How do you know how many programmers a particular project needs to be successful?
The company I work for fulfills orders for client companies. We have written an in-house warehouse management system that handles location based inventory management, order processing, bill-of-lading generation, invoicing, freight auditing and reporting (probably 50 reports). It also has barcode scanning functions and a client portal along with dozens of other smaller features. It also includes a full employee timeclock. It integrates with Quickbooks, UPS and FedEx. It handles work for at least 50 clients all differing slightly in their functionality. For example, we import orders from files the customers send but each customer sends a different file format (csv, excel, flat file and web services) so we have well over a dozen order conversion methods setup. Exports are the same story.
The project is complex and growing in complexity every day with over a quarter million lines of code. It's about 250,000 lines of VB.NET code, 6,200 lines of Ruby code and maybe 5,000 lines of PHP. It also has a MySQL database with about 200 tables.
Because of the constantly changing requirements and differing needs of dozens of clients the code itself varies greatly in the quality from extremely poor to relatively good code.
Currently, this project has only a single programmer - myself. I also currently do all the product support for our company of 75 people or so. That includes troubleshooting and setting up new clients and any new features that are needed. Plus, we're trying to rewrite the whole thing to be 100% Ruby on Rails based. And we would like to market the whole system within the next year or so to be used by other companies.
Currently, we have only myself as a programmer but I don't believe that is sufficient. Does anyone have any recommendations for how many programmers a project of this magnitude should have or how we should go about determining the answer to that question? Particularly given the fact that management would like the product to be commercial quality by next year?