// Created by: DAUTRY Philippe
// Copyright (c) 1997-1999 Matra Datavision
// Copyright (c) 1999-2014 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#ifndef _TDocStd_XLinkRoot_HeaderFile
#define _TDocStd_XLinkRoot_HeaderFile

#include "Standard.hxx"
#include "Standard_Type.hxx"

#include "TDocStd_XLinkPtr.hxx"
#include "TDF_Attribute.hxx"
#include "Standard_OStream.hxx"
class Standard_GUID;
class TDF_Data;
class TDF_RelocationTable;

//! This attribute is the root of all external
//! references contained in a Data from TDF. Only one
//! instance of this class is added to the TDF_Data
//! root label. Starting from this attribute all the
//! Reference are linked together, to be found easily.
class TDocStd_XLinkRoot : public TDF_Attribute
{

public:
  //! Returns the ID: 2a96b61d-ec8b-11d0-bee7-080009dc3333
  Standard_EXPORT static const Standard_GUID& GetID();

  //! Sets an empty XLinkRoot to Root or gets the
  //! existing one. Only one attribute per TDF_Data.
  Standard_EXPORT static occ::handle<TDocStd_XLinkRoot> Set(const occ::handle<TDF_Data>& aDF);

  //! Inserts <anXLinkPtr> at the beginning of the XLink chain.
  Standard_EXPORT static void Insert(const TDocStd_XLinkPtr& anXLinkPtr);

  //! Removes <anXLinkPtr> from the XLink chain, if it exists.
  Standard_EXPORT static void Remove(const TDocStd_XLinkPtr& anXLinkPtr);

  //! Returns the ID of the attribute.
  Standard_EXPORT const Standard_GUID& ID() const override;

  //! Returns a null handle.
  Standard_EXPORT occ::handle<TDF_Attribute> BackupCopy() const override;

  //! Does nothing.
  Standard_EXPORT void Restore(const occ::handle<TDF_Attribute>& anAttribute) override;

  //! Returns a null handle.
  Standard_EXPORT occ::handle<TDF_Attribute> NewEmpty() const override;

  //! Does nothing.
  Standard_EXPORT void Paste(
    const occ::handle<TDF_Attribute>&       intoAttribute,
    const occ::handle<TDF_RelocationTable>& aRelocationTable) const override;

  //! Dumps the attribute on <aStream>.
  Standard_EXPORT Standard_OStream& Dump(Standard_OStream& anOS) const override;

  friend class TDocStd_XLinkIterator;

  DEFINE_STANDARD_RTTIEXT(TDocStd_XLinkRoot, TDF_Attribute)

private:
  //! Initializes fields.
  Standard_EXPORT TDocStd_XLinkRoot();

  //! Sets the field <myFirst> with <anXLinkPtr>.
  void First(const TDocStd_XLinkPtr& anXLinkPtr);

  //! Returns the contents of the field <myFirst>.
  TDocStd_XLinkPtr First() const;

  TDocStd_XLinkPtr myFirst;
};

#include "TDocStd_XLinkRoot.lxx"

#endif // _TDocStd_XLinkRoot_HeaderFile