get an object from redis, modify contents, and set

getset.js

function getSet(key, obj, transmute){
   return new Bluebird(function(resolve, reject){
      function setAtomic(key, obj, count){
         var counts = count;
         var atomicClient = baseRedis.createClient();

         // lock the key
         atomicClient.watch(key);

         // get the object
         atomicClient.hgetall(key, function(o){
            if(!o){
               return {};
            }
            // parse the objects values
            o = parseObject(o);

            // TODO: make the function async?
            var newO = transmute(o);

            // set each key using the new object (after transmutation)
            var chain = Object.keys(newO).reduce(function(ch, field){
               var val = typeof newO[field] === 'string' ? newO[field] : JSON.stringify(newO[field]);
               return ch.hset(key, field, val);
            }, atomicClient.multi());

            // TODO: Delete keys?

            // finish the transaction
            chain.exec(function(err, results){
               atomicClient.quit();
               // transaction failed, try again
               if(results === null && counts < 10){
                  setAtomic(key, obj, counts++);
               }
               // too many failures
               if(counts >= 10){
                  return reject(new Error("Could not complete transaction"));
               }
               if(err){
                  return reject(err);
               }
               return resolve(results);
            });
         });
      }
      setAtomic(key, obj, 0);
   });
}