Stacking Code

I've been doing Roy's string calculator kata every day for the last few days. This morning's iteration took me just over an hour, but I suspect that's because I went a bit nuts trying to get the delimiter code out of my Calculator class. Here's what my latest version looks like.

using System;
using System.Linq;

namespace StackingCode.Katas.OsheroveTddKata1
{
    // http://osherove.com/tdd-kata-1/
    public class Calculator
    {
        public int Add(string numbers)
        {
            if (numbers == string.Empty)
                return 0;

            DelimiterStrategy strategy = DelimiterStrategy.Select(numbers);
            string[] delimiters = strategy.DetermineDelimiters(ref numbers);

            return numbers
                .Split(delimiters, StringSplitOptions.None)
                .CheckForMissingNumbers()
                .Select(int.Parse)
                .CheckForNegativeNumbers()
                .IgnoreBigNumbers()
                .Sum();
        }
    }
}

There's heavy use of Linq in there, which seems to be my style these days, and a few extension methods, which I know some people won't like but I think it makes the code more readable.

You can see what the rest of the code looks like over on Bitbucket. If you're interested in how it evolved, you can check out the log as well. There's a commit after each test went green and whenever a refactoring took place.