add ability to return a single term as n3 format for linked data

This impacts all authorities supported through the linked data module and the discogs authority

app/controllers/qa/linked_data_terms_controller.rb

@@ -59,10 +59,9 @@ def search # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
   # get "/show/linked_data/:vocab/:subauthority/:id
   # @see Qa::Authorities::LinkedData::FindTerm#find
   def show # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
-    term = @authority.find(id, subauth: subauthority, language: language, replacements: replacement_params, jsonld: jsonld?, performance_data: performance_data?)
+    term = @authority.find(id, subauth: subauthority, language: language, replacements: replacement_params, format: format, performance_data: performance_data?)
     cors_allow_origin_header(response)
-    content_type = jsonld? ? 'application/ld+json' : 'application/json'
-    render json: term, content_type: content_type
+    render json: term, content_type: content_type_for_format
   rescue Qa::TermNotFound
     msg = "Term Not Found - Fetch term #{id} unsuccessful for#{subauth_warn_msg} authority #{vocab_param}"
     logger.warn msg
@@ -90,10 +89,9 @@ def show # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
   # get "/fetch/linked_data/:vocab"
   # @see Qa::Authorities::LinkedData::FindTerm#find
   def fetch # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
-    term = @authority.find(uri, subauth: subauthority, language: language, replacements: replacement_params, jsonld: jsonld?, performance_data: performance_data?)
+    term = @authority.find(uri, subauth: subauthority, language: language, replacements: replacement_params, format: format, performance_data: performance_data?)
     cors_allow_origin_header(response)
-    content_type = jsonld? ? 'application/ld+json' : 'application/json'
-    render json: term, content_type: content_type
+    render json: term, content_type: content_type_for_format
   rescue Qa::TermNotFound
     msg = "Term Not Found - Fetch term #{uri} unsuccessful for#{subauth_warn_msg} authority #{vocab_param}"
     logger.warn msg
@@ -217,22 +215,32 @@ def format
     end
 
     def jsonld?
-      format.casecmp('jsonld').zero?
+      format.casecmp?('jsonld')
+    end
+
+    def n3?
+      format.casecmp?('n3')
+    end
+
+    def content_type_for_format
+      return 'application/ld+json' if jsonld?
+      return 'text/n3' if n3?
+      'application/json'
     end
 
     def context?
       context = params.fetch(:context, 'false')
-      context.casecmp('true').zero?
+      context.casecmp?('true')
     end
 
     def details?
       details = params.fetch(:details, 'false')
-      details.casecmp('true').zero?
+      details.casecmp?('true')
     end
 
     def performance_data?
       performance_data = params.fetch(:performance_data, 'false')
-      performance_data.casecmp('true').zero?
+      performance_data.casecmp?('true')
     end
 
     def validate_auth_reload_token

lib/qa/authorities/discogs/discogs_translation.rb

@@ -11,14 +11,14 @@ module DiscogsTranslation
       # to the URIs of corresponding objects in the Library of Congress vocabulary.
       # @param [Hash] the http response from discogs
       # @param [String] the subauthority
-      # @return [Array] jsonld
-      def build_graph(response, subauthority = "")
+      # @return [Array, String] requested RDF serialzation (supports: jsonld Array, n3 String)
+      def build_graph(response, subauthority = "", format: :jsonld)
         graph = RDF::Graph.new
 
         rdf_statements = compile_rdf_statements(response, subauthority)
         graph.insert_statements(rdf_statements)
 
-        graph.dump(:jsonld, standard_prefixes: true)
+        graph.dump(format, standard_prefixes: true)
       end
 
       # @param [Hash] the http response from discogs

lib/qa/authorities/discogs/generic_authority.rb

@@ -35,10 +35,12 @@ def search(q, tc)
     #
     # @param [String] the Discogs id of the selected item
     # @param [Class] QA::TermsController
-    # @return either json results or jsonld
+    # @return results in requested format (supports: json, jsonld, n3)
     def find(id, tc)
       response = tc.params["subauthority"].include?("all") ? fetch_discogs_results(id) : json(find_url(id, tc.params["subauthority"]))
-      return build_graph(response) unless tc.params["format"] != "jsonld" || response["message"].present?
+      return response if response["message"].present?
+      return build_graph(response, format: :jsonld) if jsonld?(tc)
+      return build_graph(response, format: :n3) if n3?(tc)
       response
     end
 
@@ -147,5 +149,23 @@ def get_context_for_string(item)
       def get_context_for_array(item)
         item.present? ? item : [""]
       end
+
+      def format(tc)
+        return 'json' unless tc.params.key?('format')
+        return 'json' if tc.params['format'].blank?
+        tc.params['format']
+      end
+
+      def jsonld?(tc)
+        format(tc).casecmp?('jsonld')
+      end
+
+      def n3?(tc)
+        format(tc).casecmp?('n3')
+      end
+
+      def graph_format?(tc)
+        jsonld?(tc) || n3?(tc)
+      end
   end
 end

