// ============================================================================
// ==                                                                        ==
// == AMDiS - Adaptive multidimensional simulations                          ==
// ==                                                                        ==
// ==  http://www.amdis-fem.org                                              ==
// ==                                                                        ==
// ============================================================================
//
// Software License for AMDiS
//
// Copyright (c) 2010 Dresden University of Technology 
// All rights reserved.
// Authors: Simon Vey, Thomas Witkowski et al.
//
// This file is part of AMDiS
//
// See also license.opensource.txt in the distribution.



/** \file Quadrature.h */

#ifndef AMDIS_QUADRATURE_H
#define AMDIS_QUADRATURE_H

#include <list>
#include "AMDiS_fwd.h"
#include "BasisFunction.h"
#include "Flag.h"
#include "FixVec.h"

namespace AMDiS {

  /** 
   * \ingroup Assembler
   *
   * \brief
   * For the assemblage of the system matrix and right hand side vector of the 
   * linear system, we have to compute integrals, for example: 
   * \f[ \int_{\Omega} f(x)\varphi_i(x) dx \f]
   * For general data A, b, c, and f, these integrals can not be calculated 
   * exactly. Quadrature formulas have to be used in order to calculate the 
   * integrals approximately. Numerical integration in finite element methods is
   * done by looping over all grid elements and using a quadrature formula on 
   * each element.
   */
  class Quadrature
  {
  protected:
    /// Avoids call of default constructor
    Quadrature();

    /** \brief
     * Constructs a Quadrature with name name_ of degree degree_ for dim dim_.
     * The Quadrature has n_points_ quadrature points with barycentric 
     * coordinates lambda_ and weights w_. The constructor is protected because
     * access to a Quadrature should be done via \ref provideQuadrature.
     */
    Quadrature(const char* name_,
	       int degree_,
	       int dim_,
	       int n_points_,
	       VectorOfFixVecs<DimVec<double> > *lambda_,
	       double* w_)
      : name(name_),
	degree(degree_),
	dim(dim_),
	n_points(n_points_),
	lambda(lambda_),
	w(w_) 
    {}

  public:
    /// Copy constructor
    Quadrature(const Quadrature&);

    /// Destructor
    ~Quadrature();

    /// Returns a Quadrature for dimension dim exact for degree degree.
    static Quadrature *provideQuadrature(int dim, int degree);

    /** \brief
     * Approximates an integral by the numerical quadrature described by quad;
     * f is a pointer to an AbstractFunction to be integrated, evaluated in 
     * barycentric coordinates; the return value is 
     * \f[ \sum_{k = 0}^{n_points-1} w[k] * (*f)(lambda[k]) \f]
     * For the approximation of \f$ \int_S f\f$ we have to multiply this value 
     * with d!|S| for a simplex S; for a parametric simplex f should be a pointer
     * to a function which calculates 
     * \f$ f(\lambda)|det DF_S(\hat{x}(\lambda))| \f$.
     */
    double integrateStdSimplex(AbstractFunction<double, DimVec<double> > *f);
  
    /// Returns \ref name
    inline std::string getName() 
    { 
      return name; 
    }

    /// Returns \ref n_points
    inline int getNumPoints() const 
    {
      return n_points;
    }

    /// Returns \ref w[p]
    inline double getWeight(int p) const 
    {
      return w[p];
    }

    /// Returns \ref w.
    inline double* getWeight() const 
    { 
      return w; 
    }

    /// Returns \ref dim
    inline int getDim() const 
    { 
      return dim; 
    }

    /// Returns \ref degree
    inline int getDegree() const 
    { 
      return degree; 
    }

    /** \brief
     * Returns a pointer to a vector storing the values of a doubled valued 
     * function at all quadrature points; f is that AbstractFunction
     * , evaluated in barycentric coordinates; if vec is not NULL, the values are
     * stored in this vector, otherwise the values are stored in some static 
     * local vector, which is overwritten on the next call
     */
    const double *fAtQp(const AbstractFunction<double, DimVec<double> >& f,
			double *vec) const ;

