source: branches/2434_crossvalidation/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/UndoStack.cs @ 18242

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
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// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using ICSharpCode.AvalonEdit.Utils;

namespace ICSharpCode.AvalonEdit.Document
{
  /// <summary>
  /// Undo stack implementation.
  /// </summary>
  [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
  public sealed class UndoStack : INotifyPropertyChanged
  {
    /// undo stack is listening for changes
    internal const int StateListen = 0;
    /// undo stack is reverting/repeating a set of changes
    internal const int StatePlayback = 1;
    // undo stack is reverting/repeating a set of changes and modifies the document to do this
    internal const int StatePlaybackModifyDocument = 2;
    /// state is used for checking that noone but the UndoStack performs changes
    /// during Undo events
    internal int state = StateListen;
    
    Deque<IUndoableOperation> undostack = new Deque<IUndoableOperation>();
    Deque<IUndoableOperation> redostack = new Deque<IUndoableOperation>();
    int sizeLimit = int.MaxValue;
    
    int undoGroupDepth;
    int actionCountInUndoGroup;
    int optionalActionCount;
    object lastGroupDescriptor;
    bool allowContinue;
    
    #region IsOriginalFile implementation
    // implements feature request SD2-784 - File still considered dirty after undoing all changes
    
    /// <summary>
    /// Number of times undo must be executed until the original state is reached.
    /// Negative: number of times redo must be executed until the original state is reached.
    /// Special case: int.MinValue == original state is unreachable
    /// </summary>
    int elementsOnUndoUntilOriginalFile;
    
    bool isOriginalFile = true;
    
    /// <summary>
    /// Gets whether the document is currently in its original state (no modifications).
    /// </summary>
    public bool IsOriginalFile {
      get { return isOriginalFile; }
    }
    
    void RecalcIsOriginalFile()
    {
      bool newIsOriginalFile = (elementsOnUndoUntilOriginalFile == 0);
      if (newIsOriginalFile != isOriginalFile) {
        isOriginalFile = newIsOriginalFile;
        NotifyPropertyChanged("IsOriginalFile");
      }
    }
    
    /// <summary>
    /// Marks the current state as original. Discards any previous "original" markers.
    /// </summary>
    public void MarkAsOriginalFile()
    {
      elementsOnUndoUntilOriginalFile = 0;
      RecalcIsOriginalFile();
    }
    
    /// <summary>
    /// Discards the current "original" marker.
    /// </summary>
    public void DiscardOriginalFileMarker()
    {
      elementsOnUndoUntilOriginalFile = int.MinValue;
      RecalcIsOriginalFile();
    }
    
    void FileModified(int newElementsOnUndoStack)
    {
      if (elementsOnUndoUntilOriginalFile == int.MinValue)
        return;
      
      elementsOnUndoUntilOriginalFile += newElementsOnUndoStack;
      if (elementsOnUndoUntilOriginalFile > undostack.Count)
        elementsOnUndoUntilOriginalFile = int.MinValue;
      
      // don't call RecalcIsOriginalFile(): wait until end of undo group
    }
    #endregion
    
    /// <summary>
    /// Gets if the undo stack currently accepts changes.
    /// Is false while an undo action is running.
    /// </summary>
    public bool AcceptChanges {
      get { return state == StateListen; }
    }
    
    /// <summary>
    /// Gets if there are actions on the undo stack.
    /// Use the PropertyChanged event to listen to changes of this property.
    /// </summary>
    public bool CanUndo {
      get { return undostack.Count > 0; }
    }
    
    /// <summary>
    /// Gets if there are actions on the redo stack.
    /// Use the PropertyChanged event to listen to changes of this property.
    /// </summary>
    public bool CanRedo {
      get { return redostack.Count > 0; }
    }
    
    /// <summary>
    /// Gets/Sets the limit on the number of items on the undo stack.
    /// </summary>
    /// <remarks>The size limit is enforced only on the number of stored top-level undo groups.
    /// Elements within undo groups do not count towards the size limit.</remarks>
    public int SizeLimit {
      get { return sizeLimit; }
      set {
        if (value < 0)
          ThrowUtil.CheckNotNegative(value, "value");
        if (sizeLimit != value) {
          sizeLimit = value;
          NotifyPropertyChanged("SizeLimit");
          if (undoGroupDepth == 0)
            EnforceSizeLimit();
        }
      }
    }
    
    void EnforceSizeLimit()
    {
      Debug.Assert(undoGroupDepth == 0);
      while (undostack.Count > sizeLimit)
        undostack.PopFront();
      while (redostack.Count > sizeLimit)
        redostack.PopFront();
    }
    
