// Copyright (c) 2020 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#ifndef _SelectMgr_BVHThreadPool_HeaderFile
#define _SelectMgr_BVHThreadPool_HeaderFile

#include <Standard_Transient.hxx>
#include <OSD_Thread.hxx>
#include <Standard_Mutex.hxx>
#include <Select3D_SensitiveEntity.hxx>
#include <Standard_Condition.hxx>
#include <Message_Messenger.hxx>

//! Class defining a thread pool for building BVH for the list of Select3D_SensitiveEntity within background thread(s).
class SelectMgr_BVHThreadPool : public Standard_Transient
{
  DEFINE_STANDARD_RTTIEXT(SelectMgr_BVHThreadPool, Standard_Transient)
public:
  //! Main constructor
  Standard_EXPORT SelectMgr_BVHThreadPool (Standard_Integer theNbThreads);

  //! Destructor
  Standard_EXPORT virtual ~SelectMgr_BVHThreadPool();

public:

  //! Thread with back reference to thread pool and thread mutex in it.
  class BVHThread : public OSD_Thread
  {
    friend class SelectMgr_BVHThreadPool;
  public:

    BVHThread()
      : OSD_Thread(),
      myPool(nullptr),
      myMutex(),
      myToCatchFpe (Standard_False)
    {

    }

    //! Returns mutex used for BVH building
    Standard_Mutex& BVHMutex()
    {
      return myMutex;
    }

    //! Assignment operator.
    BVHThread& operator= (const BVHThread& theCopy)
    {
      Assign (theCopy);
      return *this;
    }

    //! Assignment operator.
    void Assign (const BVHThread& theCopy)
    {
      OSD_Thread::Assign (theCopy);
      myPool = theCopy.myPool;
      myToCatchFpe = theCopy.myToCatchFpe;
    }

  private:
    //! Method is executed in the context of thread.
    void performThread();

    //! Method is executed in the context of thread.
    static Standard_Address runThread (Standard_Address theTask);

  private:

    SelectMgr_BVHThreadPool* myPool;
    Standard_Mutex myMutex;
    bool myToCatchFpe;
  };

public:
  //! Queue a sensitive entity to build its BVH
  Standard_EXPORT void AddEntity (const Handle(Select3D_SensitiveEntity)& theEntity);

  //! Stops threads
  Standard_EXPORT void StopThreads();

  //! Waits for all threads finish their jobs
  Standard_EXPORT void WaitThreads();

  //! Returns array of threads
  NCollection_Array1<BVHThread>& Threads()
  {
    return myBVHThreads;
  }

public:

  //! Class providing a simple interface to mutexes for list of BVHThread
  class Sentry 
  {
  public:

    //! Constructor - initializes the sentry object and locks list of mutexes immediately
    Sentry (const Handle(SelectMgr_BVHThreadPool)& thePool)
    : myPool (thePool)
    {
      Lock();
    }
    
    //! Destructor - unlocks list of mutexes if already locked.
    ~Sentry()
    {
        Unlock();
    }

    //! Lock list of mutexes
    void Lock()
    {
      if (!myPool.IsNull())
      {
        for (Standard_Integer i = myPool->Threads().Lower(); i <= myPool->Threads().Upper(); ++i)
        {
          myPool->Threads().ChangeValue(i).BVHMutex().Lock();
        }
      }
    }

    //! Unlock list of mutexes
    void Unlock()
    {
      if (!myPool.IsNull())
      {
        for (Standard_Integer i = myPool->Threads().Lower(); i <= myPool->Threads().Upper(); ++i)
        {
          myPool->Threads().ChangeValue(i).BVHMutex().Unlock();
        }
      }
    }

    //! This method should not be called (prohibited).
    Sentry (const Sentry &);
    //! This method should not be called (prohibited).
    Sentry& operator = (const Sentry &);

  private:
    Handle(SelectMgr_BVHThreadPool) myPool;
  };

protected:

  NCollection_List<Handle(Select3D_SensitiveEntity)> myBVHToBuildList; //!< list of queued sensitive entities
  NCollection_Array1<BVHThread> myBVHThreads;                          //!< threads to build BVH
  Standard_Boolean myToStopBVHThread;                                  //!< flag to stop BVH threads
  Standard_Mutex myBVHListMutex;                                       //!< mutex for interaction with myBVHToBuildList
  Standard_Condition myWakeEvent;                                      //!< raises when any sensitive is added to the BVH list
  Standard_Condition myIdleEvent;                                      //!< raises when BVH list become empty
  Standard_Boolean myIsStarted;                                        //!< indicates that threads are running
};

#endif
