/* movstat/sumacc.c

 *

 * Moving window sum accumulator

 * 

 * Copyright (C) 2018 Patrick Alken

 * 

 * This program 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.

 * 

 * This program 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, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

#include <config.h>

#include <gsl/gsl_math.h>

#include <gsl/gsl_vector.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_movstat.h>

typedef double ringbuf_type_t;

#include "ringbuf.c"

typedef struct

{

  double sum;     /* current window sum */

  ringbuf *rbuf;  /* ring buffer storing current window */

} sumacc_state_t;

static size_t

sumacc_size(const size_t n)

{

  size_t size = 0;

  size += sizeof(sumacc_state_t);

  size += ringbuf_size(n);

  return size;

}

static int

sumacc_init(const size_t n, void * vstate)

{

  sumacc_state_t * state = (sumacc_state_t *) vstate;

  state->sum = 0.0;

  state->rbuf = (ringbuf *) ((unsigned char *) vstate + sizeof(sumacc_state_t));

  ringbuf_init(n, state->rbuf);

  return GSL_SUCCESS;

}

static int

sumacc_insert(const double x, void * vstate)

{

  sumacc_state_t * state = (sumacc_state_t *) vstate;

  if (ringbuf_is_full(state->rbuf))

    {

      /* subtract oldest element from sum */

      state->sum -= ringbuf_peek_back(state->rbuf);

    }

  /* add new element to sum and ring buffer */

  state->sum += x;

  ringbuf_insert(x, state->rbuf);

  return GSL_SUCCESS;

}

static int

sumacc_delete(void * vstate)

{

  sumacc_state_t * state = (sumacc_state_t *) vstate;

  if (!ringbuf_is_empty(state->rbuf))

    {

      state->sum -= ringbuf_peek_back(state->rbuf);

      ringbuf_pop_back(state->rbuf);

    }

  return GSL_SUCCESS;

}

static int

sumacc_get(void * params, double * result, const void * vstate)

{

  const sumacc_state_t * state = (const sumacc_state_t *) vstate;

  (void) params;

  *result = state->sum;

  return GSL_SUCCESS;

}

static const gsl_movstat_accum sum_accum_type =

{

  sumacc_size,

  sumacc_init,

  sumacc_insert,

  sumacc_delete,

  sumacc_get

};

const gsl_movstat_accum *gsl_movstat_accum_sum = &sum_accum_type;