export const b2: string[] = 
  '01'.split('')

export const b16: string[] = 
  '0123456789abcdef'.split('')

export const b62: string[] = 
  '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('')

export function encode(n: bigint, charset: string[]): string {
  const base = BigInt(charset.length)

  if (n == BigInt(0)) {
    return '0'
  } else {
    var xs = []
    while (n > BigInt(0)) {
      xs.push(charset[Number(n % base)])
      n = n / base
    }
    return xs.reverse().join('')
  }
}

export function decode(xs: string, charset: string[]): bigint {
  const base = BigInt(charset.length)

  return xs
    .split('')
    .reverse()
    .reduce((acc, x, i) => acc + (BigInt(charset.indexOf(x)) * (base ** BigInt(i))), BigInt(0))
}