using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace GUI.Hook
{
    public class KeyboardHook : IHook
    {
        int hHook;
        Win32Api.HookProc KeyboardHookDelegate;

        public event KeyEventHandler OnKeyDownEvent;
        public event KeyEventHandler OnKeyUpEvent;
        public event KeyPressEventHandler OnKeyPressEvent;

        public KeyboardHook() { }

        public void SetHook()
        {
            KeyboardHookDelegate = new Win32Api.HookProc(KeyboardHookProc);
            Process cProcess = Process.GetCurrentProcess();
            ProcessModule cModule = cProcess.MainModule;
            var mh = Win32Api.GetModuleHandle(cModule.ModuleName);
            hHook = Win32Api.SetWindowsHookEx(Win32Api.WH_KEYBOARD_LL, KeyboardHookDelegate, mh, 0);
        }

        public void UnHook()
        {
            Win32Api.UnhookWindowsHookEx(hHook);
        }

        readonly List<Keys> preKeysList = new();

        int KeyboardHookProc(int nCode, int wParam, IntPtr lParam)
        {
            if ((nCode >= 0) && (OnKeyDownEvent != null || OnKeyUpEvent != null || OnKeyPressEvent != null))
            {
                Win32Api.KeyboardHookStruct KeyDataFromHook = (Win32Api.KeyboardHookStruct)Marshal.PtrToStructure(lParam, typeof(Win32Api.KeyboardHookStruct));
                Keys keyData = (Keys)KeyDataFromHook.vkCode;
                if ((OnKeyDownEvent != null || OnKeyPressEvent != null) && (wParam == Win32Api.WM_KEYDOWN || wParam == Win32Api.WM_SYSKEYDOWN))
                {
                    if (IsCtrlAltShiftKeys(keyData) && preKeysList.IndexOf(keyData) == -1)
                    {
                        preKeysList.Add(keyData);
                    }
                }
                if (OnKeyDownEvent != null && (wParam == Win32Api.WM_KEYDOWN || wParam == Win32Api.WM_SYSKEYDOWN))
                {
                    KeyEventArgs e = new(GetDownKeys(keyData));
                    OnKeyDownEvent(this, e);
                }
                if (OnKeyPressEvent != null && wParam == Win32Api.WM_KEYDOWN)
                {
                    byte[] keyState = new byte[256];
                    _ = Win32Api.GetKeyboardState(keyState);
                    byte[] inBuffer = new byte[2];
                    if (Win32Api.ToAscii(KeyDataFromHook.vkCode, KeyDataFromHook.scanCode, keyState, inBuffer, KeyDataFromHook.flags) == 1)
                    {
                        KeyPressEventArgs e = new((char)inBuffer[0]);
                        OnKeyPressEvent(this, e);
                    }
                }
                if ((OnKeyDownEvent != null || OnKeyPressEvent != null) && (wParam == Win32Api.WM_KEYUP || wParam == Win32Api.WM_SYSKEYUP))
                {
                    if (IsCtrlAltShiftKeys(keyData))
                    {
                        for (int i = preKeysList.Count - 1; i >= 0; i--)
                        {
                            if (preKeysList[i] == keyData) { preKeysList.RemoveAt(i); }
                        }
                    }
                }
                if (OnKeyUpEvent != null && (wParam == Win32Api.WM_KEYUP || wParam == Win32Api.WM_SYSKEYUP))
                {
                    KeyEventArgs e = new(GetDownKeys(keyData));
                    OnKeyUpEvent(this, e);
                }
            }
            return Win32Api.CallNextHookEx(hHook, nCode, wParam, lParam);
        }

        Keys GetDownKeys(Keys key)
        {
            Keys rtnKey = Keys.None;
            foreach (Keys i in preKeysList)
            {
                if (i == Keys.LControlKey || i == Keys.RControlKey) { rtnKey |= Keys.Control; }
                if (i == Keys.LMenu || i == Keys.RMenu) { rtnKey |= Keys.Alt; }
                if (i == Keys.LShiftKey || i == Keys.RShiftKey) { rtnKey |= Keys.Shift; }
            }
            return rtnKey | key;
        }

        static bool IsCtrlAltShiftKeys(Keys key)
        {
            if (key == Keys.LControlKey || key == Keys.RControlKey || key == Keys.LMenu || key == Keys.RMenu || key == Keys.LShiftKey || key == Keys.RShiftKey) { return true; }
            return false;
        }
    }
}