// Summation
//
// summation - sum
//
// Calculates the sum of the past k values
//
// y_i = sum_{j=i-k+1}^{i}[x_j]
//
// Inputs:    1
// Outputs:   1
// Constants: 0


#include "ts.h"


typedef struct {
    uint_t k;
} ts_summation_params_t;

ts_parameter_t const ts_summation_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 1, .params_size = sizeof(ts_summation_params_t) };


uint_t ts_summation_offset( ts_constant_t const *c )
{
	( void )c;
	return ( c ? ((ts_summation_params_t *)c)->k > 0 ? ((ts_summation_params_t *)c)->k - 1 : 0 : 0 );
}

int ts_summation(
	fp_t * const *y, uint_t y_n,
	fp_t const * const *x, uint_t x_n,
	uint_t n, ts_constant_t const *c
)
{
	TS_PROLOGUE( ts_summation_p );
	if ( !c ) return -1;
	uint_t k = ((ts_summation_params_t *)c)->k;
	if (k == 0 || n < k) return -1;
	
	uint_t xi = 0;
	uint_t yi = k;

	y[0][k - 1] = 0;

	for( ; xi < k; xi++ )
	{
		y[0][k - 1] += x[0][xi];
	}

	for( ; xi < n; xi++, yi++ )
	{
		y[0][yi] = x[0][xi] + y[0][yi - 1] - x[0][xi - k];
	}
	return 0;
}