mysociety/alaveteli

class Legislation
  InvalidReferenceType = Class.new(StandardError)

  ##
  # Reference representing a section of a legislation
  #
  # See https://en.wikipedia.org/wiki/Citation_of_United_Kingdom_legislation#Primary_legislation
  #
  # Example:
  #   Legislation::Reference.new(legislation: foi, reference: 's 12(1)') =>
  #     #<Legislation::Reference
  #       @legislation=foi,
  #       @type="Section",
  #       @elements=["12", "1"]>
  #
  class Reference
    attr_reader :legislation, :type, :elements

    def initialize(legislation:, reference:)
      @legislation = legislation

      type, elements = *reference.split(' ', 2)
      @type = parse_type(type)
      @elements = elements.gsub(
        /\.?#{Constants::BRACKETED_ELEMENT}/,
        '.\1'
      ).split('.')
    end

    def to_s
      return parent_reference if sub_elements.empty?

      parent_reference + "(#{sub_elements.join(')(')})"
    end

    def to_param
      to_s.parameterize
    end

    def parent
      self.class.new(legislation: legislation, reference: parent_reference)
    end

    def cover?(other)
      legislation == other.legislation && type == other.type &&
        elements == other.elements[0...elements.count]
    end

    def refusal?
      legislation.refusals.any? { |reference| reference.cover?(self) }
    end

    def ==(other)
      legislation == other.legislation && type == other.type &&
        elements == other.elements
    end

    private

    def parent_reference
      "#{type} #{parent_element}"
    end

    def parent_element
      elements[0]
    end

    def sub_elements
      elements[1..-1]
    end

    def parse_type(type)
      case type.downcase
      when 's', 'section'
        _('Section')
      when 'art', 'article'
        _('Article')
      when 'reg', 'regulation'
        _('Regulation')
      else
        raise InvalidReferenceType,
          "Unknown legislation reference type #{type}."
      end
    end
  end
end