feat: Add idempotency header to request for new sessions

closes #403

Author: laolubenson

src/Appium.Net/Appium/Service/AppiumCommandExecutor.cs

@@ -22,8 +22,10 @@ internal class AppiumCommandExecutor : ICommandExecutor
     {
         private readonly AppiumLocalService Service;
         private readonly Uri URL;
-        private readonly ICommandExecutor RealExecutor;
+        private ICommandExecutor RealExecutor;
         private bool isDisposed;
+        private const string IdempotencyHeader = "X-Idempotency-Key";
+
 
         private static ICommandExecutor CreateRealExecutor(Uri remoteAddress, TimeSpan commandTimeout)
         {
@@ -37,6 +39,7 @@ private static ICommandExecutor CreateRealExecutor(Uri remoteAddress, TimeSpan c
                     Activator.CreateInstance(commandType, new object[] {remoteAddress, commandTimeout}) as
                         ICommandExecutor;
             }
+            
 
             return commandExecutor;
         }
@@ -64,23 +67,29 @@ internal AppiumCommandExecutor(AppiumLocalService service, TimeSpan timeForTheSe
         public Response Execute(Command commandToExecute)
         {
             Response result = null;
-            if (commandToExecute.Name == DriverCommand.NewSession && this.Service != null)
-            {
-                Service.Start();
-            }
+
 
             try
             {
+                if (commandToExecute.Name == DriverCommand.NewSession && Service != null)
+                {
+                    Service.Start();
+                }
+                else
+                {
+                    RealExecutor = ModifyHttpRequestHeader(RealExecutor);
+                }
+
                 result = RealExecutor.Execute(commandToExecute);
                 return result;
             }
             catch (Exception e)
             {
-                if ((commandToExecute.Name == DriverCommand.NewSession) && (Service != null))
+                if ((commandToExecute.Name == DriverCommand.NewSession))
                 {
-                    Service.Dispose();
+                    Service?.Dispose();
                 }
-                throw e;
+                throw;
             }
             finally
             {
@@ -97,21 +106,29 @@ public Response Execute(Command commandToExecute)
             }
         }
 
-        public void Dispose()
+        private ICommandExecutor ModifyHttpRequestHeader(ICommandExecutor commandExecutor)
+        {
+            var modifiedCommandExecutor = commandExecutor as HttpCommandExecutor;
+            if (modifiedCommandExecutor != null)
+                    modifiedCommandExecutor.SendingRemoteHttpRequest += SendingRemoteHttpRequestHandler;
+            return modifiedCommandExecutor;
+        }
+
+        private void SendingRemoteHttpRequestHandler(
+            object sender, SendingRemoteHttpRequestEventArgs e)
         {
-            this.Dispose(true);
+            e.Request.Headers.Add(IdempotencyHeader, Guid.NewGuid().ToString());
         }
 
+        public void Dispose() => Dispose(true);
+
         protected void Dispose(bool disposing)
         {
             if (!isDisposed)
             {
                 if (disposing)
                 {
-                    if (Service != null)
-                    {
-                        Service.Dispose();
-                    }
+                    Service?.Dispose();
                 }
 
                 isDisposed = true;