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#pragma once

// PCL
#include <pcl/registration/registration.h>
#include <pcl/visualization/pcl_visualizer.h>

#include <mutex>
#include <thread>

namespace pcl
{
  /** \brief @b RegistrationVisualizer represents the base class for rendering
   * the intermediate positions occupied by the source point cloud during it's registration
   * to the target point cloud. A registration algorithm is considered as input and
   * it's convergence is rendered.
   * \author Gheorghe Lisca
   * \ingroup visualization
   */
  template<typename PointSource, typename PointTarget, typename Scalar = float>
  class RegistrationVisualizer
  {

    public:
      /** \brief Empty constructor. */
      RegistrationVisualizer () : 
        update_visualizer_ (),
        cloud_source_ (),
        cloud_target_ (),
        cloud_intermediate_ ()
      {}

      ~RegistrationVisualizer ()
      {
          stopDisplay();
      }

      /** \brief Set the registration algorithm whose intermediate steps will be rendered.
       * The method creates the local callback function pcl::RegistrationVisualizer::update_visualizer_ and
       * binds it to the local buffers update function pcl::RegistrationVisualizer::updateIntermediateCloud().
       * The local callback function pcl::RegistrationVisualizer::update_visualizer_ is then linked to
       * the pcl::Registration::update_visualizer_ callback function.
       * \param registration represents the registration method whose intermediate steps will be rendered.
       */
      bool
      setRegistration (pcl::Registration<PointSource, PointTarget, Scalar> &registration)
      {
        // Update the name of the registration method to be displayed
        registration_method_name_ = registration.getClassName();

        // Create the local callback function and bind it to the local function responsible for updating
        // the local buffers
        update_visualizer_ = [this] (const pcl::PointCloud<PointSource>& cloud_src, const pcl::Indices& indices_src,
                                     const pcl::PointCloud<PointTarget>& cloud_tgt, const pcl::Indices& indices_tgt)
        {
          updateIntermediateCloud (cloud_src, indices_src, cloud_tgt, indices_tgt);
        };

        // Flag that no visualizer update was done. It indicates to visualizer update function to copy
        // the registration input source and the target point clouds in the next call.
        visualizer_updating_mutex_.lock ();

        first_update_flag_ = false;

        visualizer_updating_mutex_.unlock ();

        // Register the local callback function to the registration algorithm callback function
        registration.registerVisualizationCallback (this->update_visualizer_);

        return true;
      }

      /** \brief Start the viewer thread
       */
      void
      startDisplay ();

      /** \brief Stop the viewer thread
       */
      void
      stopDisplay ();

      /** \brief Updates visualizer local buffers cloud_intermediate, cloud_intermediate_indices, cloud_target_indices with
       * the newest registration intermediate results.
       * \param cloud_src represents the initial source point cloud
       * \param indices_src represents the indices of the intermediate source points used for the estimation of rigid transformation
       * \param cloud_tgt represents the target point cloud
       * \param indices_tgt represents the indices of the target points used for the estimation of rigid transformation
       */
      void
      updateIntermediateCloud (const pcl::PointCloud<PointSource> &cloud_src, const pcl::Indices &indices_src,
                               const pcl::PointCloud<PointTarget> &cloud_tgt, const pcl::Indices &indices_tgt);

      /** \brief Set maximum number of correspondence lines which will be rendered. */
      inline void
      setMaximumDisplayedCorrespondences (const int maximum_displayed_correspondences)
      {
        // This method is usually called form other thread than visualizer thread
        // therefore same visualizer_updating_mutex_ will be used

        // Lock maximum_displayed_correspondences_
        visualizer_updating_mutex_.lock ();

        // Update maximum_displayed_correspondences_
        maximum_displayed_correspondences_ = maximum_displayed_correspondences;

        // Unlock maximum_displayed_correspondences_
        visualizer_updating_mutex_.unlock();
      }

      /** \brief Return maximum number of correspondence lines which are rendered. */
      inline std::size_t
      getMaximumDisplayedCorrespondences()
      {
        return maximum_displayed_correspondences_;
      }

    private:
      /** \brief Initialize and run the visualization loop. This function will run in the internal thread viewer_thread_ */
      void
      runDisplay ();

      /** \brief Return the string obtained by concatenating a root_name and an id */
      inline std::string
      getIndexedName (std::string &root_name, std::size_t &id)
      {
        return root_name + std::to_string(id);
      }

      /** \brief The registration viewer. */
      pcl::visualization::PCLVisualizer::Ptr viewer_;

      /** \brief The thread running the runDisplay() function. */
      std::thread viewer_thread_;

      /** \brief The name of the registration method whose intermediate results are rendered. */
      std::string registration_method_name_;

      /** \brief Callback function linked to pcl::Registration::update_visualizer_ */
      std::function<void
      (const pcl::PointCloud<PointSource> &cloud_src, const pcl::Indices &indices_src, const pcl::PointCloud<
          PointTarget> &cloud_tgt, const pcl::Indices &indices_tgt)> update_visualizer_;

      /** \brief Updates source and target point clouds only for the first update call. */
      bool first_update_flag_{false};

      /** \brief The local buffer for source point cloud. */
      pcl::PointCloud<PointSource> cloud_source_;

      /** \brief The local buffer for target point cloud. */
      pcl::PointCloud<PointTarget> cloud_target_;

      /** \brief The mutex used for the synchronization of updating and rendering of the local buffers. */
      std::mutex visualizer_updating_mutex_;

      /** \brief The local buffer for intermediate point cloud obtained during registration process. */
      pcl::PointCloud<PointSource> cloud_intermediate_;

      /** \brief The indices of intermediate points used for computation of rigid transformation. */
      pcl::Indices cloud_intermediate_indices_;

      /** \brief The indices of target points used for computation of rigid transformation. */
      pcl::Indices cloud_target_indices_;

      /** \brief The maximum number of displayed correspondences. */
      std::size_t maximum_displayed_correspondences_{0};

    };
}

#include <pcl/visualization/impl/registration_visualizer.hpp>
