Equation Calculator with Graphing

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Controls;
using System.Windows.Input;
using System.Xml;
using System.Collections.ObjectModel;
using System.Windows;

namespace CommonUtils
{
	[TemplatePart(Name="PART_Popup", Type=typeof(HistoryListPopup))]
	public class TextBoxWithHistory : TextBox
	{
		HistoryList m_history;
		Button m_dropButton;
		HistoryListPopup m_popup;
		static TextBoxWithHistory()
		{
			DefaultStyleKeyProperty.OverrideMetadata(typeof(TextBoxWithHistory), new FrameworkPropertyMetadata(typeof(TextBoxWithHistory)));
		}
		public override void OnApplyTemplate()
		{
			base.OnApplyTemplate();
			Popup = Template.FindName("PART_Popup", this) as HistoryListPopup;
			m_dropButton = Template.FindName("PART_DropButton", this) as Button;
			if (m_dropButton != null)
				m_dropButton.Click += OnDropButtonClick;
		}
		public HistoryListPopup Popup 
		{
			get { return m_popup;}
			private set
			{
				if (m_popup != null)
					m_popup.Closed -= OnPopupClosed;
				m_popup = value;
				if (m_popup != null)
				{
					m_popup.Closed += OnPopupClosed;
					if (History != null)
						Popup.HistoryList = m_history.Items;
				}
			}
		}
		public HistoryList History 
		{
			get 
			{
				return m_history;
			} 
			set
			{
				m_history = value;
				if (Popup != null)
					Popup.HistoryList = m_history.Items;
			}
		}
		public void AddToHistory(string text, bool clearText)
		{
			History.Add(text);
			if (clearText)
				Text = string.Empty;
		}
		public TextBoxWithHistory()
		{
			History = new HistoryList();
		}
		string m_saved = string.Empty;
		protected override void OnPreviewKeyDown(System.Windows.Input.KeyEventArgs e)
		{
			//Console.WriteLine("{0}: Key {1}, SystemKey {2}", DateTime.Now.ToLongTimeString(), e.Key, e.SystemKey);
			if (e.Key == Key.Escape && IsFocused)
			{
				History.Reset();
				Text = string.Empty;
				if (Popup != null)
					Popup.Close(false);
				e.Handled = true;
				return;
			}
			if (e.Key == Key.Up && IsFocused)
			{
				if (History.CurIndex < 0)
					m_saved = Text;
				string text = string.Empty;
				if (History.Prev(out text))
				{
					Text = text;
					CaretIndex = Text.Length;
					SelectAll();
				}
				e.Handled = true;
				return;
			}
			if (e.Key == Key.Down && IsFocused)
			{
				string text = string.Empty;
				if (History.Next(out text))
				{
					if (History.CurIndex < 0)
						text = m_saved;
					Text = text;
					CaretIndex = Text.Length;
					SelectAll();
				}
				e.Handled = true;
				return;
			}
			if (e.Key == Key.Left || e.Key == Key.Right)
			{
				// any left / right will reset the history index and clear the 'saved'
				History.Reset();
				m_saved = string.Empty;
			}
			if (e.SystemKey == Key.Down && e.KeyboardDevice.Modifiers == ModifierKeys.Alt)
			{
				if (IsFocused)
				{
					OnDropButtonClick(null, null);
					e.Handled = true;
					return;
				}
			}
			base.OnPreviewKeyDown(e);
		}
		void OnDropButtonClick(object sender, EventArgs e)
		{
			if (Popup != null)
				Popup.Open(Text);
		}
		void OnPopupClosed(object sender, EventArgs e)
		{
			HistoryListPopup popup = sender as HistoryListPopup;
			if (popup.PopupResult)
			{
				Text = popup.SelectedItem;
				CaretIndex = Text.Length;
			}
			Focus();
		}
	}
	public class HistoryList 
	{
		public int CurIndex {get; private set;}
		public int MaxCount {get; set;}
		public ObservableCollection<string> Items {get; set;}
		public HistoryList()
		{
			Items = new ObservableCollection<string>();
			MaxCount = 50;
		}
		public void Add(string text)
		{
			text = text.Trim();
