Correctly append combined search parameters to paths

lib/utils.js

@@ -45,17 +45,45 @@ const getFork = (forks, req) => {
 }
 
 /**
- * Get original query string
- * @param {object} req - Express request
- * @returns {string} Original query string
+ * Get path with combined search params
+ * @param {string} originalUrl - Original URL path
+ * @param {string} path - Path to add params to
+ * @returns {string} Path with combined search params
+ */
+const getPathWithSearchParams = (originalUrl, path) => {
+  if (!path) {
+    return ''
+  }
+
+  // Add any path params to params on original URL
+  const originalParams = getSearchParams(originalUrl)
+  const pathParams = getSearchParams(path)
+  for (let [key, value] of originalParams.entries()) {
+    pathParams.append(key, value);
+  }
+
+  // Remove query string from path
+  path = path.split('?')[0]
+
+  return pathParams.size
+    ? `${path}?${pathParams.toString()}`
+    : path
+}
+
+/**
+ * Get search parameters
+ * @param {string} originalUrl - Original URL path
+ * @returns {URLSearchParams} Search parameters
  */
-const getOriginalQuery = (req) => {
-  const originalQueryString = req.originalUrl.split('?')[1]
+const getSearchParams = (originalUrl) => {
+  const queryString = originalUrl.split('?')[1]
+  const searchParams = new URLSearchParams(queryString);
 
-  return originalQueryString ? `?${originalQueryString}` : ''
+  return searchParams
 }
 
 module.exports = {
   getFork,
-  getOriginalQuery
+  getPathWithSearchParams,
+  getSearchParams
 }

test/utils.js

@@ -83,11 +83,36 @@ describe('Utility functions', () => {
     })
   })
 
-  it('Gets original query string', () => {
-    const req1 = { originalUrl: '/admin/new?sort=desc' }
-    const req2 = { originalUrl: '/admin/new?sort=desc&page=1' }
+  it('Gets path with combined search params', async (t) => {
+    await t.test('when path has search params', () => {
+      const originalUrl = '/filter/location'
+      const path = '/list?success=1'
+      const result = utils.getPathWithSearchParams(originalUrl, path)
 
-    assert.equal(utils.getOriginalQuery(req1), '?sort=desc')
-    assert.equal(utils.getOriginalQuery(req2), '?sort=desc&page=1')
+      assert.equal(result, '/list?success=1')
+    })
+
+    await t.test('when original url has search params', () => {
+      const originalUrl = '/filter/location?page=2&sort=asc'
+      const path = '/list'
+      const result = utils.getPathWithSearchParams(originalUrl, path)
+
+      assert.equal(result, '/list?page=2&sort=asc')
+    })
+
+    await t.test('when original url and path both have search params', () => {
+      const originalUrl = '/filter/location?page=2&sort=asc'
+      const path = '/list?success=1'
+      const result = utils.getPathWithSearchParams(originalUrl, path)
+
+      assert.equal(result, '/list?success=1&page=2&sort=asc')
+    })
+  })
+
+  it('Gets search parameters', () => {
+    const result = utils.getSearchParams('/admin/new?sort=desc&page=1')
+
+    assert.equal(result.get('sort'), 'desc')
+    assert.equal(result.get('page'), '1')
   })
 })

test/wizard.js

@@ -27,6 +27,30 @@ describe('GOV.UK Prototype Wizard', () => {
     })
   })
 
+  it('Returns next path with modified query string', () => {
+    const journey = {
+      '/filter/location': {},
+      '/list?success=1': {}
+    }
+
+    const req = {
+      method: 'POST',
+      originalUrl: '/filter/location?page=2&sort=asc',
+      path: '/filter/location',
+      query: {
+        page: '2',
+        sort: 'asc'
+      },
+      session: { data: {} }
+    }
+
+    assert.deepEqual(wizard(journey, req), {
+      back: '',
+      current: '/filter/location?page=2&sort=asc',
+      next: '/list?success=1&page=2&sort=asc'
+    })
+  })
+
   it('Adds fork data pointing back to where user forked from', () => {
     const req = {
       method: 'GET',

wizard.js

@@ -8,10 +8,9 @@ const utils = require('./lib/utils.js')
  * @returns {Object} Next and back paths
  */
 const wizard = (journey, req) => {
-  const { method, path, session } = req
+  const { method, originalUrl, path, session } = req
   const { data } = session
   const paths = Object.keys(journey)
-  const query = utils.getOriginalQuery(req)
   const index = paths.indexOf(path)
   let fork
   let next
@@ -41,9 +40,9 @@ const wizard = (journey, req) => {
   }
 
   return {
-    next: next && next + query,
-    back: back && back + query,
-    current: path + query
+    next: utils.getPathWithSearchParams(originalUrl, next),
+    back: utils.getPathWithSearchParams(originalUrl, back),
+    current: originalUrl
   }
 }