twitst4tz

twitter statistics web application
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index.js (2930B)

      1 /*!
      2  * vary
      3  * Copyright(c) 2014-2017 Douglas Christopher Wilson
      4  * MIT Licensed
      5  */
      6 
      7 'use strict'
      8 
      9 /**
     10  * Module exports.
     11  */
     12 
     13 module.exports = vary
     14 module.exports.append = append
     15 
     16 /**
     17  * RegExp to match field-name in RFC 7230 sec 3.2
     18  *
     19  * field-name    = token
     20  * token         = 1*tchar
     21  * tchar         = "!" / "#" / "$" / "%" / "&" / "'" / "*"
     22  *               / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
     23  *               / DIGIT / ALPHA
     24  *               ; any VCHAR, except delimiters
     25  */
     26 
     27 var FIELD_NAME_REGEXP = /^[!#$%&'*+\-.^_`|~0-9A-Za-z]+$/
     28 
     29 /**
     30  * Append a field to a vary header.
     31  *
     32  * @param {String} header
     33  * @param {String|Array} field
     34  * @return {String}
     35  * @public
     36  */
     37 
     38 function append (header, field) {
     39   if (typeof header !== 'string') {
     40     throw new TypeError('header argument is required')
     41   }
     42 
     43   if (!field) {
     44     throw new TypeError('field argument is required')
     45   }
     46 
     47   // get fields array
     48   var fields = !Array.isArray(field)
     49     ? parse(String(field))
     50     : field
     51 
     52   // assert on invalid field names
     53   for (var j = 0; j < fields.length; j++) {
     54     if (!FIELD_NAME_REGEXP.test(fields[j])) {
     55       throw new TypeError('field argument contains an invalid header name')
     56     }
     57   }
     58 
     59   // existing, unspecified vary
     60   if (header === '*') {
     61     return header
     62   }
     63 
     64   // enumerate current values
     65   var val = header
     66   var vals = parse(header.toLowerCase())
     67 
     68   // unspecified vary
     69   if (fields.indexOf('*') !== -1 || vals.indexOf('*') !== -1) {
     70     return '*'
     71   }
     72 
     73   for (var i = 0; i < fields.length; i++) {
     74     var fld = fields[i].toLowerCase()
     75 
     76     // append value (case-preserving)
     77     if (vals.indexOf(fld) === -1) {
     78       vals.push(fld)
     79       val = val
     80         ? val + ', ' + fields[i]
     81         : fields[i]
     82     }
     83   }
     84 
     85   return val
     86 }
     87 
     88 /**
     89  * Parse a vary header into an array.
     90  *
     91  * @param {String} header
     92  * @return {Array}
     93  * @private
     94  */
     95 
     96 function parse (header) {
     97   var end = 0
     98   var list = []
     99   var start = 0
    100 
    101   // gather tokens
    102   for (var i = 0, len = header.length; i < len; i++) {
    103     switch (header.charCodeAt(i)) {
    104       case 0x20: /*   */
    105         if (start === end) {
    106           start = end = i + 1
    107         }
    108         break
    109       case 0x2c: /* , */
    110         list.push(header.substring(start, end))
    111         start = end = i + 1
    112         break
    113       default:
    114         end = i + 1
    115         break
    116     }
    117   }
    118 
    119   // final token
    120   list.push(header.substring(start, end))
    121 
    122   return list
    123 }
    124 
    125 /**
    126  * Mark that a request is varied on a header field.
    127  *
    128  * @param {Object} res
    129  * @param {String|Array} field
    130  * @public
    131  */
    132 
    133 function vary (res, field) {
    134   if (!res || !res.getHeader || !res.setHeader) {
    135     // quack quack
    136     throw new TypeError('res argument is required')
    137   }
    138 
    139   // get existing header
    140   var val = res.getHeader('Vary') || ''
    141   var header = Array.isArray(val)
    142     ? val.join(', ')
    143     : String(val)
    144 
    145   // set new header
    146   if ((val = append(header, field))) {
    147     res.setHeader('Vary', val)
    148   }
    149 }