mach/lib/headers/AcceptEncoding.js

HTTP for JavaScript

"use strict";

var _prototypeProperties = function (child, staticProps, instanceProps) { if (staticProps) Object.defineProperties(child, staticProps); if (instanceProps) Object.defineProperties(child.prototype, instanceProps); };

var _get = function get(object, property, receiver) { var desc = Object.getOwnPropertyDescriptor(object, property); if (desc === undefined) { var parent = Object.getPrototypeOf(object); if (parent === null) { return undefined; } else { return get(parent, property, receiver); } } else if ("value" in desc && desc.writable) { return desc.value; } else { var getter = desc.get; if (getter === undefined) { return undefined; } return getter.call(receiver); } };

var _inherits = function (subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) subClass.__proto__ = superClass; };

var _classCallCheck = function (instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } };

var parseMediaValue = require("../utils/parseMediaValue");
var parseMediaValues = require("../utils/parseMediaValues");
var qualityFactorForMediaValue = require("../utils/qualityFactorForMediaValue");
var stringifyMediaValues = require("../utils/stringifyMediaValues");
var Header = require("../Header");

function byHighestPrecedence(a, b) {
  // "*" gets least precedence, all others are equal
  return a === "*" ? -1 : b === "*" ? 1 : 0;
}

/**
 * Represents an HTTP Accept-Encoding header and provides several methods
 * for determining acceptable content encodings.
 *
 * http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3
 */

var AcceptEncoding = (function (Header) {
  function AcceptEncoding(value) {
    _classCallCheck(this, AcceptEncoding);

    _get(Object.getPrototypeOf(AcceptEncoding.prototype), "constructor", this).call(this, "Accept-Encoding", value);
  }

  _inherits(AcceptEncoding, Header);

  _prototypeProperties(AcceptEncoding, null, {
    value: {

      /**
       * Returns the value of this header as a string.
       */

      get: function () {
        return stringifyMediaValues(this._mediaValues) || "";
      },
      set: function (value) {
        this._mediaValues = value ? parseMediaValues(value) : [];
      },
      configurable: true
    },
    accepts: {

      /**
       * Returns true if the given encoding is acceptable.
       */

      value: function accepts(encoding) {
        return this.qualityFactorForEncoding(encoding) !== 0;
      },
      writable: true,
      configurable: true
    },
    qualityFactorForEncoding: {

      /**
       * Returns the quality factor for the given encoding.
       */

      value: function qualityFactorForEncoding(encoding) {
        var values = this._mediaValues;

        var givenValue = parseMediaValue(encoding);
        var matchingValues = values.filter(function (value) {
          if (value.type === "*") return true;

          return value.type === givenValue.type;
        }).sort(byHighestPrecedence);

        // From RFC 2616:
        // The "identity" content-coding is always acceptable, unless
        // specifically refused because the Accept-Encoding field includes
        // "identity;q=0", or because the field includes "*;q=0" and does
        // not explicitly include the "identity" content-coding. If the
        // Accept-Encoding field-value is empty, then only the "identity"
        // encoding is acceptable.
        if (givenValue.type === "identity") {
          if (matchingValues.length && matchingValues[0].type === "identity") {
            return qualityFactorForMediaValue(matchingValues[0]);
          }return 1;
        }

        if (!matchingValues.length) {
          return 0;
        }return qualityFactorForMediaValue(matchingValues[0]);
      },
      writable: true,
      configurable: true
    }
  });

  return AcceptEncoding;
})(Header);

module.exports = AcceptEncoding;