// 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.
//
// Copyright (c) 2004 Novell, Inc. (http://www.novell.com)
//
// Authors:
//	Peter Bartok	pbartok@novell.com
//
//

// NOT COMPLETE

using System;
using System.Collections;
using System.Drawing;
using System.Drawing.Text;
using System.Text;

namespace System.Windows.Forms {
	public enum LineColor {
		Red	= 0,
		Black	= 1
	}

	public enum CaretDirection {
		CharForward,	// Move a char to the right
		CharBack,	// Move a char to the left
		LineUp,		// Move a line up
		LineDown,	// Move a line down
		Home,		// Move to the beginning of the line
		End,		// Move to the end of the line
		PgUp,		// Move one page up
		PgDn,		// Move one page down
		CtrlHome,	// Move to the beginning of the document
		CtrlEnd,	// Move to the end of the document
		WordBack,	// Move to the beginning of the previous word (or beginning of line)
		WordForward	// Move to the beginning of the next word (or end of line)
	}

	// Being cloneable should allow for nice line and document copies...
	public class Line : ICloneable, IComparable {
		#region	Local Variables
		// Stuff that matters for our line
		internal StringBuilder		text;			// Characters for the line
		internal float[]		widths;			// Width of each character; always one larger than text.Length
		internal int			space;			// Number of elements in text and widths
		internal int			line_no;		// Line number
		internal LineTag		tags;			// Tags describing the text
		internal int			Y;			// Baseline
		internal int			height;			// Height of the line (height of tallest tag)

		// Stuff that's important for the tree
		internal Line			parent;			// Our parent line
		public Line			left;			// Line with smaller line number
		public Line			right;			// Line with higher line number
		internal LineColor		color;			// We're doing a black/red tree. this is the node color
		internal int			DEFAULT_TEXT_LEN;	// 
		internal static StringFormat	string_format;		// For calculating widths/heights
		internal bool			recalc;			// Line changed
		#endregion	// Local Variables

		#region Constructors
		public Line() {
			color = LineColor.Red;
			left = null;
			right = null;
			parent = null;
			text = null;
			recalc = true;

			if (string_format == null) {
				string_format = new StringFormat(StringFormat.GenericTypographic);
				string_format.Trimming = StringTrimming.None;
				string_format.FormatFlags = StringFormatFlags.MeasureTrailingSpaces;
			}
		}

		public Line(int LineNo, string Text, Font font) : this() {
			space = Text.Length > DEFAULT_TEXT_LEN ? Text.Length+1 : DEFAULT_TEXT_LEN;

			text = new StringBuilder(Text, space);
			line_no = LineNo;

			widths = new float[space + 1];
			tags = new LineTag(this, 1, text.Length);
			tags.font = font;
		}

		public Line(int LineNo, string Text, LineTag tag) : this() {
			space = Text.Length > DEFAULT_TEXT_LEN ? Text.Length+1 : DEFAULT_TEXT_LEN;

			text = new StringBuilder(Text, space);
			line_no = LineNo;

			widths = new float[space + 1];
			tags = tag;
		}

		#endregion	// Constructors

		#region Public Properties
		public int Height {
			get {
				return height;
			}

			set {
				height = value;
			}
		}

		public int LineNo {
			get {
				return line_no;
			}

			set {
				line_no = value;
			}
		}

		public string Text {
			get {
				return text.ToString();
			}

			set {
				text = new StringBuilder(value, value.Length > DEFAULT_TEXT_LEN ? value.Length : DEFAULT_TEXT_LEN);
			}
		}
#if no
		public StringBuilder Text {
			get {
				return text;
			}

			set {
				text = value;
			}
		}
#endif
		#endregion	// Public Properties

		#region Public Methods
		// Make sure we always have enoughs space in text and widths
		public void Grow(int minimum) {
			int	length;
			float[]	new_widths;

			length = text.Length;

			if ((length + minimum) > space) {
				// We need to grow; double the size

				if ((length + minimum) > (space * 2)) {
					new_widths = new float[length + minimum * 2 + 1];
					space = length + minimum * 2;
				} else {				
					new_widths = new float[space * 2 + 1];
					space *= 2;
				}
				widths.CopyTo(new_widths, 0);

				widths = new_widths;
			}
		}

		public void Streamline() {
			LineTag	current;
			LineTag	next;

			current = this.tags;
			next = current.next;

			if (next == null) {
				return;
			}

			while (next != null) {
				current.Combine(next);
				current = current.next;
				next = current.next;
			}
		}

