module Base45

# File lib/base45.rb, line 44
def decode(payload)
  map45_chars(payload).each_slice(3).flat_map do |c, d, e|
    c && d or raise ForbiddenLengthError
    v = c + d * 45
    bytes_from_base45(e, v)
  end.pack("C*")
end

# File lib/base45.rb, line 25
def encode(payload)
  sliced_bytes = payload.each_byte.each_slice(2)
  base45_bytes = sliced_bytes.flat_map do |byte_a, byte_b|
    byte_b ? encode_two_bytes(byte_a, byte_b) : encode_one_byte(byte_a)
  end

  base45_bytes.map do |byte45|
    BASE_45_TABLE[byte45.to_s.rjust(2, "0")]
  end.join
end

# File lib/base45.rb, line 54
def bytes_from_base45(last_triplet_byte, factor45)
  return [factor45] unless last_triplet_byte

  factor45 += last_triplet_byte * (45**2)
  x, y = factor45.divmod(256)
  raise OverflowError unless x < 256

  [x, y]
end

# File lib/base45.rb, line 64
def encode_one_byte(byte)
  byte.divmod(45).reverse
end

# File lib/base45.rb, line 68
def encode_two_bytes(first_byte, second_byte)
  x = (first_byte << 8) + second_byte
  e, x = x.divmod(45**2)
  d, c = x.divmod(45)

  [c, d, e]
end

# File lib/base45.rb, line 76
def map45_chars(string)
  string.upcase.each_char.map do |c|
    char_byte = INVERTED_BASE_45_TABLE[c]
    raise(IllegalCharacterError, c.inspect) unless char_byte

    char_byte.to_i
  end
end