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module.exports = preferredLanguages;
preferredLanguages.preferredLanguages = preferredLanguages;
function parseAcceptLanguage(accept) {
var accepts = accept.split(',');
for (var i = 0, j = 0; i < accepts.length; i++) {
var langauge = parseLanguage(accepts[i].trim(), i);
if (langauge) {
accepts[j++] = langauge;
}
}
// trim accepts
accepts.length = j;
return accepts;
}
function parseLanguage(s, i) {
var match = s.match(/^\s*(\S+?)(?:-(\S+?))?\s*(?:;(.*))?$/);
if (!match) return null;
var prefix = match[1],
suffix = match[2],
full = prefix;
if (suffix) full += "-" + suffix;
var q = 1;
if (match[3]) {
var params = match[3].split(';')
for (var i = 0; i < params.length; i ++) {
var p = params[i].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) {
// RFC 2616 sec 14.4: no header = *
var accepts = parseAcceptLanguage(accept === undefined ? '*' : accept || '');
if (!provided) {
// sorted list of all languages
return accepts.filter(isQuality).sort(compareSpecs).map(function getLanguage(spec) {
return spec.full;
});
}
var priorities = provided.map(function getPriority(type, index) {
return getLanguagePriority(type, accepts, index);
});
// sorted list of accepted languages
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 isQuality(spec) {
return spec.q > 0;
}
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