		//
		// Go through all tags on a line and recalculate all size-related values
		// returns true if lineheight changed
		//
		public bool RecalculateLine(Graphics g) {
			LineTag	tag;
			int	pos;
			int	len;
			SizeF	size;
			float	w;
			int	prev_height;

			pos = 0;
			len = this.text.Length;
			tag = this.tags;
			prev_height = this.height;	// For drawing optimization calculations
			this.height = 0;		// Reset line height
			tag.width = 0;
			widths[0] = 0;
			this.recalc = false;

			while (pos < len) {
				size = g.MeasureString(this.text.ToString(pos, 1), tag.font, 10000, string_format);

				w = size.Width;

				tag.width += w;

				pos++;

				widths[pos] = widths[pos-1] + w;

				if (pos == (tag.start-1 + tag.length)) {
					// We just found the end of our current tag

					tag.height = (int)size.Height;
					// Check if we're the tallest on the line (so far)
					if (tag.height > this.height) {
						this.height = tag.height;		// Yep; make sure the line knows
					}

					// Update our horizontal starting pixel position
					if (tag.previous == null) {
						tag.X = 0;
					} else {
						tag.X = tag.previous.X + (int)tag.previous.width;
					}

					tag = tag.next;
					if (tag != null) {
						tag.width = 0;
					}
				}
			}

			if (this.height == 0) {
				this.height = tags.font.Height;
				tag.height = this.height;
			}

			if (prev_height != this.height) {
				return true;
			}
			return false;
		}
		#endregion	// Public Methods

		#region Administrative
		public int CompareTo(object obj) {
			if (obj == null) {
				return 1;
			}

			if (! (obj is Line)) {
				throw new ArgumentException("Object is not of type Line", "obj");
			}

			if (line_no < ((Line)obj).line_no) {
				return -1;
			} else if (line_no > ((Line)obj).line_no) {
				return 1;
			} else {
				return 0;
			}
		}

		public object Clone() {
			Line	clone;

			clone = new Line();

			clone.text = text;

			if (left != null) {
				clone.left = (Line)left.Clone();
			}

			if (left != null) {
				clone.left = (Line)left.Clone();
			}

			return clone;
		}

		public object CloneLine() {
			Line	clone;

			clone = new Line();

			clone.text = text;

			return clone;
		}

		public override bool Equals(object obj) {
			if (obj == null) {
				return false;
			}

			if (!(obj is Line)) {
				return false;
			}

			if (obj == this) {
				return true;
			}

			if (line_no == ((Line)obj).line_no) {
				return true;
			}

			return false;
		}


		public override string ToString() {
			return "Line " + line_no;
		}

		#endregion	// Administrative
	}

	public class Document : ICloneable, IEnumerable {
		#region Structures
		internal struct Marker {
			internal Line		line;
			internal LineTag	tag;
			internal int		pos;
			internal int		height;
		}
		#endregion Structures

		#region Local Variables
		private Line		document;
		private int		lines;
		private static Line	sentinel;
		private Line		last_found;
		private int		document_id;
		private Random		random = new Random();

		internal bool		multiline;

		private Line		selection_start_line;
		private int		selection_start_pos;
		private Line		selection_end_line;
		private int		selection_end_pos;

		internal Marker		caret;
		internal Marker		selection_start;
		internal Marker		selection_end;

		internal int		viewport_x;
		internal int		viewport_y;		// The visible area of the document

		internal int		document_x;		// Width of the document
		internal int		document_y;		// Height of the document

		internal Control	owner;			// Who's owning us?
		#endregion	// Local Variables

		#region Constructors
		public Document(Control owner) {
			lines = 0;

			this.owner = owner;

			multiline = true;

			// Tree related stuff
			sentinel = new Line();
			sentinel.color = LineColor.Black;

			document = sentinel;
			last_found = sentinel;

			// We always have a blank line
			Add(1, "", owner.Font);
			this.RecalculateDocument(owner.CreateGraphics());
			PositionCaret(0, 0);
			lines=1;

			// Default selection is empty

			document_id = random.Next();
		}
		#endregion

		#region Public Properties
		public Line Root {
			get {
				return document;
			}

			set {
				document = value;
			}
		}

		public int Lines {
			get {
				return lines;
			}
		}

		public Line CaretLine {
			get {
				return caret.tag.line;
			}
		}

		public int CaretPosition {
			get {
				return caret.pos;
			}
		}

		public LineTag CaretTag {
			get {
				return caret.tag;
			}
		}

		public int ViewPortX {
			get {
				return viewport_x;
			}

			set {
				viewport_x = value;
			}
		}

		public int ViewPortY {
			get {
				return viewport_y;
			}

			set {
				viewport_y = value;
			}
		}

		#endregion	// Public Properties

		#region Private Methods
		private void IncrementLines(int line_no) {
			int	current;

			current = this.lines;
			while (current >= line_no) {
				GetLine(current).line_no++;
				current--;
			}
			return;
		}

		private void RebalanceAfterAdd(Line line1) {
			Line	line2;

			while ((line1 != document) && (line1.parent.color == LineColor.Red)) {
				if (line1.parent == line1.parent.parent.left) {
					line2 = line1.parent.parent.right;

					if ((line2 != null) && (line1.color == LineColor.Red)) {
						line1.parent.color = LineColor.Black;
						line2.color = LineColor.Black;
						line1.parent.parent.color = LineColor.Red;
						line1 = line1.parent.parent;
					} else {
						if (line1 == line1.parent.right) {
							line1 = line1.parent;
							RotateLeft(line1);
						}

						line1.parent.color = LineColor.Black;
						line1.parent.parent.color = LineColor.Red;

