Make a contact_link required when turning upload_document permission on

When a platform admin user clicks on the button to add the
'upload_document' permission to a service, they should be taken to the
page to add a contact_link if the service does not already have one.

app/main/views/service_settings.py

@@ -322,12 +322,27 @@ def service_switch_can_send_precompiled_letter(service_id):
     return redirect(url_for('.service_settings', service_id=service_id))
 
 
-@main.route("/services/<service_id>/service-settings/can-upload-document")
+@main.route("/services/<service_id>/service-settings/can-upload-document", methods=['GET', 'POST'])
 @login_required
 @user_is_platform_admin
 def service_switch_can_upload_document(service_id):
-    switch_service_permissions(service_id, 'upload_document')
-    return redirect(url_for('.service_settings', service_id=service_id))
+    form = ServiceContactLinkForm()
+
+    # If turning the permission off, or turning it on and the service already has a contact_link,
+    # don't show the form to add the link
+    if 'upload_document' in current_service['permissions'] or current_service.get('contact_link'):
+        switch_service_permissions(service_id, 'upload_document')
+        return redirect(url_for('.service_settings', service_id=service_id))
+
+    if form.validate_on_submit():
+        service_api_client.update_service(
+            current_service['id'],
+            contact_link=form.url.data
+        )
+        switch_service_permissions(service_id, 'upload_document')
+        return redirect(url_for('.service_settings', service_id=service_id))
+
+    return render_template('views/service-settings/contact_link.html', form=form)
 
 
 @main.route("/services/<service_id>/service-settings/archive", methods=['GET', 'POST'])

app/templates/views/service-settings/contact_link.html

@@ -3,13 +3,15 @@
 {% from "components/page-footer.html" import page_footer %}
 
 {% block service_page_title %}
-  Change link on ‘Download your document’ page
+  {{ 'Change link on' if 'upload_document' in current_service.permissions else 'Add link for' }} ‘Download your document’ page
 {% endblock %}
 
 {% block maincolumn_content %}
   <div class="grid-row">
     <div class="column-five-sixths">
-      <h1 class="heading-large">Change link on ‘Download your document’ page</h1>
+      <h1 class="heading-large">
+        {{ 'Change link on' if 'upload_document' in current_service.permissions else 'Add link for' }} ‘Download your document’ page
+      </h1>
       <p>
         When you send users a document to download, you need to include a link to your service
         on the download page. This is so users can contact you if there’s a problem (for example,

tests/app/main/views/test_service_settings.py

@@ -1977,6 +1977,77 @@ def test_switch_service_enable_international_sms(
     assert mocked_fn.call_args[0][0] == service_one['id']
 
 
+@pytest.mark.parametrize('start_permissions, contact_link, end_permissions', [
+    (['upload_document'], 'http://example.com/', []),
+    (['upload_document'], None, []),
+    ([], 'http://example.com/', ['upload_document']),
+])
+def test_service_switch_can_upload_document_changes_the_permission_if_not_adding_the_permission_without_a_contact_link(
+    logged_in_platform_admin_client,
+    service_one,
+    mock_update_service,
+    mock_get_service_settings_page_common,
+    mock_get_service_organisation,
+    no_reply_to_email_addresses,
+    no_letter_contact_blocks,
+    single_sms_sender,
+    start_permissions,
+    contact_link,
+    end_permissions,
+):
+    service_one['permissions'] = start_permissions
+    service_one['contact_link'] = contact_link
+
+    response = logged_in_platform_admin_client.get(
+        url_for('main.service_switch_can_upload_document', service_id=SERVICE_ONE_ID),
+        follow_redirects=True
+    )
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+
+    assert service_one['permissions'] == end_permissions
+    assert page.h1.text.strip() == 'Settings'
+
+
+def test_service_switch_can_upload_document_turning_permission_on_with_no_contact_link_shows_link_form(
+    logged_in_platform_admin_client,
+    service_one,
+    mock_get_service_settings_page_common,
+    mock_get_service_organisation,
+    no_reply_to_email_addresses,
+    no_letter_contact_blocks,
+    single_sms_sender,
+):
+    response = logged_in_platform_admin_client.get(
+        url_for('main.service_switch_can_upload_document', service_id=SERVICE_ONE_ID),
+        follow_redirects=True
+    )
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+
+    assert 'upload_document' not in service_one['permissions']
+    assert page.h1.text.strip() == "Add link for ‘Download your document’ page"
+
+
+def test_service_switch_can_upload_document_lets_contact_link_be_added_and_switches_permission(
+    logged_in_platform_admin_client,
+    service_one,
+    mock_update_service,
+    mock_get_service_settings_page_common,
+    mock_get_service_organisation,
+    no_reply_to_email_addresses,
+    no_letter_contact_blocks,
+    single_sms_sender,
+):
+    response = logged_in_platform_admin_client.post(
+        url_for('main.service_switch_can_upload_document', service_id=SERVICE_ONE_ID),
+        data={'url': 'http://example.com/'},
+        follow_redirects=True
+    )
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+
+    assert 'upload_document' in service_one['permissions']
+    assert page.h1.text.strip() == 'Settings'
+
+
 def test_archive_service_after_confirm(
     logged_in_platform_admin_client,
     service_one,
@@ -2200,7 +2271,7 @@ def test_service_set_contact_link_does_not_update_invalid_link(
         _follow_redirects=True
     )
 
-    assert page.h1.text == "Change link on ‘Download your document’ page"
+    assert page.h1.text.strip() == "Add link for ‘Download your document’ page"
     update_mock.assert_not_called()