source: branches/2915-AbsoluteSymbol/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/TextDocument.cs @ 16300

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// 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.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// 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
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Diagnostics;
using System.Globalization;
using System.Threading;
using ICSharpCode.AvalonEdit.Utils;
using ICSharpCode.NRefactory;
using ICSharpCode.NRefactory.Editor;

namespace ICSharpCode.AvalonEdit.Document
{
  /// <summary>
  /// This class is the main class of the text model. Basically, it is a <see cref="System.Text.StringBuilder"/> with events.
  /// </summary>
  /// <remarks>
  /// <b>Thread safety:</b>
  /// <inheritdoc cref="VerifyAccess"/>
  /// <para>However, there is a single method that is thread-safe: <see cref="CreateSnapshot()"/> (and its overloads).</para>
  /// </remarks>
  public sealed class TextDocument : IDocument, INotifyPropertyChanged
  {
    #region Thread ownership
    readonly object lockObject = new object();
    Thread owner = Thread.CurrentThread;
    
    /// <summary>
    /// Verifies that the current thread is the documents owner thread.
    /// Throws an <see cref="InvalidOperationException"/> if the wrong thread accesses the TextDocument.
    /// </summary>
    /// <remarks>
    /// <para>The TextDocument class is not thread-safe. A document instance expects to have a single owner thread
    /// and will throw an <see cref="InvalidOperationException"/> when accessed from another thread.
    /// It is possible to change the owner thread using the <see cref="SetOwnerThread"/> method.</para>
    /// </remarks>
    public void VerifyAccess()
    {
      if (Thread.CurrentThread != owner)
        throw new InvalidOperationException("TextDocument can be accessed only from the thread that owns it.");
    }
    
    /// <summary>
    /// Transfers ownership of the document to another thread. This method can be used to load
    /// a file into a TextDocument on a background thread and then transfer ownership to the UI thread
    /// for displaying the document.
    /// </summary>
    /// <remarks>
    /// <inheritdoc cref="VerifyAccess"/>
    /// <para>
    /// The owner can be set to null, which means that no thread can access the document. But, if the document
    /// has no owner thread, any thread may take ownership by calling <see cref="SetOwnerThread"/>.
    /// </para>
    /// </remarks>
    public void SetOwnerThread(Thread newOwner)
    {
      // We need to lock here to ensure that in the null owner case,
      // only one thread succeeds in taking ownership.
      lock (lockObject) {
        if (owner != null) {
          VerifyAccess();
        }
        owner = newOwner;
      }
    }
    #endregion
    
    #region Fields + Constructor
    readonly Rope<char> rope;
    readonly DocumentLineTree lineTree;
    readonly LineManager lineManager;
    readonly TextAnchorTree anchorTree;
    readonly TextSourceVersionProvider versionProvider = new TextSourceVersionProvider();
    
    /// <summary>
    /// Create an empty text document.
    /// </summary>
    public TextDocument()
      : this(string.Empty)
    {
    }
    
    /// <summary>
    /// Create a new text document with the specified initial text.
    /// </summary>
    public TextDocument(IEnumerable<char> initialText)
    {
      if (initialText == null)
        throw new ArgumentNullException("initialText");
      rope = new Rope<char>(initialText);
      lineTree = new DocumentLineTree(this);
      lineManager = new LineManager(lineTree, this);
      lineTrackers.CollectionChanged += delegate {
        lineManager.UpdateListOfLineTrackers();
      };
      
      anchorTree = new TextAnchorTree(this);
      undoStack = new UndoStack();
      FireChangeEvents();
    }
    
    /// <summary>
    /// Create a new text document with the specified initial text.
    /// </summary>
    public TextDocument(ITextSource initialText)
      : this(GetTextFromTextSource(initialText))
    {
    }
    
    // gets the text from a text source, directly retrieving the underlying rope where possible
    static IEnumerable<char> GetTextFromTextSource(ITextSource textSource)
    {
      if (textSource == null)
        throw new ArgumentNullException("textSource");
      
      #if NREFACTORY
      if (textSource is ReadOnlyDocument)
        textSource = textSource.CreateSnapshot(); // retrieve underlying text source, which might be a RopeTextSource
      #endif
      
      RopeTextSource rts = textSource as RopeTextSource;
      if (rts != null)
        return rts.GetRope();
      
      TextDocument doc = textSource as TextDocument;
      if (doc != null)
        return doc.rope;
      
      return textSource.Text;
    }
    #endregion
    
    #region Text
    void ThrowIfRangeInvalid(int offset, int length)
    {
      if (offset < 0 || offset > rope.Length) {
        throw new ArgumentOutOfRangeException("offset", offset, "0 <= offset <= " + rope.Length.ToString(CultureInfo.InvariantCulture));
      }
      if (length < 0 || offset + length > rope.Length) {
        throw new ArgumentOutOfRangeException("length", length, "0 <= length, offset(" + offset + ")+length <= " + rope.Length.ToString(CultureInfo.InvariantCulture));
      }
    }
    
