What is Software Complexity and Why Should You Care?

I got a call from a new client. Their WooCommerce store was bleeding money because one of their main payment gateways would randomly fail at checkout. Total mess. Their previous developer was long gone, and they were desperate. They said it only happened for certain customers, sometimes. That “sometimes” is always a red flag.

After digging in, I found the problem. A single function in their functions.php file, one that was supposed to handle gateway logic, had ballooned into a 300-line monster of nested if/else statements. It was trying to handle user roles, cart totals, specific products, coupon codes… everything. This wasn’t just messy code; it was a prime example of runaway software complexity, and it was a nightmare to debug.

What Software Complexity Actually Feels Like

Forget the academic definitions for a second. In the real world, software complexity is that feeling you get in your gut when you open a file and see a function that just won’t quit scrolling. It’s when you have to trace a single variable through a dozen conditional branches to figure out its final value. You can’t change one thing without breaking three others. That’s the pain point. It makes the code fragile, unpredictable, and expensive to maintain.

My first thought was to just patch the immediate bug. Find the broken condition, add another `elseif`, and get the client’s gateway working. And yeah, that would have taken an hour, tops. But it would have been the wrong move. The real fix had to be at the structural level. The function was trying to be a hero and do everything, and it was failing spectacularly. The concept of measuring this is often called Cyclomatic Complexity, a term I first saw explained in a great post over at carlalexander.ca, but all it really means is counting the number of unique paths through a function. When that number gets too high, you get trouble.

Don’t Patch the Mess, Refactor It

Instead of adding another patch, I broke the monster function apart. The original logic looked something like this, a tangled web of checks:

function maybe_disable_payment_gateway($gateways) {
    // A simplified, but still messy, example
    if (is_user_logged_in()) {
        $user = wp_get_current_user();
        if (in_array('wholesale_customer', $user->roles)) {
            if (WC()->cart->get_cart_contents_total() < 500) {
                unset($gateways['custom_gateway']);
            }
        } else {
            // More checks for regular customers...
        }
    } else if (WC()->cart->has_shipping_method('local_pickup')) {
         // Even more checks for guest users with local pickup...
    }
    return $gateways;
}

You can see how this gets out of hand. Fast. My solution was to refactor this into smaller, single-purpose functions with clear names. The main function becomes a simple conductor, calling on these helpers.

function maybe_disable_payment_gateway($gateways) {
    if (is_wholesale_customer_with_small_cart() || is_guest_with_local_pickup()) {
        unset($gateways['custom_gateway']);
    }
    return $gateways;
}

function is_wholesale_customer_with_small_cart() {
    if (!is_user_logged_in()) {
        return false;
    }
    $user = wp_get_current_user();
    $is_wholesale = in_array('wholesale_customer', $user->roles);
    $is_small_cart = WC()->cart->get_cart_contents_total() < 500;

    return $is_wholesale && $is_small_cart;
}

function is_guest_with_local_pickup() {
    // Logic for this condition would go here...
    return false; // Placeholder
}

See the difference? The main function is now readable. If there’s a bug with wholesale logic, I know *exactly* which function to look at. Each piece does one job, and does it well. This is how you build robust, maintainable sites.

So, What’s the Point?

The takeaway here isn’t about complex formulas. It’s about a simple rule of thumb: keep your functions small and focused. When a function starts getting long or handling too many different scenarios, it’s a code smell. Break it down. Your future self—and the next developer who has to touch your code—will thank you for it. It turns a tangled mess into a clear roadmap.

Look, this stuff gets complicated fast. If you’re tired of debugging someone else’s mess and just want your site to work, drop my team a line. We’ve probably seen it before.