response.js 27.4 KB
Newer Older
Rosanny Sihombing's avatar
Rosanny Sihombing committed
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
/*!
 * express
 * Copyright(c) 2009-2013 TJ Holowaychuk
 * Copyright(c) 2014-2015 Douglas Christopher Wilson
 * MIT Licensed
 */

'use strict';

/**
 * Module dependencies.
 * @private
 */

var Buffer = require('safe-buffer').Buffer
var contentDisposition = require('content-disposition');
var createError = require('http-errors')
var deprecate = require('depd')('express');
var encodeUrl = require('encodeurl');
var escapeHtml = require('escape-html');
var http = require('http');
var isAbsolute = require('./utils').isAbsolute;
var onFinished = require('on-finished');
var path = require('path');
var statuses = require('statuses')
var merge = require('utils-merge');
var sign = require('cookie-signature').sign;
var normalizeType = require('./utils').normalizeType;
var normalizeTypes = require('./utils').normalizeTypes;
var setCharset = require('./utils').setCharset;
var cookie = require('cookie');
var send = require('send');
var extname = path.extname;
var mime = send.mime;
var resolve = path.resolve;
var vary = require('vary');

/**
 * Response prototype.
 * @public
 */

var res = Object.create(http.ServerResponse.prototype)

/**
 * Module exports.
 * @public
 */

module.exports = res

/**
 * Module variables.
 * @private
 */

var charsetRegExp = /;\s*charset\s*=/;

/**
 * Set status `code`.
 *
 * @param {Number} code
 * @return {ServerResponse}
 * @public
 */

res.status = function status(code) {
  if ((typeof code === 'string' || Math.floor(code) !== code) && code > 99 && code < 1000) {
    deprecate('res.status(' + JSON.stringify(code) + '): use res.status(' + Math.floor(code) + ') instead')
  }
  this.statusCode = code;
  return this;
};

/**
 * Set Link header field with the given `links`.
 *
 * Examples:
 *
 *    res.links({
 *      next: 'http://api.example.com/users?page=2',
 *      last: 'http://api.example.com/users?page=5'
 *    });
 *
 * @param {Object} links
 * @return {ServerResponse}
 * @public
 */

res.links = function(links){
  var link = this.get('Link') || '';
  if (link) link += ', ';
  return this.set('Link', link + Object.keys(links).map(function(rel){
    return '<' + links[rel] + '>; rel="' + rel + '"';
  }).join(', '));
};

/**
 * Send a response.
 *
 * Examples:
 *
 *     res.send(Buffer.from('wahoo'));
 *     res.send({ some: 'json' });
 *     res.send('<p>some html</p>');
 *
 * @param {string|number|boolean|object|Buffer} body
 * @public
 */

res.send = function send(body) {
  var chunk = body;
  var encoding;
  var req = this.req;
  var type;

  // settings
  var app = this.app;

  // allow status / body
  if (arguments.length === 2) {
    // res.send(body, status) backwards compat
    if (typeof arguments[0] !== 'number' && typeof arguments[1] === 'number') {
      deprecate('res.send(body, status): Use res.status(status).send(body) instead');
      this.statusCode = arguments[1];
    } else {
      deprecate('res.send(status, body): Use res.status(status).send(body) instead');
      this.statusCode = arguments[0];
      chunk = arguments[1];
    }
  }

  // disambiguate res.send(status) and res.send(status, num)
  if (typeof chunk === 'number' && arguments.length === 1) {
    // res.send(status) will set status message as text string
    if (!this.get('Content-Type')) {
      this.type('txt');
    }

    deprecate('res.send(status): Use res.sendStatus(status) instead');
    this.statusCode = chunk;
    chunk = statuses.message[chunk]
  }

  switch (typeof chunk) {
    // string defaulting to html
    case 'string':
      if (!this.get('Content-Type')) {
        this.type('html');
      }
      break;
    case 'boolean':
    case 'number':
    case 'object':
      if (chunk === null) {
        chunk = '';
      } else if (Buffer.isBuffer(chunk)) {
        if (!this.get('Content-Type')) {
          this.type('bin');
        }
      } else {
        return this.json(chunk);
      }
      break;
  }

