// Zigzag
//
// zigzag
//
// ZigZag Filter
//
// 
//
// Inputs:    1
// Outputs:   2
// Constants: 1


#include "ts.h"


typedef struct {
    fp_t threshold;
} ts_zigzag_params_t;

ts_parameter_t const ts_zigzag_p = { .n_inputs = 1, .n_outputs = 2, .n_constants = 1, .params_size = sizeof(ts_zigzag_params_t) };


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

int ts_zigzag(
	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_zigzag_p );
	if ( !c ) return -1;

	fp_t threshold = ((ts_zigzag_params_t const *)c)->threshold;
	if (threshold <= 0 || isnan(threshold) || isinf(threshold)) return -1;

	y[0][0] = x[0][0];
	y[1][0] = 0;

	for( uint_t i = 1; i < n; ++i )
	{
		fp_t last_zz = y[0][i - 1];
		fp_t dir = y[1][i - 1];
		fp_t change = last_zz != 0 ? ( x[0][i] - last_zz ) / last_zz * 100.0 : 0;

		if( dir == 0 )
		{
			if( change >= threshold )
			{
				y[0][i] = x[0][i];
				y[1][i] = 1;
			}
			else if( change <= -threshold )
			{
				y[0][i] = x[0][i];
				y[1][i] = -1;
			}
			else
			{
				y[0][i] = last_zz;
				y[1][i] = 0;
			}
		}
		else if( dir == 1 )
		{
			if( change <= -threshold )
			{
				y[0][i] = x[0][i];
				y[1][i] = -1;
			}
			else
			{
				y[0][i] = last_zz;
				y[1][i] = 1;
			}
		}
		else
		{
			if( change >= threshold )
			{
				y[0][i] = x[0][i];
				y[1][i] = 1;
			}
			else
			{
				y[0][i] = last_zz;
				y[1][i] = -1;
			}
		}
	}
	return 0;
}