finite state machine

DesignPatternGuru/DesignPatternGuru.sln

@@ -47,6 +47,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Observer", "Observer\Observ
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "State", "State\State.csproj", "{BE9AFB6B-3AD5-4F54-91FF-7829B0FBFBCD}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "UsefulSamples", "UsefulSamples", "{7D7093A3-69ED-49A5-A6E2-D5732EB68559}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FiniteStateMachine", "FiniteStateMachine\FiniteStateMachine.csproj", "{51C2F1F3-B9FC-46D6-A6BD-6636010ABCD2}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -129,6 +133,10 @@ Global
 		{BE9AFB6B-3AD5-4F54-91FF-7829B0FBFBCD}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{BE9AFB6B-3AD5-4F54-91FF-7829B0FBFBCD}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{BE9AFB6B-3AD5-4F54-91FF-7829B0FBFBCD}.Release|Any CPU.Build.0 = Release|Any CPU
+		{51C2F1F3-B9FC-46D6-A6BD-6636010ABCD2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{51C2F1F3-B9FC-46D6-A6BD-6636010ABCD2}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{51C2F1F3-B9FC-46D6-A6BD-6636010ABCD2}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{51C2F1F3-B9FC-46D6-A6BD-6636010ABCD2}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -153,6 +161,7 @@ Global
 		{A6E39678-6214-4BD2-B616-A3350340E5AB} = {E3B8A482-1A9A-4B6E-8310-050A44C8E379}
 		{EB189FAC-7C63-48BB-92D7-3C35A277EA1D} = {E3B8A482-1A9A-4B6E-8310-050A44C8E379}
 		{BE9AFB6B-3AD5-4F54-91FF-7829B0FBFBCD} = {E3B8A482-1A9A-4B6E-8310-050A44C8E379}
+		{51C2F1F3-B9FC-46D6-A6BD-6636010ABCD2} = {7D7093A3-69ED-49A5-A6E2-D5732EB68559}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {3E5A9C6B-2E8A-466E-B5E0-4379902EFFAC}

DesignPatternGuru/FiniteStateMachine/Command.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace FiniteStateMachine
+{
+    internal enum Command
+    {
+        Begin,
+        End,
+        Paused,
+        Resume,
+        Exit,
+    }
+}

DesignPatternGuru/FiniteStateMachine/FiniteStateMachine.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

DesignPatternGuru/FiniteStateMachine/Process.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace FiniteStateMachine
+{
+    internal class Process
+    {
+        private Dictionary<StateTransition, ProcessState> _transitions;
+        
+        public ProcessState CurrentState { get; private set; }
+
+        public Process()
+        {
+            CurrentState = ProcessState.Inactive;
+
+            _transitions = new Dictionary<StateTransition, ProcessState>()
+            {
+                { new StateTransition(ProcessState.Inactive, Command.Exit), ProcessState.Trminated },
+                { new StateTransition(ProcessState.Inactive, Command.Begin), ProcessState.Active },
+                { new StateTransition(ProcessState.Active, Command.End), ProcessState.Inactive },
+                { new StateTransition(ProcessState.Active, Command.Paused), ProcessState.Paused },
+                { new StateTransition(ProcessState.Paused, Command.End), ProcessState.Inactive },
+                {  new StateTransition (ProcessState.Paused, Command.Resume), ProcessState.Active },
+            };
+        }
+
+        public ProcessState GetNext(Command command)
+        {
+            StateTransition transition = new StateTransition(CurrentState, command);
+            ProcessState nextState;
+            if (!_transitions.TryGetValue(transition, out nextState))
+                throw new Exception($"Invalid transition: {CurrentState} → {nextState}");
+
+            return nextState;
+        }
+
+        public ProcessState MoveNext(Command command)
+        {
+            CurrentState = GetNext(command);
+            return CurrentState;
+        }
+    }
+}

DesignPatternGuru/FiniteStateMachine/ProcessState.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace FiniteStateMachine
+{
+    internal enum ProcessState
+    {
+        Inactive,
+        Active,
+        Paused,
+        Trminated,
+    }
+}

DesignPatternGuru/FiniteStateMachine/Program.cs

@@ -0,0 +1,16 @@
+namespace FiniteStateMachine
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Process p = new Process();
+
+            Console.WriteLine($"Current State: {p.CurrentState}");
+            Console.WriteLine($"Command.Begin: {p.MoveNext(Command.Begin)}");
+            Console.WriteLine($"Command.Pause: {p.MoveNext(Command.Paused)}");
+            Console.WriteLine($"Command.End: {p.MoveNext(Command.End)}");
+            Console.WriteLine($"Command.Exit: {p.MoveNext(Command.Exit)}");
+        }
+    }
+}

DesignPatternGuru/FiniteStateMachine/StateTransition.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace FiniteStateMachine
+{
+    internal class StateTransition
+    {
+        private readonly ProcessState CurrentState;
+        private readonly Command Command;
+
+        public StateTransition(ProcessState currentState, Command command)
+        {
+            CurrentState = currentState;
+            Command = command;
+        }
+
+        public override int GetHashCode()
+        {
+            return 17 + 31 * CurrentState.GetHashCode() + 31 * Command.GetHashCode();
+        }
+
+        public override bool Equals(object? obj)
+        {
+            StateTransition other = obj as StateTransition;
+            return other != null && this.CurrentState == other.CurrentState;
+        }
+    }
+}