CloneVersionSystem

using System;
using System.Collections;
using System.Collections.Generic;

namespace Clones
{
    public class CloneVersionSystem : ICloneVersionSystem
    {
        static List<Clone> clones = new List<Clone>() { new Clone() };

        class Clone
        {
            List<string> programs;
            List<string> undos;
            int number;

            internal Clone()
            {
                programs = new List<string>();
                programs.Add("basic");
                undos = new List<string>();
                number = 1;
            }

            private Clone(int num)
            {
                for (int i = 0; i < clones.Count; i++)
                {
                    if (clones[i].number == num)
                    {
                        programs = new List<string>();
                        for (int j = 0; j < clones[i].programs.Count; j++)
                        {
                            programs.Add(clones[i].programs[j]);
                        }

                        undos = new List<string>();
                        for (int j = 0; j < clones[i].undos.Count; j++)
                        {
                            undos.Add(clones[i].undos[j]);
                        }

                        number = clones.Count + 1;
                        break;
                    }
                }
            }

            internal void Learn(string pi)
            {
                programs.Add(pi);
                while (undos.Count > 0)
                {
                    undos.RemoveAt(undos.Count - 1);
                }
            }

            internal void Rollback()
            {
                var prg = programs[programs.Count - 1];
                if (prg != "basic")
                {
                    undos.Add(prg);
                    programs.RemoveAt(programs.Count - 1);
                }
            }

            internal void Relearn()
            {
                if (undos.Count > 0)
                {
                    programs.Add(undos[undos.Count - 1]);
                    undos.RemoveAt(undos.Count - 1);
                }
            }

            internal void Clonefy()
            {
                Clone clone = new Clone(number);
                clones.Add(clone);
            }

            internal string Check()
            {
                return programs[programs.Count - 1];
            }
        }

        public string Execute(string query)
        {
            string[] tokens = query.Split(' ');
            int numClone = int.Parse(tokens[1]) - 1;
            switch (tokens[0])
            {
                case "learn":
                    clones[numClone].Learn(tokens[2]);
                    break;
                case "rollback":
                    clones[numClone].Rollback();
                    break;
                case "relearn":
                    clones[numClone].Relearn();
                    break;
                case "clone":
                    clones[numClone].Clonefy();
                    break;
                case "check":
                    return clones[numClone].Check();
            }

            return null;
        }
    }
}