// Helper functions for music

#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

#include "helpers.h"

// Converts a fraction formatted as X/Y to eighths
int duration(string fraction)
{
    return (8 / (fraction[2] - '0')) * (fraction[0] - '0');
}

// Calculates frequency (in Hz) of a note
int frequency(string note)
{
    int base_hz = 440;
    int semi = 0, octave = 0;

    // Set relative to 4th octave and account for accidental
    if(strlen(note) == 3)
    {
        octave = note[2] - '4';
        note[1] == '#' ? semi++ : semi--;
    }
    else
    {
        octave = note[1] - '4';
    }

    // Map note to semitone 0 to 11
    if(note[0] - 'C' < 0)
    {
        semi += note[0] == 'A' ? 9 : 11;
    }
    else
    {
        semi <<= (note[0] - 'C');
        if(semi > 5) semi--;
    }

    // Shift map relative to A4
    semi -= 9;

    octave < 0 ? (base_hz >>= abs(octave)) : (base_hz <<= octave);

    return base_hz * pow(2, semi / 12.0);
}

// Determines whether a string represents a rest
bool is_rest(string s)
{
    return *s == '\0' ? true : false;
}