#ifndef BESSELS_H
#define BESSELS_H

#include <stddef.h>
#include <complex.h>

complex double *hankelcoefftable_init(size_t maxn);

// general, gives the offset such that result[k] is 
// the coefficient corresponding to the e**(I * x) * x**(-k-1)
// term of the Hankel function; no boundary checks!
static inline complex double *
hankelcoeffs_get(complex double *hankelcoefftable, size_t n){
  return hankelcoefftable + n*(n+1)/2;
}


// general; target_longrange and target_shortrange are of size (maxn+1)
// if target_longrange is NULL, only the short-range part is calculated
void hankelparts_fill(complex double *target_longrange, complex double *target_shortrange,
		size_t maxn, size_t longrange_order_cutoff, // x**(-(order+1)-1) terms go completely to short-range part
		complex double *hankelcoefftable,
		unsigned kappa, double c, double x); // x = k0 * r


// this declaration is general; however, the implementation 
// is so far only for kappa == ???, maxn == ??? TODO
void lrhankel_recpart_fill(complex  double *target_longrange_kspace,
	       size_t maxn, size_t longrange_k_cutoff, 
	       complex double  *hankelcoefftable,
	       unsigned kappa, double c, double k0, double k);

#endif //BESSELS_H