    /// <inheritdoc/>
    public string GetText(int offset, int length)
    {
      VerifyAccess();
      return rope.ToString(offset, length);
    }
    
    /// <summary>
    /// Retrieves the text for a portion of the document.
    /// </summary>
    public string GetText(ISegment segment)
    {
      if (segment == null)
        throw new ArgumentNullException("segment");
      return GetText(segment.Offset, segment.Length);
    }
    
    /// <inheritdoc/>
    public int IndexOf(char c, int startIndex, int count)
    {
      DebugVerifyAccess();
      return rope.IndexOf(c, startIndex, count);
    }
    
    /// <inheritdoc/>
    public int LastIndexOf(char c, int startIndex, int count)
    {
      DebugVerifyAccess();
      return rope.LastIndexOf(c, startIndex, count);
    }
    
    /// <inheritdoc/>
    public int IndexOfAny(char[] anyOf, int startIndex, int count)
    {
      DebugVerifyAccess(); // frequently called (NewLineFinder), so must be fast in release builds
      return rope.IndexOfAny(anyOf, startIndex, count);
    }
    
    /// <inheritdoc/>
    public int IndexOf(string searchText, int startIndex, int count, StringComparison comparisonType)
    {
      DebugVerifyAccess();
      return rope.IndexOf(searchText, startIndex, count, comparisonType);
    }
    
    /// <inheritdoc/>
    public int LastIndexOf(string searchText, int startIndex, int count, StringComparison comparisonType)
    {
      DebugVerifyAccess();
      return rope.LastIndexOf(searchText, startIndex, count, comparisonType);
    }
    
    /// <inheritdoc/>
    public char GetCharAt(int offset)
    {
      DebugVerifyAccess(); // frequently called, so must be fast in release builds
      return rope[offset];
    }
    
    WeakReference cachedText;
    
    /// <summary>
    /// Gets/Sets the text of the whole document.
    /// </summary>
    public string Text {
      get {
        VerifyAccess();
        string completeText = cachedText != null ? (cachedText.Target as string) : null;
        if (completeText == null) {
          completeText = rope.ToString();
          cachedText = new WeakReference(completeText);
        }
        return completeText;
      }
      set {
        VerifyAccess();
        if (value == null)
          throw new ArgumentNullException("value");
        Replace(0, rope.Length, value);
      }
    }
    
    /// <inheritdoc/>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    public event EventHandler TextChanged;
    
    event EventHandler IDocument.ChangeCompleted {
      add { this.TextChanged += value; }
      remove { this.TextChanged -= value; }
    }
    
    /// <inheritdoc/>
    public int TextLength {
      get {
        VerifyAccess();
        return rope.Length;
      }
    }
    
    /// <summary>
    /// Is raised when the TextLength property changes.
    /// </summary>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    [Obsolete("This event will be removed in a future version; use the PropertyChanged event instead")]
    public event EventHandler TextLengthChanged;
    
    /// <summary>
    /// Is raised when one of the properties <see cref="Text"/>, <see cref="TextLength"/>, <see cref="LineCount"/>,
    /// <see cref="UndoStack"/> changes.
    /// </summary>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    public event PropertyChangedEventHandler PropertyChanged;
    
    /// <summary>
    /// Is raised before the document changes.
    /// </summary>
    /// <remarks>
    /// <para>Here is the order in which events are raised during a document update:</para>
    /// <list type="bullet">
    /// <item><description><b><see cref="BeginUpdate">BeginUpdate()</see></b></description>
    ///   <list type="bullet">
    ///   <item><description>Start of change group (on undo stack)</description></item>
    ///   <item><description><see cref="UpdateStarted"/> event is raised</description></item>
    ///   </list></item>
    /// <item><description><b><see cref="Insert(int,string)">Insert()</see> / <see cref="Remove(int,int)">Remove()</see> / <see cref="Replace(int,int,string)">Replace()</see></b></description>
    ///   <list type="bullet">
    ///   <item><description><see cref="Changing"/> event is raised</description></item>
    ///   <item><description>The document is changed</description></item>
    ///   <item><description><see cref="TextAnchor.Deleted">TextAnchor.Deleted</see> event is raised if anchors were
    ///     in the deleted text portion</description></item>
    ///   <item><description><see cref="Changed"/> event is raised</description></item>
    ///   </list></item>
    /// <item><description><b><see cref="EndUpdate">EndUpdate()</see></b></description>
    ///   <list type="bullet">
    ///   <item><description><see cref="TextChanged"/> event is raised</description></item>
    ///   <item><description><see cref="PropertyChanged"/> event is raised (for the Text, TextLength, LineCount properties, in that order)</description></item>
    ///   <item><description>End of change group (on undo stack)</description></item>
    ///   <item><description><see cref="UpdateFinished"/> event is raised</description></item>
    ///   </list></item>
    /// </list>
    /// <para>
    /// If the insert/remove/replace methods are called without a call to <c>BeginUpdate()</c>,
    /// they will call <c>BeginUpdate()</c> and <c>EndUpdate()</c> to ensure no change happens outside of <c>UpdateStarted</c>/<c>UpdateFinished</c>.
    /// </para><para>
    /// There can be multiple document changes between the <c>BeginUpdate()</c> and <c>EndUpdate()</c> calls.
    /// In this case, the events associated with EndUpdate will be raised only once after the whole document update is done.
    /// </para><para>
    /// The <see cref="UndoStack"/> listens to the <c>UpdateStarted</c> and <c>UpdateFinished</c> events to group all changes into a single undo step.
    /// </para>
    /// </remarks>
    public event EventHandler<DocumentChangeEventArgs> Changing;
    
