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/* Author: Ioan Sucan */

#ifndef OMPL_BASE_STATE_VALIDITY_CHECKER_
#define OMPL_BASE_STATE_VALIDITY_CHECKER_

#include "ompl/base/State.h"
#include "ompl/util/ClassForward.h"

namespace ompl
{
    namespace base
    {
        /// @cond IGNORE
        OMPL_CLASS_FORWARD(SpaceInformation);
        /// @endcond

        /// @cond IGNORE
        /** \brief Forward declaration of ompl::base::StateValidityChecker */
        OMPL_CLASS_FORWARD(StateValidityChecker);
        /// @endcond

        /** \class ompl::base::StateValidityCheckerPtr
            \brief A shared pointer wrapper for ompl::base::StateValidityChecker */

        /** \brief Properties that a state validity checker may have */
        struct StateValidityCheckerSpecs
        {
            /** \brief Specify the type of clearance computation */
            enum ClearanceComputationType
            {
                /// Clearance computation is not implemented.
                NONE = 0,
                /// Exact clearance computation is available.
                EXACT,
                /// Some approximation of clearance is computed, but it is not clear if this is above or below the exact
                /// clearance.
                APPROXIMATE,
                /// A lower bound on clearance is computed.
                BOUNDED_APPROXIMATE,
            };

            StateValidityCheckerSpecs() = default;

            /** \brief Value indicating the kind of clearance computation this
                StateValidityChecker can compute (if any). */
            ClearanceComputationType clearanceComputationType{NONE};

            /** \brief Flag indicating that this state validity checker can return
                a direction that moves a state away from being invalid. */
            bool hasValidDirectionComputation{false};
        };

        /** \brief Abstract definition for a class checking the
            validity of states. The implementation of this class must
            be thread safe. */
        class StateValidityChecker
        {
        public:
            /** \brief Constructor */
            StateValidityChecker(SpaceInformation *si) : si_(si)
            {
            }

            /** \brief Constructor */
            StateValidityChecker(const SpaceInformationPtr &si) : si_(si.get())
            {
            }

            virtual ~StateValidityChecker() = default;

            /** \brief Return true if the state \e state is valid. Usually, this means at least collision checking. If
               it is
                possible that ompl::base::StateSpace::interpolate() or ompl::control::ControlSpace::propagate() return
               states that
                are outside of bounds, this function should also make a call to
               ompl::base::SpaceInformation::satisfiesBounds(). */
            virtual bool isValid(const State *state) const = 0;

            /** \brief Return true if the state \e state is valid. In addition, set \e dist to the distance to the
             * nearest invalid state. */
            virtual bool isValid(const State *state, double &dist) const
            {
                dist = clearance(state);
                return isValid(state);
            }

            /** \brief Return true if the state \e state is valid. In addition, set \e dist to the distance to the
               nearest
                invalid state (using clearance()). If a direction that moves \e state away from being invalid is
               available,
                a valid state in that direction is also set (\e validState). \e validStateAvailable is set to true if \e
               validState
                is updated. */
            virtual bool isValid(const State *state, double &dist, State *validState, bool &validStateAvailable) const
            {
                dist = clearance(state, validState, validStateAvailable);
                return isValid(state);
            }

            /** \brief Report the distance to the nearest invalid state when starting from \e state. If the distance is
                negative, the value of clearance is the penetration depth.*/
            virtual double clearance(const State * /*state*/) const
            {
                return 0.0;
            }

            /** \brief Report the distance to the nearest invalid state when starting from \e state, and if possible,
                also specify a valid state \e validState in the direction that moves away from the colliding
                state. The \e validStateAvailable flag is set to true if \e validState is updated. */
            virtual double clearance(const State *state, State * /*validState*/, bool &validStateAvailable) const
            {
                validStateAvailable = false;
                return clearance(state);
            }

            /** \brief Return the specifications (capabilities of this state validity checker) */
            const StateValidityCheckerSpecs &getSpecs() const
            {
                return specs_;
            }

            /** \brief Checks for equivalence between two Statevaliditycheckers
             * */
            virtual bool operator ==(const StateValidityChecker&) const
            {
              return false;
            }
            bool operator !=(const StateValidityChecker &rhs) const
            {
              return !(*this == rhs);
            }


        protected:
            /** \brief The instance of space information this state validity checker operates on */
            SpaceInformation *si_;

            /** \brief The specifications of the state validity checker (its capabilities) */
            StateValidityCheckerSpecs specs_;
        };

        /** \brief The simplest state validity checker: all states are valid */
        class AllValidStateValidityChecker : public StateValidityChecker
        {
        public:
            /** \brief Constructor */
            AllValidStateValidityChecker(SpaceInformation *si) : StateValidityChecker(si)
            {
            }

            /** \brief Constructor */
            AllValidStateValidityChecker(const SpaceInformationPtr &si) : StateValidityChecker(si)
            {
            }

            /** \brief Always return true (all states are considered valid) */
            bool isValid(const State * /* state */) const override
            {
                return true;
            }
        };
    }
}

#endif
