module Digest::UUID

def self.pack_uuid_namespace(namespace)
  if [DNS_NAMESPACE, OID_NAMESPACE, URL_NAMESPACE, X500_NAMESPACE].include?(namespace)
    namespace
  else
    match_data = namespace.match(/\A(\h{8})-(\h{4})-(\h{4})-(\h{4})-(\h{4})(\h{8})\z/)
    raise ArgumentError, "Only UUIDs are valid namespace identifiers" unless match_data.present?
    match_data.captures.map { |s| s.to_i(16) }.pack("NnnnnN")
  end
end

def self.uuid_from_hash(hash_class, namespace, name)
  if hash_class == Digest::MD5 || hash_class == OpenSSL::Digest::MD5
    version = 3
  elsif hash_class == Digest::SHA1 || hash_class == OpenSSL::Digest::SHA1
    version = 5
  else
    raise ArgumentError, "Expected OpenSSL::Digest::SHA1 or OpenSSL::Digest::MD5, got #{hash_class.name}."
  end
  uuid_namespace = pack_uuid_namespace(namespace)
  hash = hash_class.new
  hash.update(uuid_namespace)
  hash.update(name)
  ary = hash.digest.unpack("NnnnnN")
  ary[2] = (ary[2] & 0x0FFF) | (version << 12)
  ary[3] = (ary[3] & 0x3FFF) | 0x8000
  "%08x-%04x-%04x-%04x-%04x%08x" % ary
end

def self.uuid_v3(uuid_namespace, name)
  uuid_from_hash(OpenSSL::Digest::MD5, uuid_namespace, name)
end

def self.uuid_v4
  SecureRandom.uuid
end

def self.uuid_v5(uuid_namespace, name)
  uuid_from_hash(OpenSSL::Digest::SHA1, uuid_namespace, name)
end