From 05709db77e620536d94e662b4d620d7039cd40ee Mon Sep 17 00:00:00 2001
From: Petrutiu Mihai <mihai.petrutiu@qubiz.com>
Date: Thu, 23 Jun 2016 21:03:26 +0300
Subject: [PATCH] Add another example of the memento pattern

---
 .../EmployeeSerialized/Caretaker.cs           | 30 ++++++++++++++
 .../EmployeeSerialized/Employee.cs            | 33 +++++++++++++++
 .../EmployeeSerialized/EmployeeMemento.cs     | 20 +++++++++
 .../EmployeeSerializedExample.cs              | 41 +++++++++++++++++++
 .../EmployeeSerialized/LimitedSizeStack.cs    | 31 ++++++++++++++
 src/MememntoPattern/MementoPatternExamples.cs | 18 ++++++++
 src/MememntoPattern/project.json              |  3 +-
 7 files changed, 175 insertions(+), 1 deletion(-)
 create mode 100644 src/MememntoPattern/EmployeeSerialized/Caretaker.cs
 create mode 100644 src/MememntoPattern/EmployeeSerialized/Employee.cs
 create mode 100644 src/MememntoPattern/EmployeeSerialized/EmployeeMemento.cs
 create mode 100644 src/MememntoPattern/EmployeeSerialized/EmployeeSerializedExample.cs
 create mode 100644 src/MememntoPattern/EmployeeSerialized/LimitedSizeStack.cs