  // write strings in utf-8
  if (typeof chunk === 'string') {
    encoding = 'utf8';
    type = this.get('Content-Type');

    // reflect this in content-type
    if (typeof type === 'string') {
      this.set('Content-Type', setCharset(type, 'utf-8'));
    }
  }

  // determine if ETag should be generated
  var etagFn = app.get('etag fn')
  var generateETag = !this.get('ETag') && typeof etagFn === 'function'

  // populate Content-Length
  var len
  if (chunk !== undefined) {
    if (Buffer.isBuffer(chunk)) {
      // get length of Buffer
      len = chunk.length
    } else if (!generateETag && chunk.length < 1000) {
      // just calculate length when no ETag + small chunk
      len = Buffer.byteLength(chunk, encoding)
    } else {
      // convert chunk to Buffer and calculate
      chunk = Buffer.from(chunk, encoding)
      encoding = undefined;
      len = chunk.length
    }

    this.set('Content-Length', len);
  }

  // populate ETag
  var etag;
  if (generateETag && len !== undefined) {
    if ((etag = etagFn(chunk, encoding))) {
      this.set('ETag', etag);
    }
  }

  // freshness
  if (req.fresh) this.statusCode = 304;

  // strip irrelevant headers
  if (204 === this.statusCode || 304 === this.statusCode) {
    this.removeHeader('Content-Type');
    this.removeHeader('Content-Length');
    this.removeHeader('Transfer-Encoding');
    chunk = '';
  }

  // alter headers for 205
  if (this.statusCode === 205) {
    this.set('Content-Length', '0')
    this.removeHeader('Transfer-Encoding')
    chunk = ''
  }

  if (req.method === 'HEAD') {
    // skip body for HEAD
    this.end();
  } else {
    // respond
    this.end(chunk, encoding);
  }

  return this;
};

/**
 * Send JSON response.
 *
 * Examples:
 *
 *     res.json(null);
 *     res.json({ user: 'tj' });
 *
 * @param {string|number|boolean|object} obj
 * @public
 */

res.json = function json(obj) {
  var val = obj;

  // allow status / body
  if (arguments.length === 2) {
    // res.json(body, status) backwards compat
    if (typeof arguments[1] === 'number') {
      deprecate('res.json(obj, status): Use res.status(status).json(obj) instead');
      this.statusCode = arguments[1];
    } else {
      deprecate('res.json(status, obj): Use res.status(status).json(obj) instead');
      this.statusCode = arguments[0];
      val = arguments[1];
    }
  }

  // settings
  var app = this.app;
  var escape = app.get('json escape')
  var replacer = app.get('json replacer');
  var spaces = app.get('json spaces');
  var body = stringify(val, replacer, spaces, escape)

  // content-type
  if (!this.get('Content-Type')) {
    this.set('Content-Type', 'application/json');
  }

  return this.send(body);
};

/**
 * Send JSON response with JSONP callback support.
 *
 * Examples:
 *
 *     res.jsonp(null);
 *     res.jsonp({ user: 'tj' });
 *
 * @param {string|number|boolean|object} obj
 * @public
 */

res.jsonp = function jsonp(obj) {
  var val = obj;

  // allow status / body
  if (arguments.length === 2) {
    // res.jsonp(body, status) backwards compat
    if (typeof arguments[1] === 'number') {
      deprecate('res.jsonp(obj, status): Use res.status(status).jsonp(obj) instead');
      this.statusCode = arguments[1];
    } else {
      deprecate('res.jsonp(status, obj): Use res.status(status).jsonp(obj) instead');
      this.statusCode = arguments[0];
      val = arguments[1];
    }
  }

  // settings
  var app = this.app;
  var escape = app.get('json escape')
  var replacer = app.get('json replacer');
  var spaces = app.get('json spaces');
  var body = stringify(val, replacer, spaces, escape)
  var callback = this.req.query[app.get('jsonp callback name')];

  // content-type
  if (!this.get('Content-Type')) {
    this.set('X-Content-Type-Options', 'nosniff');
    this.set('Content-Type', 'application/json');
  }