    /** \brief
     * Returns a pointer to a vector storing the gradient (with respect to world
     * coordinates) of a double valued function at all quadrature points;
     * grdF is a pointer to a AbstractFunction, evaluated in barycentric
     * coordinates and returning a pointer to a WorldVector storing the gradient;
     * if vec is not NULL, the values are stored in this vector, otherwise the 
     * values are stored in some local static vector, which is overwritten on the
     * next call
     */
    const WorldVector<double> *grdFAtQp(const AbstractFunction<WorldVector<double>, 
					DimVec<double> >& grdF, 
					WorldVector<double>* vec) const;
  


    /** \brief
     * Returns \ref lambda[a][b] which is the b-th coordinate entry of the a-th
     * quadrature point
     */
    inline double getLambda(int a, int b) const 
    {
      return (lambda ? (*lambda)[a][b] : 0.0);
    }

    /** \brief
     * Returns \ref lambda[a] which is a DimVec<double> containing the 
     * coordiantes of the a-th quadrature point
     */
    inline const DimVec<double>& getLambda(int a) const 
    {
      return (*lambda)[a]; 
    }

    /// Returns \ref lambda which is a VectorOfFixvecs<DimVec<double> >.
    VectorOfFixVecs<DimVec<double> > *getLambda() const 
    { 
      return lambda; 
    }


  public:
    /// Maximal number of quadrature points for the different dimensions
    static const int maxNQuadPoints[4];

  protected:
    /// Name of this Quadrature
    std::string name;

    /// Quadrature is exact of this degree
    int degree;

    /// Quadrature for dimension dim
    int dim;

    /// Number of quadrature points
    int n_points;

    /// Vector of quadrature points given in barycentric coordinates
    VectorOfFixVecs<DimVec<double> > *lambda; 

    /// Vector of quadrature weights
    double *w;

  protected:
    /** \brief
     * Initialisation of all static Quadrature objects which will be returned
     * by \ref provideQuadrature()
     */
    static void initStaticQuadratures();

    /** \name static quadratures, used weights, and barycentric coords
     * \{
     */
    static Quadrature **quad_nd[4];
    static Quadrature *quad_0d[1];
    static Quadrature *quad_1d[20];
    static Quadrature *quad_2d[18];
    static Quadrature *quad_3d[8];

    static VectorOfFixVecs<DimVec<double> > *x_0d;
    static double *w_0d;

    static VectorOfFixVecs<DimVec<double> > *x0_1d;
    static VectorOfFixVecs<DimVec<double> > *x1_1d;
    static VectorOfFixVecs<DimVec<double> > *x2_1d;
    static VectorOfFixVecs<DimVec<double> > *x3_1d;
    static VectorOfFixVecs<DimVec<double> > *x4_1d;
    static VectorOfFixVecs<DimVec<double> > *x5_1d;
    static VectorOfFixVecs<DimVec<double> > *x6_1d;
    static VectorOfFixVecs<DimVec<double> > *x7_1d;
    static VectorOfFixVecs<DimVec<double> > *x8_1d;
    static VectorOfFixVecs<DimVec<double> > *x9_1d;
    static double *w0_1d;
    static double *w1_1d;
    static double *w2_1d;
    static double *w3_1d;
    static double *w4_1d;
    static double *w5_1d;
    static double *w6_1d;
    static double *w7_1d;
    static double *w8_1d;
    static double *w9_1d;

    static VectorOfFixVecs<DimVec<double> > *x1_2d;
    static VectorOfFixVecs<DimVec<double> > *x2_2d;
    static VectorOfFixVecs<DimVec<double> > *x3_2d;
    static VectorOfFixVecs<DimVec<double> > *x4_2d;
    static VectorOfFixVecs<DimVec<double> > *x5_2d;
    static VectorOfFixVecs<DimVec<double> > *x7_2d;
    static VectorOfFixVecs<DimVec<double> > *x8_2d;
    static VectorOfFixVecs<DimVec<double> > *x9_2d;
    static VectorOfFixVecs<DimVec<double> > *x10_2d;
    static VectorOfFixVecs<DimVec<double> > *x11_2d;
    static VectorOfFixVecs<DimVec<double> > *x12_2d;
    static VectorOfFixVecs<DimVec<double> > *x17_2d;
    static double *w1_2d;
    static double *w2_2d;
    static double *w3_2d;
    static double *w4_2d;
    static double *w5_2d;
    static double *w7_2d;
    static double *w8_2d;
    static double *w9_2d;
    static double *w10_2d;
    static double *w11_2d;
    static double *w12_2d;
    static double *w17_2d;

