Adding a BNF login form for client sites. DDFHER-165

A login form, that we use to POST to BNF server, telling them who we are.

It is necessary for it to be a form, as the server will need to set some
kind of session/cookie on the actual end-users browser.

web/modules/custom/bnf/bnf_client/bnf_client.links.menu.yml

@@ -4,3 +4,8 @@ bnf_client.import_content:
   parent: system.admin_content
   route_name: bnf_client.import_form
   weight: 10
+bnf_client.login:
+  title: 'Login to BNF'
+  parent: system.admin_content
+  route_name: bnf_client.login_form
+  weight: 11

web/modules/custom/bnf/bnf_client/bnf_client.routing.yml

@@ -14,3 +14,11 @@ bnf_client.import_confirm_form:
     _title: 'Confirm import'
   requirements:
     _permission: 'bnf client import nodes'
+
+bnf_client.login_form:
+  path: '/admin/bnf/login'
+  defaults:
+    _form: '\Drupal\bnf_client\Form\BnfLoginForm'
+    _title: 'Login to BNF'
+  requirements:
+    _permission: 'bnf client import nodes'

web/modules/custom/bnf/bnf_client/src/Form/BnfLoginForm.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\bnf_client\Form;
+
+use Drupal\Core\Form\FormBase;
+
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * A login form, that we use to POST to BNF server, telling them who we are.
+ *
+ * It is necessary for it to be a form, as the server will need to set some
+ * kind of session/cookie on the actual end-users browser.
+ */
+class BnfLoginForm extends FormBase {
+
+  /**
+   * {@inheritDoc}
+   */
+  public function getFormId() {
+    return 'bnf_login_form';
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state): array {
+    $bnfServer = (string) getenv('BNF_SERVER_BASE_ENDPOINT');
+
+    $form_state->setMethod('POST');
+
+    // It would be nice if we could pull this route programmatically, but
+    // it is defined in bnf_server, which is inaccessible due to being
+    // disabled on client sites.
+    $form['#action'] = "$bnfServer/bnf/login";
+
+    $form['callbackUrl'] = [
+      '#type' => 'hidden',
+      '#value' => $this->getRequest()->getSchemeAndHttpHost(),
+    ];
+
+    $form['siteName'] = [
+      '#type' => 'hidden',
+      '#value' => $this->config('system.site')->get('name'),
+    ];
+
+    $form['info'] = [
+      '#type' => 'container',
+      '#markup' => $this->t(
+        'Login to BNF, to browse available content that you can import to your own site.<br/>
+        You have a chance to preview the content before it is imported.',
+        [], ['context' => 'BNF']
+      ),
+    ];
+
+    $form['actions']['submit'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Login to BNF', [], ['context' => 'BNF']),
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state): void {
+    // Left empty on purpose - the class demands it.
+  }
+
+}

web/modules/custom/bnf/bnf_server/bnf_server.routing.yml

@@ -0,0 +1,10 @@
+---
+bnf_server.cookie_login:
+  path: '/bnf/login'
+  defaults:
+    _controller: '\Drupal\bnf_server\Controller\LoginController::login'
+  methods: [POST]
+  requirements:
+    _permission: 'access content'
+  options:
+    no_cache: 'TRUE'

web/modules/custom/bnf/bnf_server/src/Controller/LoginController.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Drupal\bnf_server\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+use Symfony\Component\HttpFoundation\Cookie;
+use Symfony\Component\HttpFoundation\RedirectResponse;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+
+/**
+ * Recieving "login" information, used to display "import to my site" button.
+ *
+ * This endpoint is reached from library websites, when submitting the login
+ * form. It has data for where the user is coming from, so we can display
+ * a button for importing content.
+ */
+class LoginController extends ControllerBase {
+  const COOKIE_CALLBACK_URL = 'bnf_server_login.callback_url';
+  const COOKIE_SITE_NAME = 'bnf_server_login.site_name';
+
+  /**
+   * Receiving the login.
+   */
+  public function login(Request $request): RedirectResponse {
+    $url = $request->get('callbackUrl');
+    $name = $request->get('siteName');
+
+    if (empty($url)) {
+      throw new BadRequestHttpException('Callback URL cannot be empty.');
+    }
+
+    $response = new RedirectResponse('/');
+
+    $response->headers->setCookie(new Cookie(self::COOKIE_CALLBACK_URL, $url));
+    $response->headers->setCookie(new Cookie(self::COOKIE_SITE_NAME, $name));
+
+    return $response;
+  }
+
+}