/*
Copyright (C) 2007 Alexander Shirokov

This file is part of WSHAPE.

WSHAPE is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.

WSHAPE is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _WSHAPE_H_
#define _WSHAPE_H_

/* Reference laws */

/* Specifies the smoothing scale */
typedef struct wshape_smscale_t {
  float eps;
} wshape_smscale_t;

/* Newtonian potential/force law */
float wshape_law_newton (int law, float r);

/* Plummer potential/force law  */
float wshape_law_plummer(int law, wshape_smscale_t *S, float r);

/* Spline (traditional) potential/force law */
float wshape_law_spline(int law, wshape_smscale_t *S, float r);

/* Parameter 'law' takes one of the following values. */
enum  {
  /* The return value will be interaction potential law. */
  WSHAPE_LAW_POTEN,
  /* The return value will be interparticle force law. */
  WSHAPE_LAW_FORCE,
};



/* W-shape particles */

/* Specifies the smoothing scales in a generic pair */
typedef struct wshape_smscales_t {
  wshape_smscale_t particle1, particle2;
} wshape_smscales_t;


/* W-shape density profile, as function of radial position */
float wshape_density (int scaling, wshape_smscale_t *smscale
		      , float r, int n);
/* potential/force law for a pair of two general W-shape particles */
float wshape_law_gener (int law, int scaling, wshape_smscales_t *smscales
			, float r, int n);
/* potential/force law for a pair of two identical W-shape particles */
float wshape_law_ident (int law, int scaling, wshape_smscale_t *smscale
			, float r, int n);
/* Poential/force law for a pair including one W-shape and one point particle */
float wshape_law_point (int law, int scaling, wshape_smscale_t *smscale
			, float r, int n);

/* Parameter 'scaling' takes one of the following values. */
enum  {
  /* no scaling: the diameter og W-shapes equals epsilon by definition. */
  WSHAPE_SCALING_NONE,
  /* use potential-based scaling of W-shapes: the diameter and
   normalization of W-shape are scaled yo match the plummer potential
   asymptotics at zero separation */
  WSHAPE_SCALING_BY_POTEN,
  /* use force-based scaling of W-shapes: the diameter and
   normalization of W-shape are scaled yo match the plummer force
   asymptotics at zero separation */
  WSHAPE_SCALING_BY_FORCE,
};


/* Maximum allowed value of parameter 'n' */
#define WSHAPE_NMAX   4

/* Raw Hockney-Eastwood window functions */
float wshape_hockney_eastwood(int n, float s);

/* Symmetric combination \sqrt( (eps1^2+eps2^2)/2 ) motivated by gaussian */
float eps_sym(float eps1, float eps2);


/* The following routines are only available with GSL linked */
#ifdef WITH_GSL
#include "gsl_sf_bessel.h"
#include "gsl_sf_erf.h"

/* Potential/force law in a pair of gaussian clouds of general smoothing */
float wshape_gaussian_law_ident(int law, wshape_smscale_t *S, float r);

/* Plummer density cloud */
float wshape_plummer_density(wshape_smscale_t *S, float r);

/* Potential/force law in a pair of plummer clouds of general smoothing */
float wshape_plummer_law_gener(int law, wshape_smscales_t *S, float r);

/* Poential/force law for a pair including one Plummer cloud and one point particle */
float wshape_plummer_law_point(int law, wshape_smscale_t *S, float r);
#endif

#endif