using System;
using System.Runtime.InteropServices;
using System.Threading;

namespace BluetoothLENet
{
    class BetterScanner
    {
        /// <summary>
        /// The BLUETOOTH_FIND_RADIO_PARAMS structure facilitates enumerating installed Bluetooth radios.
        /// </summary>
        [StructLayout(LayoutKind.Sequential)]
        private struct BLUETOOTH_FIND_RADIO_PARAM
        {
            internal UInt32 dwSize;

            internal void Initialize()
            {
                this.dwSize = (UInt32)Marshal.SizeOf(typeof(BLUETOOTH_FIND_RADIO_PARAM));
            }
        }

        /// <summary>
        /// Closes an open object handle.
        /// </summary>
        /// <param name="handle">[In] A valid handle to an open object.</param>
        /// <returns>If the function succeeds, the return value is nonzero. If the function fails, the return value is zero. To get extended error information, call GetLastError.</returns>
        [DllImport("Kernel32.dll", SetLastError = true)]
        static extern bool CloseHandle(IntPtr handle);

        /// <summary>
        /// Finds the first bluetooth radio present in device manager
        /// </summary>
        /// <param name="pbtfrp">Pointer to a BLUETOOTH_FIND_RADIO_PARAMS structure</param>
        /// <param name="phRadio">Pointer to where the first enumerated radio handle will be returned. When no longer needed, this handle must be closed via CloseHandle.</param>
        /// <returns>In addition to the handle indicated by phRadio, calling this function will also create a HBLUETOOTH_RADIO_FIND handle for use with the BluetoothFindNextRadio function.
        /// When this handle is no longer needed, it must be closed via the BluetoothFindRadioClose.
        /// Returns NULL upon failure. Call the GetLastError function for more information on the error. The following table describe common errors:</returns>
        [DllImport("irprops.cpl", SetLastError = true)]
        static extern IntPtr BluetoothFindFirstRadio(ref BLUETOOTH_FIND_RADIO_PARAM pbtfrp, out IntPtr phRadio);

        [StructLayout(LayoutKind.Sequential)]
        private struct LE_SCAN_REQUEST
        {
            internal int scanType;
            internal ushort scanInterval;
            internal ushort scanWindow;
        }

        [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]
        static extern bool DeviceIoControl(IntPtr hDevice, uint dwIoControlCode,
            ref LE_SCAN_REQUEST lpInBuffer, uint nInBufferSize,
            IntPtr lpOutBuffer, uint nOutBufferSize,
            out uint lpBytesReturned, IntPtr lpOverlapped);

        /// <summary>
        /// Starts scanning for LE devices.
        /// Example: BetterScanner.StartScanner(0, 29, 29)
        /// </summary>
        /// <param name="scanType">0 = Passive, 1 = Active</param>
        /// <param name="scanInterval">Interval in 0.625 ms units</param>
        /// <param name="scanWindow">Window in 0.625 ms units</param>
        public static void StartScanner(int scanType, ushort scanInterval, ushort scanWindow)
        {
            var thread = new Thread(() =>
            {
                BLUETOOTH_FIND_RADIO_PARAM param = new BLUETOOTH_FIND_RADIO_PARAM();
                param.Initialize();
                IntPtr handle;
                BluetoothFindFirstRadio(ref param, out handle);
                uint outsize;
                LE_SCAN_REQUEST req = new LE_SCAN_REQUEST
                    { scanType = scanType, scanInterval = scanInterval, scanWindow = scanWindow };
                DeviceIoControl(handle, 0x41118c, ref req, 8, IntPtr.Zero, 0, out outsize, IntPtr.Zero);
            });
            thread.Start();
        }
    }
}