/* Copyright 2002-2020 CS GROUP
    * Licensed to CS GROUP (CS) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * CS licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.orekit.propagation.integration;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.hipparchus.exception.MathRuntimeException;
  import org.hipparchus.ode.DenseOutputModel;
  import org.hipparchus.ode.EquationsMapper;
  import org.hipparchus.ode.ExpandableODE;
  import org.hipparchus.ode.ODEIntegrator;
  import org.hipparchus.ode.ODEState;
  import org.hipparchus.ode.ODEStateAndDerivative;
  import org.hipparchus.ode.OrdinaryDifferentialEquation;
  import org.hipparchus.ode.SecondaryODE;
  import org.hipparchus.ode.events.Action;
  import org.hipparchus.ode.events.ODEEventHandler;
  import org.hipparchus.ode.sampling.AbstractODEStateInterpolator;
  import org.hipparchus.ode.sampling.ODEStateInterpolator;
  import org.hipparchus.ode.sampling.ODEStepHandler;
  import org.hipparchus.util.Precision;
  import org.orekit.attitudes.AttitudeProvider;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitIllegalStateException;
  import org.orekit.errors.OrekitInternalError;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.frames.Frame;
  import org.orekit.orbits.OrbitType;
  import org.orekit.orbits.PositionAngle;
  import org.orekit.propagation.AbstractPropagator;
  import org.orekit.propagation.BoundedPropagator;
  import org.orekit.propagation.PropagationType;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.propagation.events.EventDetector;
  import org.orekit.propagation.sampling.OrekitStepHandler;
  import org.orekit.propagation.sampling.OrekitStepInterpolator;
  import org.orekit.time.AbsoluteDate;
  
  
  /** Common handling of {@link org.orekit.propagation.Propagator Propagator}
   *  methods for both numerical and semi-analytical propagators.
   *  @author Luc Maisonobe
   */
  public abstract class AbstractIntegratedPropagator extends AbstractPropagator {
  
      /** Event detectors not related to force models. */
      private final List<EventDetector> detectors;
  
      /** Integrator selected by the user for the orbital extrapolation process. */
      private final ODEIntegrator integrator;
  
      /** Mode handler. */
      private ModeHandler modeHandler;
  
      /** Additional equations. */
      private List<AdditionalEquations> additionalEquations;
  
      /** Counter for differential equations calls. */
      private int calls;
  
      /** Mapper between raw double components and space flight dynamics objects. */
      private StateMapper stateMapper;
  
      /** Equations mapper. */
      private EquationsMapper equationsMapper;
  
      /** Flag for resetting the state at end of propagation. */
      private boolean resetAtEnd;
  
      /** Type of orbit to output (mean or osculating) <br/>
       * <p>
       * This is used only in the case of semianalitical propagators where there is a clear separation between
       * mean and short periodic elements. It is ignored by the Numerical propagator.
       * </p>
       */
      private PropagationType propagationType;
  
      /** Build a new instance.
       * @param integrator numerical integrator to use for propagation.
       * @param propagationType type of orbit to output (mean or osculating).
      */
     protected AbstractIntegratedPropagator(final ODEIntegrator integrator, final PropagationType propagationType) {
         detectors            = new ArrayList<EventDetector>();
         additionalEquations  = new ArrayList<AdditionalEquations>();
         this.integrator      = integrator;
         this.propagationType = propagationType;
         this.resetAtEnd      = true;
     }
 
     /** Allow/disallow resetting the initial state at end of propagation.
      * <p>
      * By default, at the end of the propagation, the propagator resets the initial state
      * to the final state, thus allowing a new propagation to be started from there without
      * recomputing the part already performed. Calling this method with {@code resetAtEnd} set
      * to false changes prevents such reset.
      * </p>
      * @param resetAtEnd if true, at end of each propagation, the {@link
      * #getInitialState() initial state} will be reset to the final state of
      * the propagation, otherwise the initial state will be preserved
      * @since 9.0
      */
     public void setResetAtEnd(final boolean resetAtEnd) {
         this.resetAtEnd = resetAtEnd;
     }
 
     /** Initialize the mapper. */
     protected void initMapper() {
         stateMapper = createMapper(null, Double.NaN, null, null, null, null);
     }
 
     /**  {@inheritDoc} */
     public void setAttitudeProvider(final AttitudeProvider attitudeProvider) {
         super.setAttitudeProvider(attitudeProvider);
         stateMapper = createMapper(stateMapper.getReferenceDate(), stateMapper.getMu(),
                                    stateMapper.getOrbitType(), stateMapper.getPositionAngleType(),
                                    attitudeProvider, stateMapper.getFrame());
     }
 