    // Unfortunately EventHandler<T> is invariant, so we have to use two separate events
    private event EventHandler<TextChangeEventArgs> textChanging;
    
    event EventHandler<TextChangeEventArgs> IDocument.TextChanging {
      add { textChanging += value; }
      remove { textChanging -= value; }
    }
    
    /// <summary>
    /// Is raised after the document has changed.
    /// </summary>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    public event EventHandler<DocumentChangeEventArgs> Changed;
    
    private event EventHandler<TextChangeEventArgs> textChanged;
    
    event EventHandler<TextChangeEventArgs> IDocument.TextChanged {
      add { textChanged += value; }
      remove { textChanged -= value; }
    }
    
    /// <summary>
    /// Creates a snapshot of the current text.
    /// </summary>
    /// <remarks>
    /// <para>This method returns an immutable snapshot of the document, and may be safely called even when
    /// the document's owner thread is concurrently modifying the document.
    /// </para><para>
    /// This special thread-safety guarantee is valid only for TextDocument.CreateSnapshot(), not necessarily for other
    /// classes implementing ITextSource.CreateSnapshot().
    /// </para><para>
    /// </para>
    /// </remarks>
    public ITextSource CreateSnapshot()
    {
      lock (lockObject) {
        return new RopeTextSource(rope, versionProvider.CurrentVersion);
      }
    }
    
    /// <summary>
    /// Creates a snapshot of a part of the current text.
    /// </summary>
    /// <remarks><inheritdoc cref="CreateSnapshot()"/></remarks>
    public ITextSource CreateSnapshot(int offset, int length)
    {
      lock (lockObject) {
        return new RopeTextSource(rope.GetRange(offset, length));
      }
    }
    
    #if NREFACTORY
    /// <inheritdoc/>
    public IDocument CreateDocumentSnapshot()
    {
      return new ReadOnlyDocument(this, fileName);
    }
    #endif
    
    /// <inheritdoc/>
    public ITextSourceVersion Version {
      get { return versionProvider.CurrentVersion; }
    }
    
    /// <inheritdoc/>
    public System.IO.TextReader CreateReader()
    {
      lock (lockObject) {
        return new RopeTextReader(rope);
      }
    }
    
    /// <inheritdoc/>
    public System.IO.TextReader CreateReader(int offset, int length)
    {
      lock (lockObject) {
        return new RopeTextReader(rope.GetRange(offset, length));
      }
    }
    
    /// <inheritdoc/>
    public void WriteTextTo(System.IO.TextWriter writer)
    {
      VerifyAccess();
      rope.WriteTo(writer, 0, rope.Length);
    }
    
    /// <inheritdoc/>
    public void WriteTextTo(System.IO.TextWriter writer, int offset, int length)
    {
      VerifyAccess();
      rope.WriteTo(writer, offset, length);
    }
    #endregion
    
    #region BeginUpdate / EndUpdate
    int beginUpdateCount;
    
    /// <summary>
    /// Gets if an update is running.
    /// </summary>
    /// <remarks><inheritdoc cref="BeginUpdate"/></remarks>
    public bool IsInUpdate {
      get {
        VerifyAccess();
        return beginUpdateCount > 0;
      }
    }
    
    /// <summary>
    /// Immediately calls <see cref="BeginUpdate()"/>,
    /// and returns an IDisposable that calls <see cref="EndUpdate()"/>.
    /// </summary>
    /// <remarks><inheritdoc cref="BeginUpdate"/></remarks>
    public IDisposable RunUpdate()
    {
      BeginUpdate();
      return new CallbackOnDispose(EndUpdate);
    }
    
