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#ifndef OPENCV_APPS_NODELET_H_
#define OPENCV_APPS_NODELET_H_

#include <ros/ros.h>
#include <nodelet/nodelet.h>
#include <boost/thread.hpp>
#include <image_transport/image_transport.h>

// https://stackoverflow.com/questions/10496824/how-to-define-nullptr-for-supporting-both-c03-and-c11
#if !defined(nullptr)
#define nullptr NULL
#endif

namespace opencv_apps
{
/** @brief
 * Enum to represent connection status.
 */
enum ConnectionStatus
{
  NOT_INITIALIZED,
  NOT_SUBSCRIBED,
  SUBSCRIBED
};

/** @brief
 * Nodelet to automatically subscribe/unsubscribe
 * topics according to subscription of advertised topics.
 *
 * It's important not to subscribe topic if no output is required.
 *
 * In order to watch advertised topics, need to use advertise template method.
 * And create subscribers in subscribe() and shutdown them in unsubscribed().
 *
 */
class Nodelet : public nodelet::Nodelet
{
public:
  Nodelet() : subscribed_(false)
  {
  }

protected:
  /** @brief
   * Initialize nodehandles nh_ and pnh_. Subclass should call
   * this method in its onInit method
   */
  virtual void onInit();

  /** @brief
   * Post processing of initialization of nodelet.
   * You need to call this method in order to use always_subscribe
   * feature.
   */
  virtual void onInitPostProcess();

  /** @brief
   * callback function which is called when new subscriber come
   */
  virtual void connectionCallback(const ros::SingleSubscriberPublisher& pub);

  /** @brief
   * callback function which is called when new subscriber come for image
   * publisher
   */
  virtual void imageConnectionCallback(const image_transport::SingleSubscriberPublisher& pub);

  /** @brief
   * callback function which is called when new subscriber come for camera
   * image publisher
   */
  virtual void cameraConnectionCallback(const image_transport::SingleSubscriberPublisher& pub);

  /** @brief
   * callback function which is called when new subscriber come for
   * camera info publisher
   */
  virtual void cameraInfoConnectionCallback(const ros::SingleSubscriberPublisher& pub);

  /** @brief
   * callback function which is called when new subscriber come for camera
   * image publisher or camera info publisher.
   * This function is called from cameraConnectionCallback
   * or cameraInfoConnectionCallback.
   */
  virtual void cameraConnectionBaseCallback();

  /** @brief
   * callback function which is called when walltimer
   * duration run out.
   */
  virtual void warnNeverSubscribedCallback(const ros::WallTimerEvent& event);

  /** @brief
   * This method is called when publisher is subscribed by other
   * nodes.
   * Set up subscribers in this method.
   */
  virtual void subscribe() = 0;

  /** @brief
   * This method is called when publisher is unsubscribed by other
   * nodes.
   * Shut down subscribers in this method.
   */
  virtual void unsubscribe() = 0;

  /** @brief
   * Advertise a topic and watch the publisher. Publishers which are
   * created by this method.
   * It automatically reads latch boolean parameter from nh and
   * publish topic with appropriate latch parameter.
   *
   * @param nh NodeHandle.
   * @param topic topic name to advertise.
   * @param queue_size queue size for publisher.
   * @param latch set true if latch topic publication.
   * @return Publisher for the advertised topic.
   */
  template <class T>
  ros::Publisher advertise(ros::NodeHandle& nh, std::string topic, int queue_size)
  {
    boost::mutex::scoped_lock lock(connection_mutex_);
    ros::SubscriberStatusCallback connect_cb = boost::bind(&Nodelet::connectionCallback, this, boost::placeholders::_1);
    ros::SubscriberStatusCallback disconnect_cb = boost::bind(&Nodelet::connectionCallback, this, boost::placeholders::_1);
    bool latch;
    nh.param("latch", latch, false);
    ros::Publisher ret = nh.advertise<T>(topic, queue_size, connect_cb, disconnect_cb, ros::VoidConstPtr(), latch);
    publishers_.push_back(ret);

