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