    /// <summary>
    /// <para>Begins a group of document changes.</para>
    /// <para>Some events are suspended until EndUpdate is called, and the <see cref="UndoStack"/> will
    /// group all changes into a single action.</para>
    /// <para>Calling BeginUpdate several times increments a counter, only after the appropriate number
    /// of EndUpdate calls the events resume their work.</para>
    /// </summary>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    public void BeginUpdate()
    {
      VerifyAccess();
      if (inDocumentChanging)
        throw new InvalidOperationException("Cannot change document within another document change.");
      beginUpdateCount++;
      if (beginUpdateCount == 1) {
        undoStack.StartUndoGroup();
        if (UpdateStarted != null)
          UpdateStarted(this, EventArgs.Empty);
      }
    }
    
    /// <summary>
    /// Ends a group of document changes.
    /// </summary>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    public void EndUpdate()
    {
      VerifyAccess();
      if (inDocumentChanging)
        throw new InvalidOperationException("Cannot end update within document change.");
      if (beginUpdateCount == 0)
        throw new InvalidOperationException("No update is active.");
      if (beginUpdateCount == 1) {
        // fire change events inside the change group - event handlers might add additional
        // document changes to the change group
        FireChangeEvents();
        undoStack.EndUndoGroup();
        beginUpdateCount = 0;
        if (UpdateFinished != null)
          UpdateFinished(this, EventArgs.Empty);
      } else {
        beginUpdateCount -= 1;
      }
    }
    
    /// <summary>
    /// Occurs when a document change starts.
    /// </summary>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    public event EventHandler UpdateStarted;
    
    /// <summary>
    /// Occurs when a document change is finished.
    /// </summary>
    /// <remarks><inheritdoc cref="Changing"/></remarks>
    public event EventHandler UpdateFinished;
    
    void IDocument.StartUndoableAction()
    {
      BeginUpdate();
    }
    
    void IDocument.EndUndoableAction()
    {
      EndUpdate();
    }
    
    IDisposable IDocument.OpenUndoGroup()
    {
      return RunUpdate();
    }
    #endregion
    
    #region Fire events after update
    int oldTextLength;
    int oldLineCount;
    bool fireTextChanged;
    
    /// <summary>
    /// Fires TextChanged, TextLengthChanged, LineCountChanged if required.
    /// </summary>
    internal void FireChangeEvents()
    {
      // it may be necessary to fire the event multiple times if the document is changed
      // from inside the event handlers
      while (fireTextChanged) {
        fireTextChanged = false;
        if (TextChanged != null)
          TextChanged(this, EventArgs.Empty);
        OnPropertyChanged("Text");
        
        int textLength = rope.Length;
        if (textLength != oldTextLength) {
          oldTextLength = textLength;
          if (TextLengthChanged != null)
            TextLengthChanged(this, EventArgs.Empty);
          OnPropertyChanged("TextLength");
        }
        int lineCount = lineTree.LineCount;
        if (lineCount != oldLineCount) {
          oldLineCount = lineCount;
          if (LineCountChanged != null)
            LineCountChanged(this, EventArgs.Empty);
          OnPropertyChanged("LineCount");
        }
      }
    }
    
    void OnPropertyChanged(string propertyName)
    {
      if (PropertyChanged != null)
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
    #endregion
    
    #region Insert / Remove  / Replace
    /// <summary>
    /// Inserts text.
    /// </summary>
    /// <param name="offset">The offset at which the text is inserted.</param>
    /// <param name="text">The new text.</param>
    /// <remarks>
    /// Anchors positioned exactly at the insertion offset will move according to their movement type.
    /// For AnchorMovementType.Default, they will move behind the inserted text.
    /// The caret will also move behind the inserted text.
    /// </remarks>
    public void Insert(int offset, string text)
    {
      Replace(offset, 0, new StringTextSource(text), null);
    }
    
    /// <summary>
    /// Inserts text.
    /// </summary>
    /// <param name="offset">The offset at which the text is inserted.</param>
    /// <param name="text">The new text.</param>
    /// <remarks>
    /// Anchors positioned exactly at the insertion offset will move according to their movement type.
    /// For AnchorMovementType.Default, they will move behind the inserted text.
    /// The caret will also move behind the inserted text.
    /// </remarks>
    public void Insert(int offset, ITextSource text)
    {
      Replace(offset, 0, text, null);
    }
    
    /// <summary>
    /// Inserts text.
    /// </summary>
    /// <param name="offset">The offset at which the text is inserted.</param>
    /// <param name="text">The new text.</param>
    /// <param name="defaultAnchorMovementType">
    /// Anchors positioned exactly at the insertion offset will move according to the anchor's movement type.
    /// For AnchorMovementType.Default, they will move according to the movement type specified by this parameter.
    /// The caret will also move according to the <paramref name="defaultAnchorMovementType"/> parameter.
    /// </param>
    public void Insert(int offset, string text, AnchorMovementType defaultAnchorMovementType)
    {
      if (defaultAnchorMovementType == AnchorMovementType.BeforeInsertion) {
        Replace(offset, 0, new StringTextSource(text), OffsetChangeMappingType.KeepAnchorBeforeInsertion);
      } else {
        Replace(offset, 0, new StringTextSource(text), null);
      }
    }
    