						RotateRight(line1.parent.parent);
					}
				} else {
					line2 = line1.parent.parent.left;

					if ((line2 != null) && (line2.color == LineColor.Red)) {
						line1.parent.color = LineColor.Black;
						line2.color = LineColor.Black;
						line1.parent.parent.color = LineColor.Red;
						line1 = line1.parent.parent;
					} else {
						if (line1 == line1.parent.left) {
							line1 = line1.parent;
							RotateRight(line1);
						}

						line1.parent.color = LineColor.Black;
						line1.parent.parent.color = LineColor.Red;
						RotateLeft(line1.parent.parent);
					}
				}
			}
			document.color = LineColor.Black;
		}

		private void RebalanceAfterDelete(Line line1) {
			Line line2;

			while ((line1 != document) && (line1.color == LineColor.Black)) {
				if (line1 == line1.parent.left) {
					line2 = line1.parent.right;
					if (line2.color == LineColor.Red) { 
						line2.color = LineColor.Black;
						line1.parent.color = LineColor.Red;
						RotateLeft(line1.parent);
						line2 = line1.parent.right;
					}
					if ((line2.left.color == LineColor.Black) && (line2.right.color == LineColor.Black)) { 
						line2.color = LineColor.Red;
						line1 = line1.parent;
					} else {
						if (line2.right.color == LineColor.Red) {
							line2.left.color = LineColor.Black;
							line2.color = LineColor.Red;
							RotateRight(line2);
							line2 = line1.parent.right;
						}
						line2.color = line1.parent.color;
						line1.parent.color = LineColor.Black;
						line2.right.color = LineColor.Black;
						RotateLeft(line1.parent);
						line1 = document;
					}
				} else { 
					line2 = line1.parent.left;
					if (line2.color == LineColor.Red) {
						line2.color = LineColor.Black;
						line1.parent.color = LineColor.Red;
						RotateRight(line1.parent);
						line2 = line1.parent.left;
					}
					if ((line2.right.color == LineColor.Black) && (line2.left.color == LineColor.Black)) {
						line2.color = LineColor.Red;
						line1 = line1.parent;
					} else {
						if (line2.left.color == LineColor.Black) {
							line2.right.color = LineColor.Black;
							line2.color = LineColor.Red;
							RotateLeft(line2);
							line2 = line1.parent.left;
						}
						line2.color = line1.parent.color;
						line1.parent.color = LineColor.Black;
						line2.left.color = LineColor.Black;
						RotateRight(line1.parent);
						line1 = document;
					}
				}
			}
			line1.color = LineColor.Black;
		}

		private void RotateLeft(Line line1) {
			Line	line2 = line1.right;

			line1.right = line2.left;

			if (line2.left != sentinel) {
				line2.left.parent = line1;
			}

			if (line2 != sentinel) {
				line2.parent = line1.parent;
			}

			if (line1.parent != null) {
				if (line1 == line1.parent.left) {
					line1.parent.left = line2;
				} else {
					line1.parent.right = line2;
				}
			} else {
				document = line2;
			}

			line2.left = line1;
			if (line1 != sentinel) {
				line1.parent = line2;
			}
		}

		private void RotateRight(Line line1) {
			Line line2 = line1.left;

			line1.left = line2.right;

			if (line2.right != sentinel) {
				line2.right.parent = line1;
			}

			if (line2 != sentinel) {
				line2.parent = line1.parent;
			}

			if (line1.parent != null) {
				if (line1 == line1.parent.right) {
					line1.parent.right = line2;
				} else {
					line1.parent.left = line2;
				}
			} else {
				document = line2;
			}

			line2.right = line1;
			if (line1 != sentinel) {
				line1.parent = line2;
			}
		}        


		public void UpdateView(Line line, int pos) {
			int	prev_width;

			// This is an optimization; we need to invalidate 
			prev_width = (int)line.widths[line.text.Length];

			if (RecalculateDocument(owner.CreateGraphics(), line.line_no, line.line_no, true)) {
				// Lineheight changed, invalidate the rest of the document
				if ((line.Y - viewport_y) >=0 ) {
					// We formatted something that's in view, only draw parts of the screen
					owner.Invalidate(new Rectangle(0, line.Y - viewport_y, owner.Width, owner.Height - line.Y - viewport_y));
				} else {
					// The tag was above the visible area, draw everything
					owner.Invalidate();
				}
			} else {
				owner.Invalidate(new Rectangle((int)line.widths[pos] - viewport_x, line.Y - viewport_y, (int)line.widths[line.text.Length], line.height));
			}
		}


		// Update display from line, down line_count lines; pos is unused, but required for the signature
		public void UpdateView(Line line, int line_count, int pos) {
			int	prev_width;