    /// <summary>
    /// If an undo group is open, gets the group descriptor of the current top-level
    /// undo group.
    /// If no undo group is open, gets the group descriptor from the previous undo group.
    /// </summary>
    /// <remarks>The group descriptor can be used to join adjacent undo groups:
    /// use a group descriptor to mark your changes, and on the second action,
    /// compare LastGroupDescriptor and use <see cref="StartContinuedUndoGroup"/> if you
    /// want to join the undo groups.</remarks>
    public object LastGroupDescriptor {
      get { return lastGroupDescriptor; }
    }
    
    /// <summary>
    /// Starts grouping changes.
    /// Maintains a counter so that nested calls are possible.
    /// </summary>
    public void StartUndoGroup()
    {
      StartUndoGroup(null);
    }
    
    /// <summary>
    /// Starts grouping changes.
    /// Maintains a counter so that nested calls are possible.
    /// </summary>
    /// <param name="groupDescriptor">An object that is stored with the undo group.
    /// If this is not a top-level undo group, the parameter is ignored.</param>
    public void StartUndoGroup(object groupDescriptor)
    {
      if (undoGroupDepth == 0) {
        actionCountInUndoGroup = 0;
        optionalActionCount = 0;
        lastGroupDescriptor = groupDescriptor;
      }
      undoGroupDepth++;
      //Util.LoggingService.Debug("Open undo group (new depth=" + undoGroupDepth + ")");
    }
    
    /// <summary>
    /// Starts grouping changes, continuing with the previously closed undo group if possible.
    /// Maintains a counter so that nested calls are possible.
    /// If the call to StartContinuedUndoGroup is a nested call, it behaves exactly
    /// as <see cref="StartUndoGroup()"/>, only top-level calls can continue existing undo groups.
    /// </summary>
    /// <param name="groupDescriptor">An object that is stored with the undo group.
    /// If this is not a top-level undo group, the parameter is ignored.</param>
    public void StartContinuedUndoGroup(object groupDescriptor = null)
    {
      if (undoGroupDepth == 0) {
        actionCountInUndoGroup = (allowContinue && undostack.Count > 0) ? 1 : 0;
        optionalActionCount = 0;
        lastGroupDescriptor = groupDescriptor;
      }
      undoGroupDepth++;
      //Util.LoggingService.Debug("Continue undo group (new depth=" + undoGroupDepth + ")");
    }
    
    /// <summary>
    /// Stops grouping changes.
    /// </summary>
    public void EndUndoGroup()
    {
      if (undoGroupDepth == 0) throw new InvalidOperationException("There are no open undo groups");
      undoGroupDepth--;
      //Util.LoggingService.Debug("Close undo group (new depth=" + undoGroupDepth + ")");
      if (undoGroupDepth == 0) {
        Debug.Assert(state == StateListen || actionCountInUndoGroup == 0);
        allowContinue = true;
        if (actionCountInUndoGroup == optionalActionCount) {
          // only optional actions: don't store them
          for (int i = 0; i < optionalActionCount; i++) {
            undostack.PopBack();
          }
          allowContinue = false;
        } else if (actionCountInUndoGroup > 1) {
          // combine all actions within the group into a single grouped action
          undostack.PushBack(new UndoOperationGroup(undostack, actionCountInUndoGroup));
          FileModified(-actionCountInUndoGroup + 1 + optionalActionCount);
        }
        //if (state == StateListen) {
        EnforceSizeLimit();
        RecalcIsOriginalFile(); // can raise event
        //}
      }
    }
    
    /// <summary>
    /// Throws an InvalidOperationException if an undo group is current open.
    /// </summary>
    void ThrowIfUndoGroupOpen()
    {
      if (undoGroupDepth != 0) {
        undoGroupDepth = 0;
        throw new InvalidOperationException("No undo group should be open at this point");
      }
      if (state != StateListen) {
        throw new InvalidOperationException("This method cannot be called while an undo operation is being performed");
      }
    }
    
    List<TextDocument> affectedDocuments;
    
    internal void RegisterAffectedDocument(TextDocument document)
    {
      if (affectedDocuments == null)
        affectedDocuments = new List<TextDocument>();
      if (!affectedDocuments.Contains(document)) {
        affectedDocuments.Add(document);
        document.BeginUpdate();
      }
    }
    
    void CallEndUpdateOnAffectedDocuments()
    {
      if (affectedDocuments != null) {
        foreach (TextDocument doc in affectedDocuments) {
          doc.EndUpdate();
        }
        affectedDocuments = null;
      }
    }
    
