--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Messages/Promise.h	Fri Sep 14 16:44:01 2018 +0200
@@ -0,0 +1,89 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2018 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#pragma once
+
+#include "MessageBroker.h"
+#include "ICallable.h"
+#include "IMessage.h"
+
+#include <boost/noncopyable.hpp>
+
+namespace OrthancStone {
+
+  class Promise : public boost::noncopyable
+  {
+  protected:
+    MessageBroker&                    broker_;
+
+    ICallable* successCallable_;
+    ICallable* failureCallable_;
+
+  public:
+    Promise(MessageBroker& broker)
+      : broker_(broker),
+        successCallable_(NULL),
+        failureCallable_(NULL)
+    {
+    }
+
+    void Success(const IMessage& message)
+    {
+      // check the target is still alive in the broker
+      if (broker_.IsActive(successCallable_->GetObserver()))
+      {
+        successCallable_->Apply(message);
+      }
+    }
+
+    void Failure(const IMessage& message)
+    {
+      // check the target is still alive in the broker
+      if (broker_.IsActive(failureCallable_->GetObserver()))
+      {
+        failureCallable_->Apply(message);
+      }
+    }
+
+    Promise& Then(ICallable* successCallable)
+    {
+      if (successCallable_ != NULL)
+      {
+        // TODO: throw throw new "Promise may only have a single success target"
+      }
+      successCallable_ = successCallable;
+      return *this;
+    }
+
+    Promise& Else(ICallable* failureCallable)
+    {
+      if (failureCallable_ != NULL)
+      {
+        // TODO: throw throw new "Promise may only have a single failure target"
+      }
+      failureCallable_ = failureCallable;
+      return *this;
+    }
+
+  };
+
+
+}