// Abstract expression
    public abstract class Goods
    {
        public abstract int Interpret(CurrentPricesContext context);
    }

    // Nonterminal expression
    public class GoodsPackage : Goods
    {
        public List<Goods> GoodsInside { get; set; }

        public override int Interpret(CurrentPricesContext context)
        {
            var totalSum = 0;
            foreach (var goods in GoodsInside)
            {
                totalSum += goods.Interpret(context);
            }
            return totalSum;
        }
    }

    // Terminal expression
    internal class TV : Goods
    {
        public override int Interpret(CurrentPricesContext context)
        {
            int price = context.GetPrice("TV");
            Console.WriteLine("TV: {0}", price);
            return price;
        }
    }

    // Here other terminal expressions go (Laptop, Bed)

        public void RunInterpreterDemo()
        {
            // create syntax tree that represents sentence
            var truckWithGoods = PrepareTruckWithGoods();
            // get latest context
            var pricesContext = GetRecentPricesContext();
            // invoke Interpret
            var totalPriceForGoods = truckWithGoods.Interpret(pricesContext);

            Console.WriteLine("Total: {0}", totalPriceForGoods);
        }

        private CurrentPricesContext GetRecentPricesContext()
        {
            var pricesContext = new CurrentPricesContext();
            pricesContext.SetPrice("Bed", 400);
            pricesContext.SetPrice("TV", 100);
            pricesContext.SetPrice("Laptop", 500);
            return pricesContext;
        }

        public GoodsPackage PrepareTruckWithGoods()
        {
            var truck = new GoodsPackage() { GoodsInside = new List<Goods>() };

            var bed = new Bed();
            var doubleTriplePackedBed = new GoodsPackage() { GoodsInside = new List<Goods>() { new GoodsPackage() { GoodsInside = new List<Goods>() { bed } } } };
            truck.GoodsInside.Add(doubleTriplePackedBed);
            truck.GoodsInside.Add(new TV());
            truck.GoodsInside.Add(new TV());
            truck.GoodsInside.Add(new GoodsPackage() { GoodsInside = new List<Goods>() { new Laptop(), new Laptop(), new Laptop() } });

            return truck;
        }

    public class RobotBombDefuser
    {
        private Random _random = new Random();
        private int _robotConfiguredWavelength = 41;
        private bool _isConnected = false;

        public void ConnectWireless(int communicationWaveLength)
        {
            if(communicationWaveLength == _robotConfiguredWavelength)
            {
                _isConnected = IsConnectedImmitatingConnectivitiyIssues();
            }
        }
        public bool IsConnected()
        {
            _isConnected = IsConnectedImmitatingConnectivitiyIssues();
            return _isConnected;
        }
        private bool IsConnectedImmitatingConnectivitiyIssues()
        {
            return _random.Next(0, 10) < 4; // immitates 40% good connection, aka. very bad
        }

        public virtual void WalkStraightForward(int steps)
        {
            Console.WriteLine("Did {0} steps forward...", steps);
        }

        public virtual void TurnRight()
        {
            Console.WriteLine("Turned right...");
        }

        public virtual void TurnLeft()
        {
            Console.WriteLine("Turned left...");
        }

        public virtual void DefuseBomb()
        {
            Console.WriteLine("Cut red or green or blue wire...");
        }
    }

    public class RobotBombDefuserProxy : RobotBombDefuser
    {
        private RobotBombDefuser _robotBombDefuser;
        private int _communicationWaveLength;
        private int _connectionAttempts = 3;

        public RobotBombDefuserProxy(int communicationWaveLength)
        {
            _robotBombDefuser = new RobotBombDefuser();
            _communicationWaveLength = communicationWaveLength;
        }

        public virtual void WalkStraightForward(int steps)
        {
            EnsureConnectedWithRobot();
            _robotBombDefuser.WalkStraightForward(steps);
        }

        public virtual void TurnRight()
        {
            EnsureConnectedWithRobot();
            _robotBombDefuser.TurnRight();
        }

        public virtual void TurnLeft()
        {
            EnsureConnectedWithRobot();
            _robotBombDefuser.TurnLeft();
        }

        public virtual void DefuseBomb()
        {
            EnsureConnectedWithRobot();
            _robotBombDefuser.DefuseBomb();
        }

