strata/lib/header/accept-language.js

A modular, streaming HTTP server

var util = require('util');
var utils = require('../utils');
var Header = require('../header');
var Accept = require('./accept');

module.exports = AcceptLanguage;

/**
 * Represents an HTTP Accept-Language header according to the HTTP 1.1
 * specification, and provides several convenience methods for determining
 * acceptable content languages.
 *
 * http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3
 */
function AcceptLanguage(value) {
  if (!(this instanceof AcceptLanguage)) {
    return new AcceptLanguage(value);
  }

  Header.call(this, 'Accept-Language', value);
}

util.inherits(AcceptLanguage, Header);

AcceptLanguage.prototype.qvalues = Accept.prototype.qvalues;
AcceptLanguage.prototype.values = Accept.prototype.values;
AcceptLanguage.prototype.accept = Accept.prototype.accept;

/**
 * Determines the quality factor (qvalue) of the given language.
 */
AcceptLanguage.prototype.qvalue = function (language) {
  var qvalues = this.qvalues();

  if (utils.isEmptyObject(qvalues)) {
    return 1;
  }

  var matches = this.matches(language);

  if (matches.length == 0) {
    return 0;
  }

  return Accept.normalizeQvalue(qvalues[matches[0]]);
};

/**
 * Returns an array of languages from this header that match the given
 * language, ordered by precedence.
 */
AcceptLanguage.prototype.matches = function (language) {
  return this.values().filter(function (value) {
    if (value == language || value == '*') {
      return true;
    }

    var match = language.match(/^(.+?)-/);

    return match && value == match[1];
  }).sort(function (a, b) {
    // "*" gets least precedence, all others are compared by length.
    return a == '*' ? -1 : (b == '*' ? 1 : utils.compareLength(a, b));
  }).reverse();
};