using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Permissions;
using System.Windows.Forms;

namespace JD.MessageService
{
    // http://support.microsoft.com/kb/830033
    // http://stackoverflow.com/questions/1612351/entrypointnotfoundexception-when-using-taskdialog-in-c-sharp

    [SuppressUnmanagedCodeSecurity]
    internal class EnableThemingInScope : IDisposable
    {
        #region Variables

        private UIntPtr m_cookie;
        private static ACTCTX ms_enableThemingActivationContext;
        private static IntPtr ms_hActCtx;
        private static bool ms_contextCreationSucceeded;

        #endregion

        public EnableThemingInScope()
        {
            m_cookie = UIntPtr.Zero;
            if (OSFeature.Feature.IsPresent(OSFeature.Themes))
            {
                if (EnsureActivateContextCreated())
                {
                    if (!ActivateActCtx(ms_hActCtx, out m_cookie))
                    {
                        // Be sure cookie always zero if activation failed
                        m_cookie = UIntPtr.Zero;
                    }
                }
            }
        }

        ~EnableThemingInScope()
        {
            Dispose(false);
        }

        void IDisposable.Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool disposing)
        {
            if (m_cookie != UIntPtr.Zero)
            {
                if (DeactivateActCtx(0, m_cookie))
                {
                    // deactivation succeeded...
                    m_cookie = UIntPtr.Zero;
                }
            }
        }

        private static bool EnsureActivateContextCreated()
        {
            if (!ms_contextCreationSucceeded)
            {
                // Pull manifest from the .NET Framework install
                // directory

                string assemblyLoc;

                FileIOPermission fiop = new FileIOPermission(PermissionState.None)
                {
                    AllFiles = FileIOPermissionAccess.PathDiscovery
                };

                fiop.Assert();

                try
                {
                    assemblyLoc = typeof(Object).Assembly.Location;
                }
                finally
                {
                    CodeAccessPermission.RevertAssert();
                }

                string manifestLoc = null;
                string installDir = null;
                if (assemblyLoc != null)
                {
                    installDir = Path.GetDirectoryName(assemblyLoc);
                    const string manifestName = "XPThemes.manifest";
                    manifestLoc = Path.Combine(installDir, manifestName);
                }

                if (manifestLoc != null && installDir != null)
                {
                    ms_enableThemingActivationContext = new ACTCTX
                    {
                        cbSize = Marshal.SizeOf(typeof(ACTCTX)),
                        lpSource = manifestLoc,
                        lpAssemblyDirectory = installDir,
                        dwFlags = ACTCTX_FLAG_ASSEMBLY_DIRECTORY_VALID
                    };

                    // Set the lpAssemblyDirectory to the install
                    // directory to prevent Win32 Side by Side from
                    // looking for comctl32 in the application
                    // directory, which could cause a bogus dll to be
                    // placed there and open a security hole.

                    // Note this will fail gracefully if file specified
                    // by manifestLoc doesn't exist.
                    ms_hActCtx = CreateActCtx(ref ms_enableThemingActivationContext);
                    ms_contextCreationSucceeded = (ms_hActCtx != new IntPtr(-1));
                }
            }

            // If we return false, we'll try again on the next call into
            // EnsureActivateContextCreated(), which is fine.
            return ms_contextCreationSucceeded;
        }

        // All the pinvoke goo...
        [DllImport("Kernel32.dll")]
        private extern static IntPtr CreateActCtx(ref ACTCTX actctx);

        [DllImport("Kernel32.dll")]
        private extern static bool ActivateActCtx(IntPtr hActCtx, out UIntPtr lpCookie);

        [DllImport("Kernel32.dll")]
        private extern static bool DeactivateActCtx(uint dwFlags, UIntPtr lpCookie);

        private const int ACTCTX_FLAG_ASSEMBLY_DIRECTORY_VALID = 0x004;

        private struct ACTCTX
        {
            public int cbSize;
            public uint dwFlags;
            public string lpSource;
            public ushort wProcessorArchitecture;
            public ushort wLangId;
            public string lpAssemblyDirectory;
            public string lpResourceName;
            public string lpApplicationName;
        }
    }
}