			// This is an optimization; we need to invalidate 
			prev_width = (int)line.widths[line.text.Length];

			if (RecalculateDocument(owner.CreateGraphics(), line.line_no, line.line_no + line_count - 1, true)) {
				// Lineheight changed, invalidate the rest of the document
				if ((line.Y - viewport_y) >=0 ) {
					// We formatted something that's in view, only draw parts of the screen
					owner.Invalidate(new Rectangle(0, line.Y - viewport_y, owner.Width, owner.Height - line.Y - viewport_y));
				} else {
					// The tag was above the visible area, draw everything
					owner.Invalidate();
				}
			} else {
				Line	end_line;

				end_line = GetLine(line.line_no + line_count -1);
				if (end_line == null) {
					end_line = line;
				}

				owner.Invalidate(new Rectangle(0 - viewport_x, line.Y - viewport_y, (int)line.widths[line.text.Length], end_line.Y + end_line.height));
			}
		}
		#endregion	// Private Methods

		#region Public Methods
		public void PositionCaret(int x, int y) {
			caret.tag = FindCursor(x, y, out caret.pos);
			caret.line = caret.tag.line;
			caret.height = caret.tag.height;

			XplatUI.DestroyCaret(owner.Handle);
			XplatUI.CreateCaret(owner.Handle, 2, caret.height);
			XplatUI.SetCaretPos(owner.Handle, (int)caret.tag.line.widths[caret.pos], caret.tag.line.Y + caret.tag.line.height - caret.height);
		}

		public void CaretHasFocus() {
			if (caret.tag != null) {
				XplatUI.CreateCaret(owner.Handle, 2, caret.height);
				XplatUI.SetCaretPos(owner.Handle, (int)caret.tag.line.widths[caret.pos], caret.tag.line.Y + caret.tag.line.height - caret.height);
				XplatUI.CaretVisible(owner.Handle, true);
			}
		}

		public void CaretLostFocus() {
			XplatUI.DestroyCaret(owner.Handle);
		}

		public void AlignCaret() {
			caret.tag = LineTag.FindTag(caret.line, caret.pos);
			caret.height = caret.tag.height;

			XplatUI.CreateCaret(owner.Handle, 2, caret.height);
			XplatUI.SetCaretPos(owner.Handle, (int)caret.tag.line.widths[caret.pos], caret.tag.line.Y + caret.tag.line.height - caret.height);
			XplatUI.CaretVisible(owner.Handle, true);
		}

		public void UpdateCaret() {
			if (caret.tag.height != caret.height) {
				caret.height = caret.tag.height;
				XplatUI.CreateCaret(owner.Handle, 2, caret.height);
			}
			XplatUI.SetCaretPos(owner.Handle, (int)caret.tag.line.widths[caret.pos], caret.tag.line.Y + caret.tag.line.height - caret.height);
			XplatUI.CaretVisible(owner.Handle, true);
		}

		public void DisplayCaret() {
			XplatUI.CaretVisible(owner.Handle, true);
		}

		public void HideCaret() {
			XplatUI.CaretVisible(owner.Handle, false);
		}

		public void MoveCaret(CaretDirection direction) {
			switch(direction) {
				case CaretDirection.CharForward: {
					caret.pos++;
					if (caret.pos > caret.line.text.Length) {
						if (multiline) {
							// Go into next line
							if (caret.line.line_no < this.lines) {
								caret.line = GetLine(caret.line.line_no+1);
								caret.pos = 0;
								caret.tag = caret.line.tags;
							} else {
								caret.pos--;
							}
						} else {
							// Single line; we stay where we are
							caret.pos--;
						}
					} else {
						if ((caret.tag.start - 1 + caret.tag.length) < caret.pos) {
							caret.tag = caret.tag.next;
						}
					}
					UpdateCaret();
					return;
				}

				case CaretDirection.CharBack: {
					if (caret.pos > 0) {
						// caret.pos--; // folded into the if below
						if (--caret.pos > 0) {
							if (caret.tag.start > caret.pos) {
								caret.tag = caret.tag.previous;
							}
						}
					} else {
						if (caret.line.line_no > 1) {
							caret.line = GetLine(caret.line.line_no - 1);
							caret.pos = caret.line.text.Length;
							caret.tag = LineTag.FindTag(caret.line, caret.pos);
						}
					}
					UpdateCaret();
					return;
				}

				case CaretDirection.WordForward: {
					int len;

					len = caret.line.text.Length;
					if (caret.pos < len) {
						while ((caret.pos < len) && (caret.line.text.ToString(caret.pos, 1) != " ")) {
							caret.pos++;
						}
						if (caret.pos < len) {
							// Skip any whitespace
							while ((caret.pos < len) && (caret.line.text.ToString(caret.pos, 1) == " ")) {
								caret.pos++;
							}
						}
					} else {
						if (caret.line.line_no < this.lines) {
							caret.line = GetLine(caret.line.line_no+1);
							caret.pos = 0;
							caret.tag = caret.line.tags;
						}
					}
					UpdateCaret();
					return;
				}