diff --git a/src/MememntoPattern/EmployeeSerialized/Caretaker.cs b/src/MememntoPattern/EmployeeSerialized/Caretaker.cs
new file mode 100644
index 0000000..c2aeb23
--- /dev/null
+++ b/src/MememntoPattern/EmployeeSerialized/Caretaker.cs
@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MememntoPattern.EmployeeSerialized
+{
+    /// <summary>
+    /// Caretaker
+    /// </summary>
+    public class Caretaker
+    {
+        private LimitedSizeStack<EmployeeMemento> employeeHistory;
+
+        public Caretaker()
+        {
+            employeeHistory = new LimitedSizeStack<EmployeeMemento>(10);
+        }
+
+        public void Save(Employee emp)
+        {
+            employeeHistory.Push(emp.Save());
+        }
+
+        public void Revert(Employee emp)
+        {
+            emp.Revert(employeeHistory.Pop());
+        }
+    }
+}
diff --git a/src/MememntoPattern/EmployeeSerialized/Employee.cs b/src/MememntoPattern/EmployeeSerialized/Employee.cs
new file mode 100644
index 0000000..b85909b
--- /dev/null
+++ b/src/MememntoPattern/EmployeeSerialized/Employee.cs
@@ -0,0 +1,33 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MememntoPattern.EmployeeSerialized
+{
+    /// <summary>
+    /// Originator
+    /// </summary>
+    public class Employee
+    {
+        public string Name { get; set; }
+
+        public string Address { get; set; }
+
+        public List<string> Phones { get; set; }
+
+        public EmployeeMemento Save()
+        {            
+            return new EmployeeMemento(JsonConvert.SerializeObject(this));
+        }
+
+        public void Revert(EmployeeMemento memento)
+        {
+            Employee newEmployee = JsonConvert.DeserializeObject<Employee>(memento.SerializedEmployee);
+            Name = newEmployee.Name;
+            Address = newEmployee.Address;
+            Phones = newEmployee.Phones;
+        }
+    }
+}
diff --git a/src/MememntoPattern/EmployeeSerialized/EmployeeMemento.cs b/src/MememntoPattern/EmployeeSerialized/EmployeeMemento.cs
new file mode 100644
index 0000000..665fbe3
--- /dev/null
+++ b/src/MememntoPattern/EmployeeSerialized/EmployeeMemento.cs
@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MememntoPattern.EmployeeSerialized
+{
+    /// <summary>
+    /// Memento object
+    /// </summary>
+    public class EmployeeMemento
+    {
+        public string SerializedEmployee;
+
+        public EmployeeMemento(string serializedEmployee)
+        {
+            SerializedEmployee = serializedEmployee;
+        }
+    }
+}
diff --git a/src/MememntoPattern/EmployeeSerialized/EmployeeSerializedExample.cs b/src/MememntoPattern/EmployeeSerialized/EmployeeSerializedExample.cs
new file mode 100644
index 0000000..9e378e9
--- /dev/null
+++ b/src/MememntoPattern/EmployeeSerialized/EmployeeSerializedExample.cs
@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MememntoPattern.EmployeeSerialized
+{
+    public class EmployeeSerializedExample
+    {
+        public void Run()
+        {
+            Caretaker caretaker = new Caretaker();
+            Employee e = new Employee();
+            e.Name = "Ghiuri";
+            e.Address = "Stairway to heaven";
+
+            Console.WriteLine("First saved address: {0}", e.Address);
+            caretaker.Save(e);
+
+            e.Address = "Highway to hell";
+
+            Console.WriteLine("Last saved address: {0}", e.Address);
+
+            caretaker.Save(e);
+
+            e.Address = "Home of the brave"; // No save, no home, no address
+
+            Console.WriteLine("Address before revert: {0}", e.Address);
+
+            caretaker.Revert(e);
+
+            Console.WriteLine("First reverted Address: {0}", e.Address);
+
+            caretaker.Revert(e);
+
+            Console.WriteLine("Second reverted Address: {0}", e.Address);
+
+        }
+       
+    }
+}
diff --git a/src/MememntoPattern/EmployeeSerialized/LimitedSizeStack.cs b/src/MememntoPattern/EmployeeSerialized/LimitedSizeStack.cs
new file mode 100644
index 0000000..c34af1f
--- /dev/null
+++ b/src/MememntoPattern/EmployeeSerialized/LimitedSizeStack.cs
@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MememntoPattern.EmployeeSerialized
+{
+    public class LimitedSizeStack<T> : LinkedList<T>
+    {
+        private readonly int maxSize;
+        public LimitedSizeStack(int maxSize)
+        {
+            this.maxSize = maxSize;
+        }
+
+        public void Push(T item)
+        {
+            AddFirst(item);
+
+            if (Count > maxSize)
+                RemoveLast();
+        }
+
+        public T Pop()
+        {
+            var item = First.Value;
+            RemoveFirst();
+            return item;
+        }
+    }
+}
diff --git a/src/MememntoPattern/MementoPatternExamples.cs b/src/MememntoPattern/MementoPatternExamples.cs
index fb49ae5..3c64def 100644
--- a/src/MememntoPattern/MementoPatternExamples.cs
+++ b/src/MememntoPattern/MementoPatternExamples.cs
@@ -1,4 +1,5 @@
 using MememntoPattern.Employee;
+using MememntoPattern.EmployeeSerialized;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -25,6 +26,15 @@ namespace MememntoPattern
 
             EmployeeExample empExample = new EmployeeExample();
             empExample.Run();
+
+            GoToNextStep();
+
+            EmployeeSerializedExample empSerExample = new EmployeeSerializedExample();
+            empSerExample.Run();
+
+            GoToNextStep();
+
+            Console.WriteLine(GetPitfalls());
         }
 
         string GetWhenToUse()
@@ -51,6 +61,14 @@ Caretaker: keeps the mementos
 Memento: (Magic cookie) internal state of the object";
         }
 
+        string GetPitfalls()
+        {
+            return @"
+Can be expensive
+Deltes/history
+Exposing information only to memento so that we don't brake encapsulation";
+        }
+
         private static void GoToNextStep()
         {
             Console.ReadKey();
diff --git a/src/MememntoPattern/project.json b/src/MememntoPattern/project.json
index 2402f0c..6a306c8 100644
--- a/src/MememntoPattern/project.json
+++ b/src/MememntoPattern/project.json
@@ -3,7 +3,8 @@
 
   "dependencies": {
     "NETStandard.Library": "1.5.0-rc2-24027",
-    "Newtonsoft.Json": "8.0.3"
+    "Newtonsoft.Json": "8.0.3",
+    "System.Runtime.Serialization.Primitives": "4.0.10-*"
   },
 
   "frameworks": {