let random = async bytes => crypto.getRandomValues(new Uint8Array(bytes))

let customAlphabet = (alphabet, defaultSize = 21) => {
  let mask = (2 << (Math.log(alphabet.length - 1) / Math.LN2)) - 1



  let step = -~((1.6 * mask * defaultSize) / alphabet.length)

  return async (size = defaultSize) => {
    let id = ''
    while (true) {
      let bytes = crypto.getRandomValues(new Uint8Array(step))
      let i = step | 0
      while (i--) {
        id += alphabet[bytes[i] & mask] || ''
        if (id.length === size) return id
      }
    }
  }
}

let nanoid = async (size = 21) => {
  let id = ''
  let bytes = crypto.getRandomValues(new Uint8Array((size |= 0)))

  while (size--) {
    let byte = bytes[size] & 63
    if (byte < 36) {
      id += byte.toString(36)
    } else if (byte < 62) {
      id += (byte - 26).toString(36).toUpperCase()
    } else if (byte < 63) {
      id += '_'
    } else {
      id += '-'
    }
  }
  return id
}

module.exports = { nanoid, customAlphabet, random }
