fact
              state.Add(fieldName, null);
            }
            else
            {
              // this is a child object, cascade the call
              ((IUndoableObject)value).CopyState(this.EditLevel + 1, BindingEdit);
            }
          }
          else if (value is IMobileObject)
          {
            // this is a mobile object, store the serialized value
            using MemoryStream buffer = new MemoryStream();
            var formatter = SerializationFormatterFactory.GetFormatter(ApplicationContext);
            formatter.Serialize(buffer, value);
            state.Add(fieldName, buffer.ToArray());
          }
          else
          {
            // this is a normal field, simply trap the value
            state.Add(fieldName, value);
          }
        }
 
        currentType = currentType.BaseType;
      } while (currentType != typeof(UndoableBase));
 
      // serialize the state and stack it
      using (MemoryStream buffer = new MemoryStream())
      {
        var formatter = SerializationFormatterFactory.GetFormatter(ApplicationContext);
        formatter.Serialize(buffer, state);
        _stateStack.Push(buffer.ToArray());
      }
      CopyStateComplete();
    }
 
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected virtual void UndoChangesComplete()
    {
    }
 
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected virtual void UndoingChanges()
    {
    }
 
    [EditorBrowsable(EditorBrowsableState.Never)]
    protected internal void UndoChanges(int parentEditLevel)
    {
      UndoingChanges();
 
      // if we are a child object we might be asked to
      // undo below the level of stacked states,
      // so just do nothing in that case
      if (EditLevel > 0)
      {
        if (this.EditLevel - 1 != parentEditLevel)
          throw new UndoException(string.Format(Resources.EditLevelMismatchException, "UndoChanges"), this.GetType().Name, null, this.EditLevel, parentEditLevel + 1);
 
        MobileDictionary<string, object> state;
        using (MemoryStream buffer = new MemoryStream(_stateStack.Pop()))
        {
          buffer.Position = 0;
          var formatter = SerializationFormatterFactory.GetFormatter(ApplicationContext);
          state = (MobileDictionary<string, object>)formatter.Deserialize(buffer);
        }
 
        Type currentType = this.GetType();
 
        do
        {
          var currentTypeName = currentType.FullName;
 
          // get the list of fields in this type
          List<DynamicMemberHandle> handlers = UndoableHandler.GetCachedFieldHandlers(currentType);
          foreach (var h in handlers)
          {
            // the field is undoable, so restore its value
            var value = h.DynamicMemberGet(this);
            var fieldName = GetFieldName(currentTypeName, h.MemberName);
 
            if (typeof(IUndoableObject).IsAssignableFrom(h.MemberType))
            {
              // this is a child object
              // see if the previous value was empty
              //if (state.Contains(h.MemberName))
              if (state.Contains(fieldName))
              {
                // previous value was empty - restore to empty
                h.DynamicMemberSet(this, null);
              }
              else
              {
                // make sure the variable has a value
                if (value != null)
                {
                  // this is a child object, cascade the call.
                  ((IUndoableObject)value).UndoChanges(this.EditLevel, BindingEdit);
                }
              }
            }
            else if (value is IMobileObject && state[fieldName] != null)
            {
              // this is a mobile object, deserialize the value
              using MemoryStream buffer = new MemoryStream((byte[])state[fieldName]);
              buffer.Position = 0;
              var formatter = SerializationFormatterFactory.GetFormatter(ApplicationContext);
              var obj = formatter.Deserialize(buffer);
              h.DynamicMemberSet(this, obj);
            }
            else
            {
              // this is a regular field, restore its value
              h.DynamicMemberSet(this, state[fieldName]);
            }
          }
 
          currentType = currentType.BaseType;
        } while (currentType != typeof(UndoableBase));
      }
      UndoChangesComplete();
    }
 
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected virtual void AcceptingChanges()
    {
    }
 
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected virtual void AcceptChangesComplete()
    {
    }
 
    [EditorBrowsable(EditorBrowsableState.Never)]
    protected internal void AcceptChanges(int parentEditLevel)
    {
      AcceptingChanges();
 
      if (this.EditLevel - 1 != parentEditLevel)
        throw new UndoException(string.Format(Resources.EditLevelMismatchException, "AcceptChanges"), this.GetType().Name, null, this.EditLevel, parentEditLevel + 1);
 
      if (EditLevel > 0)
      {
        _stateStack.Pop();
        Type currentType = this.GetType();
 
        do
        {
          // get the list of fields in this type
          List<DynamicMemberHandle> handlers = UndoableHandler.GetCachedFieldHandlers(currentType);
          foreach (var h in handlers)
          {
            // the field is undoable so see if it is a child object
            if (typeof(Csla.Core.IUndoableObject).IsAssignableFrom(h.MemberType))
            {
              object value = h.DynamicMemberGet(this);
              // make sure the variable has a value
              if (value != null)
              {
                // it is a child object so cascade the call
                ((Core.IUndoableObject)value).AcceptChanges(this.EditLevel, BindingEdit);
              }
            }
          }
 
          currentType = currentType.BaseType;
        } while (currentType != typeof(UndoableBase));
      }
      AcceptChangesComplete();
    }
 
    private static string GetFieldName(string typeName, string memberName)
    {
      return typeName + "." + memberName;
    }
 
    internal static void ResetChildEditLevel(IUndoableObject child, int parentEditLevel, bool bindingEdit)
    {
      int targetLevel = parentEditLevel;
      if (bindingEdit && targetLevel > 0 && child is not FieldManager.FieldDataManager)
        targetLevel--;
      // if item's edit level is too high,
      // reduce it to match list
      while (child.EditLevel > targetLevel)
        child.AcceptChanges(targetLevel, false);
      // if item's edit level is too low,
      // increase it to match list
      while (child.EditLevel < targetLevel)
        child.CopyState(targetLevel, false);
    }
 
    protected override void OnGetState(SerializationInfo info, StateMode mode)
    {
      if (mode != StateMode.Undo)
      {
        info.AddValue("_bindingEdit", _bindingEdit);
        if (_stateStack.Count > 0)
        {
          var stackArray = _stateStack.ToArray();
          info.AddValue("_stateStack", stackArray);
        }
      }
      base.OnGetState(info, mode);
    }
 
    protected override void OnSetState(SerializationInfo info, StateMode mode)
    {
      if (mode != StateMode.Undo)
      {
        _bindingEdit = info.GetValue<bool>("_bindingEdit");
        if (info.Values.ContainsKey("_stateStack"))
        {
          var stackArray = info.GetValue<byte[][]>("_stateStack");
          _stateStack.Clear();
          foreach (var item in stackArray.Reverse())
            _stateStack.Push(item);
        }
      }
      base.OnSetState(info, mode);
    }
  }
}