lib/qa/authorities/linked_data/find_term.rb

@@ -39,12 +39,20 @@ def initialize(term_config)
       #     "http://schema.org/name":["Cornell University","Ithaca (N.Y.). Cornell University"],
       #     "http://www.w3.org/2004/02/skos/core#altLabel":["Ithaca (N.Y.). Cornell University"],
       #     "http://schema.org/sameAs":["http://id.loc.gov/authorities/names/n79021621","https://viaf.org/viaf/126293486"] } }
-      def find(id, language: nil, replacements: {}, subauth: nil, jsonld: false, performance_data: false) # rubocop:disable Metrics/ParameterLists
+      def find(id, language: nil, replacements: {}, subauth: nil, format: nil, jsonld: false, performance_data: false) # rubocop:disable Metrics/ParameterLists, Metrics/MethodLength
+        # TODO: When jsonld parameter is removed, the format parameter should default to 'json'.  Not making this change now for backward compatibility of the default for jsonld parameter.
         raise Qa::InvalidLinkedDataAuthority, "Unable to initialize linked data term sub-authority #{subauth}" unless subauth.nil? || term_subauthority?(subauth)
         @language = language_service.preferred_language(user_language: language, authority_language: term_config.term_language)
         @id = id
         @performance_data = performance_data
-        @jsonld = jsonld
+        @format = format
+        @jsonld = jsonld if @format.blank?
+        if jsonld
+          Qa.deprecation_warning(
+            in_msg: 'Qa::Authorities::LinkedData::FindTerm',
+            msg: "jsonld parameter to find method is deprecated; use `format: 'jsonld'` instead"
+          )
+        end
         url = authority_service.build_url(action_config: term_config, action: :term, action_request: normalize_id, substitutions: replacements, subauthority: subauth, language: @language)
         Rails.logger.info "QA Linked Data term url: #{url}"
         load_graph(url: url)
@@ -80,6 +88,7 @@ def normalize_results
         def perform_normalization
           return "{}" unless full_graph.size.positive?
           return full_graph.dump(:jsonld, standard_prefixes: true) if jsonld?
+          return full_graph.dump(:n3, standard_prefixes: true) if n3?
 
           filter_graph
           extract_uri
@@ -182,10 +191,16 @@ def optional_ldpaths
           opt_ldpaths.delete_if { |_k, v| v.blank? }
         end
 
+        # Give precedent to format parameter over jsonld parameter.  NOTE: jsonld parameter for find method is deprecated.
         def jsonld?
+          return @format.casecmp?('jsonld') if @format
           @jsonld == true
         end
 
+        def n3?
+          @format && @format.casecmp?('n3')
+        end
+
         def performance_data?
           @performance_data == true && !jsonld?
         end

spec/controllers/linked_data_terms_controller_spec.rb

@@ -425,6 +425,15 @@
             expect(JSON.parse(response.body).keys).to match_array ["@context", "@graph"]
           end
         end
+
+        context 'and it was requested as n3' do
+          it 'succeeds and returns term data as n3 content type' do
+            get :show, params: { id: '530369', vocab: 'OCLC_FAST', format: 'n3' }
+            expect(response).to be_successful
+            expect(response.content_type).to eq 'text/n3'
+            expect(response.body).to start_with "@prefix"
+          end
+        end
       end
 
       context 'when cors headers are enabled' do
@@ -587,6 +596,15 @@
           end
         end
 
+        context 'and it was requested as n3' do
+          it 'succeeds and returns term data as n3 content type' do
+            get :fetch, params: { uri: 'http://id.worldcat.org/fast/530369', vocab: 'LOD_TERM_URI_PARAM_CONFIG', format: 'n3' }
+            expect(response).to be_successful
+            expect(response.content_type).to eq 'text/n3'
+            expect(response.body).to start_with "@prefix"
+          end
+        end
+
         context 'blank nodes not included in predicates list' do
           before do
             stub_request(:get, 'http://localhost/test_default/term?uri=http://id.worldcat.org/fast/530369wbn')

spec/lib/authorities/discogs/generic_authority_spec.rb

@@ -136,6 +136,28 @@
         end
       end
 
+      context "n3 format and subauthority master" do
+        let(:tc) { instance_double(Qa::TermsController) }
+        let :results do
+          authority.find("950011", tc)
+        end
+        before do
+          allow(Qa::TermsController).to receive(:new).and_return(tc)
+          allow(tc).to receive(:params).and_return('format' => "n3", 'subauthority' => "master")
+        end
+
+        it "returns the Discogs data converted to n3 for a given id" do
+          expect(results).to start_with "@prefix"
+          expect(results).to include("Blue Moon / You Go To My Head")
+          expect(results).to include("Billie Holiday And Her Orchestra")
+          expect(results).to include("Haven Gillespie")
+          expect(results).to include("1952")
+          expect(results).to include("Jazz")
+          expect(results).to include("Barney Kessel")
+          expect(results).to include("Guitar")
+        end
+      end
+
       context "json-ld format and subauthority all" do
         let(:tc) { instance_double(Qa::TermsController) }
         let :results do
@@ -161,6 +183,31 @@
           expect(results).to include("1952")
         end
       end
+
+      context "n3 format and subauthority all" do
+        let(:tc) { instance_double(Qa::TermsController) }
+        let :results do
+          authority.find("7143179", tc)
+        end
+        before do
+          allow(Qa::TermsController).to receive(:new).and_return(tc)
+          allow(tc).to receive(:params).and_return('format' => "n3", 'subauthority' => "all")
+        end
+
+        it "returns the Discogs data converted to n3 for a given id" do
+          expect(results).to start_with "@prefix"
+          expect(results).to include("You Go To My Head")
+          expect(results).to include("Rodgers & Hart")
+          expect(results).to include("Ray Brown")
+          expect(results).to include("1952")
+          expect(results).to include("Single")
+          expect(results).to include("mono")
+          expect(results).to include("45 RPM")
+          expect(results).to include("Vinyl")
+          expect(results).to include("http://id.loc.gov/vocabulary/carriers/sd")
+          expect(results).to include("1952")
+        end
+      end
     end
   end