/*

  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) 2009-2010 Michael Möller <mmoeller@openhardwaremonitor.org>

*/

using System;

using System.Collections.Generic;

using System.Reflection;

using System.Reflection.Emit;

using System.Runtime.InteropServices;

namespace OpenHardwareMonitor.Hardware {

  internal static class PInvokeDelegateFactory {

    private static readonly ModuleBuilder moduleBuilder = 

      AppDomain.CurrentDomain.DefineDynamicAssembly(

        new AssemblyName("PInvokeDelegateFactoryInternalAssembly"),

        AssemblyBuilderAccess.Run).DefineDynamicModule(

        "PInvokeDelegateFactoryInternalModule");

    private static readonly IDictionary<DllImportAttribute, Type> wrapperTypes =

      new Dictionary<DllImportAttribute, Type>();

    public static void CreateDelegate<T>(DllImportAttribute dllImportAttribute,

      out T newDelegate) where T : class 

    {

      Type wrapperType;

      wrapperTypes.TryGetValue(dllImportAttribute, out wrapperType);

      if (wrapperType == null) {

        wrapperType = CreateWrapperType(typeof(T), dllImportAttribute);

        wrapperTypes.Add(dllImportAttribute, wrapperType);

      }

      newDelegate = Delegate.CreateDelegate(typeof(T), wrapperType,

        dllImportAttribute.EntryPoint) as T;

    }

    private static Type CreateWrapperType(Type delegateType,

      DllImportAttribute dllImportAttribute) {

      TypeBuilder typeBuilder = moduleBuilder.DefineType(

        "PInvokeDelegateFactoryInternalWrapperType" + wrapperTypes.Count);

      MethodInfo methodInfo = delegateType.GetMethod("Invoke");

      ParameterInfo[] parameterInfos = methodInfo.GetParameters();

      int parameterCount = parameterInfos.GetLength(0);

      Type[] parameterTypes = new Type[parameterCount];

      for (int i = 0; i < parameterCount; i++)

        parameterTypes[i] = parameterInfos[i].ParameterType;

      MethodBuilder methodBuilder = typeBuilder.DefinePInvokeMethod(

        dllImportAttribute.EntryPoint, dllImportAttribute.Value,

        MethodAttributes.Public | MethodAttributes.Static |

        MethodAttributes.PinvokeImpl, CallingConventions.Standard,

        methodInfo.ReturnType, parameterTypes,

        dllImportAttribute.CallingConvention,

        dllImportAttribute.CharSet);

      foreach (ParameterInfo parameterInfo in parameterInfos)

        methodBuilder.DefineParameter(parameterInfo.Position + 1,

          parameterInfo.Attributes, parameterInfo.Name);

      if (dllImportAttribute.PreserveSig)

        methodBuilder.SetImplementationFlags(MethodImplAttributes.PreserveSig);

      return typeBuilder.CreateType();

    }

  }

}