text: /*****************************************************************************
   * Open MCT Web, Copyright (c) 2014-2015, United States Government
   * as represented by the Administrator of the National Aeronautics and Space
   * Administration. All rights reserved.
   *
   * Open MCT Web is 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.
   *
   * Open MCT Web includes source code licensed under additional open source
   * licenses. See the Open Source Licenses file (LICENSES.md) included with
   * this source code distribution or the Licensing information page available
   * at runtime from the About dialog for additional information.
   *****************************************************************************/
  /*global define,Promise*/
  
  /**
   * Module defining ImageTelemetryProvider. Created by vwoeltje on 06/22/15.
   */
  define(
      ["./ImageTelemetry"],
      function (ImageTelemetry) {
          "use strict";
  
          /**
           *
           * @constructor
           */
          function ImageTelemetryProvider($q, $timeout) {
              var subscriptions = [];
  
              //
              function matchesSource(request) {
                  return request.source === "imagery";
              }
  
              // Used internally; this will be repacked by doPackage
              function generateData(request) {
                  return {
                      key: request.key,
                      telemetry: new ImageTelemetry()
                  };
              }
  
              //
              function doPackage(results) {
                  var packaged = {};
                  results.forEach(function (result) {
                      packaged[result.key] = result.telemetry;
                  });
                  // Format as expected (sources -> keys -> telemetry)
                  return { imagery: packaged };
              }
  
              function requestTelemetry(requests) {
                  return $timeout(function () {
                      return doPackage(requests.filter(matchesSource).map(generateData));
                  }, 0);
              }
  
              function handleSubscriptions() {
                  subscriptions.forEach(function (subscription) {
                      var requests = subscription.requests;
                      subscription.callback(doPackage(
                          requests.filter(matchesSource).map(generateData)
                      ));
                  });
              }
  
              function startGenerating() {
                  $timeout(function () {
                      handleSubscriptions();
                      if (subscriptions.length > 0) {
                          startGenerating();
                      }
                  }, 1000);
              }
  
              function subscribe(callback, requests) {
                  var subscription = {
                      callback: callback,
                      requests: requests
                  };
  
                  function unsubscribe() {
                      subscriptions = subscriptions.filter(function (s) {
                          return s !== subscription;
                      });
                  }
  
                  subscriptions.push(subscription);
  
                  if (subscriptions.length === 1) {
                      startGenerating();
                  }
  
                  return unsubscribe;
              }
  
              return {
                  requestTelemetry: requestTelemetry,
                  subscribe: subscribe
              };
          }
  
          return ImageTelemetryProvider;
      }
  );
  