  // fixup callback
  if (Array.isArray(callback)) {
    callback = callback[0];
  }

  // jsonp
  if (typeof callback === 'string' && callback.length !== 0) {
    this.set('X-Content-Type-Options', 'nosniff');
    this.set('Content-Type', 'text/javascript');

    // restrict callback charset
    callback = callback.replace(/[^\[\]\w$.]/g, '');

    if (body === undefined) {
      // empty argument
      body = ''
    } else if (typeof body === 'string') {
      // replace chars not allowed in JavaScript that are in JSON
      body = body
        .replace(/\u2028/g, '\\u2028')
        .replace(/\u2029/g, '\\u2029')
    }

    // the /**/ is a specific security mitigation for "Rosetta Flash JSONP abuse"
    // the typeof check is just to reduce client error noise
    body = '/**/ typeof ' + callback + ' === \'function\' && ' + callback + '(' + body + ');';
  }

  return this.send(body);
};

/**
 * Send given HTTP status code.
 *
 * Sets the response status to `statusCode` and the body of the
 * response to the standard description from node's http.STATUS_CODES
 * or the statusCode number if no description.
 *
 * Examples:
 *
 *     res.sendStatus(200);
 *
 * @param {number} statusCode
 * @public
 */

res.sendStatus = function sendStatus(statusCode) {
  var body = statuses.message[statusCode] || String(statusCode)

  this.statusCode = statusCode;
  this.type('txt');

  return this.send(body);
};

/**
 * Transfer the file at the given `path`.
 *
 * Automatically sets the _Content-Type_ response header field.
 * The callback `callback(err)` is invoked when the transfer is complete
 * or when an error occurs. Be sure to check `res.headersSent`
 * if you wish to attempt responding, as the header and some data
 * may have already been transferred.
 *
 * Options:
 *
 *   - `maxAge`   defaulting to 0 (can be string converted by `ms`)
 *   - `root`     root directory for relative filenames
 *   - `headers`  object of headers to serve with file
 *   - `dotfiles` serve dotfiles, defaulting to false; can be `"allow"` to send them
 *
 * Other options are passed along to `send`.
 *
 * Examples:
 *
 *  The following example illustrates how `res.sendFile()` may
 *  be used as an alternative for the `static()` middleware for
 *  dynamic situations. The code backing `res.sendFile()` is actually
 *  the same code, so HTTP cache support etc is identical.
 *
 *     app.get('/user/:uid/photos/:file', function(req, res){
 *       var uid = req.params.uid
 *         , file = req.params.file;
 *
 *       req.user.mayViewFilesFrom(uid, function(yes){
 *         if (yes) {
 *           res.sendFile('/uploads/' + uid + '/' + file);
 *         } else {
 *           res.send(403, 'Sorry! you cant see that.');
 *         }
 *       });
 *     });
 *
 * @public
 */

res.sendFile = function sendFile(path, options, callback) {
  var done = callback;
  var req = this.req;
  var res = this;
  var next = req.next;
  var opts = options || {};

  if (!path) {
    throw new TypeError('path argument is required to res.sendFile');
  }

  if (typeof path !== 'string') {
    throw new TypeError('path must be a string to res.sendFile')
  }

  // support function as second arg
  if (typeof options === 'function') {
    done = options;
    opts = {};
  }

  if (!opts.root && !isAbsolute(path)) {
    throw new TypeError('path must be absolute or specify root to res.sendFile');
  }

  // create file stream
  var pathname = encodeURI(path);
  var file = send(req, pathname, opts);

  // transfer
  sendfile(res, file, opts, function (err) {
    if (done) return done(err);
    if (err && err.code === 'EISDIR') return next();

    // next() all but write errors
    if (err && err.code !== 'ECONNABORTED' && err.syscall !== 'write') {
      next(err);
    }
  });
};

