/*!
* vary
* Copyright(c) 2014-2017 Douglas Christopher Wilson
* MIT Licensed
*/
'use strict'
/**
* Module exports.
*/
module.exports = vary
module.exports.append = append
/**
* RegExp to match field-name in RFC 7230 sec 3.2
*
* field-name = token
* token = 1*tchar
* tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
* / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
* / DIGIT / ALPHA
* ; any VCHAR, except delimiters
*/
var FIELD_NAME_REGEXP = /^[!#$%&'*+\-.^_`|~0-9A-Za-z]+$/
/**
* Append a field to a vary header.
*
* @param {String} header
* @param {String|Array} field
* @return {String}
* @public
*/
function append (header, field) {
if (typeof header !== 'string') {
throw new TypeError('header argument is required')
}
if (!field) {
throw new TypeError('field argument is required')
}
// get fields array
var fields = !Array.isArray(field)
? parse(String(field))
: field
// assert on invalid field names
for (var j = 0; j < fields.length; j++) {
if (!FIELD_NAME_REGEXP.test(fields[j])) {
throw new TypeError('field argument contains an invalid header name')
}
}
// existing, unspecified vary
if (header === '*') {
return header
}
// enumerate current values
var val = header
var vals = parse(header.toLowerCase())
// unspecified vary
if (fields.indexOf('*') !== -1 || vals.indexOf('*') !== -1) {
return '*'
}
for (var i = 0; i < fields.length; i++) {
var fld = fields[i].toLowerCase()
// append value (case-preserving)
if (vals.indexOf(fld) === -1) {
vals.push(fld)
val = val
? val + ', ' + fields[i]
: fields[i]
}
}
return val
}
/**
* Parse a vary header into an array.
*
* @param {String} header
* @return {Array}
* @private
*/
function parse (header) {
var end = 0
var list = []
var start = 0
// gather tokens
for (var i = 0, len = header.length; i < len; i++) {
switch (header.charCodeAt(i)) {
case 0x20: /* */
if (start === end) {
start = end = i + 1
}
break
case 0x2c: /* , */
list.push(header.substring(start, end))
start = end = i + 1
break
default:
end = i + 1
break
}
}
// final token
list.push(header.substring(start, end))
return list
}
/**
* Mark that a request is varied on a header field.
*
* @param {Object} res
* @param {String|Array} field
* @public
*/
function vary (res, field) {
if (!res || !res.getHeader || !res.setHeader) {
// quack quack
throw new TypeError('res argument is required')
}
// get existing header
var val = res.getHeader('Vary') || ''
var header = Array.isArray(val)
? val.join(', ')
: String(val)
// set new header
if ((val = append(header, field))) {
res.setHeader('Vary', val)
}
}