    /// <summary>
    /// Inserts text.
    /// </summary>
    /// <param name="offset">The offset at which the text is inserted.</param>
    /// <param name="text">The new text.</param>
    /// <param name="defaultAnchorMovementType">
    /// Anchors positioned exactly at the insertion offset will move according to the anchor's movement type.
    /// For AnchorMovementType.Default, they will move according to the movement type specified by this parameter.
    /// The caret will also move according to the <paramref name="defaultAnchorMovementType"/> parameter.
    /// </param>
    public void Insert(int offset, ITextSource text, AnchorMovementType defaultAnchorMovementType)
    {
      if (defaultAnchorMovementType == AnchorMovementType.BeforeInsertion) {
        Replace(offset, 0, text, OffsetChangeMappingType.KeepAnchorBeforeInsertion);
      } else {
        Replace(offset, 0, text, null);
      }
    }
    
    /// <summary>
    /// Removes text.
    /// </summary>
    public void Remove(ISegment segment)
    {
      Replace(segment, string.Empty);
    }
    
    /// <summary>
    /// Removes text.
    /// </summary>
    /// <param name="offset">Starting offset of the text to be removed.</param>
    /// <param name="length">Length of the text to be removed.</param>
    public void Remove(int offset, int length)
    {
      Replace(offset, length, StringTextSource.Empty);
    }
    
    internal bool inDocumentChanging;
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    public void Replace(ISegment segment, string text)
    {
      if (segment == null)
        throw new ArgumentNullException("segment");
      Replace(segment.Offset, segment.Length, new StringTextSource(text), null);
    }
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    public void Replace(ISegment segment, ITextSource text)
    {
      if (segment == null)
        throw new ArgumentNullException("segment");
      Replace(segment.Offset, segment.Length, text, null);
    }
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    /// <param name="offset">The starting offset of the text to be replaced.</param>
    /// <param name="length">The length of the text to be replaced.</param>
    /// <param name="text">The new text.</param>
    public void Replace(int offset, int length, string text)
    {
      Replace(offset, length, new StringTextSource(text), null);
    }
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    /// <param name="offset">The starting offset of the text to be replaced.</param>
    /// <param name="length">The length of the text to be replaced.</param>
    /// <param name="text">The new text.</param>
    public void Replace(int offset, int length, ITextSource text)
    {
      Replace(offset, length, text, null);
    }
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    /// <param name="offset">The starting offset of the text to be replaced.</param>
    /// <param name="length">The length of the text to be replaced.</param>
    /// <param name="text">The new text.</param>
    /// <param name="offsetChangeMappingType">The offsetChangeMappingType determines how offsets inside the old text are mapped to the new text.
    /// This affects how the anchors and segments inside the replaced region behave.</param>
    public void Replace(int offset, int length, string text, OffsetChangeMappingType offsetChangeMappingType)
    {
      Replace(offset, length, new StringTextSource(text), offsetChangeMappingType);
    }
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    /// <param name="offset">The starting offset of the text to be replaced.</param>
    /// <param name="length">The length of the text to be replaced.</param>
    /// <param name="text">The new text.</param>
    /// <param name="offsetChangeMappingType">The offsetChangeMappingType determines how offsets inside the old text are mapped to the new text.
    /// This affects how the anchors and segments inside the replaced region behave.</param>
    public void Replace(int offset, int length, ITextSource text, OffsetChangeMappingType offsetChangeMappingType)
    {
      if (text == null)
        throw new ArgumentNullException("text");
      // Please see OffsetChangeMappingType XML comments for details on how these modes work.
      switch (offsetChangeMappingType) {
        case OffsetChangeMappingType.Normal:
          Replace(offset, length, text, null);
          break;
        case OffsetChangeMappingType.KeepAnchorBeforeInsertion:
          Replace(offset, length, text, OffsetChangeMap.FromSingleElement(
            new OffsetChangeMapEntry(offset, length, text.TextLength, false, true)));
          break;
        case OffsetChangeMappingType.RemoveAndInsert:
          if (length == 0 || text.TextLength == 0) {
            // only insertion or only removal?
            // OffsetChangeMappingType doesn't matter, just use Normal.
            Replace(offset, length, text, null);
          } else {
            OffsetChangeMap map = new OffsetChangeMap(2);
            map.Add(new OffsetChangeMapEntry(offset, length, 0));
            map.Add(new OffsetChangeMapEntry(offset, 0, text.TextLength));
            map.Freeze();
            Replace(offset, length, text, map);
          }
          break;
        case OffsetChangeMappingType.CharacterReplace:
          if (length == 0 || text.TextLength == 0) {
            // only insertion or only removal?
            // OffsetChangeMappingType doesn't matter, just use Normal.
            Replace(offset, length, text, null);
          } else if (text.TextLength > length) {
            // look at OffsetChangeMappingType.CharacterReplace XML comments on why we need to replace
            // the last character
            OffsetChangeMapEntry entry = new OffsetChangeMapEntry(offset + length - 1, 1, 1 + text.TextLength - length);
            Replace(offset, length, text, OffsetChangeMap.FromSingleElement(entry));
          } else if (text.TextLength < length) {
            OffsetChangeMapEntry entry = new OffsetChangeMapEntry(offset + text.TextLength, length - text.TextLength, 0, true, false);
            Replace(offset, length, text, OffsetChangeMap.FromSingleElement(entry));
          } else {
            Replace(offset, length, text, OffsetChangeMap.Empty);
          }
          break;
        default:
          throw new ArgumentOutOfRangeException("offsetChangeMappingType", offsetChangeMappingType, "Invalid enum value");
      }
    }
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    /// <param name="offset">The starting offset of the text to be replaced.</param>
    /// <param name="length">The length of the text to be replaced.</param>
    /// <param name="text">The new text.</param>
    /// <param name="offsetChangeMap">The offsetChangeMap determines how offsets inside the old text are mapped to the new text.
    /// This affects how the anchors and segments inside the replaced region behave.
    /// If you pass null (the default when using one of the other overloads), the offsets are changed as
    /// in OffsetChangeMappingType.Normal mode.
    /// If you pass OffsetChangeMap.Empty, then everything will stay in its old place (OffsetChangeMappingType.CharacterReplace mode).
    /// The offsetChangeMap must be a valid 'explanation' for the document change. See <see cref="OffsetChangeMap.IsValidForDocumentChange"/>.
    /// Passing an OffsetChangeMap to the Replace method will automatically freeze it to ensure the thread safety of the resulting
    /// DocumentChangeEventArgs instance.
    /// </param>
    public void Replace(int offset, int length, string text, OffsetChangeMap offsetChangeMap)
    {
      Replace(offset, length, new StringTextSource(text), offsetChangeMap);
    }
    
