113 lines
2.5 KiB
JavaScript
113 lines
2.5 KiB
JavaScript
module.exports = preferredLanguages;
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preferredLanguages.preferredLanguages = preferredLanguages;
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function parseAcceptLanguage(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 langauge = parseLanguage(accepts[i].trim(), i);
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if (langauge) {
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accepts[j++] = langauge;
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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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function parseLanguage(s, i) {
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var match = s.match(/^\s*(\S+?)(?:-(\S+?))?\s*(?:;(.*))?$/);
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if (!match) return null;
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var prefix = match[1],
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suffix = match[2],
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full = prefix;
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if (suffix) full += "-" + suffix;
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var q = 1;
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if (match[3]) {
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var params = match[3].split(';')
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for (var i = 0; i < params.length; i ++) {
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var p = params[i].split('=');
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if (p[0] === 'q') q = parseFloat(p[1]);
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}
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}
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return {
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prefix: prefix,
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suffix: suffix,
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q: q,
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i: i,
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full: full
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};
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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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function specify(language, spec, index) {
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var p = parseLanguage(language)
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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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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.filter(isQuality).sort(compareSpecs).map(function getLanguage(spec) {
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return spec.full;
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});
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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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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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function isQuality(spec) {
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return spec.q > 0;
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}
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