			if (text.Length == 0)
				return;
			int index = Items.IndexOf(text);
			if (index > 0)
				Items.RemoveAt(index);
			if (index != 0)
				Items.Insert(0, text);
			Items.Truncate(MaxCount);
			Reset();
		}
		public bool Prev(out string value)
		{
			value = string.Empty;
			if (CurIndex < Items.Count - 1)
			{
				CurIndex++;
				if (CurIndex >= 0 && CurIndex < Items.Count)
				{
					value = Items[CurIndex];
					return true;
				}
			}
			return false;
		}
		public bool Next(out string value)
		{
			value = string.Empty;
			if (CurIndex >= 0)
			{
				CurIndex--;
				if (CurIndex >= 0 && CurIndex < Items.Count)
					value = Items[CurIndex];
				return true;
			}
			return false;
		}
		public void Reset()
		{
			CurIndex = -1;
		}
		public void Clear()
		{
			Items.Clear();
			Reset();
		}
		public void Write(XmlTextWriter wr, string name)
		{
			wr.WriteStartElement("list");
			if (name.Length > 0)
				wr.WriteAttributeString("name", name);
			foreach (string hist in Items)
				wr.WriteElementString("item", hist);
			wr.WriteEndElement();
		}
		public void Read(XmlElement node)
		{
			if (node == null)
				return;
			Clear();
			System.Diagnostics.Debug.Assert(node.Name == "list");
			foreach (XmlElement child in node.ChildNodes)
			{
				if (child.Name == "item")
					Items.Add(child.InnerText);
			}
		}
	}
	public class HistoryListPopup : System.Windows.Controls.Primitives.Popup
	{
		ListBox m_historyListBox = null;
		public static DependencyProperty SelectedItemProperty = DependencyProperty.Register("SelectedItem", typeof(string), typeof(HistoryListPopup));
		ObservableCollection<string> m_list;
		public bool PopupResult {get; protected set;}
		public string SelectedItem 
		{
			get { return (string)GetValue(SelectedItemProperty); }
			set { SetValue(SelectedItemProperty, value); }
		}
		public ObservableCollection<string> HistoryList 
		{
			get { return m_list;}
			set
			{
				m_list = value;
				DataContext = this;
			}
		}
		public HistoryListPopup()
		{
			SelectedItem = string.Empty;
			Loaded += new RoutedEventHandler(OnLoaded);
		}
		void OnLoaded(object sender, RoutedEventArgs e)
		{
			if (m_historyListBox != null)
				return;
			m_historyListBox = VisualTreeUtils.FindVisualChildByName<ListBox>(Child, "m_historyListBox");
			if (m_historyListBox != null)
			{
				// cool, attach and receive event even if it has been handled (true)
				m_historyListBox.AddHandler(ListBox.MouseLeftButtonDownEvent,
					(RoutedEventHandler)OnLeftButtonDown,
					true);
			}
		}
		void OnLeftButtonDown(object sender, RoutedEventArgs e)
		{
			Close(SelectedItem.Length > 0);
		}
		public virtual void Open(string curText)
		{
			SelectedItem = curText;
			IsOpen = true;
			ListBox lb = Child as ListBox;
			if (lb != null)
			{
				lb.Focus();
				ListBoxItem item = lb.ItemContainerGenerator.ContainerFromItem(lb.SelectedItem) as ListBoxItem;
				if (item != null)
					item.Focus();
				else if (HistoryList.Count > 0)
					item = lb.ItemContainerGenerator.ContainerFromItem(HistoryList[0]) as ListBoxItem;
				if (item != null)
					item.Focus();
			}
		}
		public virtual void Close(bool result)
		{
			PopupResult = result;
			IsOpen = false;
			UIElement target = PlacementTarget;
			if (target != null)
				target.Focus();
		}
		protected override void OnOpened(EventArgs e)
		{
			PopupResult = false;
			base.OnOpened(e);
		}
		protected override void OnPreviewKeyDown(KeyEventArgs e)
		{
			base.OnPreviewKeyDown(e);
			if (e.Key == Key.Escape)
			{
				Close(false);
				return;
			}
			if (e.Key == Key.Enter)
			{
				Close(true);
				return;
			}
		}
	}
}