    /// <summary>
    /// Replaces text.
    /// </summary>
    /// <param name="offset">The starting offset of the text to be replaced.</param>
    /// <param name="length">The length of the text to be replaced.</param>
    /// <param name="text">The new text.</param>
    /// <param name="offsetChangeMap">The offsetChangeMap determines how offsets inside the old text are mapped to the new text.
    /// This affects how the anchors and segments inside the replaced region behave.
    /// If you pass null (the default when using one of the other overloads), the offsets are changed as
    /// in OffsetChangeMappingType.Normal mode.
    /// If you pass OffsetChangeMap.Empty, then everything will stay in its old place (OffsetChangeMappingType.CharacterReplace mode).
    /// The offsetChangeMap must be a valid 'explanation' for the document change. See <see cref="OffsetChangeMap.IsValidForDocumentChange"/>.
    /// Passing an OffsetChangeMap to the Replace method will automatically freeze it to ensure the thread safety of the resulting
    /// DocumentChangeEventArgs instance.
    /// </param>
    public void Replace(int offset, int length, ITextSource text, OffsetChangeMap offsetChangeMap)
    {
      if (text == null)
        throw new ArgumentNullException("text");
      text = text.CreateSnapshot();
      if (offsetChangeMap != null)
        offsetChangeMap.Freeze();
      
      // Ensure that all changes take place inside an update group.
      // Will also take care of throwing an exception if inDocumentChanging is set.
      BeginUpdate();
      try {
        // protect document change against corruption by other changes inside the event handlers
        inDocumentChanging = true;
        try {
          // The range verification must wait until after the BeginUpdate() call because the document
          // might be modified inside the UpdateStarted event.
          ThrowIfRangeInvalid(offset, length);
          
          DoReplace(offset, length, text, offsetChangeMap);
        } finally {
          inDocumentChanging = false;
        }
      } finally {
        EndUpdate();
      }
    }
    
    void DoReplace(int offset, int length, ITextSource newText, OffsetChangeMap offsetChangeMap)
    {
      if (length == 0 && newText.TextLength == 0)
        return;
      
      // trying to replace a single character in 'Normal' mode?
      // for single characters, 'CharacterReplace' mode is equivalent, but more performant
      // (we don't have to touch the anchorTree at all in 'CharacterReplace' mode)
      if (length == 1 && newText.TextLength == 1 && offsetChangeMap == null)
        offsetChangeMap = OffsetChangeMap.Empty;
      
