using System;
using System.Runtime.InteropServices;

namespace RtcUtil
{
    public enum MediaDeviceKind
    {
        AUDIOINPUT,
        AUDIOOUTPUT,
        VIDEOINPUT
    };

    public class MediaDeviceInfo
    {
        public string DeviceId { get; set; }
        public string Label { get; set; }
        public MediaDeviceKind Kind { get; set; }
        public string GroupId { get; set; }
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct NativeMediaDeviceInfo
    {
        public UInt32 DeviceNumber;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
        public string DeviceNameUTF8;        
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
        public string DeviceUniqueIdUTF8;        
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
        public string ProductUniqueIdUTF8;        
    }

    public class MediaDevices
    {
        [DllImport("x64\\RtcUtil.Native.x64.dll", EntryPoint = "CreateVideoDeviceInfo", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
        internal static extern int CreateVideoDeviceInfo(out IntPtr deviceInfo);
        [DllImport("x64\\RtcUtil.Native.x64.dll", EntryPoint = "GetVidoeDeviceInfo", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
        internal static extern int GetVidoeDeviceInfo(IntPtr hDeviceInfo, UInt32 deviceNumber, out IntPtr meadiaDeviceInfo);
        public static IList<string> EnumerateVideoDevices()
        {
            var list = new List<string>();  
            IntPtr ptrInfo;
            var num = CreateVideoDeviceInfo(out ptrInfo);
            if (ptrInfo != IntPtr.Zero)
            {
                for(UInt32 i =0;i< num; i++)
                {
                    IntPtr ptrMdDeviceInfo;
                    var retValue = GetVidoeDeviceInfo(ptrInfo, i, out ptrMdDeviceInfo);
                    if (retValue != -1)
                    {
                        var info = (NativeMediaDeviceInfo)Marshal.PtrToStructure(ptrMdDeviceInfo, typeof(NativeMediaDeviceInfo));
                        list.Add(info.DeviceNameUTF8);//TODO need other properties , such as ID ?
                    }
                }
                
            }

            return list;
        }
    }
}