Add logout success handler with a service parameter

Event/LogoutWithServiceSuccessHandler.php

@@ -0,0 +1,91 @@
+<?php
+/**
+ * Usage instructions.
+ *
+ * Add this to your config/services.yaml file
+ *
+ * ```yaml
+ * # config/services.yaml
+ * app.logout_success_handler:
+ *     class: PRayno\CasAuthBundle\Event\LogoutWithServiceSuccessHandler
+ *     arguments:
+ *         $casLogoutUrl: "https://cas.example.com/cas/logout"
+ *         $routeName: "homepage"
+ *         $routeParameters: { "parameter": "value" }  # optional
+ * ```
+ *
+ * And add this to your firewall config.  Don't forget to define a /logout route
+ * ```yaml
+ * # config/packages/security.yaml
+ * security:
+ *     firewalls:
+ *         main:
+ *             logout:
+ *                 path: /logout
+ *                 success_handler: app.logout_success_handler
+ * ```
+ */
+
+namespace PRayno\CasAuthBundle\Event;
+
+use Symfony\Component\HttpFoundation\RedirectResponse;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\Routing\RouterInterface;
+use Symfony\Component\Security\Http\Logout\LogoutSuccessHandlerInterface;
+
+/**
+ * This class will be used to include a service URL to CAS.  This is useful
+ * when you want your users to be able to return when they log back in
+ * to the CAS server.
+ *
+ * Intended to work the same way as  phpCAS::logoutWithRedirectService($url);
+ */
+class LogoutWithServiceSuccessHandler implements LogoutSuccessHandlerInterface
+{
+    /**
+     * URL to the CAS Logout page
+     * i.e. https://cas.example.com/cas/logout.
+     *
+     * @var string
+     */
+    private $casLogoutUrl;
+    /**
+     * @var RouterInterface
+     */
+    private $router;
+    /**
+     * Route to generate a URL to come back to.
+     *
+     * @var string
+     */
+    private $routeName;
+    /**
+     * Any required route parameters.
+     */
+    private $routeParameters;
+
+    /**
+     * @param string          $casLogoutUrl    Logout URL
+     * @param string          $routeName       Route name to return to after logout
+     * @param array           $routeParameters Route parameters
+     * @param RouterInterface $router          Symfony router to generate a return URL
+     */
+    public function __construct(string $casLogoutUrl, string $routeName, array $routeParameters = [], RouterInterface $router)
+    {
+        $this->router = $router;
+        $this->casLogoutUrl = $casLogoutUrl;
+        $this->routeName = $routeName;
+        $this->routeParameters = $routeParameters;
+    }
+
+    /**
+     * Redirects to the CAS server, but with a service parameter that directs the
+     * user back here if they wish.
+     */
+    public function onLogoutSuccess(Request $request)
+    {
+        $serviceUrl = $this->router->generate($this->routeName, $this->routeParameters, RouterInterface::ABSOLUTE_URL);
+
+        return new RedirectResponse($this->casLogoutUrl.'?'.http_build_query(['service' => $serviceUrl]));
+    }
+}