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