        private void EnsureConnectedWithRobot()
        {
            if (_robotBombDefuser == null)
            {
                _robotBombDefuser = new RobotBombDefuser();
                _robotBombDefuser.ConnectWireless(_communicationWaveLength);
            }

            for (int i = 0; i < _connectionAttempts; i++)
            {
                if (_robotBombDefuser.IsConnected() != true)
                {
                    _robotBombDefuser.ConnectWireless(_communicationWaveLength);
                }
                else
                {
                    break;
                }
            }
            if(_robotBombDefuser.IsConnected() != true)
            {
                throw new BadConnectionException("No connection with remote bomb diffuser robot could be made after few attempts.");
            }
        }
    }

        public static void Run()
        {
            int opNum = 0;
            try
            {
                var proxy = new RobotBombDefuserProxy(41);
                proxy.WalkStraightForward(100);
                opNum++;
                proxy.TurnRight();
                opNum++;
                proxy.WalkStraightForward(5);
                opNum++;
                proxy.DefuseBomb();
                opNum++;

                Console.WriteLine();
            }
            catch (BadConnectionException e)
            {
                Console.WriteLine("Exception has been caught with message: ({0}). Decided to have human operate robot there.", e.Message);

                PlanB(opNum);
            }
        }

        private static void PlanB(int nextOperationNum)
        {
            RobotBombDefuser humanOperatingRobotDirectly = new RobotBombDefuser();

            if(nextOperationNum == 0)
            {
                humanOperatingRobotDirectly.WalkStraightForward(100);
                nextOperationNum++;
            }
            if (nextOperationNum == 1)
            {
                humanOperatingRobotDirectly.TurnRight();
                nextOperationNum++;
            }
            if (nextOperationNum == 2)
            {
                humanOperatingRobotDirectly.WalkStraightForward(5);
                nextOperationNum++;
            }
            if (nextOperationNum == 3)
            {
                humanOperatingRobotDirectly.DefuseBomb();
            }
        }
    }

        // Colleague
        class BodyPart
        {
            private readonly Brain _brain;

            public BodyPart(Brain brain)
            {
                _brain = brain;
            }

            public void Changed()
            {
                _brain.SomethingHappenedToBodyPart(this);
            }
        }

    class Ear : BodyPart
    {
        private string _sounds = string.Empty;

        public Ear(Brain brain)
            : base(brain)
        {
        }

        public void HearSomething()
        {
            Console.WriteLine("Enter what you hear:");
            _sounds = Console.ReadLine();

            Changed();
        }

        public string GetSounds()
        {
            return _sounds;
        }
    }

    class Face : BodyPart
    {
        public Face(Brain brain)
            : base(brain)
        {
        }

        public void Smile()
        {
            Console.WriteLine("FACE: Smiling...");
        }
    }

    // Mediator
    class Brain
    {
        public Brain()
        {
            CreateBodyParts();
        }

        private void CreateBodyParts()
        {
            Ear = new Ear(this);
            Eye = new Eye(this);
            Face = new Face(this);
            Hand = new Hand(this);
            Leg = new Leg(this);
        }

        public Ear Ear { get; private set; }
        public Eye Eye { get; private set; }
        public Face Face { get; private set; }
        public Hand Hand { get; private set; }
        public Leg Leg { get; private set; }

        public void SomethingHappenedToBodyPart(BodyPart bodyPart)
        {
            if (bodyPart is Ear)
            {
                string heardSounds = ((Ear)bodyPart).GetSounds();

                if (heardSounds.Contains("stupid"))
                {
                    // attacking offender
                    Leg.StepForward();
                    Hand.HitPersonNearYou();
                    Leg.Kick();
                }
                else if (heardSounds.Contains("cool"))
                {
                    Face.Smile();
                }
            }
            else if (bodyPart is Eye)
            {
                // brain can analyze what you see and
                // can react appropriately using different body parts
            }
            else if (bodyPart is Hand)
            {
                var hand = (Hand)bodyPart;

                bool hurtingFeeling = hand.DoesItHurt();
                if (hurtingFeeling)
                {
                    Leg.StepBack();
                }

                bool itIsNice = hand.IsItNice();
                if (itIsNice)
                {
                    Leg.StepForward();
                    Hand.Embrace();
                }
            }
            else if (bodyPart is Leg)
            {
                // leg can also feel something if you would like it to
            }
        }
    }