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- 'use strict';
- module.exports = preferredLanguages;
- module.exports.preferredLanguages = preferredLanguages;
- var simpleLanguageRegExp = /^\s*([^\s\-;]+)(?:-([^\s;]+))?\s*(?:;(.*))?$/;
- function parseAcceptLanguage(accept) {
- var accepts = accept.split(',');
- for (var i = 0, j = 0; i < accepts.length; i++) {
- var language = parseLanguage(accepts[i].trim(), i);
- if (language) {
- accepts[j++] = language;
- }
- }
-
- accepts.length = j;
- return accepts;
- }
- function parseLanguage(str, i) {
- var match = simpleLanguageRegExp.exec(str);
- if (!match) return null;
- var prefix = match[1]
- var suffix = match[2]
- var full = prefix
- if (suffix) full += "-" + suffix;
- var q = 1;
- if (match[3]) {
- var params = match[3].split(';')
- for (var j = 0; j < params.length; j++) {
- var p = params[j].split('=');
- if (p[0] === 'q') q = parseFloat(p[1]);
- }
- }
- return {
- prefix: prefix,
- suffix: suffix,
- q: q,
- i: i,
- full: full
- };
- }
- function getLanguagePriority(language, accepted, index) {
- var priority = {o: -1, q: 0, s: 0};
- for (var i = 0; i < accepted.length; i++) {
- var spec = specify(language, accepted[i], index);
- if (spec && (priority.s - spec.s || priority.q - spec.q || priority.o - spec.o) < 0) {
- priority = spec;
- }
- }
- return priority;
- }
- function specify(language, spec, index) {
- var p = parseLanguage(language)
- if (!p) return null;
- var s = 0;
- if(spec.full.toLowerCase() === p.full.toLowerCase()){
- s |= 4;
- } else if (spec.prefix.toLowerCase() === p.full.toLowerCase()) {
- s |= 2;
- } else if (spec.full.toLowerCase() === p.prefix.toLowerCase()) {
- s |= 1;
- } else if (spec.full !== '*' ) {
- return null
- }
- return {
- i: index,
- o: spec.i,
- q: spec.q,
- s: s
- }
- };
- function preferredLanguages(accept, provided) {
-
- var accepts = parseAcceptLanguage(accept === undefined ? '*' : accept || '');
- if (!provided) {
-
- return accepts
- .filter(isQuality)
- .sort(compareSpecs)
- .map(getFullLanguage);
- }
- var priorities = provided.map(function getPriority(type, index) {
- return getLanguagePriority(type, accepts, index);
- });
-
- return priorities.filter(isQuality).sort(compareSpecs).map(function getLanguage(priority) {
- return provided[priorities.indexOf(priority)];
- });
- }
- function compareSpecs(a, b) {
- return (b.q - a.q) || (b.s - a.s) || (a.o - b.o) || (a.i - b.i) || 0;
- }
- function getFullLanguage(spec) {
- return spec.full;
- }
- function isQuality(spec) {
- return spec.q > 0;
- }
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