/**
  * @RDE_HEADER@
  * AvsCommandQueue
  * $Id$
  * $HeadURL$
  * $Author$
  * Created by Christian Fröbel, NLSE, 2018-02-23
  */

#pragma once

#include "logger.h"
#include "avm_export.h"
#include <QObject>
#include <QTimer>
#include <deque>
#include <memory>
#include <chrono>


namespace LtsUtils
{
class IConnection;
}

namespace AudioVideoManagement
{

class ICommand;

/**
 * CommandQueue used by AvaControl and VdControl.
 * The CommandQueue ensures that each command is sent after the previous command finished.
 * When a command is not finished within a defined time frame timeout() is signalled.
 *
 * @author Christian Fröbel
 */
class AVM_COMMON_EXPORT AvsCommandQueue : public QObject
{
  Q_OBJECT

public:
  /**
   * @param timeout Timeout within which each command must be completed. Use 0 to disable the timeout.
   */
  explicit AvsCommandQueue(std::chrono::milliseconds timeout);
  ~AvsCommandQueue() override;

  void queue(std::unique_ptr<ICommand> cmd, std::unique_ptr<LtsUtils::IConnection> connection);
  void done();

  ICommand *currentCommand() const;
  bool currentHasConnection() const;
  LtsUtils::IConnection *currentConnection() const;

  void flush();

  /**
   * Tell the Queue that the current command is still alive.
   * Internal Timeout timer will be reset.
   */
  void alive();

  bool isEmpty() const { return m_queue.empty(); }

signals:
  /**
   * Signalled whenever the queue is empty again. This can have several reasons:
   * - The last command finished successfully.
   * - flush() was called while commands are pending.
   * - This instance is deleted with pending commands which get flushed then.
   */
  void queueEmpty();

  /** Signalled if the current command did not finish within the defined time frame. */
  void timeout();

private:
  void nextCommand();
  void tryReduce();

private:
  /**
   * Associates a command with a Qt-connection (signal-signal or signal-slot).
   * In a scenario where multiple clients use an AvaControl instance
   * this makes it possible to give the asynchronous response only
   * to the initiator of the command.
   */
  struct CommandWithConn
  {
    std::unique_ptr<ICommand>   cmd;
    std::unique_ptr<LtsUtils::IConnection>   connection;
  };

  std::deque<CommandWithConn>   m_queue;
  QTimer                        m_timer;
  LOGGER_T                      m_logger;
};

} // namespace AudioVideoManagement