more powerful ActiveFedora::FixityService

The fedora fixity service also reports the expected message
digest and file size. It makes sense to allow these to be accessed.

Actually cache the http response. Comment erroneously implied
it was cached before, but it wasn't. #check still forces a new
check, as it did before this commit, but verified? is a more
clear method name for return value, and will not bust response
cache.

Cleaned up some erroneous comments.

lib/active_fedora/fixity_service.rb

@@ -2,26 +2,57 @@ module ActiveFedora
   class FixityService
     extend ActiveSupport::Concern
 
-    attr_accessor :target, :response
+    attr_accessor :target
 
-    # @param [String, RDF::URI] target url for a Fedora resource
+    # @param [String, RDF::URI] target url for a Fedora resource.
     def initialize(target)
       raise ArgumentError, 'You must provide a uri' unless target
       @target = target.to_s
     end
 
-    # Executes a fixity check on Fedora and saves the Faraday::Response.
+    def response
+      @response ||= fixity_response_from_fedora
+    end
+
+    # For backwards compat, check always insists on doing a new request.
+    # you might want verified? instead which uses a cached request.
     # @return true or false
     def check
-      @response = fixity_response_from_fedora
+      @response = nil
+      verified?
+    end
+
+    # Executes a fixity check on Fedora
+    # @return true or false
+    def verified?
       status.include?(success)
     end
 
+    # An array of 1 or more literals reported by Fedora.
+    # See 'success' for which one indicates fixity check is good.
     def status
       fixity_graph.query(predicate: premis_status_predicate).map(&:object) +
         fixity_graph.query(predicate: fedora_status_predicate).map(&:object)
     end
 
+    # the currently calculated checksum, as a string URI, like
+    # "urn:sha1:09a848b79f86f3a4f3f301b8baafde455d6f8e0e"
+    def expected_message_digest
+      fixity_graph.query(predicate: ::RDF::Vocab::PREMIS.hasMessageDigest).first.try(:object).try(:to_s)
+    end
+
+    # integer, as reported by fedora. bytes maybe?
+    def expected_size
+      fixity_graph.query(predicate: ::RDF::Vocab::PREMIS.hasSize).first.try(:object).try(:to_s).try(:to_i)
+    end
+
+    # Fedora response as an ::RDF::Graph object. Public API, so consumers
+    # can do with it what they will, especially if future fedora versions
+    # add more things to it.
+    def response_graph
+      fixity_graph
+    end
+
     private
 
       def premis_status_predicate
@@ -46,7 +77,7 @@ def fixity_response_from_fedora
       end
 
       def fixity_graph
-        ::RDF::Graph.new << ::RDF::Reader.for(:ttl).new(response.body)
+        @fixity_graph ||= ::RDF::Graph.new << ::RDF::Reader.for(:ttl).new(response.body)
       end
 
       # See https://jira.duraspace.org/browse/FCREPO-1247

spec/unit/fixity_service_spec.rb

@@ -4,6 +4,32 @@
   let(:service) { described_class.new(uri) }
   let(:uri) { RDF::URI("http://path/to/resource") }
 
