module Base24

# File lib/base24.rb, line 27
def self.decode24(data)
  raise "Data size must be multiple of 7" if data.size % 7 != 0

  data.chars.each_slice(7).reduce([]) do |result, chars|
    value =
      chars.reduce(0) do |value, char|
        idx = DECODE_MAP[char]
        raise "Invalid character" if idx.nil?
        value * ASIZE + idx
      end
    mask = 0xFF
    b0 = (value & (mask << 24)) >> 24
    b1 = (value & (mask << 16)) >> 16
    b2 = (value & (mask << 8)) >> 8
    b3 = value & mask

    result + [b0, b1, b2, b3]
  end.pack('C*')
end

# File lib/base24.rb, line 6
def self.encode24(data)
  raise "Data size must be multiple of 4" if data.size % 4 != 0

  data.unpack('C*').each_slice(4).reduce([]) do |result, slice|
    b0, b1, b2, b3 = slice

    value = b0 << 24 | b1 << 16 | b2 << 8 | b3

    sub_result, value = (0..6).reduce([[], value]) do |acc, i|
      res, value = acc
      idx = value % ASIZE
      value = value / ASIZE
      char = ENCODE_MAP[idx]

      [[char] + res, value]
    end

    result + sub_result
  end.join
end

# File lib/base24.rb, line 57
def self.decode_map()
  ALPHABET.chars.reduce([{}, 0]) do |acc, char|
    map, idx = acc
    map[char] = idx
    map[char.downcase] = idx
    [map, idx + 1]
  end[0]
end

# File lib/base24.rb, line 49
def self.encode_map()
  ALPHABET.chars.reduce([{}, 0]) do |acc, char|
    map, idx = acc
    map[idx] = char
    [map, idx + 1]
  end[0]
end