/*
 * Copyright 2005-2016 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 *
 * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
 * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
 */

#include "grib_api_internal.h"

/*
   This is used by make_class.pl

   START_CLASS_DEF
   CLASS      = nearest
   SUPER      = grib_nearest_class_gen
   IMPLEMENTS = init
   IMPLEMENTS = find;destroy
   MEMBERS = const char* J
   MEMBERS = const char* K
   MEMBERS = const char* M
   END_CLASS_DEF

 */

/* START_CLASS_IMP */

/*

Don't edit anything between START_CLASS_IMP and END_CLASS_IMP
Instead edit values between START_CLASS_DEF and END_CLASS_DEF
or edit "nearest.class" and rerun ./make_class.pl

*/


static void init_class              (grib_nearest_class*);

static int init               (grib_nearest* nearest,grib_handle* h,grib_arguments* args);
static int find(grib_nearest* nearest, grib_handle* h,double inlat, double inlon, unsigned long flags, double* outlats,double* outlons, double *values,double *distances, int *indexes,size_t *len);
static int destroy            (grib_nearest* nearest);

typedef struct grib_nearest_sh{
  grib_nearest nearest;
/* Members defined in gen */
	const char* values_key;
	const char* radius;
	int cargs;
/* Members defined in sh */
	const char* J;
	const char* K;
	const char* M;
} grib_nearest_sh;

extern grib_nearest_class* grib_nearest_class_gen;

static grib_nearest_class _grib_nearest_class_sh = {
    &grib_nearest_class_gen,                         /* super                     */
    "sh",                         /* name                      */
    sizeof(grib_nearest_sh),      /* size of instance          */
    0,                              /* inited */
    &init_class,                    /* init_class */
    &init,                          /* constructor               */
    &destroy,                       /* destructor                */
    &find,                          /* find nearest              */
};

grib_nearest_class* grib_nearest_class_sh = &_grib_nearest_class_sh;


static void init_class(grib_nearest_class* c)
{
}
/* END_CLASS_IMP */

#define LEGENDRE_SIZE(L) (L+1)*(L+2)/2

static void grib_trigs(int m,double lambda,double* c,double* s);
static void grib_invtrans_legendre(int L,double x,
                       double* RI,double* TR,double* TI);
static double grib_invtrans_trig(int L,double* TR,double* TI,
                                 double *c,double *s);
static double grib_invtrans(grib_context *c,int L,double latdeg,double londeg,double* values);

static int init(grib_nearest* nearest,grib_handle* h,grib_arguments* args)
{
  grib_nearest_sh* self = (grib_nearest_sh*) nearest;
  self->J  = grib_arguments_get_name(h,args,self->cargs++);
  self->K  = grib_arguments_get_name(h,args,self->cargs++);
  self->M  = grib_arguments_get_name(h,args,self->cargs++);
  return 0;
}

static int find(grib_nearest* nearest, grib_handle* h,
                double inlat, double inlon,unsigned long flags,
                double* outlats,double* outlons,
                double *outvalues,double *distances,int* indexes, size_t *len) {
  grib_nearest_sh* self = (grib_nearest_sh*) nearest;
  long J,K,M;
  double *values;
  int size,i,ret;
  size_t vsize=0;
  double val;

  if( (ret =  grib_get_long(h,self->J,&J))!= GRIB_SUCCESS)
    return ret;
  if( (ret =  grib_get_long(h,self->K,&K))!= GRIB_SUCCESS)
    return ret;
  if( (ret =  grib_get_long(h,self->M,&M))!= GRIB_SUCCESS)
    return ret;

  size=2*LEGENDRE_SIZE(J);
  vsize=size;
  values=(double*)grib_context_malloc_clear(h->context,sizeof(double)*size);
  if (!values) {
    grib_context_log(h->context,GRIB_LOG_ERROR,
                     "nearest_sh: unable to allocate %d bytes",
                     sizeof(double)*size);
    return GRIB_OUT_OF_MEMORY;
  }
  
  if( (ret =  grib_get_double_array(h,self->values_key,values,&vsize))
       != GRIB_SUCCESS)
    return ret;
  
  Assert(vsize==size);

  val=grib_invtrans(h->context,J,inlat,inlon,values);

  grib_context_free(h->context,values);

  for (i=0;i<4;i++) {
    outlats[i]=inlat;
    outlons[i]=inlon;
    outvalues[i]=val;
    indexes[i]=-1;
  }
  
  return GRIB_SUCCESS;
}

static int destroy(grib_nearest* nearest) {
  return GRIB_SUCCESS;
}


static void grib_trigs(int m,double lambda,double* c,double* s) {
  int i;
  double a,b;

  b=sin(lambda);
  a=1-2*sin(lambda/2.0)*sin(lambda/2.0);
  c[0]=1.0; s[0]=0.0;

