/**
  * @RDE_HEADER@
  * AvsSessionContext
  * $Id$
  * $HeadURL$
  * $Author$
  * Created by Christian Fröbel, SLSE, 2017-08-03
  */

#pragma once

#include <AudioVideoManagement/ava_types.h>
#include <QString>
#include <memory>
#include <functional>

namespace OperatorManagement
{
namespace Interface
{
class Dtc;
}
}


namespace AudioVideoManagement
{

namespace Interface
{
class Dtc;
}

class AvaSession;
class AvaState;
class StreamNameMapping;
class AvsMenus;
class VdSession;
class AvmExerciseContextHandle;
class AvsApp;
class PlaybackApp;

/**
 * AvsSessionContext ensures that there can only be one communication
 * channel to AVS_Workstation and AVS_Export with a defined exercise context at
 * any given time.
 * AvsSessionContext must not be used with the global exercise (exerciseId 0).
 *
 * The application can have many users of the communication channels at the same time.
 * The reason for this is that the AvmDataPlugin will be instantiated for every
 * exercise (also live and replay) and possibly multiple times for an exercise.
 * All these users shall share the same communication channels.
 * But all parallel users must use the same exercise context.
 *
 * AvsSessionContext creates the communication channels (AvaSession, VdSession) when the first user
 * calls acquire(). Subsequent users can get access to the same channels by also
 * calling acquire() -- but the exercise context must match.
 * When a user no longer needs these communication channels it calls release().
 * When all users released the communication channels, they will be deleted.
 * After that another user can call acquire() with a different exercise context.
 *
 * Use AvsSessionContextHandle to automatically acquire() and release()
 * the communication channel.
 * 
 * See AvmExerciseContext for a visualization of lifetimes of Apps, PluginInterface-instances
 * and ExerciseContext.
 * 
 * @see AvmExerciseContext
 * @author Christian Fröbel
 */
class AvsSessionContext
{
public:
  /**
   * Small helper struct that holds all parts that make up a session.
   * Only useful for AvsSessionContextHandle in order to access those parts.
   */
  struct Composite;

  AvsSessionContext();
  ~AvsSessionContext();

  /**
   * Check whether a AvsSessionContext with the given exerciseId can be acquired.
   * Yields true when no AvsSessionContext was created yet or when the currently active
   * AvsSessionContext is for the same exericse.
   */
  bool canAcquire(int exerciseId) const;

  /**
   * Need not to be called directly; use AvsSessionContextHandle instead.
   */
  ///@{
  Composite *acquire(int exerciseId, int operatorId, const QString &langCode, AvaGuiStyle, const AvmExerciseContextHandle &exerciseContextHandle);
  void release(Composite *composite);
  ///@}

private:
  std::unique_ptr<Composite>   m_composite;
  int                          m_refCount{0};
};


/**
 * Helper class to automatically call AvsSessionContext::acquire()
 * and AvsSessionContext::release() in the ctor and dtor respectively.
 * Instances can be moved but not copied.
 */
class AvsSessionContextHandle
{
public:
  AvsSessionContextHandle() = default;
  AvsSessionContextHandle(AvsSessionContext *context, int exerciseId, int operatorId, const QString &langCode, AvaGuiStyle, const AvmExerciseContextHandle &exerciseContextHandle);

  operator bool() const { return m_composite.get(); }

  AvaSession *avaSession() const;
  AvaState *avaState() const;
  AvsMenus *menus() const;

  VdSession *vdSession() const;

  AvsApp      *liveVideoApp() const;
  PlaybackApp *videoPlaybackApp() const;
  PlaybackApp *audioPlaybackApp() const;
  PlaybackApp *videoPresentationApp() const;
  PlaybackApp *audioPresentationApp() const;

private:
  using Releaser = std::function<void (AvsSessionContext::Composite *)>;
  std::unique_ptr<AvsSessionContext::Composite, Releaser>   m_composite;
};

} // namespace AudioVideoManagement