OCCT

// Copyright (c) 2025 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 _GeomHash_VectorHasher_HeaderFile
#define _GeomHash_VectorHasher_HeaderFile

#include <Standard_HashUtils.hxx>
#include <gp_Vec.hxx>
#include <cmath>
#include <Precision.hxx>

//! OCCT-style hasher for gp_Vec (3D vectors).
//! Used for geometry deduplication.
struct GeomHash_VectorHasher
{
  double CompTolerance;
  double HashTolerance;

  GeomHash_VectorHasher(double theCompTolerance = Precision::Angular(),
                        double theHashTolerance = Precision::Confusion())
      : CompTolerance(theCompTolerance),
        HashTolerance(theHashTolerance)
  {
  }

  // Hashes the 3D vector by its XYZ components.
  std::size_t operator()(const gp_Vec& theVector) const noexcept
  {
    const double aFactor = 1.0 / HashTolerance;

    // Round each component to tolerance precision before hashing
    const std::size_t aHashes[3] = {
      opencascade::hash(static_cast<int64_t>(std::round(theVector.X() * aFactor))),
      opencascade::hash(static_cast<int64_t>(std::round(theVector.Y() * aFactor))),
      opencascade::hash(static_cast<int64_t>(std::round(theVector.Z() * aFactor)))};
    return opencascade::hashBytes(aHashes, sizeof(aHashes));
  }

  // Compares two 3D vectors with fixed tolerance.
  bool operator()(const gp_Vec& theVector1, const gp_Vec& theVector2) const noexcept
  {
    return std::abs(theVector1.X() - theVector2.X()) <= CompTolerance
           && std::abs(theVector1.Y() - theVector2.Y()) <= CompTolerance
           && std::abs(theVector1.Z() - theVector2.Z()) <= CompTolerance;
  }
};

#endif // _GeomHash_VectorHasher_HeaderFile