state machine

DesignPattern/DesignPattern/Patterns/StateMachine.cs

@@ -0,0 +1,236 @@
+namespace DesignPattern.Patterns
+{
+    public class StateMachinePattern
+    {
+        public static void Work()
+        {
+            VendingMachine vendingMachine = new VendingMachine();
+
+            while (true)
+            {
+                Console.WriteLine("Please select action (AddMoney, SelectItem, ReturnChange)");
+                string input = Console.ReadLine();
+                string read;
+                switch (input.ToUpper())
+                {
+                    case "ADDMONEY":
+                        Console.Write("Money: ");
+                        read = Console.ReadLine();
+                        int.TryParse(read, out int money);
+                        vendingMachine.AddMoney(money);
+                        break;
+                    case "SELECTITEM":
+                        Console.Write("ItemId: ");
+                        read = Console.ReadLine();
+                        int.TryParse(read, out int itemId);
+                        vendingMachine.SelectItem(itemId);
+                        break;
+                    case "RETURNCHANGE":
+                        vendingMachine.ReturnChange();
+                        break;
+                }
+            }
+        }
+    }
+
+    public class VendingMachine
+    {
+        private Product product = new Product();
+        internal decimal Money { get; set; }
+
+        internal VMState ReadyState { get; private set; }
+        internal VMState HasMoneyState { get; private set; }
+        internal VMState DispenseItemState { get; private set; }
+        internal VMState DispenseChangeState { get; private set; }
+        internal VMState State { get; set; }
+
+        public VendingMachine()
+        {
+            Money = 0;
+
+            ReadyState = new ReadyState(this);
+            HasMoneyState = new HasMoneyState(this);
+            DispenseItemState = new DispenseItemState(this);
+            DispenseChangeState = new DispenseChangeState(this);
+
+            State = ReadyState;
+        }
+
+        public void AddMoney(decimal money)
+        {
+            State.AddMoney(money);
+        }
+
+        public void SelectItem(int itemId)
+        {
+            State.SelectItem(itemId);
+        }
+
+        public void ReturnChange()
+        {
+            State.ReturnChange(Money);
+        }
+
+        internal decimal? GetPrice(int itemId)
+        {
+            return product.GetPrice(itemId);
+        }
+    }
+
+    internal class Product
+    {
+        private List<Item> _items;
+
+        public Product()
+        {
+            _items = new List<Item>()
+            {
+                new Item() { Id = 101, Price = 3.5M },
+                new Item() { Id = 201, Price = 4.0M },
+                new Item() { Id = 301, Price = 4.5M },
+            };
+        }
+
+        public decimal? GetPrice(int itemid)
+        {
+            var item = _items.SingleOrDefault(p => p.Id == itemid);
+
+            return item == null ? null : (decimal?)item.Price;
+        }
+
+        private class Item
+        {
+            public int Id { get; set; }
+            public decimal Price { get; set; }
+        }
+    }
+
+    internal abstract class VMState
+    {
+        protected VendingMachine _vendingMachine;
+        public abstract void AddMoney(decimal money);
+        public abstract void SelectItem(int itemId);
+        public abstract void ReturnChange(decimal money);
+    }
+
+    internal class ReadyState : VMState
+    {
+        public ReadyState(VendingMachine context)
+        {
+            _vendingMachine = context;
+        }
+
+        public override void AddMoney(decimal money)
+        {
+            _vendingMachine.State = _vendingMachine.HasMoneyState;
+            _vendingMachine.State.AddMoney(money);
+        }
+
+        public override void ReturnChange(decimal money)
+        {
+            throw new InvalidOperationException();
+        }
+
+        public override void SelectItem(int itemId)
+        {
+            throw new InvalidOperationException();
+        }
+    }
+
+    internal class HasMoneyState : VMState
+    {
+        public HasMoneyState(VendingMachine context)
+        {
+            _vendingMachine = context;
+        }
+
+        public override void AddMoney(decimal money)
+        {
+            _vendingMachine.Money += money;
+            Console.WriteLine($"Add {money}, Balance: {_vendingMachine.Money}");
+        }
+
+        public override void ReturnChange(decimal money)
+        {
+            _vendingMachine.State = _vendingMachine.DispenseChangeState;
+            _vendingMachine.State.ReturnChange(_vendingMachine.Money);
+        }
+
+        public override void SelectItem(int itemId)
+        {
+            decimal? price = _vendingMachine.GetPrice(itemId).Value;
+            if (!price.HasValue)
+            {
+                Console.WriteLine($"{itemId} not found");
+                return;
+            }
+
+            if (_vendingMachine.Money < price.Value)
+            {
+                Console.WriteLine("Insufficient money");
+                return;
+            }
+
+            _vendingMachine.State = _vendingMachine.DispenseItemState;
+            _vendingMachine.State.SelectItem(itemId);
+        }
+    }
+
+    internal class DispenseItemState : VMState
+    {
+        public DispenseItemState(VendingMachine context)
+        {
+            _vendingMachine = context;
+        }
+
+        public override void AddMoney(decimal money)
+        {
+            throw new InvalidOperationException();
+        }
+
+        public override void ReturnChange(decimal money)
+        {
+            throw new InvalidOperationException();
+        }
+
+        public override void SelectItem(int itemId)
+        {
+            decimal? price = _vendingMachine.GetPrice(itemId).Value;
+
+            Console.WriteLine($"Dispense item#{itemId} ({price.Value})");
+            _vendingMachine.Money -= price.Value;
+
+            _vendingMachine.State = _vendingMachine.DispenseChangeState;
+            _vendingMachine.State.ReturnChange(_vendingMachine.Money);
+        }
+    }
+
+    internal class DispenseChangeState : VMState
+    {
+        public DispenseChangeState(VendingMachine context)
+        {
+            _vendingMachine = context;
+        }
+
+        public override void AddMoney(decimal money)
+        {
+            throw new InvalidOperationException();
+        }
+
+        public override void ReturnChange(decimal money)
+        {
+            if (_vendingMachine.Money > 0)
+            {
+                Console.WriteLine($"Return change {money}...");
+                _vendingMachine.Money -= money;
+            }
+
+            _vendingMachine.State = _vendingMachine.ReadyState;
+        }
+
+        public override void SelectItem(int itemId)
+        {
+            throw new InvalidOperationException();
+        }
+    }
+}

DesignPattern/DesignPattern/Program.cs

@@ -8,6 +8,8 @@ class Program
     {
         // FactoryClient.Work();
 
-        CommandClient.Work();
+        // CommandClient.Work();
+
+        StateMachinePattern.Work();
     }
 }