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1/**2 * negotiator3 * Copyright(c) 2012 Isaac Z. Schlueter4 * Copyright(c) 2014 Federico Romero5 * Copyright(c) 2014-2015 Douglas Christopher Wilson6 * MIT Licensed7 */8 9'use strict';10 11/**12 * Module exports.13 * @public14 */15 16module.exports = preferredLanguages;17module.exports.preferredLanguages = preferredLanguages;18 19/**20 * Module variables.21 * @private22 */23 24var simpleLanguageRegExp = /^\s*([^\s\-;]+)(?:-([^\s;]+))?\s*(?:;(.*))?$/;25 26/**27 * Parse the Accept-Language header.28 * @private29 */30 31function parseAcceptLanguage(accept) {32  var accepts = accept.split(',');33 34  for (var i = 0, j = 0; i < accepts.length; i++) {35    var language = parseLanguage(accepts[i].trim(), i);36 37    if (language) {38      accepts[j++] = language;39    }40  }41 42  // trim accepts43  accepts.length = j;44 45  return accepts;46}47 48/**49 * Parse a language from the Accept-Language header.50 * @private51 */52 53function parseLanguage(str, i) {54  var match = simpleLanguageRegExp.exec(str);55  if (!match) return null;56 57  var prefix = match[1]58  var suffix = match[2]59  var full = prefix60 61  if (suffix) full += "-" + suffix;62 63  var q = 1;64  if (match[3]) {65    var params = match[3].split(';')66    for (var j = 0; j < params.length; j++) {67      var p = params[j].split('=');68      if (p[0] === 'q') q = parseFloat(p[1]);69    }70  }71 72  return {73    prefix: prefix,74    suffix: suffix,75    q: q,76    i: i,77    full: full78  };79}80 81/**82 * Get the priority of a language.83 * @private84 */85 86function getLanguagePriority(language, accepted, index) {87  var priority = {o: -1, q: 0, s: 0};88 89  for (var i = 0; i < accepted.length; i++) {90    var spec = specify(language, accepted[i], index);91 92    if (spec && (priority.s - spec.s || priority.q - spec.q || priority.o - spec.o) < 0) {93      priority = spec;94    }95  }96 97  return priority;98}99 100/**101 * Get the specificity of the language.102 * @private103 */104 105function specify(language, spec, index) {106  var p = parseLanguage(language)107  if (!p) return null;108  var s = 0;109  if(spec.full.toLowerCase() === p.full.toLowerCase()){110    s |= 4;111  } else if (spec.prefix.toLowerCase() === p.full.toLowerCase()) {112    s |= 2;113  } else if (spec.full.toLowerCase() === p.prefix.toLowerCase()) {114    s |= 1;115  } else if (spec.full !== '*' ) {116    return null117  }118 119  return {120    i: index,121    o: spec.i,122    q: spec.q,123    s: s124  }125};126 127/**128 * Get the preferred languages from an Accept-Language header.129 * @public130 */131 132function preferredLanguages(accept, provided) {133  // RFC 2616 sec 14.4: no header = *134  var accepts = parseAcceptLanguage(accept === undefined ? '*' : accept || '');135 136  if (!provided) {137    // sorted list of all languages138    return accepts139      .filter(isQuality)140      .sort(compareSpecs)141      .map(getFullLanguage);142  }143 144  var priorities = provided.map(function getPriority(type, index) {145    return getLanguagePriority(type, accepts, index);146  });147 148  // sorted list of accepted languages149  return priorities.filter(isQuality).sort(compareSpecs).map(function getLanguage(priority) {150    return provided[priorities.indexOf(priority)];151  });152}153 154/**155 * Compare two specs.156 * @private157 */158 159function compareSpecs(a, b) {160  return (b.q - a.q) || (b.s - a.s) || (a.o - b.o) || (a.i - b.i) || 0;161}162 163/**164 * Get full language string.165 * @private166 */167 168function getFullLanguage(spec) {169  return spec.full;170}171 172/**173 * Check if a spec has any quality.174 * @private175 */176 177function isQuality(spec) {178  return spec.q > 0;179}180