    static VectorOfFixVecs<DimVec<double> > *x1_3d;
    static VectorOfFixVecs<DimVec<double> > *x2_3d;
    static VectorOfFixVecs<DimVec<double> > *x3_3d;
    static VectorOfFixVecs<DimVec<double> > *x4_3d;
    static VectorOfFixVecs<DimVec<double> > *x5_3d;
    static VectorOfFixVecs<DimVec<double> > *x7_3d;
    static double *w1_3d;
    static double *w2_3d;
    static double *w3_3d;
    static double *w4_3d;
    static double *w5_3d;
    static double *w7_3d;

    /** \} */
  };



  /** \brief
   * Pre-compute the values of all basis functions at all quadrature nodes;  
   */
  const Flag INIT_PHI=1;

  /** \brief
   * Pre-compute the gradients (with respect to the barycentric coordinates) of
   * all basis functions at all quadrature nodes
   */
  const Flag INIT_GRD_PHI=2; 

  /** \brief
   * pre-compute all 2nd derivatives (with respect to the barycentric 
   * coordinates) of all basis functions at all quadrature nodes;
   */
  const Flag INIT_D2_PHI=4;


  /** 
   * \ingroup Integration
   *
   *\brief
   * Often numerical integration involves basis functions, such as the assembling
   * of the system matrix and right hand side, or the integration of finite 
   * element functions. Since numerical quadrature involves only the values at 
   * the quadrature points and the values of basis functions and its derivatives
   * are the same at these points for all elements of the grid, such routines can
   * be much more efficient, if they can use pre-computed values of the basis
   * functions at the quadrature points. In this case the basis functions do not 
   * have to be evaluated for each quadrature point on every element newly.
   * Information that should be pre-computed can be specified by the following 
   * symbolic constants:
   * \ref INIT_PHI, \ref INIT_GRD_PHI, \ref INIT_D2_PHI
   */
  class FastQuadrature
  {
  protected:
    /** \brief
     * Constructs a FastQuadrature for the given Quadrature, BasisFunction, and
     * flag.
     */
    FastQuadrature(BasisFunction* basFcts, Quadrature* quad, Flag flag)
      : init_flag(flag), 
	phi(NULL), 
	grdPhi(NULL), 
	D2Phi(NULL), 
	quadrature(quad), 
	basisFunctions(basFcts) 
    {}

    /// Copy constructor
    FastQuadrature(const FastQuadrature&);

    /// Extended copy constructor
    FastQuadrature(const FastQuadrature&, const Flag);

    /// Destructor
    ~FastQuadrature();

  public:
    /// Returns a FastQuadrature for the given BasisFunction, Quadrature, and flags.
    static FastQuadrature* provideFastQuadrature(const BasisFunction*,
						 const Quadrature&,
						 Flag);

    /// inits FastQuadrature like speciefied in flag
    void init(Flag init_flag);

    inline bool initialized(Flag flag) 
    {
      if (flag == INIT_PHI)
	return (phi != NULL);

      if (flag == INIT_GRD_PHI)
	return (grdPhi != NULL);

      if (flag == INIT_D2_PHI)
	return (D2Phi != NULL);

      ERROR_EXIT("invalid flag\n");
      return false;
    }

    /// Returns \ref quadrature
    inline const Quadrature* getQuadrature() const 
    { 
      return quadrature; 
    }

    /// Returns \ref max_points
    inline int getMaxQuadPoints() 
    { 
      return max_points; 
    }

    /// Returns (*\ref D2Phi)[q][i][j][m]
    const double getSecDer(int q, int i, int j, int m) const;

    /// Returns (*\ref D2Phi)[q]
    const VectorOfFixVecs<DimMat<double> > *getSecDer(int q) const;

    /// Returns (*\ref grdPhi)[q][i][j]
    inline const double getGradient(int q, int i ,int j) const 
    {
      return (grdPhi) ? (*grdPhi)[q][i][j] : 0.0;
    }

    /// Returns (*\ref grdPhi)[q]
    inline VectorOfFixVecs<DimVec<double> >* getGradient(int q) const 
    {
      return (grdPhi) ? &((*grdPhi)[q]) : NULL;
    }

    inline DimVec<double>& getGradient(int q, int i) const
    {
      return (*grdPhi)[q][i];
    }

