#region CPL License
/*
Nuclex.NAnt.Tasks
Copyright (C) 2009 Nuclex Development Labs

This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
IBM Common Public License for more details.

You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion

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

namespace Nuclex.NAnt.Tasks.Helpers {

  /// <summary>Helper class for environment variables</summary>
  internal static class EnvironmentHelper {

    /// <summary>Initializes the environment helper class</summary>
    static EnvironmentHelper() {

      // We can determine whethr this process is a 64-bit process by
      // checking the size of a pointer
      ExecutingAs64BitCode =
        (IntPtr.Size == 8);

      if(OsHelper.IsWindows) {
        if(OsHelper.IsXpOrLater) {

          // Finding out whether we're running as an x86 on a 64-bit OS
          // is a little bit more tricky and requires a Windows API call
          using(Process self = Process.GetCurrentProcess()) {
            if(!IsWow64Process(self.Handle, out UsingWoW6432)) {
              throw new Win32Exception(
                "Could not determine whether this is a WOW64 process"
              );
            }
          }

        }
      } else {
        UsingWoW6432 = false;
      }

      // We're running on a 64 bit OS if either we're running as native
      // 64 bit code or when the OS tells us we're a WOW64 process.
      RunningOn64BitOS =
        ExecutingAs64BitCode ||
        UsingWoW6432;

    }

    /// <summary>
    ///   Determines whether the specified process is running under WOW64
    /// </summary>
    /// <param name="processHandle">Handle of the process that will be queried</param>
    /// <param name="wow64Process">Receives the result of the query</param>
    /// <returns>True if the function has succeeded</returns>
    [DllImport("kernel32", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool IsWow64Process(
        [In] IntPtr processHandle,
        [Out] out bool wow64Process
    );

    /// <summary>
    ///   Whether the current application is running on a 64 bit operating system
    /// </summary>
    /// <remarks>
    ///   Warning: This does make no guarantees as to whether the current process is
    ///   actually running as a 64 bit process. Unless explicitely flagged, .NET
    ///   assemblies can run as either, 32 bit or 64 bit code, depending on
    ///   the architecture of the entry assembly.
    /// </remarks>
    public static readonly bool RunningOn64BitOS;

    /// <summary>
    ///   Whether the currently executing assembly is running in 64 bit mode
    /// </summary>
    public static readonly bool ExecutingAs64BitCode;

    /// <summary>
    ///   Whether the currently executing assembly is running as 32 bit code on
    ///   a 64 bit operating system
    /// </summary>
    public static readonly bool UsingWoW6432;

  }

} // namespace Nuclex.NAnt.Tasks.Helpers