Generate draft origin preview links on compare page

The token helper methods are used to generate a draft origin preview
link for the Request. If the link cannot be generated due to
the required fields not being present, no link is displayed.

Author: young-rob

app/controllers/fact_check_comparison_controller.rb

@@ -11,7 +11,7 @@ def compare
     @differ = Nokodiff.diff(before, after)
     @article_title = @request.source_title
     @deadline = @request.deadline.to_date.to_s
-    @draft_url = "/"
+    @draft_url = draft_origin_preview_url(@request)
 
     render "fact_check_comparison"
   end

app/views/application/fact_check_comparison.html.erb

@@ -23,33 +23,35 @@
   </div>
   <div class="govuk-grid-column-one-third options-sidebar">
     <div class="sidebar-components">
+      <% if @draft_url %>
+        <%= render "govuk_publishing_components/components/heading", {
+            text: t("fact_check_comparison.preview_heading"),
+            heading_level: 3,
+            font_size: "s",
+            padding: true,
+        } %>
+        <p class="govuk-body"><%= link_to t("fact_check_comparison.preview_link"), @draft_url, class: "govuk-link--no-visited-state govuk-link", target: :_blank, rel: :noopener %></p>
+        <hr class="govuk-section-break govuk-section-break govuk-section-break--visible govuk-!-margin-top-6 govuk-!-margin-bottom-3" />
+      <% end %>
       <%= render "govuk_publishing_components/components/heading", {
-          text: t("fact_check_comparison.preview_heading"),
+          text: t("fact_check_comparison.guidance_heading"),
           heading_level: 3,
           font_size: "s",
           padding: true,
       } %>
-      <p class="govuk-body"><%= link_to  t("fact_check_comparison.preview_link"), @draft_url, class: "govuk-link--no-visited-state govuk-link" %></p>
+      <%= render "govuk_publishing_components/components/list", {
+        visible_counters: true,
+        items: [
+          t("fact_check_comparison.guidance_deleted"),
+          t("fact_check_comparison.guidance_added"),
+        ],
+      } %>
+      <p class="govuk-body">
+        <%= link_to t("fact_check_comparison.guidance_link"), 
+          "https://gov.uk/government/publications/how-content-requests-from-government-get-published/fact-checking-content-on-govuk",
+          class: "govuk-link--no-visited-state govuk-link", target: :_blank, rel: :noopener 
+        %>
+      </p>
     </div>
-    <hr class="govuk-section-break govuk-section-break govuk-section-break--visible govuk-!-margin-top-6 govuk-!-margin-bottom-3" />
-    <%= render "govuk_publishing_components/components/heading", {
-        text: t("fact_check_comparison.guidance_heading"),
-        heading_level: 3,
-        font_size: "s",
-        padding: true,
-    } %>
-    <%= render "govuk_publishing_components/components/list", {
-      visible_counters: true,
-      items: [
-        t("fact_check_comparison.guidance_deleted"),
-        t("fact_check_comparison.guidance_added"),
-      ],
-    } %>
-    <p class="govuk-body">
-      <%= link_to t("fact_check_comparison.guidance_link"), 
-        "https://gov.uk/government/publications/how-content-requests-from-government-get-published/fact-checking-content-on-govuk",
-        class: "govuk-link--no-visited-state govuk-link", target: :_blank, rel: :noopener 
-      %>
-    </p>
   </div>
 </div>

spec/requests/fact_check_comparison_controller_spec.rb

@@ -25,6 +25,34 @@
       expect(response.body).to include(I18n.t("fact_check_comparison.guidance_link"))
     end
 
+    it "includes a draft origin preview link with a JWT token" do
+      get compare_path(source_app: request.source_app, source_id: request.source_id)
+
+      expect(response.body).to include("draft-origin.dev.gov.uk/#{request.draft_slug}")
+      expect(response.body).to include("token=")
+    end
+
+    context "when draft origin fields are not present" do
+      let(:request) do
+        create(
+          :request,
+          draft_content_id: nil,
+          draft_auth_bypass_id: nil,
+          draft_slug: nil,
+          previous_content: { "body" => "<div>Old content</div>" },
+          current_content: { "body" => "<div>New content</div>" },
+        )
+      end
+
+      it "does not render the preview section" do
+        get compare_path(source_app: request.source_app, source_id: request.source_id)
+
+        expect(response).to have_http_status(:ok)
+        expect(response.body).not_to include(I18n.t("fact_check_comparison.preview_heading"))
+        expect(response.body).not_to include(I18n.t("fact_check_comparison.preview_link"))
+      end
+    end
+
     it "renders the diff with formatting" do
       get compare_path(source_app: request.source_app, source_id: request.source_id)
 

spec/system/fact_check_comparison_spec.rb

@@ -35,14 +35,33 @@
       expect(page).to have_text(I18n.t("fact_check_response.heading"))
     end
 
-    it "displays the guidance sidebar" do
+    it "displays the draft origin preview link" do
       visit compare_path(source_app: request.source_app, source_id: request.source_id)
 
       expect(page).to have_text(I18n.t("fact_check_comparison.preview_heading"))
+      expect(page).to have_link(I18n.t("fact_check_comparison.preview_link"))
+    end
+
+    it "displays the guidance sidebar" do
+      visit compare_path(source_app: request.source_app, source_id: request.source_id)
+
       expect(page).to have_text(I18n.t("fact_check_comparison.guidance_heading"))
       expect(page).to have_text(I18n.t("fact_check_comparison.guidance_deleted"))
       expect(page).to have_text(I18n.t("fact_check_comparison.guidance_added"))
       expect(page).to have_link(I18n.t("fact_check_comparison.guidance_link"))
     end
+
+    context "when no draft preview link can be generated" do
+      before do
+        allow_any_instance_of(TokenHelper).to receive(:draft_origin_preview_url).and_return(nil)
+      end
+
+      it "does not render the preview section or link" do
+        visit compare_path(source_app: request.source_app, source_id: request.source_id)
+
+        expect(page).not_to have_text(I18n.t("fact_check_comparison.preview_heading"))
+        expect(page).not_to have_link(I18n.t("fact_check_comparison.preview_link"))
+      end
+    end
   end
 end