--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Loaders/LoaderStateMachine.cpp	Fri Apr 03 16:13:06 2020 +0200
@@ -0,0 +1,219 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2020 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/>.
+ **/
+
+
+#include "LoaderStateMachine.h"
+
+#include "../../Loaders/ILoadersContext.h"
+
+#include <Core/OrthancException.h>
+
+namespace OrthancStone
+{
+  void LoaderStateMachine::State::Handle(const OrthancStone::OrthancRestApiCommand::SuccessMessage& message)
+  {
+    throw Orthanc::OrthancException(Orthanc::ErrorCode_NotImplemented);
+  }
+      
+
+  void LoaderStateMachine::State::Handle(const OrthancStone::GetOrthancImageCommand::SuccessMessage& message)
+  {
+    throw Orthanc::OrthancException(Orthanc::ErrorCode_NotImplemented);
+  }
+
+      
+  void LoaderStateMachine::State::Handle(const OrthancStone::GetOrthancWebViewerJpegCommand::SuccessMessage& message)
+  {
+    throw Orthanc::OrthancException(Orthanc::ErrorCode_NotImplemented);
+  }
+
+
+  void LoaderStateMachine::Schedule(OrthancStone::OracleCommandBase* command)
+  {
+    LOG(TRACE) << "LoaderStateMachine(" << std::hex << this << std::dec << ")::Schedule()";
+
+    std::unique_ptr<OrthancStone::OracleCommandBase> protection(command);
+
+    if (command == NULL)
+    {
+      throw Orthanc::OrthancException(Orthanc::ErrorCode_NullPointer);
+    }
+      
+    if (!command->HasPayload())
+    {
+      throw Orthanc::OrthancException(Orthanc::ErrorCode_ParameterOutOfRange,
+                                      "The payload must contain the next state");
+    }
+    pendingCommands_.push_back(protection.release());
+
+    Step();
+  }
+
+
+  void LoaderStateMachine::Start()
+  {
+    LOG(TRACE) << "LoaderStateMachine(" << std::hex << this << std::dec << ")::Start()";
+
+    if (active_)
+    {
+      LOG(TRACE) << "LoaderStateMachine::Start() called while active_ is true";
+      throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls);
+    }
+
+    active_ = true;
+
+    for (size_t i = 0; i < simultaneousDownloads_; i++)
+    {
+      Step();
+    }
+  }
+
+
+  void LoaderStateMachine::Step()
+  {
+    if (!pendingCommands_.empty() &&
+        activeCommands_ < simultaneousDownloads_)
+    {
+
+      OrthancStone::IOracleCommand* nextCommand = pendingCommands_.front();
+
+      LOG(TRACE) << "    LoaderStateMachine(" << std::hex << this << std::dec << 
+        ")::Step(): activeCommands_ (" << activeCommands_ << 
+        ") < simultaneousDownloads_ (" << simultaneousDownloads_ << 
+        ") --> will Schedule command addr " << std::hex << nextCommand << std::dec;
+
+      {
+        std::unique_ptr<OrthancStone::ILoadersContext::ILock> lock(loadersContext_.Lock());
+        boost::shared_ptr<IObserver> observer(GetSharedObserver());
+        lock->Schedule(observer, 0, nextCommand); // TODO: priority!
+      }
+      pendingCommands_.pop_front();
+
+      activeCommands_++;
+    }
+    else
+    {
+      LOG(TRACE) << "    LoaderStateMachine(" << std::hex << this << std::dec << 
+        ")::Step(): activeCommands_ (" << activeCommands_ << 
+        ") >= simultaneousDownloads_ (" << simultaneousDownloads_ << 
+        ") --> will NOT Schedule command";
+    }
+  }
+
+
+  void LoaderStateMachine::Clear()
+  {
+    LOG(TRACE) << "LoaderStateMachine(" << std::hex << this << std::dec << ")::Clear()";
+    for (PendingCommands::iterator it = pendingCommands_.begin();
+         it != pendingCommands_.end(); ++it)
+    {
+      delete *it;
+    }
+
+    pendingCommands_.clear();
+  }
+  
+
+  void LoaderStateMachine::HandleExceptionMessage(const OrthancStone::OracleCommandExceptionMessage& message)
+  {
+    LOG(ERROR) << "LoaderStateMachine::HandleExceptionMessage: error in the state machine, stopping all processing";
+    LOG(ERROR) << "Error: " << message.GetException().What() << " Details: " <<
+      message.GetException().GetDetails();
+      Clear();
+  }
+
+  template <typename T>
+  void LoaderStateMachine::HandleSuccessMessage(const T& message)
+  {
+    if (activeCommands_ <= 0) {
+      LOG(ERROR) << "LoaderStateMachine(" << std::hex << this << std::dec << ")::HandleSuccessMessage : activeCommands_ should be > 0 but is: " << activeCommands_;
+    }
+    else {
+      activeCommands_--;
+      try
+      {
+        dynamic_cast<State&>(message.GetOrigin().GetPayload()).Handle(message);
+        Step();
+      }
+      catch (Orthanc::OrthancException& e)
+      {
+        LOG(ERROR) << "Error in the state machine, stopping all processing: " <<
+          e.What() << " Details: " << e.GetDetails();
+        Clear();
+      }
+    }
+  }
+
+
+  LoaderStateMachine::LoaderStateMachine(
+    OrthancStone::ILoadersContext& loadersContext)
+    : loadersContext_(loadersContext)
+    , active_(false)
+    , simultaneousDownloads_(4)
+    , activeCommands_(0)
+  {
+    using OrthancStone::ILoadersContext;
+
+    LOG(TRACE) 
+      << "LoaderStateMachine(" << std::hex << this 
+      << std::dec << ")::LoaderStateMachine()";
+  }
+
+  void LoaderStateMachine::PostConstructor()
+  {
+    std::unique_ptr<OrthancStone::ILoadersContext::ILock>
+      lock(loadersContext_.Lock());
+
+    OrthancStone::IObservable& observable = lock->GetOracleObservable();
+
+    // TODO => Move this out of constructor
+    Register<OrthancStone::OrthancRestApiCommand::SuccessMessage>(
+      observable, &LoaderStateMachine::HandleSuccessMessage);
+    Register<OrthancStone::GetOrthancImageCommand::SuccessMessage>(
+      observable, &LoaderStateMachine::HandleSuccessMessage);
+    Register<OrthancStone::GetOrthancWebViewerJpegCommand::SuccessMessage>(
+      observable, &LoaderStateMachine::HandleSuccessMessage);
+    Register<OrthancStone::OracleCommandExceptionMessage>(
+      observable, &LoaderStateMachine::HandleExceptionMessage);
+  }
+
+  LoaderStateMachine::~LoaderStateMachine()
+  {
+    LOG(TRACE) << "LoaderStateMachine(" << std::hex << this << std::dec << ")::~LoaderStateMachine()";
+    Clear();
+  }
+
+  void LoaderStateMachine::SetSimultaneousDownloads(unsigned int count)
+  {
+    if (active_)
+    {
+      LOG(ERROR) << "LoaderStateMachine::SetSimultaneousDownloads called while active_ is true";
+      throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls);
+    }
+    else if (count == 0)
+    {
+      throw Orthanc::OrthancException(Orthanc::ErrorCode_ParameterOutOfRange);        
+    }
+    else
+    {
+      simultaneousDownloads_ = count;
+    }
+  }
+}