  for (i=1;i<=m;i++) {
    c[i]=a*c[i-1]-b*s[i-1];
    s[i]=a*s[i-1]+b*c[i-1];
  }

}

static double grib_invtrans_trig(int L,double* TR,double* TI,double *c,double *s) {
  double ret=0;
  int m=0;

  for (m=1;m<=L;m++) {
    ret+= TR[m] * c[m];
    printf("++ %d ++ %.20e %g %g\n",m,ret,TR[m],c[m]);
    ret-= TI[m] * s[m];
    printf("+- %d ++ %.20e %g %g\n",m,ret,TI[m],s[m]);
  }
  ret=2*ret+TR[0];

  return ret;
}

static void grib_invtrans_legendre(int L,double x,
                                   double* RI,double* TR,double* TI) {
  int l,m;
  double y2;
  double f,of,fx,p0;
  double *pP,*oP,*pRI;

  if (fabs(x) > 1.0) {
    printf("grib_legendreP: invalid x=%g must be abs(x)>0\n",x);
    exit(1);
  }
  if (L<0) {
    printf("grib_legendreP: invalid L=%d must be >0\n",L);
    exit(1);
  }

  pP=(double*)malloc(sizeof(double)*(L+1));
  if (!pP) {
    printf("unable to allocate %d bytes\n",(int)sizeof(double)*(L+1));
    exit(1);
  }

  y2=(1.0-x*x); fx=1; p0=1; oP=pP; pRI=RI;
  for (m=0;m<L;m++) {
    /* printf("\n"); */
    pP[0]=sqrt((2*m+1)*p0);
    if (m & 1) pP[0]=-pP[0];
    TR[m]=pP[0] * *(pRI++);
    TI[m]=pP[0] * *(pRI++);
    printf("-- (%d,%d) %.20e %.20e\n",m,m,TR[m],pP[0]);  
    of=sqrt(2*m+3);
    pP[1]=x*of*pP[0];
    TR[m]+=pP[1] * *(pRI++);
    TI[m]+=pP[1] * *(pRI++);
    printf("-- (%d,%d) %.20e %.20e\n",m+1,m,TR[m],pP[1]);
    for (l=m+2;l<=L;l++) {
      f=sqrt((4.0*l*l-1.0)/(l*l-m*m));
      pP[2]=(x*pP[1]-pP[0]/of)*f;
      TR[m]+=pP[2] * *(pRI++);
      TI[m]+=pP[2] * *(pRI++);
      printf("-- (%d,%d) %.20e %.20e\n",l,m,TR[m],pP[2]);
      of=f;
      pP++;
    }
    pP=oP;
    p0*=y2*fx/(fx+1.0);
    fx+=2;
  }
  /* printf("\n"); */
  pP[0]=sqrt((2*L+1)*p0);
  if (L & 1) pP[0]=-pP[0];
  TR[L]=pP[0] * *(pRI++);
  TI[L]=pP[0] * *(pRI++);
  printf("-- (%d,%d) %.20e %.20e\n",L,L,TR[m],pP[0]);
}

static double grib_invtrans(grib_context* context,int L,double latdeg,double londeg,double* values) {
  double val;
  double *c,*s,*TR,*TI;
  double sinlat,deg2rad,lonrad;
  int Lp1=L+1;

  deg2rad=acos(0.0)/90.0;
  sinlat=sin(latdeg*deg2rad);
  lonrad=londeg*deg2rad;
  
  c=(double*)grib_context_malloc_clear(context,sizeof(double)*Lp1);
  if (!c) {
    grib_context_log(context,GRIB_LOG_ERROR,
      "nearest_sh: unable to allocate %d bytes",sizeof(double)*Lp1);
    return GRIB_OUT_OF_MEMORY;
  }
  
  s=(double*)grib_context_malloc_clear(context,sizeof(double)*Lp1);
  if (!s) {
    grib_context_log(context,GRIB_LOG_ERROR,
     "nearest_sh: unable to allocate %d bytes",sizeof(double)*Lp1);
    return GRIB_OUT_OF_MEMORY;
  }
  
  grib_trigs(L,lonrad,c,s);

  TR=(double*)grib_context_malloc_clear(context,sizeof(double)*Lp1);
  if (!TR) {
    grib_context_log(context,GRIB_LOG_ERROR,
      "nearest_sh: unable to allocate %d bytes",sizeof(double)*Lp1);
    return GRIB_OUT_OF_MEMORY;
  }
  TI=(double*)grib_context_malloc_clear(context,sizeof(double)*Lp1);
  if (!TI) {
    grib_context_log(context,GRIB_LOG_ERROR,
     "nearest_sh: unable to allocate %d bytes",sizeof(double)*Lp1);
    return GRIB_OUT_OF_MEMORY;
  }
  
  grib_invtrans_legendre(L,sinlat,values,TR,TI);

  val=grib_invtrans_trig(L,TR,TI,c,s);

  grib_context_free(context,c);
  grib_context_free(context,s);
  grib_context_free(context,TR);
  grib_context_free(context,TI);

  return val;
}