/**
 * Transfer the file at the given `path`.
 *
 * Automatically sets the _Content-Type_ response header field.
 * The callback `callback(err)` is invoked when the transfer is complete
 * or when an error occurs. Be sure to check `res.headersSent`
 * if you wish to attempt responding, as the header and some data
 * may have already been transferred.
 *
 * Options:
 *
 *   - `maxAge`   defaulting to 0 (can be string converted by `ms`)
 *   - `root`     root directory for relative filenames
 *   - `headers`  object of headers to serve with file
 *   - `dotfiles` serve dotfiles, defaulting to false; can be `"allow"` to send them
 *
 * Other options are passed along to `send`.
 *
 * Examples:
 *
 *  The following example illustrates how `res.sendfile()` may
 *  be used as an alternative for the `static()` middleware for
 *  dynamic situations. The code backing `res.sendfile()` is actually
 *  the same code, so HTTP cache support etc is identical.
 *
 *     app.get('/user/:uid/photos/:file', function(req, res){
 *       var uid = req.params.uid
 *         , file = req.params.file;
 *
 *       req.user.mayViewFilesFrom(uid, function(yes){
 *         if (yes) {
 *           res.sendfile('/uploads/' + uid + '/' + file);
 *         } else {
 *           res.send(403, 'Sorry! you cant see that.');
 *         }
 *       });
 *     });
 *
 * @public
 */

res.sendfile = function (path, options, callback) {
  var done = callback;
  var req = this.req;
  var res = this;
  var next = req.next;
  var opts = options || {};

  // support function as second arg
  if (typeof options === 'function') {
    done = options;
    opts = {};
  }

  // create file stream
  var file = send(req, path, opts);

  // transfer
  sendfile(res, file, opts, function (err) {
    if (done) return done(err);
    if (err && err.code === 'EISDIR') return next();

    // next() all but write errors
    if (err && err.code !== 'ECONNABORTED' && err.syscall !== 'write') {
      next(err);
    }
  });
};

res.sendfile = deprecate.function(res.sendfile,
  'res.sendfile: Use res.sendFile instead');

/**
 * Transfer the file at the given `path` as an attachment.
 *
 * Optionally providing an alternate attachment `filename`,
 * and optional callback `callback(err)`. The callback is invoked
 * when the data transfer is complete, or when an error has
 * occurred. Be sure to check `res.headersSent` if you plan to respond.
 *
 * Optionally providing an `options` object to use with `res.sendFile()`.
 * This function will set the `Content-Disposition` header, overriding
 * any `Content-Disposition` header passed as header options in order
 * to set the attachment and filename.
 *
 * This method uses `res.sendFile()`.
 *
 * @public
 */

res.download = function download (path, filename, options, callback) {
  var done = callback;
  var name = filename;
  var opts = options || null

  // support function as second or third arg
  if (typeof filename === 'function') {
    done = filename;
    name = null;
    opts = null
  } else if (typeof options === 'function') {
    done = options
    opts = null
  }

  // support optional filename, where options may be in it's place
  if (typeof filename === 'object' &&
    (typeof options === 'function' || options === undefined)) {
    name = null
    opts = filename
  }

  // set Content-Disposition when file is sent
  var headers = {
    'Content-Disposition': contentDisposition(name || path)
  };

  // merge user-provided headers
  if (opts && opts.headers) {
    var keys = Object.keys(opts.headers)
    for (var i = 0; i < keys.length; i++) {
      var key = keys[i]
      if (key.toLowerCase() !== 'content-disposition') {
        headers[key] = opts.headers[key]
      }
    }
  }

  // merge user-provided options
  opts = Object.create(opts)
  opts.headers = headers

  // Resolve the full path for sendFile
  var fullPath = !opts.root
    ? resolve(path)
    : path

  // send file
  return this.sendFile(fullPath, opts, done)
};

/**
 * Set _Content-Type_ response header with `type` through `mime.lookup()`
 * when it does not contain "/", or set the Content-Type to `type` otherwise.
 *
 * Examples:
 *
 *     res.type('.html');
 *     res.type('html');
 *     res.type('json');
 *     res.type('application/json');
 *     res.type('png');
 *
 * @param {String} type
 * @return {ServerResponse} for chaining
 * @public
 */

res.contentType =
res.type = function contentType(type) {
  var ct = type.indexOf('/') === -1
    ? mime.lookup(type)
    : type;

  return this.set('Content-Type', ct);
};

