index.ts

import { distance as dist, note, transpose as tr } from '../core'

const fillStr = (character: string, times: number) =>
  Array(times + 1).join(character)

const REGEX = /^(_{1,}|=|\^{1,}|)([abcdefgABCDEFG])([,']*)$/

export type AbcTokens = [string, string, string]

export function tokenize(str: string): AbcTokens {
  const m = REGEX.exec(str)
  if (!m) {
    return ['', '', '']
  }
  return [m[1], m[2], m[3]]
}

/**
 * Convert a (string) note in ABC notation into a (string) note in scientific notation
 *
 * @example
 * abcToScientificNotation("c") // => "C5"
 */
export function abcToScientificNotation(str: string): string {
  const [acc, letter, oct] = tokenize(str)
  if (letter === '') {
    return ''
  }
  let o = 4
  for (let i = 0; i < oct.length; i++) {
    o += oct.charAt(i) === ',' ? -1 : 1
  }
  const a =
    acc[0] === '_'
      ? acc.replace(/_/g, 'b')
      : acc[0] === '^'
      ? acc.replace(/\^/g, '#')
      : ''
  return letter.charCodeAt(0) > 96
    ? letter.toUpperCase() + a + (o + 1)
    : letter + a + o
}

/**
 * Convert a (string) note in scientific notation into a (string) note in ABC notation
 *
 * @example
 * scientificToAbcNotation("C#4") // => "^C"
 */
export function scientificToAbcNotation(str: string): string {
  const n = note(str)
  if (n.empty || (!n.oct && n.oct !== 0)) {
    return ''
  }
  const { letter, acc, oct } = n
  const a = acc[0] === 'b' ? acc.replace(/b/g, '_') : acc.replace(/#/g, '^')
  const l = oct > 4 ? letter.toLowerCase() : letter
  const o =
    oct === 5 ? '' : oct > 4 ? fillStr("'", oct - 5) : fillStr(',', 4 - oct)
  return a + l + o
}

export function transpose(note: string, interval: string): string {
  return scientificToAbcNotation(tr(abcToScientificNotation(note), interval))
}

export function distance(from: string, to: string): string {
  return dist(abcToScientificNotation(from), abcToScientificNotation(to))
}

export default {
  abcToScientificNotation,
  scientificToAbcNotation,
  tokenize,
  transpose,
  distance,
}