An example Ruby class implementing the microformats2 "representative h-card" parsing algorithm using MicroMicro.

representative_h_card_parser.rb

# frozen_string_literal: true

class RepresentativeHCardParser
  # @param document [MicroMicro::Document]
  # @param canonical_url [String]
  def initialize(document, canonical_url)
    @document = document
    @canonical_url = canonical_url
  end

  # @return [MicroMicro::Item, nil]
  def h_card
    @h_card ||=
      h_card_with_uid_and_url_properties_matching_page_url \
        || h_card_with_url_property_matching_page_url \
        || h_card_with_url_property_matching_rel_me_relationship
  end

  private

  attr_reader :canonical_url, :document

  def h_card_with_uid_and_url_properties_matching_page_url
    document.items.find_by do |item|
      item.properties.find_by(name: 'uid', value: canonical_url) \
        && item.properties.find_by(name: 'url', value: canonical_url)
    end
  end

  def h_card_with_url_property_matching_page_url
    rel_urls = document.relationships.where(rels: ['me']).urls

    document.items.find_by do |item|
      item.properties.find_by(name: 'url', value: rel_urls)
    end
  end

  def h_card_with_url_property_matching_rel_me_relationship
    return unless document.items.where(types: 'h-card').one?

    document.items.find_by do |item|
      item.types.include?('h-card') \
        && item.properties.find_by(name: 'url', value: canonical_url)
    end
  end
end