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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
using System;
using System.Diagnostics;
namespace Tango.Scripting.Editors.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 + "]";
}
}
}
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