/*********************************************************************
* Software License Agreement (BSD License)
*
*  Copyright (c) 2008, Willow Garage, Inc.
*  All rights reserved.
*
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions
*  are met:
*
*   * Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   * Redistributions in binary form must reproduce the above
*     copyright notice, this list of conditions and the following
*     disclaimer in the documentation and/or other materials provided
*     with the distribution.
*   * Neither the name of the Willow Garage nor the names of its
*     contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
*  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
*  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
*  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
*  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
*  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
*  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
*  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
*  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
*  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
*  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
*  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
*  POSSIBILITY OF SUCH DAMAGE.
*********************************************************************/

/* Author: Ioan Sucan */

#ifndef OMPL_GEOMETRIC_PLANNERS_RRT_RRT_CONNECT_
#define OMPL_GEOMETRIC_PLANNERS_RRT_RRT_CONNECT_

#include "ompl/geometric/planners/PlannerIncludes.h"
#include "ompl/datastructures/NearestNeighbors.h"

namespace ompl
{
    namespace geometric
    {
        /**
           @anchor gRRTC
           @par Short description
           The basic idea is to grow two RRTs, one from the start and
           one from the goal, and attempt to connect them.
           @par External documentation
           J. Kuffner and S.M. LaValle, RRT-connect: An efficient approach to single-query path planning, in <em>Proc.
           2000 IEEE Intl. Conf. on Robotics and Automation</em>, pp. 995–1001, Apr. 2000. DOI:
           [10.1109/ROBOT.2000.844730](http://dx.doi.org/10.1109/ROBOT.2000.844730)<br>
           [[PDF]](http://ieeexplore.ieee.org/ielx5/6794/18246/00844730.pdf?tp=&arnumber=844730&isnumber=18246)
           [[more]](http://msl.cs.uiuc.edu/~lavalle/rrtpubs.html)
        */

        /** \brief RRT-Connect (RRTConnect) */
        class RRTConnect : public base::Planner
        {
        public:
            /** \brief Constructor */
            RRTConnect(const base::SpaceInformationPtr &si);

            ~RRTConnect() override;

            void getPlannerData(base::PlannerData &data) const override;

            base::PlannerStatus solve(const base::PlannerTerminationCondition &ptc) override;

            void clear() override;

            /** \brief Set the range the planner is supposed to use.

                This parameter greatly influences the runtime of the
                algorithm. It represents the maximum length of a
                motion to be added in the tree of motions. */
            void setRange(double distance)
            {
                maxDistance_ = distance;
            }

            /** \brief Get the range the planner is using */
            double getRange() const
            {
                return maxDistance_;
            }

            /** \brief Set a different nearest neighbors datastructure */
            template <template <typename T> class NN>
            void setNearestNeighbors()
            {
                if ((tStart_ && tStart_->size() != 0) || (tGoal_ && tGoal_->size() != 0))
                    OMPL_WARN("Calling setNearestNeighbors will clear all states.");
                clear();
                tStart_ = std::make_shared<NN<Motion *>>();
                tGoal_ = std::make_shared<NN<Motion *>>();
                setup();
            }

            void setup() override;

        protected:
            /** \brief Representation of a motion */
            class Motion
            {
            public:
                Motion() : root(nullptr), state(nullptr), parent(nullptr)
                {
                    parent = nullptr;
                    state = nullptr;
                }

                Motion(const base::SpaceInformationPtr &si) : root(nullptr), state(si->allocState()), parent(nullptr)
                {
                }

                ~Motion() = default;

                const base::State *root;
                base::State *state;
                Motion *parent;
            };

            /** \brief A nearest-neighbor datastructure representing a tree of motions */
            typedef std::shared_ptr<NearestNeighbors<Motion *>> TreeData;

            /** \brief Information attached to growing a tree of motions (used internally) */
            struct TreeGrowingInfo
            {
                base::State *xstate;
                Motion *xmotion;
                bool start;
            };

            /** \brief The state of the tree after an attempt to extend it */
            enum GrowState
            {
                /// no progress has been made
                TRAPPED,
                /// progress has been made towards the randomly sampled state
                ADVANCED,
                /// the randomly sampled state was reached
                REACHED
            };

            /** \brief Free the memory allocated by this planner */
            void freeMemory();

            /** \brief Compute distance between motions (actually distance between contained states) */
            double distanceFunction(const Motion *a, const Motion *b) const
            {
                return si_->distance(a->state, b->state);
            }

            /** \brief Grow a tree towards a random state */
            GrowState growTree(TreeData &tree, TreeGrowingInfo &tgi, Motion *rmotion);

            /** \brief State sampler */
            base::StateSamplerPtr sampler_;

            /** \brief The start tree */
            TreeData tStart_;

            /** \brief The goal tree */
            TreeData tGoal_;

            /** \brief The maximum length of a motion to be added to a tree */
            double maxDistance_;

            /** \brief The random number generator */
            RNG rng_;

            /** \brief The pair of states in each tree connected during planning.  Used for PlannerData computation */
            std::pair<base::State *, base::State *> connectionPoint_;
        };
    }
}

#endif
