generic_authority.rb

module Qa::Authorities
  class Loc::GenericAuthority < Base
    attr_reader :subauthority
    def initialize(subauthority)
      super()
      @subauthority = subauthority
    end

    include WebServiceBase

    def response(url)
      uri = URI(url)
      conn = Faraday.new "#{uri.scheme}://#{uri.host}"
      conn.options.params_encoder = Faraday::FlatParamsEncoder
      conn.get do |req|
        req.headers['Accept'] = 'application/json'
        req.url uri.path
        req.params = Rack::Utils.parse_query(uri.query)
      end
    end

    def search(q)
      @raw_response = json(build_query_url(q))
      parse_authority_response
    end

    def build_query_url(q)
      escaped_query = ERB::Util.url_encode(q)
      authority_fragment = Loc.get_url_for_authority(subauthority) + ERB::Util.url_encode(subauthority)
      "https://id.loc.gov/search/?q=#{escaped_query}&q=#{authority_fragment}&format=json"
    end

    def find(id)
      json(find_url(id))
    end

    def find_url(id)
      root_fetch_slug = Loc.root_fetch_slug_for(@subauthority)
      File.join("https://id.loc.gov/", root_fetch_slug, "/#{@subauthority}/#{id}.json")
    end

    private

      # Reformats the data received from the LOC service
      def parse_authority_response
        @raw_response.select { |response| response[0] == "atom:entry" }.map do |response|
          loc_response_to_qa(response_to_struct(response))
        end
      end

      # Converts most of the atom data into an OpenStruct object.
      #
      # Note that this is a pretty naive conversion.  There should probably just
      # be a class that properly translates and stores the various pieces of
      # data, especially if this logic could be useful in other auth lookups.
      def response_to_struct(response)
        contents = response.each_with_object({}) do |result_parts, result|
          next unless result_parts[0]
          key = result_parts[0].sub('atom:', '').sub('dcterms:', '')
          info = result_parts[1]
          val = result_parts[2]

          case key
          when 'title', 'id', 'name', 'updated', 'created'
            result[key] = val
          when 'link'
            result["links"] ||= []
            result["links"] << [info["type"], info["href"]]
          end
        end

        OpenStruct.new(contents)
      end

      # Simple conversion from LoC-based struct to QA hash
      def loc_response_to_qa(data)
        {
          "id" => data.id || data.title,
          "label" => data.title
        }
      end
  end
end