class Error

class Error {
  
  /**
   * The error severity level.
   *
   * @var int
   */
  const ERROR = 3;
  
  /**
   * The default message for logging errors.
   */
  const DEFAULT_ERROR_MESSAGE = '%type: @message in %function (line %line of %file).';
  
  /**
   * An array of ignored functions.
   *
   * @var array
   */
  protected static $ignoredFunctions = [
    'debug',
    '_drupal_error_handler',
    '_drupal_exception_handler',
  ];
  
  /**
   * Decodes an exception and retrieves the correct caller.
   *
   * @param \Throwable $exception
   *   The exception object that was thrown.
   *
   * @return array
   *   An error in the format expected by _drupal_log_error().
   */
  public static function decodeException(\Throwable $exception) : array {
    $message = $exception->getMessage();
    $backtrace = $exception->getTrace();
    // Add the line throwing the exception to the backtrace.
    array_unshift($backtrace, [
      'line' => $exception->getLine(),
      'file' => $exception->getFile(),
    ]);
    // For PDOException errors, we try to return the initial caller,
    // skipping internal functions of the database layer.
    if ($exception instanceof \PDOException || $exception instanceof DatabaseExceptionWrapper) {
      $driver_namespace = Database::getConnectionInfo()['default']['namespace'];
      $backtrace = Connection::removeDatabaseEntriesFromDebugBacktrace($backtrace, $driver_namespace);
      if (isset($exception->query_string, $exception->args)) {
        $message .= ": " . $exception->query_string . "; " . print_r($exception->args, TRUE);
      }
    }
    $caller = static::getLastCaller($backtrace);
    return [
      '%type' => get_class($exception),
      // The standard PHP exception handler considers that the exception message
      // is plain-text. We mimic this behavior here.
'@message' => $message,
      '%function' => $caller['function'],
      '%file' => $caller['file'],
      '%line' => $caller['line'],
      'severity_level' => static::ERROR,
      'backtrace' => $backtrace,
      '@backtrace_string' => $exception->getTraceAsString(),
      'exception' => $exception,
    ];
  }
  
  /**
   * Log a formatted exception message to the provided logger.
   *
   * @param \Psr\Log\LoggerInterface $logger
   *   The logger.
   * @param \Throwable $exception
   *   The exception.
   * @param string $message
   *   (optional) The message.
   * @param array $additional_variables
   *   (optional) Any additional variables.
   * @param string $level
   *   The PSR log level. Must be valid constant in \Psr\Log\LogLevel.
   */
  public static function logException(LoggerInterface $logger, \Throwable $exception, string $message = Error::DEFAULT_ERROR_MESSAGE, array $additional_variables = [], string $level = LogLevel::ERROR) : void {
    $logger->log($level, $message, static::decodeException($exception) + $additional_variables);
  }
  
  /**
   * Renders an exception error message without further exceptions.
   *
   * @param \Exception|\Throwable $exception
   *   The exception object that was thrown.
   *
   * @return string
   *   An error message.
   */
  public static function renderExceptionSafe($exception) {
    $decode = static::decodeException($exception);
    $backtrace = $decode['backtrace'];
    unset($decode['backtrace'], $decode['exception']);
    // Remove 'main()'.
    array_shift($backtrace);
    // Even though it is possible that this method is called on a public-facing
    // site, it is only called when the exception handler itself threw an
    // exception, which normally means that a code change caused the system to
    // no longer function correctly (as opposed to a user-triggered error), so
    // we assume that it is safe to include a verbose backtrace.
    $decode['@backtrace'] = Error::formatBacktrace($backtrace);
    return new FormattableMarkup(Error::DEFAULT_ERROR_MESSAGE . ' <pre class="backtrace">@backtrace</pre>', $decode);
  }
  
  /**
   * Gets the last caller from a backtrace.
   *
   * @param array $backtrace
   *   A standard PHP backtrace. Passed by reference.
   *
   * @return array
   *   An associative array with keys 'file', 'line' and 'function'.
   */
  public static function getLastCaller(array &$backtrace) {
    // Errors that occur inside PHP internal functions do not generate
    // information about file and line. Ignore the ignored functions.
    while ($backtrace && !isset($backtrace[0]['line']) || isset($backtrace[1]['function']) && in_array($backtrace[1]['function'], static::$ignoredFunctions)) {
      array_shift($backtrace);
    }
    // The first trace is the call itself.
    // It gives us the line and the file of the last call.
    $call = $backtrace[0];
    // The second call gives us the function where the call originated.
    if (isset($backtrace[1])) {
      if (isset($backtrace[1]['class'])) {
        $call['function'] = $backtrace[1]['class'] . $backtrace[1]['type'] . $backtrace[1]['function'] . '()';
      }
      else {
        $call['function'] = $backtrace[1]['function'] . '()';
      }
    }
    else {
      $call['function'] = 'main()';
    }
    return $call;
  }
  
  /**
   * Formats a backtrace into a plain-text string.
   *
   * The calls show values for scalar arguments and type names for complex ones.
   *
   * @param array $backtrace
   *   A standard PHP backtrace.
   *
   * @return string
   *   A plain-text line-wrapped string ready to be put inside <pre>.
   */
  public static function formatBacktrace(array $backtrace) {
    $return = '';
    foreach ($backtrace as $trace) {
      $call = [
        'function' => '',
        'args' => [],
      ];
      if (isset($trace['class'])) {
        $call['function'] = $trace['class'] . $trace['type'] . $trace['function'];
      }
      elseif (isset($trace['function'])) {
        $call['function'] = $trace['function'];
      }
      else {
        $call['function'] = 'main';
      }
      if (isset($trace['args'])) {
        foreach ($trace['args'] as $arg) {
          if (is_scalar($arg)) {
            $call['args'][] = is_string($arg) ? '\'' . Xss::filter($arg) . '\'' : $arg;
          }
          else {
            $call['args'][] = ucfirst(gettype($arg));
          }
        }
      }
      $line = '';
      if (isset($trace['line'])) {
        $line = " (Line: {$trace['line']})";
      }
      $return .= $call['function'] . '(' . implode(', ', $call['args']) . "){$line}\n";
    }
    return $return;
  }
  
  /**
   * Returns the current PHP error handler as a callable.
   *
   * @return callable|null
   *   The current error handler as a callable, or NULL if none is set.
   */
  public static function currentErrorHandler() : ?callable {
    $currentHandler = set_error_handler('var_dump');
    restore_error_handler();
    return $currentHandler;
  }

}