// Copyright (c) 2020 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 _OpenGl_TextureSetPairIterator_Header
#define _OpenGl_TextureSetPairIterator_Header

#include "OpenGl_TextureSet.hxx"

//! Class for iterating pair of texture sets through each defined texture slot.
//! Note that iterator considers texture slots being in ascending order within OpenGl_TextureSet.
class OpenGl_TextureSetPairIterator
{
public:
  //! Constructor.
  OpenGl_TextureSetPairIterator(const occ::handle<OpenGl_TextureSet>& theSet1,
                                const occ::handle<OpenGl_TextureSet>& theSet2)
      : myIter1(theSet1),
        myIter2(theSet2),
        myTexture1(nullptr),
        myTexture2(nullptr),
        myUnitLower(IntegerLast()),
        myUnitUpper(IntegerFirst()),
        myUnitCurrent(0)
  {
    if (!theSet1.IsNull() && !theSet1->IsEmpty())
    {
      myUnitLower = (std::min)(myUnitLower, static_cast<int>(theSet1->FirstUnit()));
      myUnitUpper = (std::max)(myUnitUpper, static_cast<int>(theSet1->LastUnit()));
    }
    if (!theSet2.IsNull() && !theSet2->IsEmpty())
    {
      myUnitLower = (std::min)(myUnitLower, static_cast<int>(theSet2->FirstUnit()));
      myUnitUpper = (std::max)(myUnitUpper, static_cast<int>(theSet2->LastUnit()));
    }
    myUnitCurrent = myUnitLower;
    myTexture1 =
      (myIter1.More() && myIter1.Unit() == myUnitCurrent) ? myIter1.ChangeValue().get() : nullptr;
    myTexture2 =
      (myIter2.More() && myIter2.Unit() == myUnitCurrent) ? myIter2.ChangeValue().get() : nullptr;
  }

  //! Return TRUE if there are more texture units to pass through.
  bool More() const { return myUnitCurrent <= myUnitUpper; }

  //! Return current texture unit.
  Graphic3d_TextureUnit Unit() const { return (Graphic3d_TextureUnit)myUnitCurrent; }

  //! Access texture from first texture set.
  const OpenGl_Texture* Texture1() const { return myTexture1; }

  //! Access texture from second texture set.
  const OpenGl_Texture* Texture2() const { return myTexture2; }

  //! Move iterator position to the next pair.
  void Next()
  {
    ++myUnitCurrent;
    myTexture1 = myTexture2 = nullptr;
    for (; myIter1.More(); myIter1.Next())
    {
      if (myIter1.Unit() >= myUnitCurrent)
      {
        myTexture1 = myIter1.Unit() == myUnitCurrent ? myIter1.ChangeValue().get() : nullptr;
        break;
      }
    }
    for (; myIter2.More(); myIter2.Next())
    {
      if (myIter2.Unit() >= myUnitCurrent)
      {
        myTexture2 = myIter2.Unit() == myUnitCurrent ? myIter2.ChangeValue().get() : nullptr;
        break;
      }
    }
  }

private:
  OpenGl_TextureSet::Iterator myIter1;
  OpenGl_TextureSet::Iterator myIter2;
  OpenGl_Texture*             myTexture1;
  OpenGl_Texture*             myTexture2;
  int                         myUnitLower;
  int                         myUnitUpper;
  int                         myUnitCurrent;
};

#endif //_OpenGl_TextureSetPairIterator_Header