class Rubocop::Formatter::FormatterSet

def add_formatter(formatter_type, output_path = nil)
  formatter_class = case formatter_type
                    when Class
                      formatter_type
                    when /\A[A-Z]/
                      custom_formatter_class(formatter_type)
                    else
                      builtin_formatter_class(formatter_type)
                    end
  output = output_path ? File.open(output_path, 'w') : $stdout
  self << formatter_class.new(output)
end

def builtin_formatter_class(specified_key)
  matching_keys = BUILTIN_FORMATTERS_FOR_KEYS.keys.select do |key|
    key.start_with?(specified_key)
  end
  if matching_keys.empty?
    fail %(No formatter for "#{specified_key}")
  elsif matching_keys.size > 1
    fail %(Cannot determine formatter for "#{specified_key}")
  end
  BUILTIN_FORMATTERS_FOR_KEYS[matching_keys.first]
end

def close_output_files
  each do |formatter|
    formatter.output.close if formatter.output.is_a?(File)
  end
end

def custom_formatter_class(specified_class_name)
  constant_names = specified_class_name.split('::')
  constant_names.shift if constant_names.first.empty?
  constant_names.reduce(Object) do |namespace, constant_name|
    namespace.const_get(constant_name, false)
  end
end