/**
 * Respond to the Acceptable formats using an `obj`
 * of mime-type callbacks.
 *
 * This method uses `req.accepted`, an array of
 * acceptable types ordered by their quality values.
 * When "Accept" is not present the _first_ callback
 * is invoked, otherwise the first match is used. When
 * no match is performed the server responds with
 * 406 "Not Acceptable".
 *
 * Content-Type is set for you, however if you choose
 * you may alter this within the callback using `res.type()`
 * or `res.set('Content-Type', ...)`.
 *
 *    res.format({
 *      'text/plain': function(){
 *        res.send('hey');
 *      },
 *
 *      'text/html': function(){
 *        res.send('<p>hey</p>');
 *      },
 *
 *      'application/json': function () {
 *        res.send({ message: 'hey' });
 *      }
 *    });
 *
 * In addition to canonicalized MIME types you may
 * also use extnames mapped to these types:
 *
 *    res.format({
 *      text: function(){
 *        res.send('hey');
 *      },
 *
 *      html: function(){
 *        res.send('<p>hey</p>');
 *      },
 *
 *      json: function(){
 *        res.send({ message: 'hey' });
 *      }
 *    });
 *
 * By default Express passes an `Error`
 * with a `.status` of 406 to `next(err)`
 * if a match is not made. If you provide
 * a `.default` callback it will be invoked
 * instead.
 *
 * @param {Object} obj
 * @return {ServerResponse} for chaining
 * @public
 */

res.format = function(obj){
  var req = this.req;
  var next = req.next;

  var keys = Object.keys(obj)
    .filter(function (v) { return v !== 'default' })

  var key = keys.length > 0
    ? req.accepts(keys)
    : false;

  this.vary("Accept");

  if (key) {
    this.set('Content-Type', normalizeType(key).value);
    obj[key](req, this, next);
  } else if (obj.default) {
    obj.default(req, this, next)
  } else {
    next(createError(406, {
      types: normalizeTypes(keys).map(function (o) { return o.value })
    }))
  }

  return this;
};

/**
 * Set _Content-Disposition_ header to _attachment_ with optional `filename`.
 *
 * @param {String} filename
 * @return {ServerResponse}
 * @public
 */

res.attachment = function attachment(filename) {
  if (filename) {
    this.type(extname(filename));
  }

  this.set('Content-Disposition', contentDisposition(filename));

  return this;
};

/**
 * Append additional header `field` with value `val`.
 *
 * Example:
 *
 *    res.append('Link', ['<http://localhost/>', '<http://localhost:3000/>']);
 *    res.append('Set-Cookie', 'foo=bar; Path=/; HttpOnly');
 *    res.append('Warning', '199 Miscellaneous warning');
 *
 * @param {String} field
 * @param {String|Array} val
 * @return {ServerResponse} for chaining
 * @public
 */

res.append = function append(field, val) {
  var prev = this.get(field);
  var value = val;

  if (prev) {
    // concat the new and prev vals
    value = Array.isArray(prev) ? prev.concat(val)
      : Array.isArray(val) ? [prev].concat(val)
        : [prev, val]
  }

  return this.set(field, value);
};

/**
 * Set header `field` to `val`, or pass
 * an object of header fields.
 *
 * Examples:
 *
 *    res.set('Foo', ['bar', 'baz']);
 *    res.set('Accept', 'application/json');
 *    res.set({ Accept: 'text/plain', 'X-API-Key': 'tobi' });
 *
 * Aliased as `res.header()`.
 *
 * @param {String|Object} field
 * @param {String|Array} val
 * @return {ServerResponse} for chaining
 * @public
 */

res.set =
res.header = function header(field, val) {
  if (arguments.length === 2) {
    var value = Array.isArray(val)
      ? val.map(String)
      : String(val);

    // add charset to content-type
    if (field.toLowerCase() === 'content-type') {
      if (Array.isArray(value)) {
        throw new TypeError('Content-Type cannot be set to an Array');
      }
      if (!charsetRegExp.test(value)) {
        var charset = mime.charsets.lookup(value.split(';')[0]);
        if (charset) value += '; charset=' + charset.toLowerCase();
      }
    }

    this.setHeader(field, value);
  } else {
    for (var key in field) {
      this.set(key, field[key]);
    }
  }
  return this;
};

