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

namespace JD.Threading
{

    public static class Win32MessageLoop
    {
        #region Methods

        public static void WaitAndPump(WaitHandle waitHandle)
        {
            var safeHandle = waitHandle.SafeWaitHandle;
            IntPtr[] handles = new IntPtr[1];

            const int QS_ALLINPUT = 0x04FF;
            const int MWMO_INPUTAVAILABLE = 0x0004;
            const int WAIT_OBJECT_0 = 0;
            const int WAIT_FAILED = -1;
            const int WAIT_MESSAGE = WAIT_OBJECT_0 + 1; // + handles.Length

            while (true)
            {
                Application.DoEvents();

                bool mustRelease = false;
                safeHandle.DangerousAddRef(ref mustRelease);
                handles[0] = safeHandle.DangerousGetHandle();

                int result = MsgWaitForMultipleObjectsEx(1, handles, Timeout.Infinite, QS_ALLINPUT, MWMO_INPUTAVAILABLE);

                if (mustRelease)
                {
                    safeHandle.DangerousRelease();
                }

                switch (result)
                {
                    case WAIT_FAILED:
                        Marshal.ThrowExceptionForHR(Marshal.GetLastWin32Error());
                        break;

                    case WAIT_OBJECT_0:
                        return;

                    case WAIT_MESSAGE:
                        break;

                    default:
                        throw new NotImplementedException();
                }
            }
        }

        #endregion

        #region Dll Interop

        [DllImport("User32.dll", SetLastError = true)]
        private static extern int MsgWaitForMultipleObjectsEx(int nCount, [In, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 0)] IntPtr[] pHandles, int dwMilliseconds, int dwWakeMask, int dwFlags);

        #endregion
    }
}