    /// Returns \ref phi[q][i]
    inline const double getPhi(int q, int i) const 
    {
      return (phi) ? phi[q][i] : 0.0;
    }

    /// Returns \ref phi[q]
    inline const double *getPhi(int q) const 
    {
      return (phi) ? phi[q] : NULL;
    }

    /// Returns \ref quadrature ->integrateStdSimplex(f)
    inline double integrateStdSimplex(AbstractFunction<double, DimVec<double> > *f) 
    {
      return quadrature->integrateStdSimplex(f); 
    }
  
    /// Returns \ref quadrature ->getNumPoints()
    inline int getNumPoints() const 
    { 
      return quadrature->getNumPoints();
    }

    /// Returns \ref quadrature ->getWeight(p)
    inline double getWeight(int p) const 
    {
      return quadrature->getWeight(p);
    }

    /// Returns \ref quadrature ->getDim()
    inline int getDim() const 
    { 
      return quadrature->getDim(); 
    }

    /// Returns \ref quadrature ->getDegree()
    inline int getDegree() const 
    { 
      return quadrature->getDegree();
    }

    /// Returns \ref quadrature ->grdFAtQp(f, vec)
    inline const WorldVector<double> 
    *grdFAtQp(const AbstractFunction<WorldVector<double>, 
	      DimVec<double> >& f,
	      WorldVector<double>* vec) const 
    { 
      return quadrature->grdFAtQp(f, vec);
    }
  
    /// Returns \ref quadrature ->fAtQp(f, vec)
    inline const double *fAtQp(const AbstractFunction<double, 
			       DimVec<double> >& f, double *vec) const 
    {
      return quadrature->fAtQp(f, vec);    
    }

    /// Returns \ref quadrature ->getLambda(a,b)
    inline double getLambda(int a,int b) const 
    {
      return quadrature->getLambda(a,b);
    }

    /// Returns \ref quadrature ->getLambda(a)
    inline const DimVec<double>& getLambda(int a) const 
    { 
      return quadrature->getLambda(a); 
    }

    /// Returns \ref basisFunctions
    inline BasisFunction* getBasisFunctions() const 
    { 
      return basisFunctions; 
    }

  protected:
    /** \brief
     * Specifies which information should be pre-computed. Can be \ref INIT_PHI, 
     * \ref INIT_GRD_PHI, or \ref INIT_D2_PHI
     */
    Flag init_flag;

    /** \brief
     * Matrix storing function values if the flag \ref INIT_PHI is set;
     * phi[i][j] stores the value \ref basisFunctions->phi[j]
     * (quadrature->lambda[i]), 0 <= j < basisFunctions->getNumber()  and 
     * 0 <= i < n_points
     */
    double **phi;

    /** \brief
     * Matrix storing all gradients (with respect to the barycentric coordinates)
     * if the flag \ref INIT_GRD_PHI is set; grdPhi[i][j][k] stores the value 
     * basisFunctions->grdPhi[j](quadrature->lambda[i])[k] 
     * for 0 <= j < basisFunctions->getNumber(),
     * 0 <= i < . . . , n_points, and 0 <= k < DIM
     */
    MatrixOfFixVecs<DimVec<double> > *grdPhi;

    /** \brief
     * Matrix storing all second derivatives (with respect to the barycentric
     * coordinates) if the flag \ref INIT_D2_PHI is set; D2Phi[i][j][k][l] stores
     * the value basisFunctions->D2Phi[j](quadrature->lambda[i])[k][l] 
     * for 0 <= j < basisFunctions->getNumber(), 
     * 0 <= i < n_points, and 0 <= k,l < DIM
     */
    MatrixOfFixVecs<DimMat<double> > *D2Phi;

    /** \brief
     * List of all used FastQuadratures
     */
    static std::list<FastQuadrature*> fastQuadList;

    /** \brief
     * Maximal number of quadrature points for all yet initialised FastQuadrature
     * objects. This value may change after a new initialisation of a
     * FastQuadrature
     */
    static int max_points;

    /// This FastQuadrature stores values for Quadrature quadrature
    Quadrature* quadrature;

    /// Values stored for basis functions basisFunctions
    BasisFunction* basisFunctions;

  };

}

#endif  // AMDIS_QUADRATURE_H