<?php

namespace Drupal\Core\EventSubscriber;

use Drupal\Core\Logger\LoggerChannelFactoryInterface;
use Drupal\Core\Utility\Error;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\ExceptionEvent;
use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Log exceptions without further handling.
 */
class ExceptionLoggingSubscriber implements EventSubscriberInterface {

  /**
   * The logger channel factory.
   *
   * @var \Drupal\Core\Logger\LoggerChannelFactoryInterface
   */
  protected $logger;

  /**
   * Constructs a new ExceptionLoggingSubscriber.
   *
   * @param \Drupal\Core\Logger\LoggerChannelFactoryInterface $logger
   *   The logger channel factory.
   */
  public function __construct(LoggerChannelFactoryInterface $logger) {
    $this->logger = $logger;
  }

  /**
   * Log 403 errors.
   *
   * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
   *   The event to process.
   */
  public function on403(ExceptionEvent $event) {
    // Log the exception with the page where it happened so that admins know
    // why access was denied.
    $exception = $event->getThrowable();
    $error = Error::decodeException($exception);
    unset($error['@backtrace_string']);
    $error['@uri'] = $event->getRequest()->getRequestUri();
    $this->logger->get('access denied')->warning('Path: @uri. ' . Error::DEFAULT_ERROR_MESSAGE, $error);
  }

  /**
   * Log 404 errors.
   *
   * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
   *   The event to process.
   */
  public function on404(ExceptionEvent $event) {
    $request = $event->getRequest();
    $this->logger->get('page not found')->warning('@uri', ['@uri' => $request->getRequestUri()]);
  }

  /**
   * Log not-otherwise-specified errors, including HTTP 500.
   *
   * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
   *   The event to process.
   */
  public function onError(ExceptionEvent $event) {
    $exception = $event->getThrowable();
    $error = Error::decodeException($exception);
    $this->logger->get('php')->log($error['severity_level'], Error::DEFAULT_ERROR_MESSAGE, $error);

    $is_critical = !$exception instanceof HttpExceptionInterface || $exception->getStatusCode() >= 500;
    if ($is_critical) {
      error_log(sprintf('Uncaught PHP Exception %s: "%s" at %s line %s', get_class($exception), $exception->getMessage(), $exception->getFile(), $exception->getLine()));
    }
  }

  /**
   * Log 4xx errors that are not 403 or 404.
   *
   * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
   *   The event to process.
   */
  public function onClientError(ExceptionEvent $event) {
    $exception = $event->getThrowable();
    $error = Error::decodeException($exception);
    $error += [
      'status_code' => $exception->getStatusCode(),
    ];
    unset($error['@backtrace_string']);
    $this->logger->get('client error')
      ->warning(Error::DEFAULT_ERROR_MESSAGE, $error);
  }

  /**
   * Log all exceptions.
   *
   * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
   *   The event to process.
   */
  public function onException(ExceptionEvent $event) {
    $exception = $event->getThrowable();

    $method = 'onError';

    // Treat any non-HTTP exception as if it were one, so we log it the same.
    if ($exception instanceof HttpExceptionInterface) {
      $status_code = $exception->getStatusCode();
      $possible_method = 'on' . $status_code;
      if (method_exists($this, $possible_method)) {
        $method = $possible_method;
      }
      elseif ($status_code >= 400 && $status_code < 500) {
        $method = 'onClientError';
      }
    }

    $this->$method($event);
  }

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents(): array {
    $events[KernelEvents::EXCEPTION][] = ['onException', 50];
    return $events;
  }

}