const encodeTable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'.split('')
const decodeTable = {}
for (const idx in encodeTable) {
  decodeTable[encodeTable[idx]] = idx
}

const base32 = {}
module.exports = base32

base32.encode = (b) => {
  if (!(b instanceof Buffer)) return ''
  if (b.length === 0) return ''

  let str = ''
  const len = b.length
  let v1, v2, v3, v4, v5

  const count = parseInt(len / 5) * 5
  let i = 0
  while (i < count) {
    v1 = b[i++]
    v2 = b[i++]
    v3 = b[i++]
    v4 = b[i++]
    v5 = b[i++]
    str += encodeTable[v1 >>> 3] +
      encodeTable[(v1 << 2 | v2 >>> 6) & 31] +
      encodeTable[(v2 >>> 1) & 31] +
      encodeTable[(v2 << 4 | v3 >>> 4) & 31] +
      encodeTable[(v3 << 1 | v4 >>> 7) & 31] +
      encodeTable[(v4 >>> 2) & 31] +
      encodeTable[(v4 << 3 | v5 >>> 5) & 31] +
      encodeTable[v5 & 31]
  }

  const remain = len - count
  switch (remain) {
    case 1:
      v1 = b[i]
      str += encodeTable[v1 >>> 3] +
        encodeTable[(v1 << 2) & 31] + '======'
      break
    case 2:
      v1 = b[i++]
      v2 = b[i]
      str += encodeTable[v1 >>> 3] +
        encodeTable[(v1 << 2 | v2 >>> 6) & 31] +
        encodeTable[(v2 >>> 1) & 31] +
        encodeTable[(v2 << 4) & 31] + '===='
      break
    case 3:
      v1 = b[i++]
      v2 = b[i++]
      v3 = b[i]
      str += encodeTable[v1 >>> 3] +
        encodeTable[(v1 << 2 | v2 >>> 6) & 31] +
        encodeTable[(v2 >>> 1) & 31] +
        encodeTable[(v2 << 4 | v3 >>> 4) & 31] +
        encodeTable[(v3 << 1) & 31] + '==='
      break
    case 4:
      v1 = b[i++]
      v2 = b[i++]
      v3 = b[i++]
      v4 = b[i]
      str += encodeTable[v1 >>> 3] +
        encodeTable[(v1 << 2 | v2 >>> 6) & 31] +
        encodeTable[(v2 >>> 1) & 31] +
        encodeTable[(v2 << 4 | v3 >>> 4) & 31] +
        encodeTable[(v3 << 1 | v4 >>> 7) & 31] +
        encodeTable[(v4 >>> 2) & 31] +
        encodeTable[(v4 << 3) & 31] + '='
      break
  }

  return str
}