using System;
using System.Windows.Forms;
using SystemTrayMenu.UserInterface.Controls;
using SystemTrayMenu.Utilities;

namespace SystemTrayMenu.Helper
{
    public sealed class KeyboardHook : IDisposable
    {
        /// <summary>
        /// Represents the window that is used internally to get the messages.
        /// </summary>
        private class Window : NativeWindow, IDisposable
        {
            private const int WM_HOTKEY = 0x0312;

            public Window()
            {
                // create the handle for the window.
                CreateHandle(new CreateParams());
            }

            /// <summary>
            /// Overridden to get the notifications.
            /// </summary>
            /// <param name="m"></param>
            protected override void WndProc(ref Message m)
            {
                base.WndProc(ref m);

                // check if we got a hot key pressed.
                if (m.Msg == WM_HOTKEY)
                {
                    // get the keys.
                    Keys key = (Keys)(((int)m.LParam >> 16) & 0xFFFF);
                    KeyboardHookModifierKeys modifier = (KeyboardHookModifierKeys)((int)m.LParam & 0xFFFF);

                    // invoke the event to notify the parent.
                    KeyPressed?.Invoke(this, new KeyPressedEventArgs(modifier, key));
                }
            }

            public event EventHandler<KeyPressedEventArgs> KeyPressed;

            #region IDisposable Members

            public void Dispose()
            {
                DestroyHandle();
            }

            #endregion
        }

        private readonly Window _window = new Window();
        private int _currentId;

        public KeyboardHook()
        {
            // register the event of the inner native window.
            _window.KeyPressed += delegate (object sender, KeyPressedEventArgs args)
            {
                KeyPressed?.Invoke(this, args);
            };
        }

        /// <summary>
        /// Registers a hot key in the system.
        /// </summary>
        /// <param name="key">The key itself that is associated with the hot key.</param>
        internal void RegisterHotKey(Keys key)
        {
            uint keyModifiersNone = 0;
            RegisterHotKey(keyModifiersNone, key);
        }

        internal void RegisterHotKey()
        {
            KeyboardHookModifierKeys modifiers = KeyboardHookModifierKeys.None;
            string modifiersString = Properties.Settings.Default.HotKey;
            if (!string.IsNullOrEmpty(modifiersString))
            {
                if (modifiersString.ToUpperInvariant().Contains("ALT", StringComparison.InvariantCulture))
                {
                    modifiers |= KeyboardHookModifierKeys.Alt;
                }
                if (modifiersString.ToUpperInvariant().Contains("CTRL", StringComparison.InvariantCulture) ||
                    modifiersString.ToUpperInvariant().Contains("STRG", StringComparison.InvariantCulture))
                {
                    modifiers |= KeyboardHookModifierKeys.Control;
                }
                if (modifiersString.ToUpperInvariant().Contains("SHIFT", StringComparison.InvariantCulture))
                {
                    modifiers |= KeyboardHookModifierKeys.Shift;
                }
                if (modifiersString.ToUpperInvariant().Contains("WIN", StringComparison.InvariantCulture))
                {
                    modifiers |= KeyboardHookModifierKeys.Win;
                }
            }

            RegisterHotKey(modifiers,
                HotkeyControl.HotkeyFromString(
                    Properties.Settings.Default.HotKey));
        }

        /// <summary>
        /// Registers a hot key in the system.
        /// </summary>
        /// <param name="modifier">The modifiers that are associated with the hot key.</param>
        /// <param name="key">The key itself that is associated with the hot key.</param>
        //internal void RegisterHotKey(KeyboardHookModifierKeys modifier, Keys key)
        internal void RegisterHotKey(KeyboardHookModifierKeys modifier, Keys key)
        {
            RegisterHotKey((uint)modifier, key);
        }

        private void RegisterHotKey(uint modifier, Keys key)
        {
            _currentId += 1;

            if (!DllImports.NativeMethods.User32RegisterHotKey(
                _window.Handle, _currentId, modifier, (uint)key))
            {
                throw new InvalidOperationException(
                    Translator.GetText("Could not register the hot key."));
            }
        }

        /// <summary>
        /// A hot key has been pressed.
        /// </summary>
        internal event EventHandler<KeyPressedEventArgs> KeyPressed;

        #region IDisposable Members

        public void Dispose()
        {
            // unregister all the registered hot keys.
            for (int i = _currentId; i > 0; i--)
            {
                DllImports.NativeMethods.User32UnregisterHotKey(_window.Handle, i);
            }

            // dispose the inner native window.
            _window.Dispose();
        }

        #endregion
    }

    /// <summary>
    /// Event Args for the event that is fired after the hot key has been pressed.
    /// </summary>
    internal class KeyPressedEventArgs : EventArgs
    {
        private readonly KeyboardHookModifierKeys _modifier;
        private readonly Keys _key;

        internal KeyPressedEventArgs(KeyboardHookModifierKeys modifier, Keys key)
        {
            _modifier = modifier;
            _key = key;
        }

        internal KeyboardHookModifierKeys Modifier => _modifier;

        internal Keys Key => _key;
    }

    /// <summary>
    /// The enumeration of possible modifiers.
    /// </summary>
    [Flags]
    internal enum KeyboardHookModifierKeys : uint
    {
        None = 0,
        Alt = 1,
        Control = 2,
        Shift = 4,
        Win = 8
    }
}