using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Memento
{
    class Program
    {

        /// <summary>

        /// MainApp startup class for Structural 

        /// Memento Design Pattern.

        /// </summary>
        /// 

       // Without violating encapsulation, capture and externalize an object's 
        //internal state so that the object can be restored to this state later.


        class MainApp
        {
            /// <summary>

            /// Entry point into console application.

            /// </summary>

            static void Main()
            {
                Originator o = new Originator();
                o.State = "On";

                // Store internal state

                Caretaker c = new Caretaker();
                c.Memento = o.CreateMemento();

                // Continue changing originator

                o.State = "Off";

                // Restore saved state

                o.SetMemento(c.Memento);

                // Wait for user

                Console.ReadKey();
            }
        }

        /// <summary>

        /// The 'Originator' class

        /// </summary>

        class Originator
        {
            private string _state;

            // Property

            public string State
            {
                get { return _state; }
                set
                {
                    _state = value;
                    Console.WriteLine("State = " + _state);
                }
            }

            // Creates memento 

            public Memento CreateMemento()
            {
                return (new Memento(_state));
            }

            // Restores original state

            public void SetMemento(Memento memento)
            {
                Console.WriteLine("Restoring state...");
                State = memento.State;
            }
        }

        /// <summary>

        /// The 'Memento' class

        /// </summary>

        class Memento
        {
            private string _state;

            // Constructor

            public Memento(string state)
            {
                this._state = state;
            }

            // Gets or sets state

            public string State
            {
                get { return _state; }
            }
        }

        /// <summary>

        /// The 'Caretaker' class

        /// </summary>

        class Caretaker
        {
            private Memento _memento;

            // Gets or sets memento

            public Memento Memento
            {
                set { _memento = value; }
                get { return _memento; }
            }
        }
    }
}