159 lines
3.2 KiB
JavaScript
159 lines
3.2 KiB
JavaScript
/**
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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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var contentType = require('content-type');
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var parseAccept = require('./accept');
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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 = preferredLanguages;
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module.exports.preferredLanguages = preferredLanguages;
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/**
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* Module variables.
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* @private
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*/
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function parseAcceptLanguage(accept) {
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var accepts = parseAccept(accept);
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for (var i = 0, j = 0; i < accepts.length; i++) {
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var language = formatLanguage(accepts[i], i);
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if (language) accepts[j++] = language;
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}
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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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* Format a parsed language for negotiation.
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* @private
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*/
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function formatLanguage(parsed, i) {
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if (!parsed.type) return null;
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var hyphen = parsed.type.indexOf('-');
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var prefix = hyphen === -1 ? parsed.type : parsed.type.slice(0, hyphen);
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var suffix = hyphen === -1 ? undefined : parsed.type.slice(hyphen + 1);
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return {
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prefix: prefix,
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suffix: suffix,
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q: parsed.parameters.q ? parseFloat(parsed.parameters.q) : 1,
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i: i,
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full: parsed.type
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};
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}
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/**
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* Get the priority of a language.
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* @private
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*/
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function getLanguagePriority(language, 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(language, 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 language.
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* @private
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*/
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function specify(language, spec, index) {
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var p = formatLanguage(contentType.parse(language), 0)
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if (!p) return null;
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var s = 0;
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if(spec.full.toLowerCase() === p.full.toLowerCase()){
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s |= 4;
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} else if (spec.prefix.toLowerCase() === p.full.toLowerCase()) {
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s |= 2;
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} else if (spec.full.toLowerCase() === p.prefix.toLowerCase()) {
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s |= 1;
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} else if (spec.full !== '*' ) {
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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 languages from an Accept-Language header.
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* @public
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*/
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function preferredLanguages(accept, provided) {
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// RFC 2616 sec 14.4: no header = *
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var accepts = parseAcceptLanguage(accept === undefined ? '*' : accept || '');
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if (!provided) {
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// sorted list of all languages
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return accepts
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.filter(isQuality)
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.sort(compareSpecs)
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.map(getFullLanguage);
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}
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var priorities = provided.map(function getPriority(type, index) {
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return getLanguagePriority(type, accepts, index);
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});
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// sorted list of accepted languages
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return priorities.filter(isQuality).sort(compareSpecs).map(function getLanguage(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 language string.
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* @private
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*/
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function getFullLanguage(spec) {
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return spec.full;
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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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