// Copyright 2010 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * @fileoverview Interface for a factory for creating XMLHttpRequest objects
 * and metadata about them.
 * @author dbk@google.com (David Barrett-Kahn)
 */

goog.provide('goog.net.XmlHttpFactory');



/**
 * Abstract base class for an XmlHttpRequest factory.
 * @constructor
 */
goog.net.XmlHttpFactory = function() {
};


/**
 * Cache of options - we only actually call internalGetOptions once.
 * @type {Object}
 * @private
 */
goog.net.XmlHttpFactory.prototype.cachedOptions_ = null;


/**
 * @return {!(XMLHttpRequest|GearsHttpRequest)} A new XMLHttpRequest instance.
 */
goog.net.XmlHttpFactory.prototype.createInstance = goog.abstractMethod;


/**
 * @return {Object} Options describing how xhr objects obtained from this
 *     factory should be used.
 */
goog.net.XmlHttpFactory.prototype.getOptions = function() {
  return this.cachedOptions_ ||
      (this.cachedOptions_ = this.internalGetOptions());
};


/**
 * Override this method in subclasses to preserve the caching offered by
 * getOptions().
 * @return {Object} Options describing how xhr objects obtained from this
 *     factory should be used.
 * @protected
 */
goog.net.XmlHttpFactory.prototype.internalGetOptions = goog.abstractMethod;