using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace VdiDiagnostics {
    public class AdapterResult {
        public string Name;
        public uint VendorId;
        public int DeviceResult;
    }

    // Enumerate the actual DXGI adapters and create a D3D11 device on each NVIDIA
    // adapter. A WMI/PnP model name alone does not prove that D3D is operational.
    public static class D3DProbe {
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        private struct AdapterDesc {
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)] public string Description;
            public uint VendorId, DeviceId, SubSysId, Revision;
            public UIntPtr DedicatedVideoMemory, DedicatedSystemMemory, SharedSystemMemory;
            public long AdapterLuid;
        }
        [UnmanagedFunctionPointer(CallingConvention.StdCall)]
        private delegate int EnumAdapters(IntPtr factory, uint index, out IntPtr adapter);
        [UnmanagedFunctionPointer(CallingConvention.StdCall)]
        private delegate int GetDesc(IntPtr adapter, out AdapterDesc desc);
        [DllImport("dxgi.dll")]
        private static extern int CreateDXGIFactory1(ref Guid iid, out IntPtr factory);
        [DllImport("d3d11.dll")]
        private static extern int D3D11CreateDevice(IntPtr adapter, uint driverType,
            IntPtr software, uint flags, IntPtr levels, uint levelCount, uint sdkVersion,
            out IntPtr device, out uint featureLevel, out IntPtr context);

        public static AdapterResult[] Check() {
            var results = new List<AdapterResult>();
            var iid = new Guid("770aae78-f26f-4dba-a829-253c83d1b387");
            IntPtr factory;
            Marshal.ThrowExceptionForHR(CreateDXGIFactory1(ref iid, out factory));
            try {
                var table = Marshal.ReadIntPtr(factory);
                var enumerate = (EnumAdapters)Marshal.GetDelegateForFunctionPointer(
                    Marshal.ReadIntPtr(table, 7 * IntPtr.Size), typeof(EnumAdapters));
                for (uint i = 0; i < 32; i++) {
                    IntPtr adapter;
                    int hr = enumerate(factory, i, out adapter);
                    if (hr == unchecked((int)0x887A0002)) break;
                    Marshal.ThrowExceptionForHR(hr);
                    try {
                        var descMethod = (GetDesc)Marshal.GetDelegateForFunctionPointer(
                            Marshal.ReadIntPtr(Marshal.ReadIntPtr(adapter), 8 * IntPtr.Size), typeof(GetDesc));
                        AdapterDesc desc;
                        Marshal.ThrowExceptionForHR(descMethod(adapter, out desc));
                        if (desc.VendorId != 0x10de) continue;
                        IntPtr device, context;
                        uint level;
                        hr = D3D11CreateDevice(adapter, 0, IntPtr.Zero, 0, IntPtr.Zero,
                            0, 7, out device, out level, out context);
                        if (context != IntPtr.Zero) Marshal.Release(context);
                        if (device != IntPtr.Zero) Marshal.Release(device);
                        results.Add(new AdapterResult { Name = desc.Description,
                            VendorId = desc.VendorId, DeviceResult = hr });
                    } finally { Marshal.Release(adapter); }
                }
            } finally { Marshal.Release(factory); }
            return results.ToArray();
        }
    }
}