     /** Set propagation orbit type.
      * @param orbitType orbit type to use for propagation, null for
      * propagating using {@link org.orekit.utils.AbsolutePVCoordinates AbsolutePVCoordinates}
      * rather than {@link org.orekit.orbits Orbit}
      */
     protected void setOrbitType(final OrbitType orbitType) {
         stateMapper = createMapper(stateMapper.getReferenceDate(), stateMapper.getMu(),
                                    orbitType, stateMapper.getPositionAngleType(),
                                    stateMapper.getAttitudeProvider(), stateMapper.getFrame());
     }
 
     /** Get propagation parameter type.
      * @return orbit type used for propagation, null for
      * propagating using {@link org.orekit.utils.AbsolutePVCoordinates AbsolutePVCoordinates}
      * rather than {@link org.orekit.orbits Orbit}
      */
     protected OrbitType getOrbitType() {
         return stateMapper.getOrbitType();
     }
 
     /** Check if only the mean elements should be used in a semianalitical propagation.
      * @return {@link PropagationType MEAN} if only mean elements have to be used or
      *         {@link PropagationType OSCULATING} if osculating elements have to be also used.
      */
     protected PropagationType isMeanOrbit() {
         return propagationType;
     }
 
     /** Set position angle type.
      * <p>
      * The position parameter type is meaningful only if {@link
      * #getOrbitType() propagation orbit type}
      * support it. As an example, it is not meaningful for propagation
      * in {@link OrbitType#CARTESIAN Cartesian} parameters.
      * </p>
      * @param positionAngleType angle type to use for propagation
      */
     protected void setPositionAngleType(final PositionAngle positionAngleType) {
         stateMapper = createMapper(stateMapper.getReferenceDate(), stateMapper.getMu(),
                                    stateMapper.getOrbitType(), positionAngleType,
                                    stateMapper.getAttitudeProvider(), stateMapper.getFrame());
     }
 
     /** Get propagation parameter type.
      * @return angle type to use for propagation
      */
     protected PositionAngle getPositionAngleType() {
         return stateMapper.getPositionAngleType();
     }
 
     /** Set the central attraction coefficient μ.
      * @param mu central attraction coefficient (m³/s²)
      */
     public void setMu(final double mu) {
         stateMapper = createMapper(stateMapper.getReferenceDate(), mu,
                                    stateMapper.getOrbitType(), stateMapper.getPositionAngleType(),
                                    stateMapper.getAttitudeProvider(), stateMapper.getFrame());
     }
 
     /** Get the central attraction coefficient μ.
      * @return mu central attraction coefficient (m³/s²)
      * @see #setMu(double)
      */
     public double getMu() {
         return stateMapper.getMu();
     }
 
     /** Get the number of calls to the differential equations computation method.
      * <p>The number of calls is reset each time the {@link #propagate(AbsoluteDate)}
      * method is called.</p>
      * @return number of calls to the differential equations computation method
      */
     public int getCalls() {
         return calls;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean isAdditionalStateManaged(final String name) {
 
         // first look at already integrated states
         if (super.isAdditionalStateManaged(name)) {
             return true;
         }
 
         // then look at states we integrate ourselves
         for (final AdditionalEquations equation : additionalEquations) {
             if (equation.getName().equals(name)) {
                 return true;
             }
         }
 
         return false;
     }
 
     /** {@inheritDoc} */
     @Override
     public String[] getManagedAdditionalStates() {
         final String[] alreadyIntegrated = super.getManagedAdditionalStates();
         final String[] managed = new String[alreadyIntegrated.length + additionalEquations.size()];
         System.arraycopy(alreadyIntegrated, 0, managed, 0, alreadyIntegrated.length);
         for (int i = 0; i < additionalEquations.size(); ++i) {
             managed[i + alreadyIntegrated.length] = additionalEquations.get(i).getName();
         }
         return managed;
     }
 
     /** Add a set of user-specified equations to be integrated along with the orbit propagation.
      * @param additional additional equations
      */
     public void addAdditionalEquations(final AdditionalEquations additional) {
 
         // check if the name is already used
         if (isAdditionalStateManaged(additional.getName())) {
             // this set of equations is already registered, complain
             throw new OrekitException(OrekitMessages.ADDITIONAL_STATE_NAME_ALREADY_IN_USE,
                                       additional.getName());
         }
 
         // this is really a new set of equations, add it
         additionalEquations.add(additional);
 
     }
 
     /** {@inheritDoc} */
     public void addEventDetector(final EventDetector detector) {
         detectors.add(detector);
     }
 
     /** {@inheritDoc} */
     public Collection<EventDetector> getEventsDetectors() {
         return Collections.unmodifiableCollection(detectors);
     }
 
     /** {@inheritDoc} */
     public void clearEventsDetectors() {
         detectors.clear();
     }
 
     /** Set up all user defined event detectors.
      */
     protected void setUpUserEventDetectors() {
         for (final EventDetector detector : detectors) {
             setUpEventDetector(integrator, detector);
         }
     }
 
