LnBlog: Blogging the redesign

Today, we're going to talk a little about design and refactoring.  As a case-study, we're going to use a little blogging application called LnBlog.  You probably haven't heard of it - it's not very popular.  However, you have used it, at least peripherally, because it's running this site.  And you also have at least a passing familiarity with the author of that application, because it's me. 

Motivation

Software is an "interesting" field.  The cool new technologies, frameworks, and languages get all the press and they're what everybody wants to work with.  But let's be honest: it's generally not what makes the money.  I mean, how could it be?  It just came out last week!

No, if you have the good fortune to work on a grown-up, profitable product, it's almost certainly going to be the "old and busted" tech.  It might not be COBOL or Fortran, but it's almost certainly "legacy code".  It might be C++ or Java or, in our case, PHP, but it's probably old, poorly organized, lacking unit tests, and generally hard to work with.

I work on such a product for my day job.  It's a 10-year-old PHP codebase, written in an old-fashioned procedural style.  There are no unit tests for the old code, and you couldn't really write them even if you wanted to.  Sure, there's a newer part with proper design, tests, etc., but the old code is the kind of stuff that "works for the most part", but everybody is afraid to touch it because it's so brittle and tightly coupled that God alone knows what will break when you make a change.

This also applies to LnBlog.  It was my very first PHP application.  I started it way back in early 2005, in the bad old days of PHP 4.  Over the next two or three years, I managed to turn it into something that was relatively functional and full-featured.  And for the last ten years or so, I've managed to keep it working.

Of course, it hasn't gotten a whole lot of love in that time.  I've been busy and, for the most part, it worked and was "good enough".  However, I occasionally need to fix bugs or want to add features, and doing that is a truly painful process.  So I would very much like to 

The Issue

Let me be honest: I didn't really know what I was doing when I wrote LnBlog.  I was about four years out of school and had only been coding for about six or seven years total.  And I was working mostly in Visual Basic 6 at the time, which just barely counts.  It was also only my third web-based project, and the first two were written in classic ASP and VBScript, which also just barely counts.

As a result, it contains a lot of questionable design decisions and overly-complicated algorithms.  The code is largely procedural, kind of buggy, and makes poor use of abstraction.  So, in short, it's not great.

But, in fairness to myself, I've seen worse.  In fact, I've seen a lot worse.  It does have a class hierarchy for the domain objects (though it's a naive design), an abstraction layer for data access (though it's inconsistently used), and a templating system for separating markup from domain logic (though the templates are an ungodly mess).  And it's not like I had a role model or mentor to guide me through this - I was figuring out what worked on my own.  So while it's not great, I think it's actually surprisingly good given the circumstances under which it was built.

The Goal - Make the Code "Good"

So I want to make LnBlog better.  I've thought about rewriting it, but decided that I wouldn't be doing myself any favors by going that route.  I also hold no illusions of a grand re-architecture that will fix all the problems and be a shining beacon of design perfection.  Rather, I have a relatively modest list of new features and bug fixes, and I just want to make the code good enough that I can make changes easily when I need to and be reasonably confident that I'm not breaking things.  In other words, I want to do a true refactoring.

If you haven't read Martin Fowler's book, the word "refactoring" is not a synonym for "changing code" or "rewriting code".  Rather, it has a very specific meaning: improving the internal design of code without changing the external behavior.  In other words, all you do is make the code easier to work with - you don't change what it does in any way.  This is why people like Bob Martin tell you that "refactor X" should never be an item in your Scrum backlog.  It is purely a design and "code cleanliness" activity, not a "feature" you can deliver.

So my goal with LnBlog is to gradually reshape it into what it should have been in the first place.  This is partially to make changing it easier in the future.  But more importantly, it's a professional development goal, an exercise in code craftsmanship.  As I mentioned above, I've worked professionally on many systems that are even more messed up than LnBlog.  So this is a study in how to approach refactoring a system.  

And So It Begins...

My intention is to write a number of articles describing this process.  I've already completed the first step, which is rewriting some of the persistence and publication logic.  I'm using the PSP to track my planned and actual performance, so I'll have some actual data to use in my discussion of that process.  Hint: so far, the two are very different.

With any luck, this project will enable me to draw some useful or interesting conclusions about good and bad ways to approach reworking legacy systems.  Maybe it will also enlighten some other people along the way.  And if nothing else, I should at least get a better codebase out of it.

You can reply to this entry by leaving a comment below. You can send TrackBack pings to this URL. This entry accepts Pingbacks from other blogs. You can follow comments on this entry by subscribing to the RSS feed.

Related entries

Add your comments #

A comment body is required. No HTML code allowed. URLs starting with http:// or ftp:// will be automatically converted to hyperlinks.