#ifndef _CHISQMIN_H_
#define _CHISQMIN_H_

class residFunc {
 public:
  virtual ~residFunc();
  virtual void resid(const HepVector *x, void *data, HepVector *f) = 0;
  virtual void deriv(const HepVector *x, void *data, HepMatrix *J) = 0;
  virtual void residAndDeriv(const HepVector *x, void *data, HepVector *f, HepMatrix *J) = 0;
  virtual unsigned getn() = 0;
  virtual unsigned getp() = 0;
};

extern "C" {
#include <gsl/gsl_vector.h> 
#include <gsl/gsl_blas.h>
#include <gsl/gsl_multifit_nlin.h>
}

class chisqMin {
 public:
  chisqMin(residFunc *f);
  ~chisqMin();
  void setStartParams(HepVector &x);
  void fit();
  HepVector getParams();
  HepMatrix getCovar();
 private:
  const gsl_multifit_fdfsolver_type *T; /* pointer to solver type */
  gsl_multifit_fdfsolver *s; /* pointer to solver */
  gsl_multifit_function_fdf f; /* function structure */
  residFunc *residFuncPtr;
  unsigned int iter; /* fit iteration */
  int status; /* status from fit */
  gsl_matrix *covar; /* covariance matrix */
  unsigned int p; /* number of parameters, local copy for convenience */
  unsigned int n; /* number of data points, local copy for convenience */
};

extern "C" {
  int fGsl(const gsl_vector *x, void *data, gsl_vector *f);
  int dfGsl(const gsl_vector *x, void *data, gsl_matrix *J);
  int fdfGsl(const gsl_vector *x, void *data, gsl_vector *f, gsl_matrix *J);
}

#endif // _CHISQMIN_H_