using System.Collections.Generic;
using OpenTK.Input;

namespace BizHawk.Client.EmuHawk
{
	public static class OTK_Keyboard
	{
		private static readonly Key[] KeyList = {
			// A-Z
			Key.A, Key.B, Key.C, Key.D, Key.E, Key.F, Key.G, Key.H, Key.I, Key.J, Key.K, Key.L, Key.M, Key.N, Key.O, Key.P, Key.Q, Key.R, Key.S, Key.T, Key.U, Key.V, Key.W, Key.X, Key.Y, Key.Z,
			// 0-9
			Key.Number1, Key.Number2, Key.Number3, Key.Number4, Key.Number5, Key.Number6, Key.Number7, Key.Number8, Key.Number9, Key.Number0,
			// misc. printables (ASCII order)
			Key.Space, Key.Quote, Key.Comma, Key.Minus, Key.Period, Key.Slash, Key.Semicolon, Key.Plus, Key.BracketLeft, Key.BackSlash, Key.BracketRight, Key.Tilde,
			// misc. (alphabetically)
			Key.BackSpace, Key.CapsLock, Key.Delete, Key.Down, Key.End, Key.Enter, Key.Escape, Key.Home, Key.Insert, Key.Left, Key.PageDown, Key.PageUp, Key.Pause, Key.Right, Key.ScrollLock, Key.Tab, Key.Up,
			// modifier
			Key.WinLeft, Key.WinRight, Key.ControlLeft, Key.ControlRight, Key.AltLeft, Key.AltRight, Key.ShiftLeft, Key.ShiftRight,

			// function
			Key.F1, Key.F2, Key.F3, Key.F4, Key.F5, Key.F6, Key.F7, Key.F8, Key.F9, Key.F10, Key.F11, Key.F12,
			// keypad (alphabetically)
			Key.Keypad0, Key.Keypad1, Key.Keypad2, Key.Keypad3, Key.Keypad4, Key.Keypad5, Key.Keypad6, Key.Keypad7, Key.Keypad8, Key.Keypad9, Key.KeypadAdd, Key.KeypadDecimal, Key.KeypadDivide, Key.KeypadEnter, Key.KeypadMultiply, Key.KeypadSubtract
		};

		private static readonly List<KeyEvent> EventList = new List<KeyEvent>();
		private static KeyboardState _kbState;

		public static void Initialize ()
		{
			_kbState = Keyboard.GetState();
		}

		public static IEnumerable<KeyEvent> Update()
		{
			EventList.Clear();
			var lastState = _kbState;
			try
			{
				_kbState = Keyboard.GetState();
				foreach (var key in KeyList)
				{
					if (lastState.IsKeyUp(key) && _kbState.IsKeyDown(key))
						EventList.Add(new KeyEvent { Key = key, Pressed = true });
					else if (lastState.IsKeyDown(key) && _kbState.IsKeyUp(key))
						EventList.Add(new KeyEvent { Key = key, Pressed = false });
				}
			}
			catch
			{
				// OpenTK's keyboard class isn't thread safe.
				// In rare cases (sometimes it takes up to 10 minutes to occur) it will
				// be updating the keyboard state when we call GetState() and choke.
				// Until I fix OpenTK, it's fine to just swallow it because input continues working.
				if (System.Diagnostics.Debugger.IsAttached)
				{
					System.Console.WriteLine("OpenTK Keyboard thread is angry.");
				}
			}
			return EventList;
		}

		public static bool IsPressed(Key key)
		{
			return _kbState.IsKeyDown(key);
		}

		public static bool ShiftModifier => IsPressed(Key.ShiftLeft) || IsPressed(Key.ShiftRight);

		public static bool CtrlModifier => IsPressed(Key.ControlLeft) || IsPressed(Key.ControlRight);

		public static bool AltModifier => IsPressed(Key.AltLeft) || IsPressed(Key.AltRight);

		public static Input.ModifierKey GetModifierKeysAsKeys()
		{
			Input.ModifierKey ret = Input.ModifierKey.None;
			if (ShiftModifier)
				ret |= Input.ModifierKey.Shift;
			if (CtrlModifier)
				ret |= Input.ModifierKey.Control;
			if (AltModifier)
				ret |= Input.ModifierKey.Alt;
			return ret;
		}
	}

	internal static class KeyExtensions
	{
		public static bool IsModifier (this Key key)
		{
			if (key == Key.ShiftLeft)
				return true;
			if (key == Key.ShiftRight)
				return true;
			if (key == Key.ControlLeft)
				return true;
			if (key == Key.ControlRight)
				return true;
			if (key == Key.AltLeft)
				return true;
			if (key == Key.AltRight)
				return true;
			return false;
		}
	}

	public struct KeyEvent
	{
		public Key Key;
		public bool Pressed;
	}
}