      ITextSource removedText;
      if (length == 0) {
        removedText = StringTextSource.Empty;
      } else if (length < 100) {
        removedText = new StringTextSource(rope.ToString(offset, length));
      } else {
        // use a rope if the removed string is long
        removedText = new RopeTextSource(rope.GetRange(offset, length));
      }
      DocumentChangeEventArgs args = new DocumentChangeEventArgs(offset, removedText, newText, offsetChangeMap);
      
      // fire DocumentChanging event
      if (Changing != null)
        Changing(this, args);
      if (textChanging != null)
        textChanging(this, args);
      
      undoStack.Push(this, args);
      
      cachedText = null; // reset cache of complete document text
      fireTextChanged = true;
      DelayedEvents delayedEvents = new DelayedEvents();
      
      lock (lockObject) {
        // create linked list of checkpoints
        versionProvider.AppendChange(args);
        
        // now update the textBuffer and lineTree
        if (offset == 0 && length == rope.Length) {
          // optimize replacing the whole document
          rope.Clear();
          var newRopeTextSource = newText as RopeTextSource;
          if (newRopeTextSource != null)
            rope.InsertRange(0, newRopeTextSource.GetRope());
          else
            rope.InsertText(0, newText.Text);
          lineManager.Rebuild();
        } else {
          rope.RemoveRange(offset, length);
          lineManager.Remove(offset, length);
          #if DEBUG
          lineTree.CheckProperties();
          #endif
          var newRopeTextSource = newText as RopeTextSource;
          if (newRopeTextSource != null)
            rope.InsertRange(offset, newRopeTextSource.GetRope());
          else
            rope.InsertText(offset, newText.Text);
          lineManager.Insert(offset, newText);
          #if DEBUG
          lineTree.CheckProperties();
          #endif
        }
      }
      
      // update text anchors
      if (offsetChangeMap == null) {
        anchorTree.HandleTextChange(args.CreateSingleChangeMapEntry(), delayedEvents);
      } else {
        foreach (OffsetChangeMapEntry entry in offsetChangeMap) {
          anchorTree.HandleTextChange(entry, delayedEvents);
        }
      }
      
      lineManager.ChangeComplete(args);
      
      // raise delayed events after our data structures are consistent again
      delayedEvents.RaiseEvents();
      
      // fire DocumentChanged event
      if (Changed != null)
        Changed(this, args);
      if (textChanged != null)
        textChanged(this, args);
    }
    #endregion
    
    #region GetLineBy...
    /// <summary>
    /// Gets a read-only list of lines.
    /// </summary>
    /// <remarks><inheritdoc cref="DocumentLine"/></remarks>
    public IList<DocumentLine> Lines {
      get { return lineTree; }
    }
    
    /// <summary>
    /// Gets a line by the line number: O(log n)
    /// </summary>
    public DocumentLine GetLineByNumber(int number)
    {
      VerifyAccess();
      if (number < 1 || number > lineTree.LineCount)
        throw new ArgumentOutOfRangeException("number", number, "Value must be between 1 and " + lineTree.LineCount);
      return lineTree.GetByNumber(number);
    }
    
    IDocumentLine IDocument.GetLineByNumber(int lineNumber)
    {
      return GetLineByNumber(lineNumber);
    }
    
    /// <summary>
    /// Gets a document lines by offset.
    /// Runtime: O(log n)
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Globalization", "CA1305:SpecifyIFormatProvider", MessageId = "System.Int32.ToString")]
    public DocumentLine GetLineByOffset(int offset)
    {
      VerifyAccess();
      if (offset < 0 || offset > rope.Length) {
        throw new ArgumentOutOfRangeException("offset", offset, "0 <= offset <= " + rope.Length.ToString());
      }
      return lineTree.GetByOffset(offset);
    }
    
    IDocumentLine IDocument.GetLineByOffset(int offset)
    {
      return GetLineByOffset(offset);
    }
    #endregion
    
    #region GetOffset / GetLocation
    /// <summary>
    /// Gets the offset from a text location.
    /// </summary>
    /// <seealso cref="GetLocation"/>
    public int GetOffset(TextLocation location)
    {
      return GetOffset(location.Line, location.Column);
    }
    
    /// <summary>
    /// Gets the offset from a text location.
    /// </summary>
    /// <seealso cref="GetLocation"/>
    public int GetOffset(int line, int column)
    {
      DocumentLine docLine = GetLineByNumber(line);
      if (column <= 0)
        return docLine.Offset;
      if (column > docLine.Length)
        return docLine.EndOffset;
      return docLine.Offset + column - 1;
    }
    
