// Aroon
//
// aroon - ar
//
// Measures the time since the highest high and lowest low in a lookback window.
// Aroon Up = ((period - days since highest high) / period) * 100
// Aroon Down = ((period - days since lowest low) / period) * 100
//
// Inputs:    4 (OHLC)
// Outputs:   2 (Aroon Up, Aroon Down)
// Constants: 1 (period)

#include "ts.h"

typedef struct {
    uint_t k;
} ts_aroon_params_t;

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

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

int ts_aroon(
	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_aroon_p );
	if ( !c ) return -1;
    uint_t k = ((ts_aroon_params_t *)c)->k;
    if (k == 0 || n < k) return -1;

    for ( uint_t i = k - 1; i < n; ++i )
    {
        fp_t highest_high = ts_h( x, i - k + 1 );
        uint_t age_highest = 0;
        for ( uint_t j = i - k + 1; j <= i; ++j )
        {
            if ( ts_h( x, j ) > highest_high )
            {
                highest_high = ts_h( x, j );
                age_highest = i - j;
            }
        }

        fp_t lowest_low = ts_l( x, i - k + 1 );
        uint_t age_lowest = 0;
        for ( uint_t j = i - k + 1; j <= i; ++j )
        {
            if ( ts_l( x, j ) < lowest_low )
            {
                lowest_low = ts_l( x, j );
                age_lowest = i - j;
            }
        }

        y[0][i] = ( ( fp_t )( k - age_highest ) / ( fp_t )k ) * 100.0;
        y[1][i] = ( ( fp_t )( k - age_lowest ) / ( fp_t )k ) * 100.0;
    }
	return 0;
}