lib/src/handlers/logger.dart

// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:async';

import 'package:stack_trace/stack_trace.dart';

import '../hijack_exception.dart';
import '../middleware.dart';

/// Middleware which prints the time of the request, the elapsed time for the
/// inner handlers, the response's status code and the request URI.
///
/// If [logger] is passed, it's called for each request. The `msg` parameter is
/// a formatted string that includes the request time, duration, request method,
/// and requested path. When an exception is thrown, it also includes the
/// exception's string and stack trace; otherwise, it includes the status code.
/// The `isError` parameter indicates whether the message is caused by an error.
///
/// If [logger] is not passed, the message is just passed to [print].
Middleware logRequests({void logger(String msg, bool isError)}) =>
    (innerHandler) {
  if (logger == null) logger = _defaultLogger;

  return (request) {
    var startTime = new DateTime.now();
    var watch = new Stopwatch()..start();

    return new Future.sync(() => innerHandler(request)).then((response) {
      var msg = _getMessage(startTime, response.statusCode,
          request.requestedUri, request.method, watch.elapsed);

      logger(msg, false);

      return response;
    }, onError: (error, stackTrace) {
      if (error is HijackException) throw error;

      var msg = _getErrorMessage(startTime, request.requestedUri,
          request.method, watch.elapsed, error, stackTrace);

      logger(msg, true);

      throw error;
    });
  };
};

String _formatQuery(String query) {
  return query == '' ? '' : '?$query';
}

String _getMessage(DateTime requestTime, int statusCode, Uri requestedUri,
    String method, Duration elapsedTime) {
  return '${requestTime}\t$elapsedTime\t$method\t[${statusCode}]\t'
      '${requestedUri.path}${_formatQuery(requestedUri.query)}';
}

String _getErrorMessage(DateTime requestTime, Uri requestedUri, String method,
    Duration elapsedTime, Object error, StackTrace stack) {
  var chain = new Chain.current();
  if (stack != null) {
    chain = new Chain.forTrace(stack)
        .foldFrames((frame) => frame.isCore || frame.package == 'shelf').terse;
  }

  var msg = '${requestTime}\t$elapsedTime\t$method\t${requestedUri.path}'
      '${_formatQuery(requestedUri.query)}\n$error';
  if (chain == null) return msg;

  return '$msg\n$chain';
}

void _defaultLogger(String msg, bool isError) {
  if (isError) {
    print('[ERROR] $msg');
  } else {
    print(msg);
  }
}