/**
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* negotiator
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* Copyright(c) 2012 Isaac Z. Schlueter
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* Copyright(c) 2014 Federico Romero
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* Copyright(c) 2014-2015 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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* @public
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*/
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module.exports = preferredCharsets;
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module.exports.preferredCharsets = preferredCharsets;
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/**
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* Module variables.
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* @private
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*/
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var simpleCharsetRegExp = /^\s*([^\s;]+)\s*(?:;(.*))?$/;
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/**
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* Parse the Accept-Charset header.
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* @private
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*/
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function parseAcceptCharset(accept) {
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var accepts = accept.split(',');
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for (var i = 0, j = 0; i < accepts.length; i++) {
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var charset = parseCharset(accepts[i].trim(), i);
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if (charset) {
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accepts[j++] = charset;
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}
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}
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// trim accepts
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accepts.length = j;
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return accepts;
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}
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/**
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* Parse a charset from the Accept-Charset header.
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* @private
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*/
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function parseCharset(str, i) {
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var match = simpleCharsetRegExp.exec(str);
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if (!match) return null;
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var charset = match[1];
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var q = 1;
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if (match[2]) {
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var params = match[2].split(';')
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for (var j = 0; j < params.length; j++) {
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var p = params[j].trim().split('=');
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if (p[0] === 'q') {
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q = parseFloat(p[1]);
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break;
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}
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}
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}
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return {
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charset: charset,
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q: q,
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i: i
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};
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}
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/**
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* Get the priority of a charset.
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* @private
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*/
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function getCharsetPriority(charset, accepted, index) {
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var priority = {o: -1, q: 0, s: 0};
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for (var i = 0; i < accepted.length; i++) {
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var spec = specify(charset, accepted[i], index);
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if (spec && (priority.s - spec.s || priority.q - spec.q || priority.o - spec.o) < 0) {
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priority = spec;
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}
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}
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return priority;
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}
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/**
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* Get the specificity of the charset.
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* @private
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*/
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function specify(charset, spec, index) {
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var s = 0;
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if(spec.charset.toLowerCase() === charset.toLowerCase()){
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s |= 1;
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} else if (spec.charset !== '*' ) {
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return null
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}
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return {
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i: index,
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o: spec.i,
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q: spec.q,
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s: s
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}
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}
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/**
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* Get the preferred charsets from an Accept-Charset header.
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* @public
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*/
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function preferredCharsets(accept, provided) {
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// RFC 2616 sec 14.2: no header = *
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var accepts = parseAcceptCharset(accept === undefined ? '*' : accept || '');
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if (!provided) {
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// sorted list of all charsets
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return accepts
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.filter(isQuality)
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.sort(compareSpecs)
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.map(getFullCharset);
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}
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var priorities = provided.map(function getPriority(type, index) {
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return getCharsetPriority(type, accepts, index);
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});
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// sorted list of accepted charsets
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return priorities.filter(isQuality).sort(compareSpecs).map(function getCharset(priority) {
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return provided[priorities.indexOf(priority)];
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});
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}
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/**
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* Compare two specs.
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* @private
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*/
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function compareSpecs(a, b) {
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return (b.q - a.q) || (b.s - a.s) || (a.o - b.o) || (a.i - b.i) || 0;
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}
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/**
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* Get full charset string.
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* @private
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*/
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function getFullCharset(spec) {
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return spec.charset;
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}
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/**
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* Check if a spec has any quality.
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* @private
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*/
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function isQuality(spec) {
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return spec.q > 0;
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}
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