social-login-redirect: Redirection added for social auth users

web/modules/custom/ct_user/ct_user.module

@@ -6,6 +6,7 @@
  */
 
 use Drupal\Core\Routing\RouteMatchInterface;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
  * Implements hook_help().
@@ -22,3 +23,52 @@ function ct_user_help($route_name, RouteMatchInterface $route_match) {
     default:
   }
 }
+
+/**
+ * Implements hook_form_alter().
+ */
+function ct_user_form_alter(&$form, $form_state, $form_id) {
+  // Check if the form is the user login form.
+  if ($form_id == 'user_login_form') {
+    // Add a custom validation function to the form.
+    $form['#validate'][] = 'ct_user_user_login_form_validate';
+  }
+}
+
+/**
+ * Custom validation function for the user login form.
+ */
+function ct_user_user_login_form_validate(&$form, $form_state) {
+  // Get the name value from the form.
+  $name = $form_state->getValue('name');
+
+  // Get the id of the user.
+  $ids = \Drupal::entityQuery('user')
+    ->condition('name', $name)
+    ->range(0, 1)
+    ->accessCheck(FALSE)
+    ->execute();
+
+  // Check if there is a User ID available.
+  if (empty($ids)) {
+    return;
+  }
+  else {
+    // Check if there is a social auth profile.
+    $socialIds = \Drupal::entityQuery("social_auth")
+      ->accessCheck(FALSE)
+      ->condition("user_id", reset($ids))
+      ->execute();
+
+    // If the user has no social auth profile, allow the login to continue.
+    if (empty($socialIds)) {
+      return;
+    }
+    else {
+      // If the user has social auth profile, redirect them to /user/login/google.
+      $response = new RedirectResponse('/user/login/google');
+      $response->send();
+      user_logout();
+    }
+  }
+}