// 
// Copyright (c) Microsoft and contributors.  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.
// 

'use strict';

var util = require('util');
var Constants = require('../../util/constants');
var HeaderConstants = Constants.HeaderConstants;

var moduleVersion = require('../../../package.json').version;

/**
* Creates a filter to add the user agent header in a request.
*
* @param {string} userAgent The user agent string to use.
*/
exports.create = function (userAgent) {
  return function handle (resource, next, callback) {
    if (!resource.headers[HeaderConstants.USER_AGENT]) {
      exports._tagRequest(resource, userAgent);
    }

    return next(resource, callback);
  };
};

exports._tagRequest = function (requestOptions, userAgent) {
  if (!userAgent) {
    userAgent = util.format('Azure-SDK-For-Node.js/%s', moduleVersion);
  }

  requestOptions.headers[HeaderConstants.USER_AGENT] = userAgent;
};