// Created on: 1996-10-08
// Created by: Jeannine PANTIATICI
// Copyright (c) 1996-1999 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 _PLib_JacobiPolynomial_HeaderFile
#define _PLib_JacobiPolynomial_HeaderFile

#include "Standard.hxx"

#include "Standard_Integer.hxx"
#include "GeomAbs_Shape.hxx"
#include "NCollection_Array1.hxx"
#include "NCollection_Array2.hxx"

//! This class provides method to work with Jacobi Polynomials
//! relatively to an order of constraint
//! q  = myWorkDegree-2*(myNivConstr+1)
//! Jk(t)  for k=0,q compose the Jacobi Polynomial base relatively to the weight W(t)
//! iorder is the integer value for the constraints:
//! iorder = 0 <=> ConstraintOrder  = GeomAbs_C0
//! iorder = 1 <=>  ConstraintOrder = GeomAbs_C1
//! iorder = 2 <=> ConstraintOrder = GeomAbs_C2
//! P(t) = R(t) + W(t) * Q(t) Where W(t) = (1-t**2)**(2*iordre+2)
//! the coefficients JacCoeff represents P(t) JacCoeff are stored as follow:
//!
//! c0(1)      c0(2) ....       c0(Dimension)
//! c1(1)      c1(2) ....       c1(Dimension)
//!
//! cDegree(1) cDegree(2) ....  cDegree(Dimension)
//!
//! The coefficients
//! c0(1)                  c0(2) ....            c0(Dimension)
//! c2*ordre+1(1)                ...          c2*ordre+1(dimension)
//!
//! represents the part of the polynomial in the
//! canonical base: R(t)
//! R(t) = c0 + c1   t + ...+ c2*iordre+1 t**2*iordre+1
//! The following coefficients represents the part of the
//! polynomial in the Jacobi base ie Q(t)
//! Q(t) = c2*iordre+2  J0(t) + ...+ cDegree JDegree-2*iordre-2
class PLib_JacobiPolynomial
{

public:
  //! Initialize the polynomial class
  //! Degree has to be <= 30
  //! ConstraintOrder has to be GeomAbs_C0
  //! GeomAbs_C1
  //! GeomAbs_C2
  Standard_EXPORT PLib_JacobiPolynomial(const int           theWorkDegree,
                                        const GeomAbs_Shape theConstraintOrder);

  //! returns the Jacobi Points for Gauss integration ie
  //! the positive values of the Legendre roots by increasing values
  //! NbGaussPoints is the number of points chosen for the integral
  //! computation.
  //! TabPoints (0,NbGaussPoints/2)
  //! TabPoints (0) is loaded only for the odd values of NbGaussPoints
  //! The possible values for NbGaussPoints are : 8, 10,
  //! 15, 20, 25, 30, 35, 40, 50, 61
  //! NbGaussPoints must be greater than Degree
  Standard_EXPORT void Points(const int                   theNbGaussPoints,
                              NCollection_Array1<double>& theTabPoints) const;

  //! returns the Jacobi weights for Gauss integration only for
  //! the positive values of the Legendre roots in the order they
  //! are given by the method Points
  //! NbGaussPoints is the number of points chosen for the integral
  //! computation.
  //! TabWeights (0,NbGaussPoints/2,0,Degree)
  //! TabWeights (0,.) are only loaded for the odd values of NbGaussPoints
  //! The possible values for NbGaussPoints are: 8, 10, 15, 20, 25, 30,
  //! 35, 40, 50, 61 NbGaussPoints must be greater than Degree
  Standard_EXPORT void Weights(const int                   theNbGaussPoints,
                               NCollection_Array2<double>& theTabWeights) const;

  //! this method loads for k=0,q the maximum value of
  //! abs ( W(t)*Jk(t) ) for t bellonging to [-1,1]
  //! This values are loaded is the array TabMax(0,myWorkDegree-2*(myNivConst+1))
  //! MaxValue ( me ; TabMaxPointer : in  out  Real );
  Standard_EXPORT void MaxValue(NCollection_Array1<double>& theTabMax) const;

  //! This method computes the maximum error on the polynomial
  //! W(t) Q(t) obtained by missing the coefficients of JacCoeff from
  //! NewDegree +1 to Degree
  Standard_EXPORT double MaxError(const int theDimension,
                                  double&   theJacCoeff,
                                  const int theNewDegree) const;

  //! Compute NewDegree <= MaxDegree so that MaxError is lower
  //! than Tol.
  //! MaxError can be greater than Tol if it is not possible
  //! to find a NewDegree <= MaxDegree.
  //! In this case NewDegree = MaxDegree
  Standard_EXPORT void ReduceDegree(const int    theDimension,
                                    const int    theMaxDegree,
                                    const double theTol,
                                    double&      theJacCoeff,
                                    int&         theNewDegree,
                                    double&      theMaxError) const;

  Standard_EXPORT double AverageError(const int theDimension,
                                      double&   theJacCoeff,
                                      const int theNewDegree) const;

  //! Convert the polynomial P(t) = R(t) + W(t) Q(t) in the canonical base.
  Standard_EXPORT void ToCoefficients(const int                         theDimension,
                                      const int                         theDegree,
                                      const NCollection_Array1<double>& theJacCoeff,
                                      NCollection_Array1<double>&       theCoefficients) const;

  //! Compute the values of the basis functions in u
  Standard_EXPORT void D0(const double theU, NCollection_Array1<double>& theBasisValue) const;

  //! Compute the values and the derivatives values of
  //! the basis functions in u
  Standard_EXPORT void D1(const double                theU,
                          NCollection_Array1<double>& theBasisValue,
                          NCollection_Array1<double>& theBasisD1) const;

  //! Compute the values and the derivatives values of
  //! the basis functions in u
  Standard_EXPORT void D2(const double                theU,
                          NCollection_Array1<double>& theBasisValue,
                          NCollection_Array1<double>& theBasisD1,
                          NCollection_Array1<double>& theBasisD2) const;

  //! Compute the values and the derivatives values of
  //! the basis functions in u
  Standard_EXPORT void D3(const double                theU,
                          NCollection_Array1<double>& theBasisValue,
                          NCollection_Array1<double>& theBasisD1,
                          NCollection_Array1<double>& theBasisD2,
                          NCollection_Array1<double>& theBasisD3) const;

  //! returns WorkDegree
  int WorkDegree() const noexcept { return myWorkDegree; }

  //! returns NivConstr
  int NivConstr() const noexcept { return myNivConstr; }

protected:
  //! Compute the values and the derivatives values of
  //! the basis functions in u
  Standard_EXPORT void D0123(const int                   theNDeriv,
                             const double                theU,
                             NCollection_Array1<double>& theBasisValue,
                             NCollection_Array1<double>& theBasisD1,
                             NCollection_Array1<double>& theBasisD2,
                             NCollection_Array1<double>& theBasisD3) const;

private:
  const int myWorkDegree;
  const int myNivConstr;
  const int myDegree;
};

#endif // _PLib_JacobiPolynomial_HeaderFile