source: stable/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/TextSegment.cs

// 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
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// DEALINGS IN THE SOFTWARE.

using System;
using System.Diagnostics;
#if NREFACTORY
using ICSharpCode.NRefactory.Editor;
#endif

namespace ICSharpCode.AvalonEdit.Document
{
  /// <summary>
  /// A segment that can be put into a <see cref="TextSegmentCollection{T}"/>.
  /// </summary>
  /// <remarks>
  /// <para>
  /// A <see cref="TextSegment"/> can be stand-alone or part of a <see cref="TextSegmentCollection{T}"/>.
  /// If the segment is stored inside a TextSegmentCollection, its Offset and Length will be updated by that collection.
  /// </para>
  /// <para>
  /// When the document changes, the offsets of all text segments in the TextSegmentCollection will be adjusted accordingly.
  /// Start offsets move like <see cref="AnchorMovementType">AnchorMovementType.AfterInsertion</see>,
  /// end offsets move like <see cref="AnchorMovementType">AnchorMovementType.BeforeInsertion</see>
  /// (i.e. the segment will always stay as small as possible).</para>
  /// <para>
  /// If a document change causes a segment to be deleted completely, it will be reduced to length 0, but segments are
  /// never automatically removed from the collection.
  /// Segments with length 0 will never expand due to document changes, and they move as <c>AfterInsertion</c>.
  /// </para>
  /// <para>
  /// Thread-safety: a TextSegmentCollection that is connected to a <see cref="TextDocument"/> may only be used on that document's owner thread.
  /// A disconnected TextSegmentCollection is safe for concurrent reads, but concurrent access is not safe when there are writes.
  /// Keep in mind that reading the Offset properties of a text segment inside the collection is a read access on the
  /// collection; and setting an Offset property of a text segment is a write access on the collection.
  /// </para>
  /// </remarks>
  /// <seealso cref="ISegment"/>
  /// <seealso cref="AnchorSegment"/>
  /// <seealso cref="TextSegmentCollection{T}"/>
  public class TextSegment : ISegment
  {
    internal ISegmentTree ownerTree;
    internal TextSegment left, right, parent;
    
    /// <summary>
    /// The color of the segment in the red/black tree.
    /// </summary>
    internal bool color;
    
    /// <summary>
    /// The "length" of the node (distance to previous node)
    /// </summary>
    internal int nodeLength;
    
    /// <summary>
    /// The total "length" of this subtree.
    /// </summary>
    internal int totalNodeLength; // totalNodeLength = nodeLength + left.totalNodeLength + right.totalNodeLength
    
    /// <summary>
    /// The length of the segment (do not confuse with nodeLength).
    /// </summary>
    internal int segmentLength;
    
    /// <summary>
    /// distanceToMaxEnd = Max(segmentLength,
    ///                        left.distanceToMaxEnd + left.Offset - Offset,
    ///                        left.distanceToMaxEnd + right.Offset - Offset)
    /// </summary>
    internal int distanceToMaxEnd;
    
    int ISegment.Offset {
      get { return StartOffset; }
    }
    
    /// <summary>
    /// Gets whether this segment is connected to a TextSegmentCollection and will automatically
    /// update its offsets.
    /// </summary>
    protected bool IsConnectedToCollection {
      get {
        return ownerTree != null;
      }
    }
    
    /// <summary>
    /// Gets/Sets the start offset of the segment.
    /// </summary>
    /// <remarks>
    /// When setting the start offset, the end offset will change, too: the Length of the segment will stay constant.
    /// </remarks>
    public int StartOffset {
      get {
        // If the segment is not connected to a tree, we store the offset in "nodeLength".
        // Otherwise, "nodeLength" contains the distance to the start offset of the previous node
        Debug.Assert(!(ownerTree == null && parent != null));
        Debug.Assert(!(ownerTree == null && left != null));
        
