/*eseries.c*/

#include"eseries.h"

ESeriesMaxValue get_E_MAX(ESeries E_series) {

    ESeriesMaxValue output;

    switch(E_series) {
        case E3:
            output = E3_MAX;
            break;
        case E6:
            output = E6_MAX;
            break;
        case E12:
            output = E12_MAX;
            break;
        case E24:
            output = E24_MAX;
            break;
        case E48:
            output = E48_MAX;
            break;
        case E96:
            output = E96_MAX;
            break;
        case E192:
            output = E192_MAX;
            break;
        default:
            output = E_NIL;
            break;
    }

    return output;
}

ESeries get_E_Series(int number) {

    ESeries output;

    switch (number) {
        case 3:
            output = E3;
            break;
        case 6:
            output = E6;
            break;
        case 12:
            output = E12;
            break;
        case 24:
            output = E24;
            break;
        case 48:
            output = E48;
            break;
        case 96:
            output = E96;
            break;
        case 192:
            output = E192;
            break;
        default:
            output = E0;
            break;
    }

    return output;
}

double round_to_E_series (double continuous_value, ESeries E_series) {

    /*
     * check for range. An E series is defined within one decade.
     * values from 1 to 10 are accepted
     */
    if (continuous_value >= 10 || continuous_value < 1) {
        printf("eseries:round_to_E_series: Value out of range.\n");
        return E_NIL;
    }

    double e_value = 0.0;

    // set the max array index for given e series.
    unsigned int e_max_values = get_E_MAX(E_series);
    if (e_max_values == E_NIL) {
        printf("eseries:round_to_E_series: Unknown E series.\n");
        return E_NIL;
    }

    int upper_e_limit = e_max_values;
    int lower_e_limit = 0;

    for (int i = 0 ; i < log2((e_max_values + 1 / 3)); i++) {

        if (continuous_value < E_values[E_series][(((upper_e_limit - lower_e_limit) + 1) / 2) + lower_e_limit]) {
            upper_e_limit = (((upper_e_limit - lower_e_limit) + 1) / 2) + lower_e_limit - 1;
        }
        else {
            lower_e_limit = (((upper_e_limit - lower_e_limit) + 1) / 2) + lower_e_limit;
        }
    }

    if (continuous_value < E_values[E_series][lower_e_limit + 1])
    {
        if (fabs(continuous_value - E_values[E_series][lower_e_limit]) < fabs(continuous_value - E_values[E_series][lower_e_limit + 1])) {
            e_value = E_values[E_series][lower_e_limit];
        }
        else {
            e_value = E_values[E_series][lower_e_limit + 1];
        }
    }
    else {
        if (fabs(continuous_value - E_values[E_series][upper_e_limit]) < fabs(continuous_value - E_values[E_series][upper_e_limit - 1])) {
            e_value = E_values[E_series][upper_e_limit];
        }
        else {
            e_value = E_values[E_series][upper_e_limit - 1];
        }
    }

    return e_value;
}