The Haunting of a Business Calculator

The Haunting of a Business Calculator

Purpose

Working for an online retail company has been full of many ups and downs. Since the start of my time here, I have been haunted by one software project more than any other, the product pricing calculator. It is not the most complicated project. It is not a large project. It documentation is mediocre. Its number of users is moderate. Its impact on the company is higher than the sum of its parts. The only special thing about this calculator is its ability to consume developer souls across multiple generations, programming languages, stakeholders and ultimately space and time. The purpose of this article is to warn other about the possible dangers of working on a business calculator.

The Origin

I first started working on the calculator when I was a still new to programming (a sophomore in college). The calculator suffered from a case of the person who built this no longer works here. It was a standalone desktop application written in C# by a person we will call Bob. While I never meet Bob, I got to know them through their work. Bob was never a part of the IT team, but was able to code and distribute their own tools. At the time, this was great for the company, but later became complicated as people would contact the IT team for support with an application we had never heard of. Bobs work was often self titled, including the subject of this post, BobCalc. This calculator and appeared to be the organic evolution of some excel sheet. It seemed that the logic became too hot for Excel and was implemented in C# by Bob who was very competent business analyst, but a modest programmer. BobCalc was written as a suite of small tools and was never intended to grow into a collaborative project.

After Bob left, the calculator suffered from a few issues. While the implementation was simple, the calculator was very difficult to maintain. The calculator read from local excel files and was a part of a all-in-one C# application containing all of Bob’s work. Furthermore, the application was an executable with no real release strategy. This means the application would be build locally on Bob’s computer and distributed to others via DropBox or some other file sharing application. This lead to users having different versions requiring different excel data file schema.

It was clear that we could not maintain this application and the IT department must absorb the Bob tool suite. What better task for an fresh programming student who still has hope! I was assigned the task of fixing BobCalc by any means. After some thought I decided to port the desktop app to be a Python Flask application. This seemed like the correct choice at the time since the project was small. After a few weeks of coding I ported the calculator to a simple web app with three endpoints, bootstrap css and a few python files. While this solved many problems, it opened up another can of worms as more features were hastily requested. At this point the calculator was formally renamed to “The Pricing Calculator formally known as BobCalc”. I was told we should move to new branding since Bob was no longer with the company. Little did Bob know, their branding and legacy would remain for many years.

Within the next few months, the complexity of the calculator grew tremendously as features were implemented as fast as possible to satisfy the business (see extreme go-horse development methodology). During this time the calculator split into two different calculators and relied on API calls to external services. The project was handed off to my boss at the time who proceeded to do the lords work and write documentation before things got too out of hand. While the documentation was very useful for defining formulas it did not cover the river of upstream data that the calculator grew to depend on. My boss maintained the project for the next year or so until it landed my desk again. By this point the calculator had grown in complexity and popularity. Yay!

The Haunting

The price calculator can haunt one in many ways, the most common of which being a bug fix. Wherever you find yourself in your work day, the calculator will find you. The haunting puts technical debt to shame… It is not quite important enough to refactor, so we just add another log to the fire. A typical bug fix on the calculator starts when a users says “this calculation is wrong”. You start your investigation and find that the formulas are behaving exactly as the documentation states and test cases verify. You notify the user providing the concrete values used for their calculation. They are not satisfied. One of the values is incorrect. You must put on your life preserver and start paddling up the data swamp. There you will find tables that feed other tables that feed calculations for tables that feed tables. You find the source of the river Nile, but by this point you have have forgotten your way home. The value that was incorrect is because of an anomaly in FedEx shipping costs because a ship got stuck in the Suez Canal. You have successfully debugged the calculator and the only fix is to add more features. You futile programming efforts did not account for geopolitical events. You notify the user and begin working on a feature that splits calculations based on time of year to avoid shipping anomalies.

One source of the calculators power is its perceived simplicity. Surly adding another input should not take time out of your current responsibilities right? Its just a simple calculator with 2 different forms right? Wrong. You are powerless when working with the calculator. After several years of service, it became time to sunset the python version of BobCalc and refactor it once again. Working on the calculator had become cumbersome since it was a standalone application. Each time we would make changes to the calculator, it would require re-learning how the entire application was build and deployed since it was our only standalone flask application. Furthermore, the feature requests were becoming very detached from the original calculators design. It was decided that we would move the calculator to our new internal platform called Pulse. This is the third time I would see the calculator implemented, however, this time the calculator would haunt multiple victims.

BobCalc is like a cruel spirit moving from host to host, language to language, taking control of vessels to inflict pain on its subjects. Porting BobCalc to our internal platform was like performing an exorcism just to have the spirit occupy a more powerful vessel and ultimately… become more powerful. Porting BobCalc to its current home was no trivial task. By this point, BobCalc had multiple functions and modes and depending on scheduled processes to pull and aggregate large amounts of data. Some percentages were expressed as integers and others as floating point numbers. Variable names were misleading and outdated. There was an copious amounts of conditional validation that had to be carefully ported and tested. As a manager, I had a dubious decision to make - fully port BobCalc, or give this important task to a fresh programmer with hope… I did the latter as I had already paid my dues to BobCalc. After taking much longer than expected BobCalc was fully ported with a full Brazilian style face-lift complete with React, Tailwind and thoughtful design from our UX team.

The Future

Bobcalc finally has a new home and is mostly free of technical debt. I am rather happy with the current state of the program however I feel this is temporary as there is a heaping Jira board full of complicated feature requests that are “urgent”. At the time of this there is only 1 real piece of technical debt remaining - a massive SQL file full of complicated CTEs and dirty data. It is my goal to absolve this technical debt and free the souls of those who must maintain the calculator. While I have mostly written this as a satire, I must pay my respects to the calculator. All of my software development mentors have multiple stories like this one (often ore interesting) and I feel that this has been a sort of “rite of passage” into the community. While I will eventually move on to some other project at some other place, I will carry a new knowledge that only BobCalc can teach - say no to calculators!