/*
 
  This Source Code Form is subject to the terms of the Mozilla Public
  License, v. 2.0. If a copy of the MPL was not distributed with this
  file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
  Copyright (C) 2020 Michael Möller <mmoeller@openhardwaremonitor.org>
 
*/

using System;
using System.Runtime.InteropServices;

namespace OpenHardwareMonitor.Hardware.Nvidia {
  internal class NVML {

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate NvmlReturn nvmlInitDelegate();
    private static readonly nvmlInitDelegate nvmlInit;

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate NvmlReturn nvmlInit_v2Delegate();
    private static readonly nvmlInit_v2Delegate nvmlInit_v2;
      
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public delegate NvmlReturn nvmlShutdownDelegate();
    public static readonly nvmlShutdownDelegate NvmlShutdown;

    public delegate NvmlReturn nvmlDeviceGetHandleByPciBusIdDelegate(
      string pciBusId, out NvmlDevice device);
    public static readonly nvmlDeviceGetHandleByPciBusIdDelegate
      NvmlDeviceGetHandleByPciBusId;

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public delegate NvmlReturn nvmlDeviceGetPowerUsageDelegate(
      NvmlDevice device, out int power);
    public static readonly nvmlDeviceGetPowerUsageDelegate 
      NvmlDeviceGetPowerUsage;

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public delegate NvmlReturn nvmlDeviceGetPcieThroughputDelegate(
      NvmlDevice devicee, NvmlPcieUtilCounter counter, out uint value);
    public static readonly nvmlDeviceGetPcieThroughputDelegate
      NvmlDeviceGetPcieThroughput;


    public static NvmlReturn NvmlInit() {
      try {
        var result = nvmlInit_v2();
        initialized = result == NvmlReturn.Success;
        return result;
      } catch {
        try {
          var result = nvmlInit();
          initialized = result == NvmlReturn.Success;
          return result;
        } catch {
          return NvmlReturn.ErrorLibraryNotFound;
        }
      }
    }

    private static string GetDllName() {
      if (OperatingSystem.IsUnix)
        return "libnvidia-ml.so";
      else
        return "nvml.dll";
    }

    private static T CreateDelegate<T>(string entryPoint) where T : Delegate {
      var attribute = new DllImportAttribute(GetDllName()) {
        CallingConvention = CallingConvention.Cdecl,
        PreserveSig = true,
        EntryPoint = entryPoint
      };
      PInvokeDelegateFactory.CreateDelegate(attribute, out T newDelegate);
      return newDelegate;
    }

    static NVML() {
      nvmlInit = 
        CreateDelegate<nvmlInitDelegate>(
        "nvmlInit");
      nvmlInit_v2 = 
        CreateDelegate<nvmlInit_v2Delegate>(
        "nvmlInit_v2");
      NvmlShutdown = 
        CreateDelegate<nvmlShutdownDelegate>(
        "nvmlShutdown");
      NvmlDeviceGetHandleByPciBusId = 
        CreateDelegate<nvmlDeviceGetHandleByPciBusIdDelegate>(
        "nvmlDeviceGetHandleByPciBusId_v2");
      NvmlDeviceGetPowerUsage = 
        CreateDelegate<nvmlDeviceGetPowerUsageDelegate>(
        "nvmlDeviceGetPowerUsage");
      NvmlDeviceGetPcieThroughput =
        CreateDelegate<nvmlDeviceGetPcieThroughputDelegate>(
        "nvmlDeviceGetPcieThroughput");
    }

    private static bool initialized;
    public static bool IsInitialized {
      get { return initialized; }
    }

    [StructLayout(LayoutKind.Sequential)]
    internal struct NvmlDevice {
      private readonly IntPtr ptr;      
    }

    internal enum NvmlPcieUtilCounter {
      TxBytes = 0,
      RxBytes = 1
    }

    internal enum NvmlReturn {
      /// <summary>
      /// The operation was successful
      /// </summary>
      Success = 0,

      /// <summary>
      /// NVML was not first initialized with nvmlInit()
      /// </summary>
      ErrorUninitialized = 1,

      /// <summary>
      /// A supplied argument is invalid
      /// </summary>
      ErrorInvalidArgument = 2,

      /// <summary>
      /// The requested operation is not available on target device
      /// </summary>
      ErrorNotSupported = 3,

      /// <summary>
      /// The current user does not have permission for operation
      /// </summary>
      ErrorNoPermission = 4,

      /// <summary>
      /// Deprecated: Multiple initializations are now allowed through ref 
      /// counting
      /// </summary>
      ErrorAlreadyInitialized = 5,

      /// <summary>
      /// A query to find an object was unsuccessful
      /// </summary>
      ErrorNotFound = 6,

      /// <summary>
      /// An input argument is not large enough
      /// </summary>
      ErrorInsufficientSize = 7,

      /// <summary>
      /// A device's external power cables are not properly attached
      /// </summary>
      ErrorInsufficientPower = 8,

      /// <summary>
      /// NVIDIA driver is not loaded
      /// </summary>
      ErrorDriverNotLoaded = 9,

      /// <summary>
      /// User provided timeout passed
      /// </summary>
      ErrorTimeout = 10,

      /// <summary>
      /// NVIDIA Kernel detected an interrupt issue with a GPU
      /// </summary>
      ErrorIrqIssue = 11,

      /// <summary>
      /// NVML Shared Library couldn't be found or loaded
      /// </summary>
      ErrorLibraryNotFound = 12,

      /// <summary>
      /// Local version of NVML doesn't implement this function
      /// </summary>
      ErrorFunctionNotFound = 13,

      /// <summary>
      /// infoROM is corruptedinfoROM is corrupted
      /// </summary>
      ErrorCorruptedInforom = 14,

      /// <summary>
      /// The GPU has fallen off the bus or has otherwise become inaccessible
      /// </summary>
      ErrorGpuIsLost = 15,

      /// <summary>
      /// The GPU requires a reset before it can be used again
      /// </summary>
      ErrorResetRequired = 16,

      /// <summary>
      /// The GPU control device has been blocked by the operating 
      /// system/cgroups
      /// </summary>
      ErrorOperatingSystem = 17,

      /// <summary>
      /// RM detects a driver/library version mismatch
      /// </summary>
      ErrorLibRmVersionMismatch = 18,

      /// <summary>
      /// An operation cannot be performed because the GPU is currently in use
      /// </summary>
      ErrorInUse = 19,

      /// <summary>
      /// Insufficient memory
      /// </summary>
      ErrorMemory = 20,

      /// <summary>
      /// No data
      /// </summary>
      ErrorNoData = 21,

      /// <summary>
      /// The requested vgpu operation is not available on target device, 
      /// becasue ECC is enabled
      /// </summary>
      ErrorvGpuEccNotSupported = 22,

      /// <summary>
      /// An internal driver error occurred
      /// </summary>
      ErrorUnknown = 999
    };

  }
}