/*
 * 
 *                This source code is part of
 * 
 *                 G   R   O   M   A   C   S
 * 
 *          GROningen MAchine for Chemical Simulations
 * 
 *                        VERSION 3.2.0
 * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
 * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
 * Copyright (c) 2001-2004, The GROMACS development team,
 * check out http://www.gromacs.org for more information.

 * This program is free software; you can redistribute it and/or
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 * as published by the Free Software Foundation; either version 2
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 */


#ifndef _ifunc_h
#define _ifunc_h

#include "../typedefs.h"

#ifdef __cplusplus
extern "C" {
#endif


typedef real t_ifunc(int nbonds,const t_iatom iatoms[],
		     const t_iparams iparams[],
                     const rvec x[],rvec f[],rvec fshift[],
		     const t_pbc *pbc,const t_graph *g,
		     real lambda,real *dvdlambda,
		     const t_mdatoms *md,t_fcdata *fcd,
		     int *ddgatindex);

/*
 * The function type t_ifunc() calculates one interaction, using iatoms[] 
 * and iparams. Within the function the number of atoms to be used is 
 * known. Within the function only the atomid part of the iatoms[] array 
 * is supplied, not the type field (see also t_ilist). The function 
 * returns the potential energy. If pbc==NULL the coordinates in x are
 * assumed to be such that no calculation of PBC is necessary,
 * If pbc!=NULL a full PBC calculation is performed.
 * If g!=NULL it is used for determining the shift forces.
 * With domain decomposition ddgatindex can be used for getting global
 * atom numbers for warnings and error messages.
 * ddgatindex is NULL when domain decomposition is not used.
 */

#define IF_NULL       0
#define IF_BOND       1
#define IF_VSITE      1<<1
#define IF_CONSTRAINT 1<<2
#define IF_CHEMBOND   1<<3
#define IF_BTYPE      1<<4
#define IF_ATYPE      1<<5
#define IF_TABULATED  1<<6
#define IF_LIMZERO    1<<7
/* These flags tell to some of the routines what can be done with this
 * item in the list.
 * With IF_BOND a bonded interaction will be calculated.
 * With IF_BTYPE grompp can convert the bond to a Morse potential.
 * With IF_BTYPE or IF_ATYPE the bond/angle can be converted to
 * a constraint or used for vsite parameter determination by grompp.
 * IF_LIMZERO indicates that for a bonded interaction the potential
 * does goes to zero for large distances, thus if such an interaction
 * it not assigned to any node by the domain decompostion, the simulation
 * still continue, if mdrun has been told so.
 */
typedef struct
{
  const char *name;	/* the name of this function			*/
  const char *longname; /* The name for printing etc.                   */
  int     nratoms;	/* nr of atoms needed for this function		*/
  int     nrfpA,nrfpB;  /* number of parameters for this function.      */
                        /* this corresponds to the number of params in  */
                        /* iparams struct! (see idef.h)                 */
  /* A and B are for normal and free energy components respectively.    */
  unsigned long   flags;        /* Flags (see above)                            */
  int     nrnb_ind;     /* index for nrnb (-1 if unknown)               */
  t_ifunc *ifunc;	/* the function it self				*/
} t_interaction_function;

#define NRFPA(ftype) (interaction_function[(ftype)].nrfpA)
#define NRFPB(ftype) (interaction_function[(ftype)].nrfpB)
#define NRFP(ftype)  (NRFPA(ftype)+NRFPB(ftype))
#define NRAL(ftype) (interaction_function[(ftype)].nratoms)

#define IS_CHEMBOND(ftype) (interaction_function[(ftype)].nratoms==2 && interaction_function[(ftype)].flags & IF_CHEMBOND)
/* IS_CHEMBOND tells if function type ftype represents a chemical bond */

/* IS_ANGLE tells if a function type ftype represents an angle 
 * Per Larsson, 2007-11-06
 */
#define IS_ANGLE(ftype) (interaction_function[(ftype)].nratoms==3 && interaction_function[(ftype)].flags & IF_ATYPE)
#define IS_VSITE(ftype) (interaction_function[(ftype)].flags & IF_VSITE)

#define IS_TABULATED(ftype) (interaction_function[(ftype)].flags & IF_TABULATED)

extern const t_interaction_function interaction_function[F_NRE];
/* initialised interaction functions descriptor				*/

#ifdef __cplusplus
}
#endif


#endif
