study

StateMachine/CarStateMachine/CarStateMachine.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

StateMachine/CarStateMachine/Model/Car.cs

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+namespace CarStateMachine.Model
+{
+    public class Car
+    {
+        public enum State
+        {
+            Stopped,
+            Started,
+            Running,
+        }
+
+        public enum Action
+        {
+            Stop,
+            Start,
+            Accelerate,
+        }
+
+        private State _state = State.Stopped;
+        public State CurrentState { get { return _state; } }
+
+        public void TakeAction(Action action)
+        {
+            State state = _state;
+            switch (_state, action)
+            {
+                case (State.Stopped, Action.Start):
+                    state = State.Started;
+                    break;
+                case (State.Started, Action.Accelerate):
+                    state = State.Running;
+                    break;
+                case (State.Started, Action.Stop):
+                    state = State.Stopped;
+                    break;
+                case (State.Running, Action.Stop):
+                    state = State.Stopped;
+                    break;
+            }
+
+            _state = state;
+
+            // _state = (_state, action) switch
+            // {
+            //     (State.Stopped, Action.Start) => State.Started,
+            //     (State.Started, Action.Accelerate) => State.Running,
+            //     (State.Started, Action.Stop) => State.Stopped,
+            //     (State.Running, Action.Stop) => State.Stopped,
+            //     _ => _state
+            // };
+        }
+    }
+}

StateMachine/CarStateMachine/Program.cs

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+using CarStateMachine.Model;
+
+namespace CarStateMachine;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        Car car = new Car();
+        System.Console.WriteLine($"State: {car.CurrentState}");
+
+        car.TakeAction(Car.Action.Start);
+        System.Console.WriteLine($"State: {car.CurrentState}");
+
+        car.TakeAction(Car.Action.Start);
+        System.Console.WriteLine($"State: {car.CurrentState}");
+
+        car.TakeAction(Car.Action.Accelerate);
+        System.Console.WriteLine($"State: {car.CurrentState}");
+
+        car.TakeAction(Car.Action.Stop);
+        System.Console.WriteLine($"State: {car.CurrentState}");
+    }
+}

StateMachine/StateMachine.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "StateMachine", "StateMachine\StateMachine.csproj", "{C90D550D-277E-4321-A01E-542FB4B5F57E}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CarStateMachine", "CarStateMachine\CarStateMachine.csproj", "{F1C27B6E-1E78-40CA-9564-81074AB955B1}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{C90D550D-277E-4321-A01E-542FB4B5F57E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{C90D550D-277E-4321-A01E-542FB4B5F57E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{C90D550D-277E-4321-A01E-542FB4B5F57E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{C90D550D-277E-4321-A01E-542FB4B5F57E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{F1C27B6E-1E78-40CA-9564-81074AB955B1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{F1C27B6E-1E78-40CA-9564-81074AB955B1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{F1C27B6E-1E78-40CA-9564-81074AB955B1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{F1C27B6E-1E78-40CA-9564-81074AB955B1}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

StateMachine/StateMachine/Model/Order.cs

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+namespace StateMachine.Model
+{
+    public class Order
+    {
+        public OrderState State { get; private set; }
+
+        public Order()
+        {
+            State = OrderState.New;
+        }
+
+        public void ProcessOrder()
+        {
+            switch (State)
+            {
+                case OrderState.New:
+                    State = OrderState.Processing;
+                    System.Console.WriteLine("Order is being processed.");
+                    break;
+                case OrderState.Processing:
+                    State = OrderState.Shipped;
+                    System.Console.WriteLine("Order has been shipped.");
+                    break;
+                case OrderState.Shipped:
+                    State = OrderState.Delivered;
+                    System.Console.WriteLine("Order has been delivered.");
+                    break;
+                default:
+                System.Console.WriteLine("Invalid state transition.");
+                    break;
+            }
+        }
+
+        public void CancelOrder()
+        {
+            if (State != OrderState.Delivered && State != OrderState.Canceled)
+            {
+                State = OrderState.Canceled;
+                System.Console.WriteLine("Order has been canceled.");
+            }
+            else
+            {
+                System.Console.WriteLine("Unable to cancel order in this state.");
+            }
+        }
+    }
+}

StateMachine/StateMachine/Model/OrderState.cs

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+namespace StateMachine.Model
+{
+    public enum OrderState
+    {
+        New,
+        Processing,
+        Shipped,
+        Delivered,
+        Canceled
+    }
+}

StateMachine/StateMachine/Program.cs

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+using StateMachine.Model;
+
+namespace StateMachine;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        Order order = new Order();
+        System.Console.WriteLine($"Initial order state: {order.State}");
+
+        // process
+        order.ProcessOrder();
+        System.Console.WriteLine($"Current order state: {order.State}");
+
+        // ship
+        order.ProcessOrder();
+        System.Console.WriteLine($"Current order state: {order.State}");
+
+        // deliver
+        order.ProcessOrder();
+        System.Console.WriteLine($"Current order state: {order.State}");
+
+        // cancel
+        order.CancelOrder();
+        System.Console.WriteLine($"Current order state: {order.State}");
+
+        
+        order.ProcessOrder();
+        System.Console.WriteLine($"Current order state: {order.State}");
+    }
+}

StateMachine/StateMachine/StateMachine.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>