Using AvalonEdit (WPF Text Editor)

// 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.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Text;

using ICSharpCode.AvalonEdit.Document;
using ICSharpCode.AvalonEdit.Utils;

namespace ICSharpCode.AvalonEdit.Highlighting
{
	/// <summary>
	/// Represents a highlighted document line.
	/// </summary>
	public class HighlightedLine
	{
		/// <summary>
		/// Creates a new HighlightedLine instance.
		/// </summary>
		public HighlightedLine(TextDocument document, DocumentLine documentLine)
		{
			if (document == null)
				throw new ArgumentNullException("document");
			if (!document.Lines.Contains(documentLine))
				throw new ArgumentException("Line is null or not part of document");
			this.Document = document;
			this.DocumentLine = documentLine;
			this.Sections = new NullSafeCollection<HighlightedSection>();
		}
		
		/// <summary>
		/// Gets the document associated with this HighlightedLine.
		/// </summary>
		public TextDocument Document { get; private set; }
		
		/// <summary>
		/// Gets the document line associated with this HighlightedLine.
		/// </summary>
		public DocumentLine DocumentLine { get; private set; }
		
		/// <summary>
		/// Gets the highlighted sections.
		/// The sections are not overlapping, but they may be nested.
		/// In that case, outer sections come in the list before inner sections.
		/// The sections are sorted by start offset.
		/// </summary>
		public IList<HighlightedSection> Sections { get; private set; }
		
		/// <summary>
		/// Gets the default color of all text outside a <see cref="HighlightedSection"/>.
		/// </summary>
		public HighlightingColor DefaultTextColor { get; set; }
		
		sealed class HtmlElement : IComparable<HtmlElement>
		{
			internal readonly int Offset;
			internal readonly int Nesting;
			internal readonly bool IsEnd;
			internal readonly HighlightingColor Color;
			
			public HtmlElement(int offset, int nesting, bool isEnd, HighlightingColor color)
			{
				this.Offset = offset;
				this.Nesting = nesting;
				this.IsEnd = isEnd;
				this.Color = color;
			}
			
			public int CompareTo(HtmlElement other)
			{
				int r = Offset.CompareTo(other.Offset);
				if (r != 0)
					return r;
				if (IsEnd != other.IsEnd) {
					if (IsEnd)
						return -1;
					else
						return 1;
				} else {
					if (IsEnd)
						return other.Nesting.CompareTo(Nesting);
					else
						return Nesting.CompareTo(other.Nesting);
				}
			}
		}
		
		/// <summary>
		/// Produces HTML code for the line, with &lt;span class="colorName"&gt; tags.
		/// </summary>
		public string ToHtml(HtmlOptions options)
		{
			int startOffset = this.DocumentLine.Offset;
			return ToHtml(startOffset, startOffset + this.DocumentLine.Length, options);
		}
		
		/// <summary>
		/// Produces HTML code for a section of the line, with &lt;span class="colorName"&gt; tags.
		/// </summary>
		public string ToHtml(int startOffset, int endOffset, HtmlOptions options)
		{
			if (options == null)
				throw new ArgumentNullException("options");
			int documentLineStartOffset = this.DocumentLine.Offset;
			int documentLineEndOffset = documentLineStartOffset + this.DocumentLine.Length;
			if (startOffset < documentLineStartOffset || startOffset > documentLineEndOffset)
				throw new ArgumentOutOfRangeException("startOffset", startOffset, "Value must be between " + documentLineStartOffset + " and " + documentLineEndOffset);
			if (endOffset < startOffset || endOffset > documentLineEndOffset)
				throw new ArgumentOutOfRangeException("endOffset", endOffset, "Value must be between startOffset and " + documentLineEndOffset);
			ISegment requestedSegment = new SimpleSegment(startOffset, endOffset - startOffset);
			
			List<HtmlElement> elements = new List<HtmlElement>();
			for (int i = 0; i < this.Sections.Count; i++) {
				HighlightedSection s = this.Sections[i];
				if (s.GetOverlap(requestedSegment).Length > 0) {
					elements.Add(new HtmlElement(s.Offset, i, false, s.Color));
					elements.Add(new HtmlElement(s.Offset + s.Length, i, true, s.Color));
				}
			}
			elements.Sort();
			
			TextDocument document = this.Document;
			StringWriter w = new StringWriter(CultureInfo.InvariantCulture);
			int textOffset = startOffset;
			foreach (HtmlElement e in elements) {
				int newOffset = Math.Min(e.Offset, endOffset);
				if (newOffset > startOffset) {
					HtmlClipboard.EscapeHtml(w, document.GetText(textOffset, newOffset - textOffset), options);
				}
				textOffset = Math.Max(textOffset, newOffset);
				if (options.ColorNeedsSpanForStyling(e.Color)) {
					if (e.IsEnd) {
						w.Write("</span>");
					} else {
						w.Write("<span");
						options.WriteStyleAttributeForColor(w, e.Color);
						w.Write('>');
					}
				}
			}
			HtmlClipboard.EscapeHtml(w, document.GetText(textOffset, endOffset - textOffset), options);
			return w.ToString();
		}
		
		/// <inheritdoc/>
		public override string ToString()
		{
			return "[" + GetType().Name + " " + ToHtml(new HtmlOptions()) + "]";
		}
	}
}