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 _ExtremaPC2d_Line_HeaderFile
#define _ExtremaPC2d_Line_HeaderFile

#include <ExtremaPC2d.hxx>
#include <gp_Lin2d.hxx>
#include <gp_Pnt2d.hxx>
#include <gp_Vec2d.hxx>
#include <Standard_DefineAlloc.hxx>

#include <algorithm>
#include <optional>

//! @brief Point-Line extrema computation.
//!
//! Computes the extremum (closest point) between a 2D point and a line.
//! Uses direct analytical projection via dot product.
//!
//! For a line defined by origin O and direction D, the closest point
//! to P is at parameter u = (P - O) . D, which gives the minimum distance.
//!
//! The domain is fixed at construction time for optimal performance.
//! For unbounded line, construct without domain or with nullopt.
//!
//! @note Lines always have exactly one extremum (minimum) if within bounds.
class ExtremaPC2d_Line
{
public:
  DEFINE_STANDARD_ALLOC

  //! Constructor with line geometry (unbounded).
  //! @param[in] theLine the line to compute extrema for
  explicit ExtremaPC2d_Line(const gp_Lin2d& theLine)
      : myLine(theLine),
        myDomain(std::nullopt)
  {
  }

  //! Constructor with line geometry and parameter domain.
  //! @param[in] theLine the line to compute extrema for
  //! @param[in] theDomain parameter domain (fixed for all queries)
  ExtremaPC2d_Line(const gp_Lin2d& theLine, const ExtremaPC2d::Domain1D& theDomain)
      : myLine(theLine),
        myDomain(theDomain)
  {
  }

  //! Copy constructor is deleted.
  ExtremaPC2d_Line(const ExtremaPC2d_Line&) = delete;

  //! Copy assignment operator is deleted.
  ExtremaPC2d_Line& operator=(const ExtremaPC2d_Line&) = delete;

  //! Move constructor.
  ExtremaPC2d_Line(ExtremaPC2d_Line&&) = default;

  //! Move assignment operator.
  ExtremaPC2d_Line& operator=(ExtremaPC2d_Line&&) = default;

  //! Evaluates point on line at parameter.
  //! @param theU parameter
  //! @return point on line
  gp_Pnt2d Value(double theU) const
  {
    return myLine.Location().Translated(theU * gp_Vec2d(myLine.Direction()));
  }

  //! Returns true if domain is bounded.
  bool IsBounded() const { return myDomain.has_value(); }

  //! Returns the domain (only valid if IsBounded() is true).
  const ExtremaPC2d::Domain1D& Domain() const { return *myDomain; }

  //! Compute extrema between point P and the line.
  //! Uses domain specified at construction time.
  //! @param theP query point
  //! @param theTol tolerance for parameter comparison
  //! @param theMode search mode (Max returns no interior extremum)
  //! @return const reference to result containing the extremum
  [[nodiscard]] const ExtremaPC2d::Result& Perform(
    const gp_Pnt2d&         theP,
    double                  theTol,
    ExtremaPC2d::SearchMode theMode = ExtremaPC2d::SearchMode::MinMax) const
  {
    myResult.Clear();

    if (!ExtremaPC2d::IsValidTolerance(theTol) || !ExtremaPC2d::IsFinitePoint(theP)
        || (myDomain.has_value() && !myDomain->IsValid()))
    {
      myResult.Status = ExtremaPC2d::Status::InvalidInput;
      return myResult;
    }

    if (theMode == ExtremaPC2d::SearchMode::Max)
    {
      myResult.Status = ExtremaPC2d::Status::NoSolution;
      return myResult;
    }

    // Compute projection parameter: u = (P - O) . Direction
    const gp_Dir2d& aDir    = myLine.Direction();
    const gp_Pnt2d& aOrigin = myLine.Location();
    gp_Vec2d        aVec(aOrigin, theP);
    double          aU = aVec.Dot(gp_Vec2d(aDir));

    // Check bounds if domain is specified
    if (myDomain.has_value())
    {
      if (aU < myDomain->Min - theTol || aU > myDomain->Max + theTol)
      {
        // Projection is outside bounds - no interior extremum
        myResult.Status = ExtremaPC2d::Status::NoSolution;
        return myResult;
      }
      // Clamp to bounds
      aU = std::clamp(aU, myDomain->Min, myDomain->Max);
    }

    // Compute point on line at projected parameter
    gp_Pnt2d aPtOnLine = aOrigin.Translated(aU * gp_Vec2d(aDir));

    // Store result
    ExtremaPC2d::ExtremumResult anExt;
    anExt.Parameter      = aU;
    anExt.Point          = aPtOnLine;
    anExt.SquareDistance = theP.SquareDistance(aPtOnLine);
    anExt.IsMinimum      = true;
    anExt.IsMaximum      = false;

    myResult.Extrema.Append(anExt);
    myResult.Status = ExtremaPC2d::Status::OK;
    return myResult;
  }

  //! Compute extrema between point P and the line segment including endpoints.
  //! Uses domain specified at construction time.
  //! @param theP query point
  //! @param theTol tolerance for parameter comparison
  //! @param theMode search mode (MinMax, Min, or Max)
  //! @return const reference to result containing interior + endpoint extrema
  [[nodiscard]] const ExtremaPC2d::Result& PerformWithEndpoints(
    const gp_Pnt2d&         theP,
    double                  theTol,
    ExtremaPC2d::SearchMode theMode = ExtremaPC2d::SearchMode::MinMax) const
  {
    if (!ExtremaPC2d::IsValidTolerance(theTol) || !ExtremaPC2d::IsFinitePoint(theP)
        || (myDomain.has_value() && !myDomain->IsValid()))
    {
      myResult.Clear();
      myResult.Status = ExtremaPC2d::Status::InvalidInput;
      return myResult;
    }

    if (myDomain.has_value() && myDomain->Min == myDomain->Max)
    {
      myResult.Clear();
      ExtremaPC2d::AddEndpointExtrema(myResult, theP, *myDomain, *this, theMode, false);
      myResult.Status =
        myResult.Extrema.IsEmpty() ? ExtremaPC2d::Status::NoSolution : ExtremaPC2d::Status::OK;
      return myResult;
    }

    (void)Perform(theP, theTol, theMode);

    if ((myResult.Status == ExtremaPC2d::Status::OK
         || myResult.Status == ExtremaPC2d::Status::NoSolution)
        && myDomain.has_value())
    {
      ExtremaPC2d::AddEndpointExtrema(myResult, theP, *myDomain, *this, theMode, false);
      if (!myResult.Extrema.IsEmpty())
      {
        myResult.Status = ExtremaPC2d::Status::OK;
      }
    }

    return myResult;
  }

  //! Returns the line geometry.
  const gp_Lin2d& Line() const { return myLine; }

private:
  gp_Lin2d                             myLine;   //!< Line geometry
  std::optional<ExtremaPC2d::Domain1D> myDomain; //!< Parameter domain (nullopt for unbounded)
  mutable ExtremaPC2d::Result          myResult; //!< Reusable result storage
};

#endif // _ExtremaPC2d_Line_HeaderFile