/*
  GuiFacade  -  access point for communicating with the Lumiera GTK GUI

  Copyright (C)         Lumiera.org
    2008,               Hermann Vosseler <Ichthyostega@web.de>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 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 General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

* *****************************************************/


/** @file guifacade.cpp
 ** Implementation of the GUI loader. Code generated from this
 ** translation unit is linked into the core application, where it implements
 ** the [Subsystem descriptor](\ref subsys.hpp) for the _UI Subsystem._ When main()
 ** activates and starts this subsystem, an instance of stage::GuiRunner will be
 ** created, which causes the Lumiera UI plug-in to be loaded and a new thread
 ** to be spawned, which launches the UI and performs the event loop.
 */


#include "stage/guifacade.hpp"
#include "include/gui-notification-facade.h"
#include "lib/sync.hpp"
#include "lib/error.hpp"
#include "lib/depend.hpp"
#include "common/instancehandle.hpp"
#include "common/option.hpp"

#include <memory>
#include <string>


namespace stage {
  
  using std::string;
  using std::unique_ptr;
  using lumiera::Subsys;
  using lumiera::InstanceHandle;
  using lib::Sync;
  using lib::RecursiveLock_NoWait;
  
  
  
  /** load and start the GUI as a plugin */
  struct GuiRunner
    : util::NonCopyable
    {
      typedef InstanceHandle<LUMIERA_INTERFACE_INAME(lumieraorg_Gui, 1)> GuiHandle;
      
      GuiHandle theGUI_;
      
      
      GuiRunner (Subsys::SigTerm terminationHandle)
        : theGUI_("lumieraorg_Gui", 1, 1, "lumieraorg_GuiStarterPlugin") // load GuiStarterPlugin
        {
          ASSERT (theGUI_);
          bool res = this->launchUI (terminationHandle);
          
          if (!res || lumiera_error_peek())
            throw lumiera::error::Fatal{"failed to bring up the GUI", lumiera_error()};
        }
      
      
      /*  ===== control interface for the GuiStarterPlugin ======= */
      
      /** start the actual GUI thread(s), after successfully loading
       *  the GuiStarterPlugin, that is. The implementation of this function
       *  must ensure to invoke the given termination signal reliably after
       *  shutting down the GUI, otherwise the application will hang on exit.
       *  @internal this function is invoked automatically during the GUI
       *            loading and startup process. Don't call it manually.
       */
      bool launchUI (Subsys::SigTerm& terminationHandle)
        { 
          return theGUI_->launchUI (reinterpret_cast<void*> (&terminationHandle));
        }
    };
  
  
  
  
  namespace { // implementation of GUI-"Subsystem" : start GUI through GuiStarterPlugin
    
    unique_ptr<GuiRunner> facade;
    
    
    class GuiSubsysDescriptor
      : public lumiera::Subsys,
        public Sync<RecursiveLock_NoWait>
      {
        operator string()  const { return "Lumiera GTK GUI"; }
        
        bool 
        shouldStart (lumiera::Option& opts)  override
          {
            if (opts.isHeadless() or 0 < opts.getPort())
              {
                INFO (guifacade, "*not* starting the GUI...");
                return false;
              }
            else
              return true;
          }
        
        bool
        start (lumiera::Option&, Subsys::SigTerm termNotification)  override
          {
            Lock guard (this);
            if (facade)
              return false;    // already started
            
            facade.reset (   //  trigger loading of the GuiStarterPlugin...
              new GuiRunner (
                    [=] (string* problemMessage)
                        { //     will be invoked when the UI thread exits
                          closeGuiModule();
                          termNotification(problemMessage);
                        }));
            
            return true;
          }
        
        /**
         * @warning there is a possible race here,
         *  when shutdown is triggered before the GUI was able to open the GuiNotification interface.
         *  However, the Lumiera thread handling wrapper/framework ensures that a new thread actually
         *  starts to execute (and picks up the arguments), prior to returning from the thread starting
         *  function. For this reason, it is rather unlikely this race actually happens in practice,
         *  since opening the GuiNotification interface is done early, while starting the UI-Bus.
         */
        void
        triggerShutdown ()  noexcept override
          {
            try { GuiNotification::facade().triggerGuiShutdown ("Application shutdown"); }
            
            ERROR_LOG_AND_IGNORE (guifacade, "trigger shutdown of the GUI");
          }
        
        bool
        checkRunningState ()  noexcept override
          {
            return bool(facade);
          }
        
        
        void
        closeGuiModule ()
          {
            Lock guard (this);
            if (!facade)
              {
                WARN (guifacade, "Termination signal invoked, but GUI is currently closed. "
                                 "Probably this is due to some broken startup logic and should be fixed.");
              }
            else
              facade.reset (nullptr);
          }
        
        
        
      public:
        GuiSubsysDescriptor() { }
        
       ~GuiSubsysDescriptor()
          {
            if (facade)
              {
                WARN (guifacade, "GUI subsystem terminates, but GuiFacade isn't properly closed. "
                                 "Closing it forcedly; this indicates broken startup logic and should be fixed.");
                try { facade.reset (0); }
                ERROR_LOG_AND_IGNORE (guifacade, "forcibly closing the GUI");
                ENSURE (not lumiera_error_peek());
              }
          }
      };
    
    lib::Depend<GuiSubsysDescriptor> theDescriptor;
    
  } // (End) impl details
  
  
  
  
  
  
  /** @internal intended for use by main(). */
  lumiera::Subsys&
  GuiFacade::getDescriptor()
  {
    return theDescriptor();
  }
  
  
  bool
  GuiFacade::isUp ()
  {
    return bool(facade);
  }
  
  
} // namespace stage