From e0bac4a96c538d9cf13e12e6d1df2cff35475b4b Mon Sep 17 00:00:00 2001
From: Claudiu Farcas <claudiu.farcas@cgm.com>
Date: Mon, 26 Apr 2021 08:25:59 +0300
Subject: [PATCH] command design pattern

---
 Program.cs                                    |  4 +-
 .../ChainOfResponsabilitySample.cs            | 10 ++-
 behavioral/command/CommandSample.cs           | 65 +++++++++++++++++++
 3 files changed, 75 insertions(+), 4 deletions(-)
 create mode 100644 behavioral/command/CommandSample.cs

diff --git a/Program.cs b/Program.cs
index 8b23897..2c9b28a 100644
--- a/Program.cs
+++ b/Program.cs
@@ -15,6 +15,7 @@ using design_patterns.structural.facade;
 using design_patterns.structural.flyweight;
 using design_patterns.structural.proxy;
 using design_patterns.behavioral.chainofresponsability;
+using design_patterns.behavioral.command;
 
 namespace design_patterns
 {
@@ -43,7 +44,8 @@ namespace design_patterns
                 // await ProxySample.Run();
 
                 // behavioral
-                await ChainOfResponsabilitySample.Run();
+                // await ChainOfResponsabilitySample.Run();
+                await CommandSample.Run();
             }
             catch (System.Exception ex)
             {
diff --git a/behavioral/chainofresponsability/ChainOfResponsabilitySample.cs b/behavioral/chainofresponsability/ChainOfResponsabilitySample.cs
index 0994369..e5e1c07 100644
--- a/behavioral/chainofresponsability/ChainOfResponsabilitySample.cs
+++ b/behavioral/chainofresponsability/ChainOfResponsabilitySample.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Threading.Tasks;
-using System.Collections.Generic
 
 namespace design_patterns.behavioral.chainofresponsability
 {
@@ -29,16 +28,18 @@ namespace design_patterns.behavioral.chainofresponsability
                 Date = DateTime.Now
             };
             
+            //define chain of handlers
             var handler = new BaseReqHandler { Request = request };
             handler.Add(new SecurityCheckReqHandler(false));
             handler.Add(new DataValidationReqHandler());
-
+            // issue the handler
             handler.Handle();
 
+            //define chain of handlers
             handler = new BaseReqHandler { Request = request };
             handler.Add(new SecurityCheckReqHandler(true));
             handler.Add(new DataValidationReqHandler());
-
+            // issue the handler
             handler.Handle();
         }
     }
@@ -47,6 +48,9 @@ namespace design_patterns.behavioral.chainofresponsability
         RequestInfo Request {get; set;}
         void Add(IReqHandler reqHandler);
         void Handle();
+        // alternatively we can invoke Handle with the main request object
+        // instead storing it as property
+        // void Handle(RequestInfo request);
     }
 
     public class BaseReqHandler : IReqHandler {
diff --git a/behavioral/command/CommandSample.cs b/behavioral/command/CommandSample.cs
new file mode 100644
index 0000000..e270ea6
--- /dev/null
+++ b/behavioral/command/CommandSample.cs
@@ -0,0 +1,65 @@
+using System;
+using System.Threading.Tasks;
+
+namespace design_patterns.behavioral.command
+{
+    /// <summary>
+    /// Command is a behavioral design pattern that turns a request 
+    /// into a stand-alone object that contains all information about the request.
+    /// This transformation lets you pass requests 
+    /// as a method arguments, delay or queue a request’s execution, 
+    /// and support undoable operations.
+    /// 
+    /// Use when:
+    /// - you want to parametrize objects with operations.
+    /// - you want to queue operations, schedule their execution, 
+    ///     or execute them remotely. (serialize commands)
+    /// - you want to implement reversible operations.
+    /// </summary>
+    public class CommandSample
+    {
+        public static async Task Run()
+        {
+            Console.WriteLine("Behavioral - Command");
+
+            var order = new Order {
+                ID = Guid.NewGuid().ToString()
+            };
+            ICommand addCommand = new AddOrderCommand(order);
+            addCommand.Execute();
+            ICommand removeCommand = new RemoveOrderCommand(order.ID);
+            removeCommand.Execute();
+        }
+    }
+
+    public interface ICommand
+    {
+        void Execute();
+    }
+
+    public class AddOrderCommand : ICommand {
+        public AddOrderCommand(Order order) => this.Order = order;
+
+        public Order Order { get; private set; }
+
+        public void Execute()
+        {
+            Console.WriteLine($"Execute add order command for order {Order.ID}");
+        }
+    }
+
+    public class RemoveOrderCommand : ICommand {
+        public RemoveOrderCommand(string orderId) => this.OrderID = orderId;
+
+        public string OrderID { get; private set; }
+
+        public void Execute()
+        {
+            Console.WriteLine($"Execute remove order command for order {OrderID}");
+        }
+    }
+
+    public class Order {
+        public string ID { get; set; }
+    }
+}
\ No newline at end of file