/**
 * Get value for header `field`.
 *
 * @param {String} field
 * @return {String}
 * @public
 */

res.get = function(field){
  return this.getHeader(field);
};

/**
 * Clear cookie `name`.
 *
 * @param {String} name
 * @param {Object} [options]
 * @return {ServerResponse} for chaining
 * @public
 */

res.clearCookie = function clearCookie(name, options) {
  var opts = merge({ expires: new Date(1), path: '/' }, options);

  return this.cookie(name, '', opts);
};

/**
 * Set cookie `name` to `value`, with the given `options`.
 *
 * Options:
 *
 *    - `maxAge`   max-age in milliseconds, converted to `expires`
 *    - `signed`   sign the cookie
 *    - `path`     defaults to "/"
 *
 * Examples:
 *
 *    // "Remember Me" for 15 minutes
 *    res.cookie('rememberme', '1', { expires: new Date(Date.now() + 900000), httpOnly: true });
 *
 *    // same as above
 *    res.cookie('rememberme', '1', { maxAge: 900000, httpOnly: true })
 *
 * @param {String} name
 * @param {String|Object} value
 * @param {Object} [options]
 * @return {ServerResponse} for chaining
 * @public
 */

res.cookie = function (name, value, options) {
  var opts = merge({}, options);
  var secret = this.req.secret;
  var signed = opts.signed;

  if (signed && !secret) {
    throw new Error('cookieParser("secret") required for signed cookies');
  }

  var val = typeof value === 'object'
    ? 'j:' + JSON.stringify(value)
    : String(value);

  if (signed) {
    val = 's:' + sign(val, secret);
  }

  if (opts.maxAge != null) {
    var maxAge = opts.maxAge - 0

    if (!isNaN(maxAge)) {
      opts.expires = new Date(Date.now() + maxAge)
      opts.maxAge = Math.floor(maxAge / 1000)
    }
  }

  if (opts.path == null) {
    opts.path = '/';
  }

  this.append('Set-Cookie', cookie.serialize(name, String(val), opts));

  return this;
};

/**
 * Set the location header to `url`.
 *
 * The given `url` can also be "back", which redirects
 * to the _Referrer_ or _Referer_ headers or "/".
 *
 * Examples:
 *
 *    res.location('/foo/bar').;
 *    res.location('http://example.com');
 *    res.location('../login');
 *
 * @param {String} url
 * @return {ServerResponse} for chaining
 * @public
 */

res.location = function location(url) {
  var loc = url;

  // "back" is an alias for the referrer
  if (url === 'back') {
    loc = this.req.get('Referrer') || '/';
  }

  // set location
  return this.set('Location', encodeUrl(loc));
};

/**
 * Redirect to the given `url` with optional response `status`
 * defaulting to 302.
 *
 * The resulting `url` is determined by `res.location()`, so
 * it will play nicely with mounted apps, relative paths,
 * `"back"` etc.
 *
 * Examples:
 *
 *    res.redirect('/foo/bar');
 *    res.redirect('http://example.com');
 *    res.redirect(301, 'http://example.com');
 *    res.redirect('../login'); // /blog/post/1 -> /blog/login
 *
 * @public
 */

res.redirect = function redirect(url) {
  var address = url;
  var body;
  var status = 302;

  // allow status / url
  if (arguments.length === 2) {
    if (typeof arguments[0] === 'number') {
      status = arguments[0];
      address = arguments[1];
    } else {
      deprecate('res.redirect(url, status): Use res.redirect(status, url) instead');
      status = arguments[1];
    }
  }

  // Set location header
  address = this.location(address).get('Location');

  // Support text/{plain,html} by default
  this.format({
    text: function(){
      body = statuses.message[status] + '. Redirecting to ' + address
    },

    html: function(){
      var u = escapeHtml(address);
      body = '<p>' + statuses.message[status] + '. Redirecting to <a href="' + u + '">' + u + '</a></p>'
    },

    default: function(){
      body = '';
    }
  });