				case CaretDirection.WordBack: {
					if (caret.pos > 0) {
						int	len;

						len = caret.line.text.Length;

						caret.pos--;

						while ((caret.pos > 0) && (caret.line.text.ToString(caret.pos, 1) == " ")) {
							caret.pos--;
						}

						while ((caret.pos > 0) && (caret.line.text.ToString(caret.pos, 1) != " ")) {
							caret.pos--;
						}

						if (caret.line.text.ToString(caret.pos, 1) == " ") {
							if (caret.pos != 0) {
								caret.pos++;
							} else {
								caret.line = GetLine(caret.line.line_no - 1);
								caret.pos = caret.line.text.Length;
								caret.tag = LineTag.FindTag(caret.line, caret.pos);
							}
						}
					} else {
						if (caret.line.line_no > 1) {
							caret.line = GetLine(caret.line.line_no - 1);
							caret.pos = caret.line.text.Length;
							caret.tag = LineTag.FindTag(caret.line, caret.pos);
						}
					}
					UpdateCaret();
					return;
				}

				case CaretDirection.LineUp: {
					if (caret.line.line_no > 1) {
						int	pixel;

						pixel = (int)caret.line.widths[caret.pos];
						PositionCaret(pixel, GetLine(caret.line.line_no - 1).Y);
						XplatUI.CaretVisible(owner.Handle, true);
					}
					return;
				}

				case CaretDirection.LineDown: {
					if ((caret.line.line_no + 1) < lines) {
						int	pixel;

						pixel = (int)caret.line.widths[caret.pos];
						PositionCaret(pixel, GetLine(caret.line.line_no + 1).Y);
						XplatUI.CaretVisible(owner.Handle, true);
					}
					return;
				}

				case CaretDirection.Home: {
					if (caret.pos > 0) {
						caret.pos = 0;
						caret.tag = caret.line.tags;
						UpdateCaret();
					}
					return;
				}

				case CaretDirection.End: {
					if (caret.pos < caret.line.text.Length) {
						caret.pos = caret.line.text.Length;
						caret.tag = LineTag.FindTag(caret.line, caret.pos);
						UpdateCaret();
					}
					return;
				}

				case CaretDirection.PgUp: {
					return;
				}

				case CaretDirection.PgDn: {
					return;
				}

				case CaretDirection.CtrlHome: {
					caret.line = GetLine(1);
					caret.pos = 0;
					caret.tag = caret.line.tags;

					UpdateCaret();
					return;
				}

				case CaretDirection.CtrlEnd: {
					caret.line = GetLine(lines);
					caret.pos = 0;
					caret.tag = caret.line.tags;

					UpdateCaret();
					return;
				}
			}
		}

		// Draw the document
		public void Draw(Graphics g, Rectangle clip, Brush brush) {
			Line	line;		// Current line being drawn
			LineTag	tag;		// Current tag being drawn
			int	start;		// First line to draw
			int	end;		// Last line to draw
			string	s;		// String representing the current line
			int	line_no;	//

			// First, figure out from what line to what line we need to draw
			start = GetLineByPixel(clip.Top - viewport_y, false).line_no;
			end = GetLineByPixel(clip.Bottom - viewport_y, false).line_no;

			// Now draw our elements; try to only draw those that are visible
			line_no = start;
			while (line_no <= end) {
				line = GetLine(line_no);
				tag = line.tags;
				s = line.text.ToString();
				while (tag != null) {
					if (((tag.X + tag.width) > (clip.Left - viewport_x)) || (tag.X < (clip.Right - viewport_x))) {
						g.DrawString(s.Substring(tag.start-1, tag.length), tag.font, brush, tag.X - viewport_x, line.Y+line.height-tag.height  - viewport_y, StringFormat.GenericTypographic);
					}

					tag = tag.next;
				}

				line_no++;
			}
		}

		// Inserts a character at the given position
		public void InsertChar(LineTag tag, int pos, char ch) {
			Line	line;

			line = tag.line;
			line.text.Insert(pos, ch);
			tag.length++;
			if (tag.next != null) {
				tag.next.start++;
			}
			line.Grow(1);
			line.recalc = true;

			UpdateView(line, pos);
		}

		// Inserts a character at the given position
		public void InsertCharAtCaret(char ch, bool move_caret) {
			caret.line.text.Insert(caret.pos, ch);
			caret.tag.length++;
			if (caret.tag.next != null) {
				caret.tag.next.start++;
			}
			caret.line.Grow(1);
			caret.line.recalc = true;

			UpdateView(caret.line, caret.pos);
			if (move_caret) {
				caret.pos++;
				UpdateCaret();
			}
		}

		// Split the line at the position into two
		public void Split(int LineNo, int pos) {
			Line	line;
			LineTag	tag;

			line = GetLine(LineNo);
			tag = LineTag.FindTag(line, pos);
			Split(line, tag, pos);
		}

		public void Split(Line line, int pos) {
			LineTag	tag;

			tag = LineTag.FindTag(line, pos);
			Split(line, tag, pos);
		}

		public void Split(Line line, LineTag tag, int pos) {
			LineTag	new_tag;
			Line	new_line;

