using System;

using System.Runtime.InteropServices;

using System.Diagnostics;

namespace Win32

{

    /// <summary>

    /// Provide some utility functions for raw input handling.

    /// </summary>

    static class RawInput

    {

        /// <summary>

        /// 

        /// </summary>

        /// <param name="aRawInputHandle"></param>

        /// <param name="aRawInput"></param>

        /// <param name="rawInputBuffer">Caller must free up memory on the pointer using Marshal.FreeHGlobal</param>

        /// <returns></returns>

        public static bool GetRawInputData(IntPtr aRawInputHandle, ref RAWINPUT aRawInput, ref IntPtr rawInputBuffer)

        {

            bool success = true;

            rawInputBuffer = IntPtr.Zero;

            try

            {

                uint dwSize = 0;

                uint sizeOfHeader = (uint)Marshal.SizeOf(typeof(RAWINPUTHEADER));

                //Get the size of our raw input data.

                Win32.Function.GetRawInputData(aRawInputHandle, Const.RID_INPUT, IntPtr.Zero, ref dwSize, sizeOfHeader);

                //Allocate a large enough buffer

                 rawInputBuffer = Marshal.AllocHGlobal((int)dwSize);

                //Now read our RAWINPUT data

                if (Win32.Function.GetRawInputData(aRawInputHandle, Const.RID_INPUT, rawInputBuffer, ref dwSize, (uint)Marshal.SizeOf(typeof(RAWINPUTHEADER))) != dwSize)

                {

                    return false;

                }

                //Cast our buffer

                aRawInput = (RAWINPUT)Marshal.PtrToStructure(rawInputBuffer, typeof(RAWINPUT));

            }

            catch

            {

                Debug.WriteLine("GetRawInputData failed!");

                success = false;

            }

            return success;

        }

        /// <summary>

        /// 

        /// </summary>

        /// <param name="aRawInputHandle"></param>

        /// <param name="aUsagePage"></param>

        /// <param name="aUsage"></param>

        /// <returns></returns>

        public static bool GetDeviceInfo(IntPtr hDevice, ref RID_DEVICE_INFO deviceInfo)

        {

            bool success = true;

            IntPtr deviceInfoBuffer = IntPtr.Zero;

            try

            {

                //Get Device Info

                uint deviceInfoSize = (uint)Marshal.SizeOf(typeof(RID_DEVICE_INFO));

                deviceInfoBuffer = Marshal.AllocHGlobal((int)deviceInfoSize);

                int res = Win32.Function.GetRawInputDeviceInfo(hDevice, Const.RIDI_DEVICEINFO, deviceInfoBuffer, ref deviceInfoSize);

                if (res <= 0)

                {

                    Debug.WriteLine("WM_INPUT could not read device info: " + Marshal.GetLastWin32Error().ToString());

                    return false;

                }

                //Cast our buffer

                deviceInfo = (RID_DEVICE_INFO)Marshal.PtrToStructure(deviceInfoBuffer, typeof(RID_DEVICE_INFO));

            }

            catch

            {

                Debug.WriteLine("GetRawInputData failed!");

                success = false;

            }

            finally

            {

                //Always executes, prevents memory leak

                Marshal.FreeHGlobal(deviceInfoBuffer);

            }

            return success;

        }

        /// <summary>

        /// Fetch pre-parsed data corresponding to HID descriptor for the given HID device.

        /// </summary>

        /// <param name="device"></param>

        /// <returns></returns>

        public static IntPtr GetPreParsedData(IntPtr hDevice)

        {

            uint ppDataSize = 256;

            int result = Win32.Function.GetRawInputDeviceInfo(hDevice, Win32.Const.RIDI_PREPARSEDDATA, IntPtr.Zero, ref ppDataSize);

            if (result != 0)

            {

                Debug.WriteLine("Failed to get raw input pre-parsed data size" + result + Marshal.GetLastWin32Error());

                return IntPtr.Zero;

            }

            IntPtr ppData = Marshal.AllocHGlobal((int)ppDataSize);

            result = Win32.Function.GetRawInputDeviceInfo(hDevice, Win32.Const.RIDI_PREPARSEDDATA, ppData, ref ppDataSize);

            if (result <= 0)

            {

                Debug.WriteLine("Failed to get raw input pre-parsed data" + result + Marshal.GetLastWin32Error());

                return IntPtr.Zero;

            }

            return ppData;

        }

        /// <summary>

        /// 

        /// </summary>

        /// <param name="device"></param>

        /// <returns></returns>

        public static string GetDeviceName(IntPtr device)

        {

            uint deviceNameSize = 256;

            int result = Win32.Function.GetRawInputDeviceInfo(device, Win32.Const.RIDI_DEVICENAME, IntPtr.Zero, ref deviceNameSize);

            if (result != 0)

            {

                return string.Empty;

            }

            IntPtr deviceName = Marshal.AllocHGlobal((int)deviceNameSize * 2);  // size is the character count not byte count

            try

            {

                result = Win32.Function.GetRawInputDeviceInfo(device, Win32.Const.RIDI_DEVICENAME, deviceName, ref deviceNameSize);

                if (result > 0)

                {

                    return Marshal.PtrToStringAnsi(deviceName, result - 1); // -1 for NULL termination

                }

                return string.Empty;

            }

            finally

            {

                Marshal.FreeHGlobal(deviceName);

            }

        }

    }

}