class ActiveModel::Validations::FormatValidator

def check_options_validity(name)
  if option = options[name]
    if option.is_a?(Regexp)
      if options[:multiline] != true && regexp_using_multiline_anchors?(option)
        raise ArgumentError, "The provided regular expression is using multiline anchors (^ or $), " \
        "which may present a security risk. Did you mean to use \\A and \\z, or forgot to add the " \
        ":multiline => true option?"
      end
    elsif !option.respond_to?(:call)
      raise ArgumentError, "A regular expression or a proc or lambda must be supplied as :#{name}"
    end
  end
end

def check_validity!
  unless options.include?(:with) ^ options.include?(:without)  # ^ == xor, or "exclusive or"
    raise ArgumentError, "Either :with or :without must be supplied (but not both)"
  end
  check_options_validity :with
  check_options_validity :without
end

def option_call(record, name)
  option = options[name]
  option.respond_to?(:call) ? option.call(record) : option
end

def record_error(record, attribute, name, value)
  record.errors.add(attribute, :invalid, **options.except(name).merge!(value: value))
end

def regexp_using_multiline_anchors?(regexp)
  source = regexp.source
  source.start_with?("^") || (source.end_with?("$") && !source.end_with?("\\$"))
end

def validate_each(record, attribute, value)
  if options[:with]
    regexp = option_call(record, :with)
    record_error(record, attribute, :with, value) unless regexp.match?(value.to_s)
  elsif options[:without]
    regexp = option_call(record, :without)
    record_error(record, attribute, :without, value) if regexp.match?(value.to_s)
  end
end