index.js

/**
 * @module wavefont
 * Values → wavefont string: 0–127 map to chars U+0100–U+017F.
 */

/** Max value a single char can encode (higher codepoints render blank). */
export const MAX = 127

const BASE = 0x0100, CHUNK = 8192

const clamp = v => Math.round(Math.min(Math.max(v || 0, 0), MAX))

/**
 * Char for a single value.
 * @param {number} value 0–127, clamped & rounded
 * @returns {string} char in U+0100–U+017F
 */
export const char = value => String.fromCharCode(BASE + clamp(value))

/**
 * Combining marks shifting the preceding bar by ±steps.
 * Emits the canonical order the font recognizes: 10-step marks first, then 1-step marks
 * (up: U+0302 then U+0301, down: U+030C then U+0300), up to ±100.
 * Unordered runs are ignored by the font past the first 10 steps.
 * @param {number} steps −100..100, clamped & rounded
 * @returns {string}
 */
export const shift = steps => {
  steps = Math.round(Math.min(Math.max(steps || 0, -100), 100))
  if (!steps) return ''
  const n = Math.abs(steps), [ten, one] = steps > 0 ? ['\u0302', '\u0301'] : ['\u030C', '\u0300']
  return ten.repeat(n / 10 | 0) + one.repeat(n % 10)
}

/**
 * Wavefont string for values.
 * @param {...number | ArrayLike<number>} values numbers 0–127, or a single (typed) array of them
 * @returns {string}
 */
export default (...values) => {
  const v = values.length === 1 && typeof values[0] === 'object' && values[0] !== null ? values[0] : values
  let out = ''
  for (let i = 0, n = v.length; i < n; i += CHUNK) {
    const end = Math.min(i + CHUNK, n), codes = new Array(end - i)
    for (let j = i; j < end; j++) codes[j - i] = BASE + clamp(v[j])
    out += String.fromCharCode(...codes)
  }
  return out
}