// Elder Ray Index
//
// elder_ray - ERI
//
// Bull Power: High - EMA(Close)
// Bear Power: Low - EMA(Close)
//
// Inputs:    4 (OHLC)
// Outputs:   2 (Bull Power, Bear Power)
// Constants: 1 (EMA period)

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

typedef struct {
    fp_t k;
} ts_elder_ray_params_t;

ts_parameter_t const ts_elder_ray_p = { .n_inputs = 4, .n_outputs = 2, .n_constants = 1, .params_size = sizeof(ts_elder_ray_params_t) };

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

int ts_elder_ray(
	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_elder_ray_p );
	if ( !c ) return -1;
	fp_t k = ((ts_elder_ray_params_t *)c)->k;
	if (k == 0 || n < k) return -1;
	fp_t a = 1.0 / k;
	fp_t *ema = calloc( n, sizeof( fp_t ) );
	if( !ema ) return -1;

	ema[0] = ts_c( x, 0 );

	for( uint_t i = 0; i < n; ++i )
	{
		if( i > 0 )
		{
			ema[i] = ema[i - 1] + a * ( ts_c( x, i ) - ema[i - 1] );
		}
		y[0][i] = ts_h( x, i ) - ema[i];
		y[1][i] = ts_l( x, i ) - ema[i];
	}

	free( ema );
	return 0;
}