WattDepot Katas

Continuing off my last blog entry about energy in Hawaii, there is an energy conservation competition going on over at the first-year dorms called the Kukui Cup. The system that facilitates this competition is the WattDepot web service which collects electricity data from meters found in these dorms. To get my feet wet with the use of the WattDepot API, I implemented some of the following katas.

All katas will accept a URL to a WattDepot server that will provide energy consumption data in the Hale Aloha residence halls at the University of Hawaii. All katas will lists all sourced defined at this URL and will also display specific information per kata.

Kata 1: SourceListing
Lists all sources defined at a given URL.
Kata 2: SourceLatency
Lists the number of seconds since data was received sorted in ascending order.
Kata 3: SourceHierarchy
Show the hierarchy of all subsources of a given source.
Kata 4: EnergyYesterday
Lists amount of energy in watt-hours consumed during the previous day for each source.
Kata 5: HighestRecordedPowerYesterday
Lists highest recorded power associated with a source during the previous day.
Kata 6: MondayAverageEnergy
Lists average energy consumed by a source during the previous two Mondays. Sorted in ascending order by watt-hours.

One obvious thing I've noticed about WattDepot is that it's very complex! Some of these katas seem trivial on paper, but trying to implement them was a different story. With the first kata, a simply copy and paste of an example program did half the work. But the other half involved learning the intricacies of the System.out.format method. Like the System.out.println method which simply prints data to standard output (the computer screen), System.out.format allows data to be printed in a nicely formatted list. With the SourceLatency kata, I found that the latency given by the WattDepot server may have already been sorted since printing each source with its computed latency shows that it is indeed in ascending order. To make sure, I've tried setting variables involved with computing latency to zero before computing the latency of the next source. Finally, SourceHierarchy proved interesting since the subsources given by each source was provided in a not so nice format. For example, given a source Ilima, the sub sources of Ilima would look something like this:

[http://someurl.com/subsource, http://someurl.com/subsource]

It wasn't perfect, but using a combination of Java's Split operator to break up the URI's and WattDepot's UriUtils class, I was able to extract the subsource from each subsource URI.

However, I wasn't able to complete the last three katas in time since each kata builds upon the last one. The EnergyYesterday kata requires the computation of the previous day which carries on to the fifth and sixth katas. Even though I was able to get the previous days time stamp in a nice format, I wasn't able to properly compute the energy consumed for each source. Looking at the last two katas, they both do something similar with respect to computing some previous day along with some data recorded at that day.

Finally, in terms of time spent on each kata, I found that more time was required to complete a kata than the previous kata. Not surprising since each new kata gets progressively more difficult. Overall, I found these katas enlightening in that it showed me how to approach a programming problem. Working with one of my peers last week getting started with these katas, I was overwhelmed with the amount of complexity he put into the second kata with respect to sorting by latency. There is always a brute force approach to solving some of these katas, but I like to stop and ask myself "Is there a better way?". Surely there exists some method in Java that can help solve these programming katas without having to produce spaghetti code.