// Double Exponential Moving Average
//
// average_exponential_double - dema
//
// y[i] = 
//
// Inputs:    1
// Outputs:   1
// Constants: 1


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


typedef struct {
    fp_t a;
} ts_average_exponential_double_params_t;

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


uint_t ts_average_exponential_double_offset( ts_constant_t const *c )
{
	( void )c;
	return ( 0 );
}

int ts_average_exponential_double(
	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_exponential_double_p );
	if ( !c ) return -1;
	TS_CHECK_INPUT(x, x_n, n);
	fp_t a = ((ts_average_exponential_double_params_t const *)c)->a;
	if (a == 0) return -1;

	fp_t ema1 = x[0][0];
	fp_t ema2 = x[0][0];

	y[0][0] = x[0][0];

	for( uint_t i = 1; i < n; ++i )
	{
    	ema1 = ema1 + a * ( x[0][i] - ema1 );
    	ema2 = ema2 + a * ( ema1 - ema2 );

		y[0][i] = 2 * ema1 - ema2;
	}
	return 0;
}