			// cover the easy case first
			if (pos == line.text.Length) {
				Add(line.line_no + 1, "", tag.font);
				return;
			}

			// We need to move the rest of the text into the new line
			Add(line.line_no + 1, line.text.ToString(pos, line.text.Length - pos), tag.font);

			// Now transfer our tags from this line to the next
			new_line = GetLine(line.line_no + 1);
			line.recalc = true;

			if ((tag.start - 1) == pos) {
				int	shift;

				// We can simply break the chain and move the tag into the next line
				if (tag == line.tags) {
					new_tag = new LineTag(line, 1, 0);
					new_tag.font = tag.font;
					line.tags = new_tag;
				}

				if (tag.previous != null) {
					tag.previous.next = null;
				}
				new_line.tags = tag;
				tag.previous = null;
				tag.line = new_line;

				// Walk the list and correct the start location of the tags we just bumped into the next line
				shift = tag.start - 1;

				new_tag = tag;
				while (new_tag != null) {
					new_tag.start -= shift;
					new_tag.line = new_line;
					new_tag = new_tag.next;
				}
			} else {
				int	shift;

				new_tag = new LineTag(new_line, 1, tag.start - 1 + tag.length - pos);
				new_tag.next = tag.next;
				new_tag.font = tag.font;
				new_line.tags = new_tag;
				if (new_tag.next != null) {
					new_tag.next.previous = new_tag;
				}
				tag.next = null;
				tag.length = pos - tag.start + 1;

				shift = pos;
				new_tag = new_tag.next;
				while (new_tag != null) {
					new_tag.start -= shift;
					new_tag.line = new_line;
					new_tag = new_tag.next;

				}
			}
			line.text.Remove(pos, line.text.Length - pos);
		}

		// Adds a line of text, with given font.
		// Bumps any line at that line number that already exists down
		public void Add(int LineNo, string Text, Font font) {
			Line	add;
			Line	line;
			int	line_no;

			if (LineNo<1 || Text == null) {
				if (LineNo<1) {
					throw new ArgumentNullException("LineNo", "Line numbers must be positive");
				} else {
					throw new ArgumentNullException("Text", "Cannot insert NULL line");
				}
			}

			add = new Line(LineNo, Text, font);

			line = document;
			while (line != sentinel) {
				add.parent = line;
				line_no = line.line_no;

				if (LineNo > line_no) {
					line = line.right;
				} else if (LineNo < line_no) {
					line = line.left;
				} else {
					// Bump existing line numbers; walk all nodes to the right of this one and increment line_no
					IncrementLines(line.line_no);
					line = line.left;
				}
			}

			add.left = sentinel;
			add.right = sentinel;

			if (add.parent != null) {
				if (LineNo > add.parent.line_no) {
					add.parent.right = add;
				} else {
					add.parent.left = add;
				}
			} else {
				// Root node
				document = add;
			}

			RebalanceAfterAdd(add);

			lines++;
		}

		public virtual void Clear() {
			lines = 0;
			document = sentinel;
		}

		public virtual object Clone() {
			Document clone;

			clone = new Document(null);

			clone.lines = this.lines;
			clone.document = (Line)document.Clone();

			return clone;
		}

		public void Delete(int LineNo) {
			if (LineNo>lines) {
				return;
			}

			Delete(GetLine(LineNo));
		}

		public void Delete(Line line1) {
			Line	line2 = new Line();
			Line	line3;

			if ((line1.left == sentinel) || (line1.right == sentinel)) {
				line3 = line1;
			} else {
				line3 = line1.right;
				while (line3.left != sentinel) {
					line3 = line3.left;
				}
			}

			if (line3.left != sentinel) {
				line2 = line3.left;
			} else {
				line2 = line3.right;
			}

			line2.parent = line3.parent;
			if (line3.parent != null) {
				if(line3 == line3.parent.left) {
					line3.parent.left = line2;
				} else {
					line3.parent.right = line2;
				}
			} else {
				document = line2;
			}

			if (line3 != line1) {
				line1.line_no = line3.line_no;
				line1.text = line3.text;
			}

			if (line3.color == LineColor.Black)
				RebalanceAfterDelete(line2);

			last_found = sentinel;
		}

		// Set our selection markers
		public void SetSelection(Line start, int start_pos, Line end, int end_pos) {
			selection_start_line = start;
			selection_start_pos = start_pos;
			selection_end_line = end;
			selection_end_pos = end_pos;
		}

		public void SetSelection(Line start, int start_pos) {
			selection_start_line = start;
			selection_start_pos = start_pos;
			selection_end_line = start;
			selection_end_pos = start_pos;
		}


