OOC-4383 Add back button to check your answers page

runner/src/server/plugins/engine/models/SummaryViewModel.ts

@@ -53,6 +53,7 @@ export class SummaryViewModel {
         message: string;
       }[]
     | undefined;
+  backLink?: string;
 
   _outputs: any; // TODO
   _payApiKey: FormDefinition["payApiKey"];
@@ -67,6 +68,7 @@ export class SummaryViewModel {
   ) {
     this.pageTitle = pageTitle;
     this.name = model.name;
+    this.backLink = state?.progress?.[state?.progress.length - 1];
     const { relevantPages, endPage } = this.getRelevantPages(model, state);
     const details = this.summaryDetails(request, model, state, relevantPages);
     const { def } = model;

runner/src/server/plugins/engine/pageControllers/SummaryPageController.ts

@@ -62,8 +62,21 @@ export class SummaryPageController extends PageController {
         return this.makePostRouteHandler()(request, h);
       }
       const state = await cacheService.getState(request);
-      const viewModel = new SummaryViewModel(this.title, model, state, request);
+      const progress = state.progress || [];
+      const currentPath = `/${this.model.basePath}${this.path}${request.url.search}`;
 
+      const viewModel = new SummaryViewModel(this.title, model, state, request);
+      /**
+       * used for when a user clicks the "back" link. Progress is stored in the state. This is a safer alternative to running javascript that pops the history `onclick`.
+       */
+      const lastVisited = progress[progress.length - 1];
+      if (!lastVisited || !lastVisited.startsWith(currentPath)) {
+        if (progress[progress.length - 2] === currentPath) {
+          progress.pop();
+        } else {
+          progress.push(currentPath);
+        }
+      }
       if (viewModel.endPage) {
         return redirectTo(
           request,

runner/src/server/views/summary.html

@@ -10,6 +10,15 @@
   html: 'This is a new service – your <a class="govuk-link" href=" + feedbackLink + " target="_blank">feedback</a> will help us to improve
   it.'
   }) }}
+
+  {% if backLink %}
+  {{
+    govukBackLink({
+      href: backLink,
+      text: "Back"
+    })
+  }}
+{% endif %} 
 {% endblock %} 
 
 {% block content %}