/*

  Version: MPL 1.1/GPL 2.0/LGPL 2.1

  The contents of this file are subject to the Mozilla Public License Version

  1.1 (the "License"); you may not use this file except in compliance with

  the License. You may obtain a copy of the License at

  http://www.mozilla.org/MPL/

  Software distributed under the License is distributed on an "AS IS" basis,

  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License

  for the specific language governing rights and limitations under the License.

  The Original Code is the Open Hardware Monitor code.

  The Initial Developer of the Original Code is 

  Michael Möller <m.moeller@gmx.ch>.

  Portions created by the Initial Developer are Copyright (C) 2009-2010

  the Initial Developer. All Rights Reserved.

  Contributor(s):

  Alternatively, the contents of this file may be used under the terms of

  either the GNU General Public License Version 2 or later (the "GPL"), or

  the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),

  in which case the provisions of the GPL or the LGPL are applicable instead

  of those above. If you wish to allow use of your version of this file only

  under the terms of either the GPL or the LGPL, and not to allow others to

  use your version of this file under the terms of the MPL, indicate your

  decision by deleting the provisions above and replace them with the notice

  and other provisions required by the GPL or the LGPL. If you do not delete

  the provisions above, a recipient may use your version of this file under

  the terms of any one of the MPL, the GPL or the LGPL.

*/

using System;

using System.Collections.Generic;

using System.Reflection;

using System.Reflection.Emit;

using System.Runtime.InteropServices;

namespace OpenHardwareMonitor.Hardware {

  public sealed class PInvokeDelegateFactory {

    private static AssemblyBuilder assemblyBuilder;

    private static ModuleBuilder moduleBuilder;

    private static IDictionary<DllImportAttribute, Type> wrapperTypes =

      new Dictionary<DllImportAttribute, Type>();

    static PInvokeDelegateFactory() {

      AssemblyName assemblyName = new AssemblyName();

      assemblyName.Name = "PInvokeDelegateFactoryInternalAssembly";

      assemblyBuilder =

        AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName,

        AssemblyBuilderAccess.Run);

      moduleBuilder = assemblyBuilder.DefineDynamicModule(

        "PInvokeDelegateFactoryInternalModule");

    }

    private PInvokeDelegateFactory() { }

    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();

    }

  }

}