		// Give it a Line number and it returns the Line object at with that line number
		public Line GetLine(int LineNo) {
			Line	line = document;

			while (line != sentinel) {
				if (LineNo == line.line_no) {
					return line;
				} else if (LineNo < line.line_no) {
					line = line.left;
				} else {
					line = line.right;
				}
			}

			return null;
		}

		// Give it a Y pixel coordinate and it returns the Line covering that Y coordinate
		///
		public Line GetLineByPixel(int y, bool exact) {
			Line	line = document;
			Line	last = null;

			while (line != sentinel) {
				last = line;
				if ((y >= line.Y) && (y < (line.Y+line.height))) {
					return line;
				} else if (y < line.Y) {
					line = line.left;
				} else {
					line = line.right;
				}
			}

			if (exact) {
				return null;
			}
			return last;
		}

		// Give it x/y pixel coordinates and it returns the Tag at that position; optionally the char position is returned in index
		public LineTag FindTag(int x, int y, out int index, bool exact) {
			Line	line;
			LineTag	tag;

			line = GetLineByPixel(y, exact);
			if (line == null) {
				index = 0;
				return null;
			}
			tag = line.tags;

			while (true) {
				if (x >= tag.X && x < (tag.X+tag.width)) {
					int	end;

					end = tag.start + tag.length - 1;

					for (int pos = tag.start; pos < end; pos++) {
						if (x < line.widths[pos]) {
							index = pos;
							return tag;
						}
					}
					index=end;
					return tag;
				}
				if (tag.next != null) {
					tag = tag.next;
				} else {
					if (exact) {
						index = 0;
						return null;
					}

					index = line.text.Length;
					return tag;
				}
			}
		}

		// Give it x/y pixel coordinates and it returns the Tag at that position; optionally the char position is returned in index
		public LineTag FindCursor(int x, int y, out int index) {
			Line	line;
			LineTag	tag;

			line = GetLineByPixel(y, false);
			tag = line.tags;

			while (true) {
				if (x >= tag.X && x < (tag.X+tag.width)) {
					int	end;

					end = tag.start + tag.length - 1;

					for (int pos = tag.start-1; pos < end; pos++) {
						// When clicking on a character, we position the cursor to whatever edge
						// of the character the click was closer
						if (x < (line.widths[pos] + ((line.widths[pos+1]-line.widths[pos])/2))) {
							index = pos;
							return tag;
						}
					}
					index=end;
					return tag;
				}
				if (tag.next != null) {
					tag = tag.next;
				} else {
					index = line.text.Length;
					return tag;
				}
			}
		}

		// Calculate formatting for the whole document
		public bool RecalculateDocument(Graphics g) {
			return RecalculateDocument(g, 1, this.lines, false);
		}

		// Calculate formatting starting at a certain line
		public bool RecalculateDocument(Graphics g, int start) {
			return RecalculateDocument(g, start, this.lines, false);
		}

		// Calculate formatting within two given line numbers
		public bool RecalculateDocument(Graphics g, int start, int end) {
			return RecalculateDocument(g, start, end, false);
		}

		// With optimize on, returns true if line heights changed
		public bool RecalculateDocument(Graphics g, int start, int end, bool optimize) {
			Line	line;
			int	line_no;
			int	Y;

			Y = GetLine(start).Y;
			line_no = start;
			if (optimize) {
				bool	changed;

				changed = false;

				while (line_no <= end) {
					line = GetLine(line_no++);
					line.Y = Y;
					if (line.recalc) {
						if (line.RecalculateLine(g)) {
							changed = true;
							// If the height changed, all subsequent lines change
							end = this.lines;
						}
					}

					Y += line.height;
				}

				return changed;
			} else {
				while (line_no <= end) {
					line = GetLine(line_no++);
					line.Y = Y;
					line.RecalculateLine(g);
					Y += line.height;
				}
				return true;
			}
		}

		public bool SetCursor(int x, int y) {
			return true;
		}

		public int Size() {
			return lines;
		}
		#endregion	// Public Methods

		#region Administrative
		public IEnumerator GetEnumerator() {
			// FIXME
			return null;
		}

		public override bool Equals(object obj) {
			if (obj == null) {
				return false;
			}

			if (!(obj is Document)) {
				return false;
			}

			if (obj == this) {
				return true;
			}

			if (ToString().Equals(((Document)obj).ToString())) {
				return true;
			}

			return false;
		}

		public override int GetHashCode() {
			return document_id;
		}

		public override string ToString() {
			return "document " + this.document_id;
		}

		#endregion	// Administrative
	}

	public class LineTag {
		#region	Local Variables;
		// Payload; formatting
		internal Font		font;		// System.Drawing.Font object for this tag

		// Payload; text
		internal int		start;		// start, in chars; index into Line.text
		internal int		length;		// length, in chars
		internal bool		r_to_l;		// Which way is the font

		// Drawing support
		internal int		height;		// Height in pixels of the text this tag describes
		internal int		X;		// X location of the text this tag describes
		internal float		width;		// Width in pixels of the text this tag describes

