module JsonSchema::ErrorFormatter

def to_list(list)
  words_connector     = ', '
  two_words_connector = ' or '
  last_word_connector = ', or '
  length = list.length
  joined_list = case length
                when 1
                  list[0]
                when 2
                  "#{list[0]}#{two_words_connector}#{list[1]}"
                 else
                  "#{list[0...-1].join(words_connector)}#{last_word_connector}#{list[-1]}"
                end
  if joined_list[0] =~ /^[aeiou]/
    "an #{joined_list}"
  else
    "a #{joined_list}"
  end
end