using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace FLSystem.Win32Api
{
    public class Win32Api

    {

        #region 常数和结构

        public const int WM_KEYDOWN = 0x100;

        public const int WM_KEYUP = 0x101;

        public const int WM_SYSKEYDOWN = 0x104;

        public const int WM_SYSKEYUP = 0x105;

        public const int WH_KEYBOARD_LL = 13;



        [StructLayout(LayoutKind.Sequential)] //声明键盘钩子的封送结构类型 

        public class KeyboardHookStruct

        {

            public int vkCode; //表示一个在1到254间的虚似键盘码 

            public int scanCode; //表示硬件扫描码 

            public int flags;

            public int time;

            public int dwExtraInfo;

        }

        #endregion

        #region Api

        public delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);

        //安装钩子的函数 

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

        //卸下钩子的函数 

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern bool UnhookWindowsHookEx(int idHook);

        //下一个钩挂的函数 

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern int CallNextHookEx(int idHook, int nCode, Int32 wParam, IntPtr lParam);

        [DllImport("user32")]

        public static extern int ToAscii(int uVirtKey, int uScanCode, byte[] lpbKeyState, byte[] lpwTransKey, int fuState);

        [DllImport("user32")]

        public static extern int GetKeyboardState(byte[] pbKeyState);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern IntPtr GetModuleHandle(string lpModuleName);

        #endregion

    }

    public class KeyboardHook
    {
        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);
        }

        private List<Keys> preKeysList = new List<Keys>();//存放被按下的控制键，用来生成具体的键

        private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
        {
            //如果该消息被丢弃（nCode<0）或者没有事件绑定处理程序则不会触发事件
            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;

                //按下控制键
                if ((OnKeyDownEvent != null || OnKeyPressEvent != null) && (wParam == Win32Api.WM_KEYDOWN || wParam == Win32Api.WM_SYSKEYDOWN))
                {
                    if (IsCtrlAltShiftKeys(keyData) && preKeysList.IndexOf(keyData) == -1)
                    {
                        preKeysList.Add(keyData);
                    }
                }
                //WM_KEYDOWN和WM_SYSKEYDOWN消息，将会引发OnKeyDownEvent事件
                if (OnKeyDownEvent != null && (wParam == Win32Api.WM_KEYDOWN || wParam == Win32Api.WM_SYSKEYDOWN))
                {
                    KeyEventArgs e = new KeyEventArgs(GetDownKeys(keyData));
                    OnKeyDownEvent(this, e);
                }

                //WM_KEYDOWN消息将引发OnKeyPressEvent 

                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 KeyPressEventArgs((char)inBuffer[0]);
                        OnKeyPressEvent(this, e);
                    }
                }
                //松开控制键
                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); }
                        }
                    }
                }
                //WM_KEYUP和WM_SYSKEYUP消息，将引发OnKeyUpEvent事件 
                if (OnKeyUpEvent != null && (wParam == Win32Api.WM_KEYUP || wParam == Win32Api.WM_SYSKEYUP))
                {
                    KeyEventArgs e = new KeyEventArgs(GetDownKeys(keyData));
                    OnKeyUpEvent(this, e);
                }
            }
            return Win32Api.CallNextHookEx(hHook, nCode, wParam, lParam);
        }

        //根据已经按下的控制键生成key

        private Keys GetDownKeys(Keys key)
        {
            Keys rtnKey = Keys.None;

            foreach (Keys i in preKeysList)
            {
                if (i == Keys.LControlKey || i == Keys.RControlKey) { rtnKey = rtnKey | Keys.Control; }

                if (i == Keys.LMenu || i == Keys.RMenu) { rtnKey = rtnKey | Keys.Alt; }

                if (i == Keys.LShiftKey || i == Keys.RShiftKey) { rtnKey = rtnKey | Keys.Shift; }
            }
            return rtnKey | key;
        }

        private Boolean 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;

        }

    }

}