  // Respond
  this.statusCode = status;
  this.set('Content-Length', Buffer.byteLength(body));

  if (this.req.method === 'HEAD') {
    this.end();
  } else {
    this.end(body);
  }
};

/**
 * Add `field` to Vary. If already present in the Vary set, then
 * this call is simply ignored.
 *
 * @param {Array|String} field
 * @return {ServerResponse} for chaining
 * @public
 */

res.vary = function(field){
  // checks for back-compat
  if (!field || (Array.isArray(field) && !field.length)) {
    deprecate('res.vary(): Provide a field name');
    return this;
  }

  vary(this, field);

  return this;
};

/**
 * Render `view` with the given `options` and optional callback `fn`.
 * When a callback function is given a response will _not_ be made
 * automatically, otherwise a response of _200_ and _text/html_ is given.
 *
 * Options:
 *
 *  - `cache`     boolean hinting to the engine it should cache
 *  - `filename`  filename of the view being rendered
 *
 * @public
 */

res.render = function render(view, options, callback) {
  var app = this.req.app;
  var done = callback;
  var opts = options || {};
  var req = this.req;
  var self = this;

  // support callback function as second arg
  if (typeof options === 'function') {
    done = options;
    opts = {};
  }

  // merge res.locals
  opts._locals = self.locals;

  // default callback to respond
  done = done || function (err, str) {
    if (err) return req.next(err);
    self.send(str);
  };

  // render
  app.render(view, opts, done);
};

// pipe the send file stream
function sendfile(res, file, options, callback) {
  var done = false;
  var streaming;

  // request aborted
  function onaborted() {
    if (done) return;
    done = true;

    var err = new Error('Request aborted');
    err.code = 'ECONNABORTED';
    callback(err);
  }

  // directory
  function ondirectory() {
    if (done) return;
    done = true;

    var err = new Error('EISDIR, read');
    err.code = 'EISDIR';
    callback(err);
  }

  // errors
  function onerror(err) {
    if (done) return;
    done = true;
    callback(err);
  }

  // ended
  function onend() {
    if (done) return;
    done = true;
    callback();
  }

  // file
  function onfile() {
    streaming = false;
  }

  // finished
  function onfinish(err) {
    if (err && err.code === 'ECONNRESET') return onaborted();
    if (err) return onerror(err);
    if (done) return;

    setImmediate(function () {
      if (streaming !== false && !done) {
        onaborted();
        return;
      }

      if (done) return;
      done = true;
      callback();
    });
  }

  // streaming
  function onstream() {
    streaming = true;
  }

  file.on('directory', ondirectory);
  file.on('end', onend);
  file.on('error', onerror);
  file.on('file', onfile);
  file.on('stream', onstream);
  onFinished(res, onfinish);

  if (options.headers) {
    // set headers on successful transfer
    file.on('headers', function headers(res) {
      var obj = options.headers;
      var keys = Object.keys(obj);

      for (var i = 0; i < keys.length; i++) {
        var k = keys[i];
        res.setHeader(k, obj[k]);
      }
    });
  }

  // pipe
  file.pipe(res);
}

/**
 * Stringify JSON, like JSON.stringify, but v8 optimized, with the
 * ability to escape characters that can trigger HTML sniffing.
 *
 * @param {*} value
 * @param {function} replacer
 * @param {number} spaces
 * @param {boolean} escape
 * @returns {string}
 * @private
 */

function stringify (value, replacer, spaces, escape) {
  // v8 checks arguments.length for optimizing simple call
  // https://bugs.chromium.org/p/v8/issues/detail?id=4730
  var json = replacer || spaces
    ? JSON.stringify(value, replacer, spaces)
    : JSON.stringify(value);

  if (escape && typeof json === 'string') {
    json = json.replace(/[<>&]/g, function (c) {
      switch (c.charCodeAt(0)) {
        case 0x3c:
          return '\\u003c'
        case 0x3e:
          return '\\u003e'
        case 0x26:
          return '\\u0026'
        /* istanbul ignore next: unreachable default */
        default:
          return c
      }
    })
  }

  return json
}