// Stoch Rsi
//
// stoch_rsi
//
// Stochastic RSI
//
// 
//
// Inputs:    1
// Outputs:   2
// Constants: 2


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

typedef struct {
    uint_t rsi_period;
    uint_t stoch_period;
} ts_stoch_rsi_params_t;

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

uint_t ts_stoch_rsi_offset( ts_constant_t const *c )
{
	( void )c;
	return ( c ? ((ts_stoch_rsi_params_t *)c)->rsi_period + ((ts_stoch_rsi_params_t *)c)->stoch_period - 1 : 0 );
}

int ts_stoch_rsi(
	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_stoch_rsi_p );
	if ( !c ) return -1;
	uint_t rsi_period = ((ts_stoch_rsi_params_t *)c)->rsi_period;
	uint_t stoch_period = ((ts_stoch_rsi_params_t *)c)->stoch_period;
	if (rsi_period == 0 || stoch_period == 0) return -1;

	fp_t *rsi_values = NULL;
	if( n > 0 )
	{
		rsi_values = calloc( n, sizeof( fp_t ) );
		if( !rsi_values ) return -1;
	}

	for( uint_t i = rsi_period; i < n; ++i )
	{
		fp_t sum_gain = 0;
		fp_t sum_loss = 0;

		for( uint_t j = 0; j < rsi_period; ++j )
		{
			fp_t change = x[0][i - rsi_period + 1 + j] - x[0][i - rsi_period + j];
			if( change > 0 )
				sum_gain += change;
			else if( change < 0 )
				sum_loss += (-change);
		}

		if( sum_loss == 0 )
			rsi_values[i] = 100.0;
		else
		{
			fp_t rs = sum_gain / sum_loss;
			rsi_values[i] = 100.0 - ( 100.0 / ( 1.0 + rs ) );
		}
	}

	for (uint_t j = 0; j < n && j < rsi_period + stoch_period - 1; ++j) { y[0][j] = 0; y[1][j] = 0; }
	for( uint_t i = rsi_period + stoch_period - 1; i < n; ++i )
	{
		fp_t rsi_min = rsi_values[i - stoch_period + 1];
		fp_t rsi_max = rsi_values[i - stoch_period + 1];

		for( uint_t j = 1; j < stoch_period; ++j )
		{
			rsi_min = fmin( rsi_min, rsi_values[i - stoch_period + 1 + j] );
			rsi_max = fmax( rsi_max, rsi_values[i - stoch_period + 1 + j] );
		}

		fp_t denom = rsi_max - rsi_min;
		fp_t stoch_k = denom != 0 ? ( rsi_values[i] - rsi_min ) / denom : 0;
		fp_t stoch_d = stoch_k;

		y[0][i] = stoch_k;
		y[1][i] = stoch_d;
	}

	free( rsi_values );
	return 0;
}