storer.js

// fetch document or return null
function getDoc(db, id) {
  return new Promise(function(resolve, reject) {
    db.get(id).then(resolve).catch(function(err) {
      resolve(null);
    });
  });
};

function main(message) {
  var cloudant = require('cloudant')({url: message.cloudantURL, plugin:'promises'});
  var db = cloudant.db.use(message.dbname);
  var id = message.question.question_id.toString();
 
  // see if there is pre-existing Cloudant document
  return getDoc(db, id).then(function(data) {
    // if there was no pre-existing document
    if (data === null) {
      // create new question object
      message.question.tags = message.question.tags.sort();
      var obj = {
        _id: id,
        type: 'question',
        owner: null,
        status: 'new',
        question: message.question
      };
    
      // write it to the database
      return db.insert(obj).then(function(data) {

        // pass on the new object to the next action
        console.log("Question " + id + " created");
        return obj;
      });
    } else {
      
      // update the existing document

      // don't bother updating questions we have already saved
      if (message.question.last_activity_date <= data.question.last_activity_date) {
        throw new Error('no action required - same data received.');
      }

      // if we're here we need to update the question - sort the tags first
      message.question.tags = message.question.tags.sort();
      data.question = message.question;
      data.status = 'updated';

      // and write it back
      return db.insert(data).then(function(reply) {
        return data;
      });
    }
  });
}