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module.exports = preferredLanguages;
preferredLanguages.preferredLanguages = preferredLanguages;
function parseAcceptLanguage(accept) {
return accept.split(',').map(function(e, i) {
return parseLanguage(e.trim(), i);
}).filter(function(e) {
return e;
});
}
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) {
return (accepted.map(function(a){
return specify(language, a);
}).filter(Boolean).sort(function (a, b) {
if(a.s == b.s) {
return a.q > b.q ? -1 : 1;
} else {
return a.s > b.s ? -1 : 1;
}
})[0] || {s: 0, q: 0});
}
function specify(language, spec) {
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 {
s: s,
q: spec.q,
}
};
function preferredLanguages(accept, provided) {
// RFC 2616 sec 14.4: no header = *
accept = parseAcceptLanguage(accept === undefined ? '*' : accept || '');
if (provided) {
var ret = provided.map(function(type) {
return [type, getLanguagePriority(type, accept)];
}).filter(function(pair) {
return pair[1].q > 0;
}).sort(function(a, b) {
var pa = a[1];
var pb = b[1];
return (pb.q - pa.q) || (pb.s - pa.s) || (pa.i - pb.i);
}).map(function(pair) {
return pair[0];
});
return ret;
} else {
return accept.sort(function (a, b) {
// revsort
return (b.q - a.q) || (a.i - b.i);
}).filter(function(type) {
return type.q > 0;
}).map(function(type) {
return type.full;
});
}
}
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