Function romanByDigit

src/cli.ts:66–87

(
  progDigits: string,
  mode: string
)

`;

const romanByDigit = (
  progDigits: string,
  mode: string
): { chordDegrees: string; raw: string } => {
  const modeForDegrees = mode.toLowerCase();
  const chordDegrees = getChordDegrees(modeForDegrees);
  if (!chordDegrees.length) {
    throw new TypeError(`Unsupported mode "${mode}" for progression digits`);
  }

  const romans = progDigits.split('').map(digit => {
    const idx = Number(digit) - 1;
    if (idx < 0 || idx >= chordDegrees.length) {
      throw new TypeError(
        `Invalid progression digit "${digit}" in "${progDigits}"`
      );
    }
    return chordDegrees[idx];
  });

  return { chordDegrees: romans.join(' '), raw: progDigits };
};

const parseProgression = (
  root: string,