Check Tool: 'back' link takes user to referrer page , when arriving via deep link.

src/controllers/deepLinkController.js

@@ -33,8 +33,11 @@ class DeepLinkController extends PageController {
     req.sessionModel.set('dataset', dataset)
     const datasetInfo = datasets.get(dataset) ?? { dataSubject: '', requiresGeometryTypeSelection: false }
     req.sessionModel.set('data-subject', datasetInfo.dataSubject)
-    req.sessionModel.set(this.checkToolDeepLinkSessionKey,
-      { 'data-subject': datasetInfo.dataSubject, orgName, dataset, datasetName: datasetInfo.text })
+    const sessionData = { 'data-subject': datasetInfo.dataSubject, orgName, dataset, datasetName: datasetInfo.text }
+    if (req.headers.referer) {
+      sessionData.referrer = req.headers.referer
+    }
+    req.sessionModel.set(this.checkToolDeepLinkSessionKey, sessionData)
 
     this.#addHistoryStep(req, '/check/dataset')
 

src/controllers/pageController.js

@@ -2,6 +2,27 @@ import hmpoFormWizard from 'hmpo-form-wizard'
 import { logPageView } from '../utils/logging.js'
 const { Controller } = hmpoFormWizard
 
+/**
+ * If we arrived at the page via deep from another page, we'll use that page as the back link.
+ *
+ * @param {string} url current page URL
+ * @param {{ referrer?: string, dataset: string }} deepLinkInfo deep link info from the session
+ * @returns {string|undefined} back link URL
+ */
+function wizardBackLink (currentUrl, deepLinkInfo) {
+  if (deepLinkInfo && 'referrer' in deepLinkInfo) {
+    const { referrer, dataset } = deepLinkInfo
+    if (dataset === 'tree' && currentUrl === '/check/geometry-type') {
+      return referrer
+    }
+    if (dataset !== 'tree' && currentUrl === '/check/upload-method') {
+      return referrer
+    }
+  }
+
+  return undefined
+}
+
 class PageController extends Controller {
   checkToolDeepLinkSessionKey = 'check-tool-deep-link'
 
@@ -11,11 +32,16 @@ class PageController extends Controller {
   }
 
   locals (req, res, next) {
-    if (this.options.backLink) {
-      req.form.options.lastPage = this.options.backLink
+    let backLink
+    const deepLinkInfo = req?.sessionModel?.get(this.checkToolDeepLinkSessionKey)
+    if (deepLinkInfo) {
+      req.form.options.deepLink = deepLinkInfo
+      backLink = wizardBackLink(req.originalUrl, deepLinkInfo)
     }
-    if (req.sessionModel) {
-      req.form.options.deepLink = req.sessionModel.get(this.checkToolDeepLinkSessionKey)
+
+    backLink = backLink ?? this.options.backLink
+    if (backLink) {
+      req.form.options.lastPage = backLink
     }
     super.locals(req, res, next)
   }

test/unit/PageController.test.js

@@ -39,3 +39,48 @@ describe('PageController', () => {
     expect(callArgs.service).toEqual('lpa-data-validation-frontend')
   })
 })
+
+describe('Correctly detects the wizard back link', () => {
+  const referrer = '/this-is-where-we-came-from'
+  const makeReq = () => {
+    return ({
+      originalUrl: '/check/upload-method',
+      sessionID: '123',
+      sessionModel: {
+        get: vi.fn().mockReturnValue({ referrer })
+      },
+      form: {
+        options: {}
+      }
+    })
+  }
+
+  it('arriving at the deep link entry point', () => {
+    const pageController = new PageController({ route: '/upload-method' })
+    const req = makeReq()
+    pageController.locals(req, {}, vi.fn())
+    expect(req.form.options.lastPage).toEqual(referrer)
+  })
+
+  it('arriving at some other step', () => {
+    const pageController = new PageController({ route: '/upload-method' })
+    const req = { ...makeReq(), originalUrl: '/check/another-step' }
+    pageController.locals(req, {}, vi.fn())
+    expect(req.form.options.lastPage).toBe(undefined)
+  })
+
+  it('don\'t touch the back link if there\'s no deep link session info (lastPage not set)', () => {
+    const pageController = new PageController({ route: '/upload-method' })
+    const req = { ...makeReq(), sessionModel: new Map() }
+    pageController.locals(req, {}, vi.fn())
+    expect(req.form.options.lastPage).toEqual(undefined)
+  })
+
+  it('don\'t touch the back link if there\'s no deep link session info (lastPage set)', () => {
+    const pageController = new PageController({ route: '/upload-method' })
+    pageController.options.backLink = '/go-back'
+    const req = { ...makeReq(), sessionModel: new Map() }
+    pageController.locals(req, {}, vi.fn())
+    expect(req.form.options.lastPage).toEqual('/go-back')
+  })
+})

test/unit/deepLinkController.test.js

@@ -4,7 +4,7 @@ import DeepLinkController from '../../src/controllers/deepLinkController.js'
 function mockRequestObject () {
   const sessionModel = new Map()
   const journeyModel = new Map()
-  return { sessionModel, journeyModel, query: {} }
+  return { sessionModel, journeyModel, query: {}, headers: {} }
 }
 
 function mockMiddlewareArgs (reqOpts) {