// Simple Moving Average
//
// average_simple - sma
//
// Unweighted mean of previous k data points
//
// SMA_k = ( 1 / k ) * SUM[ i = 1, k ] x_i
//
// Initial Values
//
//   Cumulative moving average to n = k
//
// Successive Value
//
//   SMA_n = x_n-1 + ( 1 / n )( x_n - x_n-1 )
//
// Inputs:    1
// Outputs:   1
// Constants: 1


#include <math.h>
#include "ts.h"


typedef struct {
    uint_t k;
} ts_average_params_t;

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


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

int ts_average(
	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_average_p );
	if ( !c ) return -1;
	TS_CHECK_INPUT(x, x_n, n);
	uint_t k = ((ts_average_params_t *)c)->k;
	if (k == 0 || n < k) return -1;

	uint_t xi = 0;
	uint_t yi = k;

	fp_t sum = 0;

	for( ; xi < k; ++xi )
	{
		sum += x[0][xi];
	}

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

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