module ShortUUID

# File lib/shortuuid.rb, line 28
def self.convert_alphabet_to_decimal(word, alphabet = DEFAULT_BASE62)
  num = 0
  radix = alphabet.length
  word.chars.to_a.reverse.each_with_index do |char, index|
    num += alphabet.index(char) * (radix**index)
  end
  num
end

# File lib/shortuuid.rb, line 14
def self.convert_decimal_to_alphabet(decimal, alphabet = DEFAULT_BASE62)
  alphabet = alphabet.to_a
  radix = alphabet.length
  i = decimal.to_i
  out = []
  return alphabet[0] if i.zero?
  loop do
    break if i.zero?
    out.unshift(alphabet[i % radix])
    i /= radix
  end
  out.join
end

# File lib/shortuuid.rb, line 41
def self.decode(word, alphabet = DEFAULT_BASE62)
  convert_alphabet_to_decimal(word, alphabet)
end

# File lib/shortuuid.rb, line 37
def self.encode(number, alphabet = DEFAULT_BASE62)
  convert_decimal_to_alphabet(number, alphabet)
end

# File lib/shortuuid.rb, line 45
def self.expand(short_uuid, alphabet = DEFAULT_BASE62)
  return nil unless short_uuid && !short_uuid.empty?
  decimal_value = convert_alphabet_to_decimal(short_uuid, alphabet)
  uuid = decimal_value.to_s(16).rjust(32, '0')
  [
    uuid[0..7],
    uuid[8..11],
    uuid[12..15],
    uuid[16..19],
    uuid[20..31]
  ].join('-')
end

# File lib/shortuuid.rb, line 8
def self.shorten(uuid, alphabet = DEFAULT_BASE62)
  return nil unless uuid && !uuid.empty?
  decimal_value = uuid.split('-').join.to_i(16)
  convert_decimal_to_alphabet(decimal_value, alphabet)
end