using System;

using System.Collections.Generic;

using System.Linq;

​

using MyState = System.Collections.Generic.HashSet<string>;

​

public class Program

{

    public static void Main()

    {

        var methods = new List<Method>();

        methods.Add(new Method{name = "Start", inState = new MyState{"Stopped"}, outState = new MyState{ "Started" }});

        methods.Add(new Method{name = "Stop", inState = new MyState{"Started"}, outState = new MyState{ "Stopped", "Paused" }});

        methods.Add(new Method{name = "Unpause", inState = new MyState{"Paused"}, outState = new MyState{ "Started" }});

        var uncallable = FindUncallableMethods(new MyState{"Started"}, methods);

        foreach (var m in uncallable) {

            Console.WriteLine(m.name);  

        }

    }

​

​

    public static HashSet<Method> FindUncallableMethods(MyState startState, List<Method> methods) {

        HashSet<Method> notCalled = new HashSet<Method>(methods);

        FindUncallableMethodsRec(startState, methods, notCalled);

​

        return notCalled;

    }

​

    private static void FindUncallableMethodsRec(MyState state, List<Method> methods, HashSet<Method> notCalled) {

        foreach (var method in methods.Where(m => m.Accepts(state))) {

            if (!notCalled.Contains(method)) continue;

            notCalled.Remove(method);

            FindUncallableMethodsRec(method.Produces(state), methods, notCalled);

        }

    }

}

​

​

​

public class Method {

    public string name { get; set; }

    public MyState inState { get; set; }

    public MyState outState  { get; set; }

    public bool Accepts(MyState state) {

        return inState.All(s => state.Contains(s));

    }

    public MyState Produces(MyState state) {

      if (!Accepts(state)) throw new Exception("busted");

      return new MyState(state.Where(s => !inState.Contains(s)).Union(outState));

    }

}

​

​