Function convertChordsToNotes

src/utils.ts:159–198

(
  el: string | (string | string[])[]
)

 * Single notes become `['C4']`, chord names are expanded via harmonics.
 */
export const convertChordsToNotes = (
  el: string | (string | string[])[]
): string[] => {
  if (typeof el === 'string' && isNote(el as string)) {
    // A note needs to be an array so that it can accomodate chords or single notes with a single interface
    return [el];
  }

  if (Array.isArray(el)) {
    // This could be a chord provided as an array or an array of arrays
    el.forEach(n => {
      // This could be a chord provided as an array
      if (Array.isArray(n)) {
        // TODO: Can we convert it to something useful?
        // make sure it uses valid notes
        n.forEach(n1 => {
          if (typeof n1 !== 'string' || !isNote(n1)) {
            throw new TypeError('array of arrays must comprise valid notes');
          }
        });
        // throw new TypeError('cannot decode array of arrays');
      } else if (typeof n !== 'string' || !isNote(n)) {
        // make sure it uses valid notes
        throw new TypeError('array must comprise valid notes');
      }
    });

    return el as string[];
    // ? return el as (string | string[])[];
  }

  if (!Array.isArray(el)) {
    const c = convertChordToNotes(el);
    if (c?.length) {
      return c;
    }
  }

  throw new Error(`Chord ${el} not found`);
};

/** Return a random integer from 0 to `num` (inclusive). */
export const randomInt = (num = 1): number => Math.round(Math.random() * num);