Add ability to reject links

app/services/discovery_engine/search.rb

@@ -33,6 +33,7 @@ def discovery_engine_params
         page_size:,
         offset:,
         order_by:,
+        filter:,
         boost_spec:,
       }.compact
     end
@@ -68,6 +69,17 @@ def order_by
       end
     end
 
+    def filter
+      reject_links_filter
+    end
+
+    def reject_links_filter
+      return nil if query_params[:reject_link].blank?
+
+      reject_links = Array(query_params[:reject_link]).map { "\"#{_1}\"" }.join(",")
+      "NOT link: ANY(#{reject_links})"
+    end
+
     def serving_config
       Rails.configuration.discovery_engine_serving_config
     end

spec/services/discovery_engine/search_spec.rb

@@ -107,6 +107,26 @@
         end
       end
 
+      context "with a single reject_link parameter" do
+        let(:query_params) { { q: "garden centres", reject_link: "/foo" } }
+
+        it "calls the client with the expected parameters" do
+          expect(client).to have_received(:search).with(
+            hash_including(filter: 'NOT link: ANY("/foo")'),
+          )
+        end
+      end
+
+      context "with several reject_link parameter" do
+        let(:query_params) { { q: "garden centres", reject_link: ["/foo", "/bar"] } }
+
+        it "calls the client with the expected parameters" do
+          expect(client).to have_received(:search).with(
+            hash_including(filter: 'NOT link: ANY("/foo","/bar")'),
+          )
+        end
+      end
+
       context "when searching for a query that has a single best bets defined" do
         # see test section in YAML config
         let(:query_params) { { q: "i want to test a single best bet" } }