steelseries-live-scale/src/scale.js

'use strict';

const { HID } = require('./hid');

const NOTE_NAMES = ['C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B'];

const NOTE_ALIASES = {
  C: 0, 'B#': 0,
  'C#': 1, DB: 1,
  D: 2,
  'D#': 3, EB: 3,
  E: 4, FB: 4,
  F: 5, 'E#': 5,
  'F#': 6, GB: 6,
  G: 7,
  'G#': 8, AB: 8,
  A: 9,
  'A#': 10, BB: 10,
  B: 11, CB: 11,
};

/** Interval sets, matching Live 12's `scale_intervals`. */
const SCALES = {
  major: [0, 2, 4, 5, 7, 9, 11],
  minor: [0, 2, 3, 5, 7, 8, 10],
  'harmonic-minor': [0, 2, 3, 5, 7, 8, 11],
  'melodic-minor': [0, 2, 3, 5, 7, 9, 11],
  dorian: [0, 2, 3, 5, 7, 9, 10],
  phrygian: [0, 1, 3, 5, 7, 8, 10],
  lydian: [0, 2, 4, 6, 7, 9, 11],
  mixolydian: [0, 2, 4, 5, 7, 9, 10],
  locrian: [0, 1, 3, 5, 6, 8, 10],
  'major-pentatonic': [0, 2, 4, 7, 9],
  'minor-pentatonic': [0, 3, 5, 7, 10],
  blues: [0, 3, 5, 6, 7, 10],
  'whole-tone': [0, 2, 4, 6, 8, 10],
  chromatic: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
};

/**
 * Ableton's computer MIDI keyboard, one octave laid out like a piano:
 * white keys on the home row, black keys on the row above, plus the octave C.
 */
const NOTE_KEYS = [
  { key: 'a', hid: HID.a, pitchClass: 0, frameKey: 'note-a' },
  { key: 'w', hid: HID.w, pitchClass: 1, frameKey: 'note-w' },
  { key: 's', hid: HID.s, pitchClass: 2, frameKey: 'note-s' },
  { key: 'e', hid: HID.e, pitchClass: 3, frameKey: 'note-e' },
  { key: 'd', hid: HID.d, pitchClass: 4, frameKey: 'note-d' },
  { key: 'f', hid: HID.f, pitchClass: 5, frameKey: 'note-f' },
  { key: 't', hid: HID.t, pitchClass: 6, frameKey: 'note-t' },
  { key: 'g', hid: HID.g, pitchClass: 7, frameKey: 'note-g' },
  { key: 'y', hid: HID.y, pitchClass: 8, frameKey: 'note-y' },
  { key: 'h', hid: HID.h, pitchClass: 9, frameKey: 'note-h' },
  { key: 'u', hid: HID.u, pitchClass: 10, frameKey: 'note-u' },
  { key: 'j', hid: HID.j, pitchClass: 11, frameKey: 'note-j' },
  // The octave key: same pitch class as A, one octave up.
  { key: 'k', hid: HID.k, pitchClass: 0, frameKey: 'note-k', octaveUp: true },
];

const NOTE_KEY_HIDS = NOTE_KEYS.map((k) => k.hid);

/** "C", "f#", "Bb", "3" -> 0..11. Throws on garbage. */
function parseRoot(input) {
  if (typeof input === 'number') {
    if (!Number.isInteger(input) || input < 0 || input > 11) {
      throw new Error(`root must be an integer 0-11, got ${input}`);
    }
    return input;
  }
  const raw = String(input).trim();
  if (/^\d+$/.test(raw)) return parseRoot(Number(raw));

  const normalized = raw.toUpperCase().replace(/♯/g, '#').replace(/♭/g, 'B');
  if (normalized in NOTE_ALIASES) return NOTE_ALIASES[normalized];
  throw new Error(`unknown root note: ${input}`);
}

/** "major", "Harmonic Minor", "minor_pentatonic" -> interval array. */
function parseScale(input) {
  const normalized = String(input).trim().toLowerCase().replace(/[\s_]+/g, '-');
  if (normalized in SCALES) return SCALES[normalized];
  throw new Error(
    `unknown scale: ${input} (known: ${Object.keys(SCALES).join(', ')})`
  );
}

/** "0,2,4,5,7,9,11" or [0,2,...] -> normalized, deduped, sorted interval array. */
function parseIntervals(input) {
  const list = Array.isArray(input) ? input : String(input).split(/[,\s]+/);
  const parsed = list
    .filter((v) => String(v).length > 0)
    .map((v) => {
      const n = Number(v);
      if (!Number.isInteger(n)) throw new Error(`interval is not an integer: ${v}`);
      return n;
    });
  if (parsed.length === 0) throw new Error('interval list is empty');
  return parsed;
}

/**
 * The core of the whole project:
 *   lit = { (root + interval) % 12 }
 * Returns a sorted array of pitch classes.
 */
function pitchClassesFor(root, intervals) {
  const set = new Set(intervals.map((i) => (((root + i) % 12) + 12) % 12));
  return [...set].sort((a, b) => a - b);
}

/** Pitch classes -> the QWERTY keys Ableton maps them to (includes 'k'). */
function keysFor(pitchClasses) {
  const set = new Set(pitchClasses);
  return NOTE_KEYS.filter((k) => set.has(k.pitchClass)).map((k) => k.key);
}

function noteName(pitchClass) {
  return NOTE_NAMES[(((pitchClass % 12) + 12) % 12)];
}

module.exports = {
  NOTE_NAMES,
  NOTE_ALIASES,
  SCALES,
  NOTE_KEYS,
  NOTE_KEY_HIDS,
  parseRoot,
  parseScale,
  parseIntervals,
  pitchClassesFor,
  keysFor,
  noteName,
};