refactor: extract index.php to RssBridge.php (#2961)

* refactor: extract entry point into class

* refactor: js

* refactor: extract frontpage action

lib/RssBridge.php

@@ -0,0 +1,58 @@
+<?php
+
+final class RssBridge
+{
+    public function main(array $argv = [])
+    {
+        if ($argv) {
+            parse_str(implode('&', array_slice($argv, 1)), $cliArgs);
+            $request = $cliArgs;
+        } else {
+            $request = $_GET;
+        }
+
+        try {
+            $this->run($request);
+        } catch (\Throwable $e) {
+            error_log($e);
+            $message = sprintf(
+                'Uncaught Exception %s: %s at %s line %s',
+                get_class($e),
+                $e->getMessage(),
+                trim_path_prefix($e->getFile()),
+                $e->getLine()
+            );
+            http_response_code(500);
+            print render('error.html.php', [
+                'message' => $message,
+                'stacktrace' => create_sane_stacktrace($e),
+            ]);
+        }
+    }
+
+    private function run($request): void
+    {
+        Configuration::verifyInstallation();
+        Configuration::loadConfiguration();
+
+        date_default_timezone_set(Configuration::getConfig('system', 'timezone'));
+
+        define('CUSTOM_CACHE_TIMEOUT', Configuration::getConfig('cache', 'custom_timeout'));
+
+        $authenticationMiddleware = new AuthenticationMiddleware();
+        if (Configuration::getConfig('authentication', 'enable')) {
+            $authenticationMiddleware();
+        }
+
+        foreach ($request as $key => $value) {
+            if (!is_string($value)) {
+                throw new \Exception("Query parameter \"$key\" is not a string.");
+            }
+        }
+
+        $actionFactory = new ActionFactory();
+        $action = $request['action'] ?? 'Frontpage';
+        $action = $actionFactory->create($action);
+        $action->execute($request);
+    }
+}