Don't allow goto page to be before routing page in show routes page

Author: lfdebrux

app/services/routes/build_service.rb

@@ -30,15 +30,26 @@ def options_for_goto_page(page, selected = nil)
 
     return [] unless next_page
 
-    # Don't include the current page in the options
-    options_without_page = all_goto_options.reject { |_, value| value == page.id }
-
-    # Replace the next page with the default option
-    options_without_page.map do |name, value|
-      if value == next_page.id
-        ["Go to question #{page.position.next}", Forms::RouteInput::DEFAULT_VALUE]
+    # Don't include the current page or pages before in the options,
+    # unless the goto page for the existing condition is before the current page,
+    # in which case do include that one. Also, change the option for the next page
+    # to a different default option.
+    next_page_id = next_page.id
+    drop = true
+
+    all_goto_options.filter_map do |option|
+      _, value = option
+
+      if drop
+        if selected && value == selected
+          option
+        elsif value == next_page_id
+          drop = false
+          ["Go to question #{page.position.next}", Forms::RouteInput::DEFAULT_VALUE]
+        end
+        # return nil
       else
-        [name, value]
+        option
       end
     end
   end

spec/services/routes/build_service_spec.rb

@@ -219,5 +219,26 @@
 
       expect(page_ids).not_to include(pages.first.id)
     end
+
+    it "does not include pages before the current page in the options" do
+      options = service.options_for_goto_page(pages.second)
+
+      expect(options).to eq [
+        ["Go to question 3", Forms::RouteInput::DEFAULT_VALUE],
+        ["End of the form", "end_of_form"],
+      ]
+    end
+
+    context "when there is a selected goto page and the goto page is before the current page" do
+      it "includes the goto page in the options" do
+        options = service.options_for_goto_page(pages.second, pages.first.id)
+
+        expect(options).to eq [
+          ["1. #{pages.first.question_text}", pages.first.id],
+          ["Go to question 3", Forms::RouteInput::DEFAULT_VALUE],
+          ["End of the form", "end_of_form"],
+        ]
+      end
+    end
   end
 end

spec/views/routes/show.html.erb_spec.rb

@@ -88,7 +88,7 @@ def select_options(select_field)
       end
 
       expect(rendered).to have_selector('.govuk-select[name="forms_routes_input[routes_attributes][1][goto]"]') do |field|
-        expect(select_options(field)).to end_with [
+        expect(select_options(field)).to eq [
           ["default", "Go to question 3"],
           ["end_of_form", "End of the form"],
         ]
@@ -110,5 +110,36 @@ def select_options(select_field)
         end
       end
     end
+
+    context "when the route goes to a page before the routing page" do
+      let(:pages) do
+        [
+          build_stubbed(:page, id: 101),
+          build_stubbed(
+            :page,
+            id: 102,
+            routing_conditions: [
+              build_stubbed(
+                :condition,
+                routing_page_id: 102,
+                goto_page_id: 101,
+                answer_value: nil,
+              ),
+            ],
+          ),
+          build_stubbed(:page, id: 103),
+        ]
+      end
+
+      it "shows the selected goto page for the route" do
+        render_page
+
+        expect(rendered).to have_selector('.govuk-select[name="forms_routes_input[routes_attributes][1][goto]"]') do |field|
+          expect(field).to have_selector("option[selected]") do |option|
+            expect(option["value"]).to eq "101"
+          end
+        end
+      end
+    end
   end
 end