        TextSegment n = this;
        int offset = n.nodeLength;
        if (n.left != null)
          offset += n.left.totalNodeLength;
        while (n.parent != null) {
          if (n == n.parent.right) {
            if (n.parent.left != null)
              offset += n.parent.left.totalNodeLength;
            offset += n.parent.nodeLength;
          }
          n = n.parent;
        }
        return offset;
      }
      set {
        if (value < 0)
          throw new ArgumentOutOfRangeException("value", "Offset must not be negative");
        if (this.StartOffset != value) {
          // need a copy of the variable because ownerTree.Remove() sets this.ownerTree to null
          ISegmentTree ownerTree = this.ownerTree;
          if (ownerTree != null) {
            ownerTree.Remove(this);
            nodeLength = value;
            ownerTree.Add(this);
          } else {
            nodeLength = value;
          }
          OnSegmentChanged();
        }
      }
    }
    
    /// <summary>
    /// Gets/Sets the end offset of the segment.
    /// </summary>
    /// <remarks>
    /// Setting the end offset will change the length, the start offset will stay constant.
    /// </remarks>
    public int EndOffset {
      get {
        return StartOffset + Length;
      }
      set {
        int newLength = value - StartOffset;
        if (newLength < 0)
          throw new ArgumentOutOfRangeException("value", "EndOffset must be greater or equal to StartOffset");
        Length = newLength;
      }
    }
    
    /// <summary>
    /// Gets/Sets the length of the segment.
    /// </summary>
    /// <remarks>
    /// Setting the length will change the end offset, the start offset will stay constant.
    /// </remarks>
    public int Length {
      get {
        return segmentLength;
      }
      set {
        if (value < 0)
          throw new ArgumentOutOfRangeException("value", "Length must not be negative");
        if (segmentLength != value) {
          segmentLength = value;
          if (ownerTree != null)
            ownerTree.UpdateAugmentedData(this);
          OnSegmentChanged();
        }
      }
    }
    
    /// <summary>
    /// This method gets called when the StartOffset/Length/EndOffset properties are set.
    /// It is not called when StartOffset/Length/EndOffset change due to document changes
    /// </summary>
    protected virtual void OnSegmentChanged()
    {
    }
    
    internal TextSegment LeftMost {
      get {
        TextSegment node = this;
        while (node.left != null)
          node = node.left;
        return node;
      }
    }
    
    internal TextSegment RightMost {
      get {
        TextSegment node = this;
        while (node.right != null)
          node = node.right;
        return node;
      }
    }
    
    /// <summary>
    /// Gets the inorder successor of the node.
    /// </summary>
    internal TextSegment Successor {
      get {
        if (right != null) {
          return right.LeftMost;
        } else {
          TextSegment node = this;
          TextSegment oldNode;
          do {
            oldNode = node;
            node = node.parent;
            // go up until we are coming out of a left subtree
          } while (node != null && node.right == oldNode);
          return node;
        }
      }
    }
    
    /// <summary>
    /// Gets the inorder predecessor of the node.
    /// </summary>
    internal TextSegment Predecessor {
      get {
        if (left != null) {
          return left.RightMost;
        } else {
          TextSegment node = this;
          TextSegment oldNode;
          do {
            oldNode = node;
            node = node.parent;
            // go up until we are coming out of a right subtree
          } while (node != null && node.left == oldNode);
          return node;
        }
      }
    }
    
    #if DEBUG
    internal string ToDebugString()
    {
      return "[nodeLength=" + nodeLength + " totalNodeLength=" + totalNodeLength
        + " distanceToMaxEnd=" + distanceToMaxEnd + " MaxEndOffset=" + (StartOffset + distanceToMaxEnd) + "]";
    }
    #endif
    
    /// <inheritdoc/>
    public override string ToString()
    {
      return "[" + GetType().Name + " Offset=" + StartOffset + " Length=" + Length + " EndOffset=" + EndOffset + "]";
    }
  }
}