class Error

class Error {
    
    /**
     * The error severity level.
     *
     * @var int
     */
    const ERROR = 3;
    
    /**
     * An array of blacklisted functions.
     *
     * @var array
     */
    protected static $blacklistFunctions = [
        'debug',
        '_drupal_error_handler',
        '_drupal_exception_handler',
    ];
    
    /**
     * Decodes an exception and retrieves the correct caller.
     *
     * @param \Exception|\Throwable $exception
     *   The exception object that was thrown.
     *
     * @return array
     *   An error in the format expected by _drupal_log_error().
     */
    public static function decodeException($exception) {
        $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) {
            // The first element in the stack is the call, the second element gives us
            // the caller. We skip calls that occurred in one of the classes of the
            // database layer or in one of its global functions.
            $db_functions = [
                'db_query',
                'db_query_range',
            ];
            while (!empty($backtrace[1]) && ($caller = $backtrace[1]) && (isset($caller['class']) && (strpos($caller['class'], 'Query') !== FALSE || strpos($caller['class'], 'Database') !== FALSE || strpos($caller['class'], 'PDO') !== FALSE) || in_array($caller['function'], $db_functions))) {
                // We remove that call.
                array_shift($backtrace);
            }
            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(),
        ];
    }
    
    /**
     * 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']);
        // 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('%type: @message in %function (line %line of %file). <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 black listed functions.
        while ($backtrace && !isset($backtrace[0]['line']) || isset($backtrace[1]['function']) && in_array($backtrace[1]['function'], static::$blacklistFunctions)) {
            array_shift($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;
    }

}