//Aldo Antonio Montaño De La Paz 

//Memento

​

using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading;

​

namespace RefactoringGuru.DesignPatterns.Memento.Conceptual

{

    // The Originator holds some important state that may change over time. It

    // also defines a method for saving the state inside a memento and another

    // method for restoring the state from it.

    class Originator

    {

        // For the sake of simplicity, the originator's state is stored inside a

        // single variable.

        private string _state;

​

        public Originator(string state)

        {

            this._state = state;

            Console.WriteLine("Originator: My initial state is: " + state);

        }

​

        // The Originator's business logic may affect its internal state.

        // Therefore, the client should backup the state before launching

        // methods of the business logic via the save() method.

        public void DoSomething()

        {

            Console.WriteLine("Originator: I'm doing something important.");

            this._state = this.GenerateRandomString(30);

            Console.WriteLine($"Originator: and my state has changed to: {_state}");

        }

​

        private string GenerateRandomString(int length = 10)

        {

            string allowedSymbols = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

            string result = string.Empty;

​

            while (length > 0)

            {

                result += allowedSymbols[new Random().Next(0, allowedSymbols.Length)];

​

                Thread.Sleep(12);

​

                length--;

            }

​

            return result;

        }

​

        // Saves the current state inside a memento.

        public IMemento Save()

        {

            return new ConcreteMemento(this._state);

        }

​

        // Restores the Originator's state from a memento object.

        public void Restore(IMemento memento)

        {

            if (!(memento is ConcreteMemento))

            {

                throw new Exception("Unknown memento class " + memento.ToString());

            }

​

            this._state = memento.GetState();

            Console.Write($"Originator: My state has changed to: {_state}");

        }

    }

​

    // The Memento interface provides a way to retrieve the memento's metadata,

    // such as creation date or name. However, it doesn't expose the

    // Originator's state.

    public interface IMemento

    {

        string GetName();

​

        string GetState();

​

        DateTime GetDate();

    }

​

    // The Concrete Memento contains the infrastructure for storing the

    // Originator's state.

    class ConcreteMemento : IMemento

    {

        private string _state;

​

        private DateTime _date;

​

        public ConcreteMemento(string state)

        {

            this._state = state;

            this._date = DateTime.Now;

        }

​

        // The Originator uses this method when restoring its state.

        public string GetState()

        {

            return this._state;

        }

        // The rest of the methods are used by the Caretaker to display

        // metadata.

        public string GetName()

        {

            return $"{this._date} / ({this._state.Substring(0, 9)})...";

        }

​

        public DateTime GetDate()

        {

            return this._date;

        }

    }

​

    // The Caretaker doesn't depend on the Concrete Memento class. Therefore, it

    // doesn't have access to the originator's state, stored inside the memento.

    // It works with all mementos via the base Memento interface.

    class Caretaker

    {

        private List<IMemento> _mementos = new List<IMemento>();

​

        private Originator _originator = null;

​

        public Caretaker(Originator originator)

        {

            this._originator = originator;

        }

​

        public void Backup()

        {

            Console.WriteLine("\nCaretaker: Saving Originator's state...");

            this._mementos.Add(this._originator.Save());

        }

​

        public void Undo()

        {

            if (this._mementos.Count == 0)

            {

                return;

            }

​

            var memento = this._mementos.Last();

            this._mementos.Remove(memento);

​

            Console.WriteLine("Caretaker: Restoring state to: " + memento.GetName());

​

            try

            {

                this._originator.Restore(memento);

            }

            catch (Exception)

            {

                this.Undo();

            }

        }

​

        public void ShowHistory()

        {

            Console.WriteLine("Caretaker: Here's the list of mementos:");

​

            foreach (var memento in this._mementos)

            {

                Console.WriteLine(memento.GetName());

            }

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            // Client code.

            Originator originator = new Originator("Super-duper-super-puper-super.");

            Caretaker caretaker = new Caretaker(originator);

​

            caretaker.Backup();

            originator.DoSomething();

​

            caretaker.Backup();

            originator.DoSomething();

​

            caretaker.Backup();

            originator.DoSomething();

​

            Console.WriteLine();

            caretaker.ShowHistory();

​

            Console.WriteLine("\nClient: Now, let's rollback!\n");

            caretaker.Undo();

​

            Console.WriteLine("\n\nClient: Once more!\n");

            caretaker.Undo();

​

            Console.WriteLine();

        }

    }

}

​

​

​

​