    /// <summary>
    /// Gets the location from an offset.
    /// </summary>
    /// <seealso cref="GetOffset(TextLocation)"/>
    public TextLocation GetLocation(int offset)
    {
      DocumentLine line = GetLineByOffset(offset);
      return new TextLocation(line.LineNumber, offset - line.Offset + 1);
    }
    #endregion
    
    #region Line Trackers
    readonly ObservableCollection<ILineTracker> lineTrackers = new ObservableCollection<ILineTracker>();
    
    /// <summary>
    /// Gets the list of <see cref="ILineTracker"/>s attached to this document.
    /// You can add custom line trackers to this list.
    /// </summary>
    public IList<ILineTracker> LineTrackers {
      get {
        VerifyAccess();
        return lineTrackers;
      }
    }
    #endregion
    
    #region UndoStack
    UndoStack undoStack;
    
    /// <summary>
    /// Gets the <see cref="UndoStack"/> of the document.
    /// </summary>
    /// <remarks>This property can also be used to set the undo stack, e.g. for sharing a common undo stack between multiple documents.</remarks>
    public UndoStack UndoStack {
      get { return undoStack; }
      set {
        if (value == null)
          throw new ArgumentNullException();
        if (value != undoStack) {
          undoStack.ClearAll(); // first clear old undo stack, so that it can't be used to perform unexpected changes on this document
          // ClearAll() will also throw an exception when it's not safe to replace the undo stack (e.g. update is currently in progress)
          undoStack = value;
          OnPropertyChanged("UndoStack");
        }
      }
    }
    #endregion
    
    #region CreateAnchor
    /// <summary>
    /// Creates a new <see cref="TextAnchor"/> at the specified offset.
    /// </summary>
    /// <inheritdoc cref="TextAnchor" select="remarks|example"/>
    public TextAnchor CreateAnchor(int offset)
    {
      VerifyAccess();
      if (offset < 0 || offset > rope.Length) {
        throw new ArgumentOutOfRangeException("offset", offset, "0 <= offset <= " + rope.Length.ToString(CultureInfo.InvariantCulture));
      }
      return anchorTree.CreateAnchor(offset);
    }
    
    ITextAnchor IDocument.CreateAnchor(int offset)
    {
      return CreateAnchor(offset);
    }
    #endregion
    
    #region LineCount
    /// <summary>
    /// Gets the total number of lines in the document.
    /// Runtime: O(1).
    /// </summary>
    public int LineCount {
      get {
        VerifyAccess();
        return lineTree.LineCount;
      }
    }
    
    /// <summary>
    /// Is raised when the LineCount property changes.
    /// </summary>
    [Obsolete("This event will be removed in a future version; use the PropertyChanged event instead")]
    public event EventHandler LineCountChanged;
    #endregion
    
    #region Debugging
    [Conditional("DEBUG")]
    internal void DebugVerifyAccess()
    {
      VerifyAccess();
    }
    
    /// <summary>
    /// Gets the document lines tree in string form.
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate")]
    internal string GetLineTreeAsString()
    {
      #if DEBUG
      return lineTree.GetTreeAsString();
      #else
      return "Not available in release build.";
      #endif
    }
    
    /// <summary>
    /// Gets the text anchor tree in string form.
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate")]
    internal string GetTextAnchorTreeAsString()
    {
      #if DEBUG
      return anchorTree.GetTreeAsString();
      #else
      return "Not available in release build.";
      #endif
    }
    #endregion
    
    #region Service Provider
    IServiceProvider serviceProvider;
    
    /// <summary>
    /// Gets/Sets the service provider associated with this document.
    /// By default, every TextDocument has its own ServiceContainer; and has the document itself
    /// registered as <see cref="IDocument"/> and <see cref="TextDocument"/>.
    /// </summary>
    public IServiceProvider ServiceProvider {
      get {
        VerifyAccess();
        if (serviceProvider == null) {
          var container = new ServiceContainer();
          container.AddService(typeof(IDocument), this);
          container.AddService(typeof(TextDocument), this);
          serviceProvider = container;
        }
        return serviceProvider;
      }
      set {
        VerifyAccess();
        if (value == null)
          throw new ArgumentNullException();
        serviceProvider = value;
      }
    }
    
    object IServiceProvider.GetService(Type serviceType)
    {
      return this.ServiceProvider.GetService(serviceType);
    }
    #endregion
    
    #region FileName
    string fileName;
    
    /// <inheritdoc/>
    public event EventHandler FileNameChanged;
    
    void OnFileNameChanged(EventArgs e)
    {
      EventHandler handler = this.FileNameChanged;
      if (handler != null)
        handler(this, e);
    }
    
    /// <inheritdoc/>
    public string FileName {
      get { return fileName; }
      set {
        if (fileName != value) {
          fileName = value;
          OnFileNameChanged(EventArgs.Empty);
        }
      }
    }
    #endregion
  }
}