    return ret;
  }

  /** @brief
   * Advertise an image topic and watch the publisher. Publishers which are
   * created by this method.
   * It automatically reads latch boolean parameter from nh and it and
   * publish topic with appropriate latch parameter.
   *
   * @param nh NodeHandle.
   * @param topic topic name to advertise.
   * @param queue_size queue size for publisher.
   * @param latch set true if latch topic publication.
   * @return Publisher for the advertised topic.
   */
  image_transport::Publisher advertiseImage(ros::NodeHandle& nh, const std::string& topic, int queue_size)
  {
    boost::mutex::scoped_lock lock(connection_mutex_);
    image_transport::SubscriberStatusCallback connect_cb = boost::bind(&Nodelet::imageConnectionCallback, this, boost::placeholders::_1);
    image_transport::SubscriberStatusCallback disconnect_cb = boost::bind(&Nodelet::imageConnectionCallback, this, boost::placeholders::_1);
    bool latch;
    nh.param("latch", latch, false);
    image_transport::Publisher pub =
        image_transport::ImageTransport(nh).advertise(topic, 1, connect_cb, disconnect_cb, ros::VoidPtr(), latch);
    image_publishers_.push_back(pub);
    return pub;
  }

  /** @brief
   * Advertise an image topic camera info topic and watch the publisher.
   * Publishers which are
   * created by this method.
   * It automatically reads latch boolean parameter from nh and it and
   * publish topic with appropriate latch parameter.
   *
   * @param nh NodeHandle.
   * @param topic topic name to advertise.
   * @param queue_size queue size for publisher.
   * @param latch set true if latch topic publication.
   * @return Publisher for the advertised topic.
   */
  image_transport::CameraPublisher advertiseCamera(ros::NodeHandle& nh, const std::string& topic, int queue_size)
  {
    boost::mutex::scoped_lock lock(connection_mutex_);
    image_transport::SubscriberStatusCallback connect_cb = boost::bind(&Nodelet::cameraConnectionCallback, this, boost::placeholders::_1);
    image_transport::SubscriberStatusCallback disconnect_cb = boost::bind(&Nodelet::cameraConnectionCallback, this, boost::placeholders::_1);
    ros::SubscriberStatusCallback info_connect_cb = boost::bind(&Nodelet::cameraInfoConnectionCallback, this, boost::placeholders::_1);
    ros::SubscriberStatusCallback info_disconnect_cb = boost::bind(&Nodelet::cameraInfoConnectionCallback, this, boost::placeholders::_1);
    bool latch;
    nh.param("latch", latch, false);
    image_transport::CameraPublisher pub = image_transport::ImageTransport(nh).advertiseCamera(
        topic, 1, connect_cb, disconnect_cb, info_connect_cb, info_disconnect_cb, ros::VoidPtr(), latch);
    camera_publishers_.push_back(pub);
    return pub;
  }

  /** @brief
   * mutex to call subscribe() and unsubscribe() in
   * critical section.
   */
  boost::mutex connection_mutex_;

  /** @brief
   * List of watching publishers
   */
  std::vector<ros::Publisher> publishers_;

  /** @brief
   * List of watching image publishers
   */
  std::vector<image_transport::Publisher> image_publishers_;

  /** @brief
   * List of watching camera publishers
   */
  std::vector<image_transport::CameraPublisher> camera_publishers_;

  /** @brief
   * Shared pointer to nodehandle.
   */
  boost::shared_ptr<ros::NodeHandle> nh_;

  /** @brief
   * Shared pointer to private nodehandle.
   */
  boost::shared_ptr<ros::NodeHandle> pnh_;

  /** @brief
   * WallTimer instance for warning about no connection.
   */
  ros::WallTimer timer_;

  /** @brief
   * A flag to check if any publisher is already subscribed
   * or not.
   */
  bool subscribed_;

  /** @brief
   * A flag to check if the node has been ever subscribed
   * or not.
   */
  bool ever_subscribed_;

  /** @brief
   * A flag to disable watching mechanism and always subscribe input
   * topics. It can be specified via ~always_subscribe parameter.
   */
  bool always_subscribe_;

  /** @brief
   * Status of connection
   */
  ConnectionStatus connection_status_;

  /** @brief
   * true if `~verbose_connection` or `verbose_connection` parameter is true.
   */
  bool verbose_connection_;

private:
};
}

#endif