// 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;
using System.Windows;
using System.Windows.Documents;
using System.Windows.Media;
using System.Windows.Media.TextFormatting;
using System.Windows.Threading;

using Tango.Scripting.Editors.Document;
using Tango.Scripting.Editors.Rendering;
using Tango.Scripting.Editors.Utils;

namespace Tango.Scripting.Editors.Editing
{
	/// <summary>
	/// Helper class with caret-related methods.
	/// </summary>
	public sealed class Caret
	{
		readonly TextArea textArea;
		readonly TextView textView;
		readonly CaretLayer caretAdorner;
		bool visible;
		
		internal Caret(TextArea textArea)
		{
			this.textArea = textArea;
			this.textView = textArea.TextView;
			position = new TextViewPosition(1, 1, 0);
			
			caretAdorner = new CaretLayer(textView);
			textView.InsertLayer(caretAdorner, KnownLayer.Caret, LayerInsertionPosition.Replace);
			textView.VisualLinesChanged += TextView_VisualLinesChanged;
			textView.ScrollOffsetChanged += TextView_ScrollOffsetChanged;
		}
		
		void TextView_VisualLinesChanged(object sender, EventArgs e)
		{
			if (visible) {
				Show();
			}
			// required because the visual columns might have changed if the
			// element generators did something differently than on the last run
			// (e.g. a FoldingSection was collapsed)
			InvalidateVisualColumn();
		}
		
		void TextView_ScrollOffsetChanged(object sender, EventArgs e)
		{
			if (caretAdorner != null) {
				caretAdorner.InvalidateVisual();
			}
		}
		
		double desiredXPos = double.NaN;
		TextViewPosition position;
		
		/// <summary>
		/// Gets/Sets the position of the caret.
		/// Retrieving this property will validate the visual column (which can be expensive).
		/// Use the <see cref="Location"/> property instead if you don't need the visual column.
		/// </summary>
		public TextViewPosition Position {
			get {
				ValidateVisualColumn();
				return position;
			}
			set {
				if (position != value) {
					position = value;
					
					storedCaretOffset = -1;
					
					//Debug.WriteLine("Caret position changing to " + value);
					
					ValidatePosition();
					InvalidateVisualColumn();
					RaisePositionChanged();
					Log("Caret position changed to " + value);
					if (visible)
						Show();
				}
			}
		}
		
		/// <summary>
		/// Gets the caret position without validating it.
		/// </summary>
		internal TextViewPosition NonValidatedPosition {
			get {
				return position;
			}
		}
		
		/// <summary>
		/// Gets/Sets the location of the caret.
		/// The getter of this property is faster than <see cref="Position"/> because it doesn't have
		/// to validate the visual column.
		/// </summary>
		public TextLocation Location {
			get {
				return position.Location;
			}
			set {
				this.Position = new TextViewPosition(value);
			}
		}
		
		/// <summary>
		/// Gets/Sets the caret line.
		/// </summary>
		public int Line {
			get { return position.Line; }
			set {
				this.Position = new TextViewPosition(value, position.Column);
			}
		}
		
		/// <summary>
		/// Gets/Sets the caret column.
		/// </summary>
		public int Column {
			get { return position.Column; }
			set {
				this.Position = new TextViewPosition(position.Line, value);
			}
		}
		
		/// <summary>
		/// Gets/Sets the caret visual column.
		/// </summary>
		public int VisualColumn {
			get {
				ValidateVisualColumn();
				return position.VisualColumn;
			}
			set {
				this.Position = new TextViewPosition(position.Line, position.Column, value);
			}
		}
		
		bool isInVirtualSpace;
		
		/// <summary>
		/// Gets whether the caret is in virtual space.
		/// </summary>
		public bool IsInVirtualSpace {
			get {
				ValidateVisualColumn();
				return isInVirtualSpace;
			}
		}
		
		int storedCaretOffset;
		
		internal void OnDocumentChanging()
		{
			storedCaretOffset = this.Offset    bc f8 15 dc 68 a5 8c 75 1b 97 b5 40 a5 c2 1f 08