paging.js

/*
* ugCollectionForEachPaging
*
* Iterates through all items in a collection within
* Apigee Edge BaaS.  Uses the Usergrid client object from the usergrid
* module. Notice - this logic calls {has,get}NextPage().
*
* @param ugClient - the authenticated client object
* @param options - the options for a collection. Pass type and qs.
* @param f - function called with each UG entity. Accepts a single argument.
* @param doneCb - called in case of error or success.
*
*********************************************/
function ugCollectionForEachPaging (ugClient, options, f, doneCb) {
  var results = {count: 0, failCount: 0};
  if ( ! options.qs) {
    doneCb(new Error('missing qs property in the options argument'), null);
  }
  if ( ! options.type) {
    doneCb(new Error('missing type property in the options argument'), null);
  }

  ugClient.createCollection(options, function (e, collection) {
    var e2;
    function doOnePage(collection, cb) {
      while(collection.hasNextEntity()) {
        f(collection.getNextEntity(), results);
        results.count++;
      }
      if (collection.hasNextPage()) {
        collection.getNextPage(function(e){
          if (e) {
            e2 = new Error('could not get next page of entities');
            e2.wrappedError = e;
            cb(e2, results);
          }
          else {
            doOnePage(collection, cb);
          }
        });
      }
      else {
        cb(null, results);
      }
    }

    if (e) {
      e2 = new Error('could not make or get collection');
      e2.wrappedError = e;
      doneCb(e2, null);
    }
    else {
      doOnePage(collection, doneCb);
    }
  });
}