    /// <summary>
    /// Call this method to undo the last operation on the stack
    /// </summary>
    public void Undo()
    {
      ThrowIfUndoGroupOpen();
      if (undostack.Count > 0) {
        // disallow continuing undo groups after undo operation
        lastGroupDescriptor = null; allowContinue = false;
        // fetch operation to undo and move it to redo stack
        IUndoableOperation uedit = undostack.PopBack();
        redostack.PushBack(uedit);
        state = StatePlayback;
        try {
          RunUndo(uedit);
        } finally {
          state = StateListen;
          FileModified(-1);
          CallEndUpdateOnAffectedDocuments();
        }
        RecalcIsOriginalFile();
        if (undostack.Count == 0)
          NotifyPropertyChanged("CanUndo");
        if (redostack.Count == 1)
          NotifyPropertyChanged("CanRedo");
      }
    }
    
    internal void RunUndo(IUndoableOperation op)
    {
      IUndoableOperationWithContext opWithCtx = op as IUndoableOperationWithContext;
      if (opWithCtx != null)
        opWithCtx.Undo(this);
      else
        op.Undo();
    }
    
    /// <summary>
    /// Call this method to redo the last undone operation
    /// </summary>
    public void Redo()
    {
      ThrowIfUndoGroupOpen();
      if (redostack.Count > 0) {
        lastGroupDescriptor = null; allowContinue = false;
        IUndoableOperation uedit = redostack.PopBack();
        undostack.PushBack(uedit);
        state = StatePlayback;
        try {
          RunRedo(uedit);
        } finally {
          state = StateListen;
          FileModified(1);
          CallEndUpdateOnAffectedDocuments();
        }
        RecalcIsOriginalFile();
        if (redostack.Count == 0)
          NotifyPropertyChanged("CanRedo");
        if (undostack.Count == 1)
          NotifyPropertyChanged("CanUndo");
      }
    }
    
    internal void RunRedo(IUndoableOperation op)
    {
      IUndoableOperationWithContext opWithCtx = op as IUndoableOperationWithContext;
      if (opWithCtx != null)
        opWithCtx.Redo(this);
      else
        op.Redo();
    }
    
    /// <summary>
    /// Call this method to push an UndoableOperation on the undostack.
    /// The redostack will be cleared if you use this method.
    /// </summary>
    public void Push(IUndoableOperation operation)
    {
      Push(operation, false);
    }
    
    /// <summary>
    /// Call this method to push an UndoableOperation on the undostack.
    /// However, the operation will be only stored if the undo group contains a
    /// non-optional operation.
    /// Use this method to store the caret position/selection on the undo stack to
    /// prevent having only actions that affect only the caret and not the document.
    /// </summary>
    public void PushOptional(IUndoableOperation operation)
    {
      if (undoGroupDepth == 0)
        throw new InvalidOperationException("Cannot use PushOptional outside of undo group");
      Push(operation, true);
    }
    
    void Push(IUndoableOperation operation, bool isOptional)
    {
      if (operation == null) {
        throw new ArgumentNullException("operation");
      }
      
      if (state == StateListen && sizeLimit > 0) {
        bool wasEmpty = undostack.Count == 0;
        
        bool needsUndoGroup = undoGroupDepth == 0;
        if (needsUndoGroup) StartUndoGroup();
        undostack.PushBack(operation);
        actionCountInUndoGroup++;
        if (isOptional)
          optionalActionCount++;
        else
          FileModified(1);
        if (needsUndoGroup) EndUndoGroup();
        if (wasEmpty)
          NotifyPropertyChanged("CanUndo");
        ClearRedoStack();
      }
    }
    
    /// <summary>
    /// Call this method, if you want to clear the redo stack
    /// </summary>
    public void ClearRedoStack()
    {
      if (redostack.Count != 0) {
        redostack.Clear();
        NotifyPropertyChanged("CanRedo");
        // if the "original file" marker is on the redo stack: remove it
        if (elementsOnUndoUntilOriginalFile < 0)
          elementsOnUndoUntilOriginalFile = int.MinValue;
      }
    }
    
    /// <summary>
    /// Clears both the undo and redo stack.
    /// </summary>
    public void ClearAll()
    {
      ThrowIfUndoGroupOpen();
      actionCountInUndoGroup = 0;
      optionalActionCount = 0;
      if (undostack.Count != 0) {
        lastGroupDescriptor = null;
        allowContinue = false;
        undostack.Clear();
        NotifyPropertyChanged("CanUndo");
      }
      ClearRedoStack();
    }
    
    internal void Push(TextDocument document, DocumentChangeEventArgs e)
    {
      if (state == StatePlayback)
        throw new InvalidOperationException("Document changes during undo/redo operations are not allowed.");
      if (state == StatePlaybackModifyDocument)
        state = StatePlayback; // allow only 1 change per expected modification
      else
        Push(new DocumentChangeOperation(document, e));
    }
    
    /// <summary>
    /// Is raised when a property (CanUndo, CanRedo) changed.
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;
    
    void NotifyPropertyChanged(string propertyName)
    {
      if (PropertyChanged != null)
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
  }
}