memento

DesignPatternGuru/DesignPatternGuru.sln

@@ -41,6 +41,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Iterator", "Iterator\Iterat
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Mediator", "Mediator\Mediator.csproj", "{08D296F6-6698-4FCB-B605-318D9381F975}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Memonto", "Memonto\Memonto.csproj", "{A6E39678-6214-4BD2-B616-A3350340E5AB}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -111,6 +113,10 @@ Global
 		{08D296F6-6698-4FCB-B605-318D9381F975}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{08D296F6-6698-4FCB-B605-318D9381F975}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{08D296F6-6698-4FCB-B605-318D9381F975}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A6E39678-6214-4BD2-B616-A3350340E5AB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A6E39678-6214-4BD2-B616-A3350340E5AB}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A6E39678-6214-4BD2-B616-A3350340E5AB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A6E39678-6214-4BD2-B616-A3350340E5AB}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -132,6 +138,7 @@ Global
 		{629A51B1-04D9-4636-8E21-1712DCFF21DF} = {E3B8A482-1A9A-4B6E-8310-050A44C8E379}
 		{6619433E-476B-404C-94A0-D0C0FE52DE41} = {E3B8A482-1A9A-4B6E-8310-050A44C8E379}
 		{08D296F6-6698-4FCB-B605-318D9381F975} = {E3B8A482-1A9A-4B6E-8310-050A44C8E379}
+		{A6E39678-6214-4BD2-B616-A3350340E5AB} = {E3B8A482-1A9A-4B6E-8310-050A44C8E379}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {3E5A9C6B-2E8A-466E-B5E0-4379902EFFAC}

DesignPatternGuru/Memonto/Mementos/Caretaker.cs

@@ -0,0 +1,57 @@
+using Memonto.Originators;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Memonto.Mementos
+{
+    internal class Caretaker
+    {
+        private List<IMemento> _mementos = new List<IMemento>();
+
+        private Originator _originator = null;
+
+        public Caretaker(Originator originator)
+        {
+            _originator = originator;
+        }
+
+        public void Backup()
+        {
+            Console.WriteLine();
+            Console.WriteLine("Caretaker: Saving originator's state...");
+            _mementos.Add(_originator.Save());
+        }
+
+        public void Undo()
+        {
+            if (_mementos.Count < 1)
+                return;
+
+            IMemento memento = _mementos.Last();
+            _mementos.Remove(memento);
+
+            Console.WriteLine($"Caretaker: Restoring state to: {memento.GetName()}");
+            try
+            {
+                _originator.Restore(memento);
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"Undo exception: {ex.Message}");
+                Undo();
+            }
+        }
+
+        public void ShowHistory()
+        {
+            Console.WriteLine("Caretaker: Here's the list of mementos: ");
+            foreach (var memento in _mementos)
+            {
+                Console.WriteLine(memento.GetName());
+            }
+        }
+    }
+}

DesignPatternGuru/Memonto/Mementos/ConcreteMemento.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Memonto.Mementos
+{
+    internal class ConcreteMemento : IMemento
+    {
+        private string _state;
+
+        private DateTime _date;
+
+        public ConcreteMemento(string state)
+        {
+            _state = state;
+            _date = DateTime.Now;
+        }
+
+        public DateTime GetDate()
+        {
+            return _date;
+        }
+
+        public string GetName()
+        {
+            return $"[{_date}] {_state.Substring(0, 9)}...";
+        }
+
+        public string GetState()
+        {
+            return _state;
+        }
+    }
+}

DesignPatternGuru/Memonto/Mementos/IMemento.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Memonto.Mementos
+{
+    internal interface IMemento
+    {
+        string GetName();
+
+        string GetState();
+
+        DateTime GetDate();
+    }
+}

DesignPatternGuru/Memonto/Memonto.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/Memonto/Originators/Originator.cs

@@ -0,0 +1,55 @@
+using Memonto.Mementos;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Memonto.Originators
+{
+    internal class Originator
+    {
+        private string _state;
+
+        public Originator(string state)
+        {
+            _state = state;
+            Console.WriteLine($"Originator: My initial state is: {state}");
+        }
+
+        public void DoSomething()
+        {
+            Console.WriteLine("Originator: I'm doing something important.");
+            _state = GenerateRandomString(30);
+            Console.WriteLine($"Originator: And my state has changed to: {_state}");
+        }
+
+        private string GenerateRandomString(int length = 10)
+        {
+            string allowedSymbols = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+            string result = string.Empty;
+
+            while (length > 0 )
+            {
+                result += allowedSymbols[new Random().Next(0, allowedSymbols.Length)];
+                length--;
+            }
+
+            return result;
+        }
+
+        public IMemento Save()
+        {
+            return new ConcreteMemento( _state );
+        }
+
+        public void Restore(IMemento memento )
+        {
+            if (!(memento is ConcreteMemento))
+                throw new Exception("Unknown memento class " + memento.ToString());
+
+            _state = memento.GetState();
+            Console.WriteLine($"Originator: My state has changed to: {_state}");
+        }
+    }
+}

DesignPatternGuru/Memonto/Program.cs

@@ -0,0 +1,38 @@
+using Memonto.Mementos;
+using Memonto.Originators;
+
+namespace Memonto
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Originator originator = new Originator("Super-duper-super-puper-super.");
+            Caretaker caretaker = new Caretaker(originator);
+
+            caretaker.Backup();
+            originator.DoSomething();
+
+            caretaker.Backup();
+            originator.DoSomething();
+
+            caretaker.Backup();
+            originator.DoSomething();
+
+            Console.WriteLine();
+            caretaker.ShowHistory();
+
+            Console.WriteLine();
+            Console.WriteLine("Client: Now, let's rollback!");
+            Console.WriteLine();
+            caretaker.Undo();
+
+            Console.WriteLine();
+            Console.WriteLine("Client: Once more!");
+            Console.WriteLine();
+            caretaker.Undo();
+
+            Console.WriteLine();
+        }
+    }
+}