+  let(:passing_fedora44_response_body) {
+    <<-EOF
+@prefix premis: <http://www.loc.gov/premis/rdf/v1#> .
+
+<http://127.0.0.1:8080/rest/dev/0k/22/5b/04/0k225b04p/files/9f296a1f-10e7-44a3-83eb-4811d611edc6/fcr:versions/version1> premis:hasFixity <http://127.0.0.1:8080/rest/dev/0k/22/5b/04/0k225b04p/files/9f296a1f-10e7-44a3-83eb-4811d611edc6/fcr:versions/version1#fixity/1493843767961> .
+
+<http://127.0.0.1:8080/rest/dev/0k/22/5b/04/0k225b04p/files/9f296a1f-10e7-44a3-83eb-4811d611edc6/fcr:versions/version1#fixity/1493843767961> a premis:Fixity , premis:EventOutcomeDetail ;
+  premis:hasEventOutcome "SUCCESS"^^<http://www.w3.org/2001/XMLSchema#string> ;
+  premis:hasMessageDigest <urn:sha1:b995eef5262dd1c74f0ed9c96be1f404394d45dc> ;
+  premis:hasSize "103945"^^<http://www.w3.org/2001/XMLSchema#long> .
+  EOF
+  }
+
+  let(:failing_fedora44_response_body) {
+    <<-EOF
+@prefix premis: <http://www.loc.gov/premis/rdf/v1#> .
+
+<http://127.0.0.1:8080/rest/dev/ks/65/hc/20/ks65hc20t/files/e316b4b5-4627-44f8-9fdb-d2016e0e7380/fcr:versions/version3> premis:hasFixity <http://127.0.0.1:8080/rest/dev/ks/65/hc/20/ks65hc20t/files/e316b4b5-4627-44f8-9fdb-d2016e0e7380/fcr:versions/version3#fixity/1493844791463> .
+
+<http://127.0.0.1:8080/rest/dev/ks/65/hc/20/ks65hc20t/files/e316b4b5-4627-44f8-9fdb-d2016e0e7380/fcr:versions/version3#fixity/1493844791463> a premis:Fixity , premis:EventOutcomeDetail ;
+  premis:hasEventOutcome "BAD_CHECKSUM"^^<http://www.w3.org/2001/XMLSchema#string> , "BAD_SIZE"^^<http://www.w3.org/2001/XMLSchema#string> ;
+  premis:hasMessageDigest <urn:sha1:1a89571e25dd372563a10740a883e93f8af2d146> ;
+  premis:hasSize "1878582"^^<http://www.w3.org/2001/XMLSchema#long> .
+EOF
+  }
+
   describe "the instance" do
     subject { described_class.new(uri) }
     it { is_expected.to respond_to(:response) }
@@ -22,21 +48,21 @@
     end
   end
 
-  describe "#check" do
+  describe "#verified?" do
     before { allow(service).to receive(:fixity_response_from_fedora).and_return(response) }
-    subject { service.check }
+    subject { service.verified? }
 
     context "with Fedora version >= 4.4.0" do
       context "with a passing result" do
         let(:response) do
-          instance_double("Response", body: '<subject> <http://www.loc.gov/premis/rdf/v1#hasEventOutcome> "SUCCESS"^^<http://www.w3.org/2001/XMLSchema#string> .')
+          instance_double("Response", body: passing_fedora44_response_body)
         end
         it { is_expected.to be true }
       end
 
       context "with a failing result" do
         let(:response) do
-          instance_double("Response", body: '<subject> <http://www.loc.gov/premis/rdf/v1#hasEventOutcome> "BAD_CHECKSUM"^^<http://www.w3.org/2001/XMLSchema#string> .')
+          instance_double("Response", body: failing_fedora44_response_body)
         end
         it { is_expected.to be false }
       end
@@ -65,4 +91,38 @@
       it { is_expected.to be false }
     end
   end
+
+  describe "expected_message_digest" do
+    before { allow(service).to receive(:fixity_response_from_fedora).and_return(response) }
+    subject { service.expected_message_digest }
+    context "with success response" do
+      let(:response) do
+        instance_double("Response", body: passing_fedora44_response_body)
+      end
+      it { is_expected.to match(/urn:sha1:[a-f0-9]+/) }
+    end
+    context "with failure response" do
+      let(:response) do
+        instance_double("Response", body: failing_fedora44_response_body)
+      end
+      it { is_expected.to match(/urn:sha1:[a-f0-9]+/) }
+    end
+  end
+
+  describe "expected_size" do
+    before { allow(service).to receive(:fixity_response_from_fedora).and_return(response) }
+    subject { service.expected_size }
+    context "with success response" do
+      let(:response) do
+        instance_double("Response", body: passing_fedora44_response_body)
+      end
+      it { is_expected.to be_kind_of Numeric }
+    end
+    context "with failure response" do
+      let(:response) do
+        instance_double("Response", body: failing_fedora44_response_body)
+      end
+      it { is_expected.to be_kind_of Numeric }
+    end
+  end
 end