Query/Query/Controls/QueryTextBox.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using Base;
using Query.Core;

namespace Query.Controls {
	sealed partial class QueryTextBox : UserControl {
		public event EventHandler<CommandEventArgs> CommandRan;

		private CommandHistory history;
		private Action<string> log;

		public QueryTextBox() {
			InitializeComponent();
		}

		public void Setup(CommandHistory historyObj, Action<string> logFunc) {
			history = historyObj;
			log = logFunc;
		}

		private void OnCommandRan() {
			CommandRan?.Invoke(this, new CommandEventArgs(tb.Text));
		}

		private sealed class CustomTextBox : TextBox {
			private string lastInputStr = string.Empty;
			private int lastInputPos = 0;

			private bool doResetHistoryMemory;
			private bool lastArrowShift;
			private int historyOffset;

			public CustomTextBox() {
				TextChanged += CustomTextBox_TextChanged;
			}

			protected override void OnKeyDown(KeyEventArgs e) {
				QueryTextBox input = (QueryTextBox) Parent;
				CommandHistory history = input.history;

				Keys key = e.KeyCode;
				bool handled = false;

				switch (key) {
					case Keys.Enter:
						if (Text != string.Empty) {
							input.OnCommandRan();

							Text = string.Empty;
							doResetHistoryMemory = true;
							handled = true;
						}

						break;

					case Keys.Up:
						if (lastArrowShift != e.Shift) {
							lastArrowShift = e.Shift;
							historyOffset = 0;
						}

						--historyOffset;

						if (InsertFromHistory(e.Shift ? history.Results : history.Queries)) {
							++historyOffset;
						}

						handled = true;
						break;

					case Keys.Down:
						if (lastArrowShift != e.Shift) {
							lastArrowShift = e.Shift;
							historyOffset = 0;
						}

						++historyOffset;

						if (InsertFromHistory(e.Shift ? history.Results : history.Queries)) {
							--historyOffset;
						}

						handled = true;
						break;

					case Keys.C:
						if (e.Modifiers == Keys.Control) {
							if (SelectionLength == 0 && history.Results.Count > 0) {
								Clipboard.SetText(history.Results.Last(), TextDataFormat.UnicodeText);
								input.log("Copied to clipboard.");
								handled = true;
							}
						}

						break;
				}

				if (!handled && key != Keys.ControlKey && key != Keys.ShiftKey && key != Keys.Menu) {
					doResetHistoryMemory = true;
				}

				e.Handled = e.SuppressKeyPress = handled;
				base.OnKeyDown(e);
			}

			protected override void OnKeyUp(KeyEventArgs e) {
				base.OnKeyUp(e);

				if (doResetHistoryMemory) {
					doResetHistoryMemory = false;
					ResetHistoryMemory();
				}
			}

			private void CustomTextBox_TextChanged(object sender, EventArgs e) {
				ResetHistoryMemory();
			}

			// Management

			private void ResetHistoryMemory() {
				lastInputStr = Text;
				lastInputPos = SelectionStart;
				historyOffset = 0;
			}

			private bool InsertFromHistory(IList<string> collection) {
				if (collection.Count == 0) {
					return true;
				}

				int index = collection.Count + historyOffset;
				bool wasClamped = false;

				if (index < 0) {
					index = 0;
					wasClamped = true;
				}
				else if (index >= collection.Count) {
					index = collection.Count - 1;
					wasClamped = true;
				}

				TextChanged -= CustomTextBox_TextChanged;

				Text = lastInputStr.Insert(lastInputPos, collection[index]);
				SelectionStart = lastInputPos + collection[index].Length;
				SelectionLength = 0;

				TextChanged += CustomTextBox_TextChanged;
				return wasClamped;
			}
		}
	}
}