		// Administrative
		internal Line		line;		// The line we're on
		internal LineTag	next;		// Next tag on the same line
		internal LineTag	previous;	// Previous tag on the same line
		#endregion;

		#region Constructors
		public LineTag(Line line, int start, int length) {
			this.line = line;
			this.start = start;
			this.length = length;
			this.X = 0;
			this.width = 0;
		}
		#endregion	// Constructors

		#region Public Methods
		//
		// Applies 'font' to characters starting at 'start' for 'length' chars
		// Removes any previous tags overlapping the same area
		// returns true if lineheight has changed
		//
		public static bool FormatText(Line line, int start, int length, Font font) {
			LineTag	tag;
			LineTag	start_tag;
			LineTag	end_tag;
			int	end;
			int	state;
			int	left;
			bool	retval = false;		// Assume line-height doesn't change

			// Too simple?
			if (font.Height != line.height) {
				retval = true;
			}
			line.recalc = true;		// This forces recalculation of the line in RecalculateDocument

			// A little sanity, not sure if it's needed, might be able to remove for speed
			if (length > line.text.Length) {
				length = line.text.Length;
			}

			tag = line.tags;
			end = start + length;
			state = 0;

			// Common special case
			if ((start == 1) && (length == tag.length)) {
				tag.font = font;
				return retval;
			}

			start_tag = FindTag(line, start);
			end_tag = FindTag(line, end);

			tag = new LineTag(line, start, length);
			tag.font = font;

			if (start == 1) {
				line.tags = tag;
			}

			if (start_tag.start == start) {
				tag.next = start_tag;
				tag.previous = start_tag.previous;
				if (start_tag.previous != null) {
					start_tag.previous.next = tag;
				}
				start_tag.previous = tag;
			} else {
				// Insert ourselves 'in the middle'
				if ((start_tag.next != null) && (start_tag.next.start < end)) {
					tag.next = start_tag.next;
				} else {
					tag.next = new LineTag(line, start_tag.start, start_tag.length);
					tag.next.font = start_tag.font;

					if (start_tag.next != null) {
						tag.next.next = start_tag.next;
						tag.next.next.previous = tag.next;
					}
				}
				tag.next.previous = tag;

				start_tag.length = start - start_tag.start;

				tag.previous = start_tag;
				start_tag.next = tag;
#if crap
				if (tag.next.start > (tag.start + tag.length)) {
					tag.next.length  += tag.next.start - (tag.start + tag.length);
					tag.next.start = tag.start + tag.length;
				}
#endif
			}

			// Elimination loop
			tag = tag.next;
			while ((tag != null) && (tag.start < end)) {
				if ((tag.start + tag.length) <= end) {
					// remove the tag
					tag.previous.next = tag.next;
					if (tag.next != null) {
						tag.next.previous = tag.previous;
					}
					tag = tag.previous;
				} else {
					// Adjust the length of the tag
					tag.length = (tag.start + tag.length) - end;
					tag.start = end;
				}
				tag = tag.next;
			}

			return retval;
		}


		//
		// Finds the tag that describes the character at position 'pos' on 'line'
		//
		public static LineTag FindTag(Line line, int pos) {
			LineTag tag = line.tags;

			// Beginning of line is a bit special
			if (pos == 0) {
				return tag;
			}

			while (tag != null) {
				if ((tag.start <= pos) && (pos < (tag.start+tag.length))) {
					return tag;
				}

				tag = tag.next;
			}

			return null;
		}

		//
		// Combines 'this' tag with 'other' tag.
		//
		public void Combine(LineTag other) {
			if (!this.Equals(other)) {
				return;
			}

			this.width += other.width;
			this.length += other.length;
			this.next = other.next;
			if (this.next != null) {
				this.next.previous = this;
			}
		}


		//
		// Remove 'this' tag ; to be called when formatting is to be removed
		//
		public bool Remove() {
			if ((this.start == 1) && (this.next == null)) {
				// We cannot remove the only tag
				return false;
			}
			if (this.start != 1) {
				this.previous.length += this.length;
				this.previous.width = -1;
				this.previous.next = this.next;
				this.next.previous = this.previous;
			} else {
				this.next.start = 1;
				this.next.length += this.length;
				this.next.width = -1;
				this.line.tags = this.next;
				this.next.previous = null;
			}
			return true;
		}


		//
		// Checks if 'this' tag describes the same formatting options as 'obj'
		//
		public override bool Equals(object obj) {
			LineTag	other;

			if (obj == null) {
				return false;
			}

			if (!(obj is LineTag)) {
				return false;
			}

			if (obj == this) {
				return true;
			}

			other = (LineTag)obj;

			if (this.font.Equals(other.font)) {	// FIXME add checking for things like link or type later
				return true;
			}

			return false;
		}

		public override string ToString() {
			return "Tag starts at index " + this.start + "length " + this.length + " text: " + this.line.Text.Substring(this.start-1, this.length) + "Font " + this.font.ToString();
		}

		#endregion	// Public Methods
	}
}