How I Used AI to Refactor 10,000 Lines of Legacy Code Without Breaking the Project
When I first opened the codebase, I just sat there for a minute. I'd been brought onto a project mid-stream — a freelance contract to add three new features to an existing platform that had been running in production for about six years. The platform worked. Customers were using it daily. Revenue depended on it. My job was, in theory, to add a customer segmentation feature, improve the reporting dashboard, and optimize a slow checkout flow. What I found when I actually opened the repository was a PHP monolith with no tests, inconsistent naming conventions across files that had clearly been written by four or five different developers over the years, business logic scattered between controllers and database queries and occasional JavaScript files that did things that should have happened server-side, and approximately zero documentation. The original developer had left the company two years earlier. Nobody currently at the company fully understood how the whole system fit together...