     /** Wrap an Orekit event detector and register it to the integrator.
      * @param integ integrator into which event detector should be registered
      * @param detector event detector to wrap
      */
     protected void setUpEventDetector(final ODEIntegrator integ, final EventDetector detector) {
         integ.addEventHandler(new AdaptedEventDetector(detector),
                               detector.getMaxCheckInterval(),
                               detector.getThreshold(),
                               detector.getMaxIterationCount());
     }
 
     /** {@inheritDoc}
      * <p>Note that this method has the side effect of replacing the step handlers
      * of the underlying integrator set up in the {@link
      * #AbstractIntegratedPropagator(ODEIntegrator, PropagationType) constructor}. So if a specific
      * step handler is needed, it should be added after this method has been callled.</p>
      */
     public void setSlaveMode() {
         super.setSlaveMode();
         if (integrator != null) {
             integrator.clearStepHandlers();
         }
         modeHandler = null;
     }
 
     /** {@inheritDoc}
      * <p>Note that this method has the side effect of replacing the step handlers
      * of the underlying integrator set up in the {@link
      * #AbstractIntegratedPropagator(ODEIntegrator, PropagationType) constructor}. So if a specific
      * step handler is needed, it should be added after this method has been callled.</p>
      */
     public void setMasterMode(final OrekitStepHandler handler) {
         super.setMasterMode(handler);
         integrator.clearStepHandlers();
         final AdaptedStepHandler wrapped = new AdaptedStepHandler(handler);
         integrator.addStepHandler(wrapped);
         modeHandler = wrapped;
     }
 
     /** {@inheritDoc}
      * <p>Note that this method has the side effect of replacing the step handlers
      * of the underlying integrator set up in the {@link
      * #AbstractIntegratedPropagator(ODEIntegrator, PropagationType) constructor}. So if a specific
      * step handler is needed, it should be added after this method has been called.</p>
      */
     public void setEphemerisMode() {
         super.setEphemerisMode();
         integrator.clearStepHandlers();
         final EphemerisModeHandler ephemeris = new EphemerisModeHandler();
         modeHandler = ephemeris;
         integrator.addStepHandler(ephemeris);
     }
 
     /**
      * {@inheritDoc}
      *
      * <p>Note that this method has the side effect of replacing the step handlers of the
      * underlying integrator set up in the {@link #AbstractIntegratedPropagator(ODEIntegrator,
      * PropagationType) constructor}.</p>
      */
     @Override
     public void setEphemerisMode(final OrekitStepHandler handler) {
         super.setEphemerisMode();
         integrator.clearStepHandlers();
         final EphemerisModeHandler ephemeris = new EphemerisModeHandler(handler);
         modeHandler = ephemeris;
         integrator.addStepHandler(ephemeris);
     }
 
     /** {@inheritDoc} */
     public BoundedPropagator getGeneratedEphemeris()
         throws IllegalStateException {
         if (getMode() != EPHEMERIS_GENERATION_MODE) {
             throw new OrekitIllegalStateException(OrekitMessages.PROPAGATOR_NOT_IN_EPHEMERIS_GENERATION_MODE);
         }
         return ((EphemerisModeHandler) modeHandler).getEphemeris();
     }
 
     /** Create a mapper between raw double components and spacecraft state.
     /** Simple constructor.
      * <p>
      * The position parameter type is meaningful only if {@link
      * #getOrbitType() propagation orbit type}
      * support it. As an example, it is not meaningful for propagation
      * in {@link OrbitType#CARTESIAN Cartesian} parameters.
      * </p>
      * @param referenceDate reference date
      * @param mu central attraction coefficient (m³/s²)
      * @param orbitType orbit type to use for mapping
      * @param positionAngleType angle type to use for propagation
      * @param attitudeProvider attitude provider
      * @param frame inertial frame
      * @return new mapper
      */
     protected abstract StateMapper createMapper(AbsoluteDate referenceDate, double mu,
                                                 OrbitType orbitType, PositionAngle positionAngleType,
                                                 AttitudeProvider attitudeProvider, Frame frame);
 
     /** Get the differential equations to integrate (for main state only).
      * @param integ numerical integrator to use for propagation.
      * @return differential equations for main state
      */
     protected abstract MainStateEquations getMainStateEquations(ODEIntegrator integ);
 
     /** {@inheritDoc} */
     public SpacecraftState propagate(final AbsoluteDate target) {
         if (getStartDate() == null) {
             if (getInitialState() == null) {
                 throw new OrekitException(OrekitMessages.INITIAL_STATE_NOT_SPECIFIED_FOR_ORBIT_PROPAGATION);
             }
             setStartDate(getInitialState().getDate());
         }
         return propagate(getStartDate(), target);
     }
 
     /** {@inheritDoc} */
     public SpacecraftState propagate(final AbsoluteDatebsoluteDate">AbsoluteDate tStart, final AbsoluteDate tEnd) {
 
         if (getInitialState() == null) {
             throw new OrekitException(OrekitMessages.INITIAL_STATE_NOT_SPECIFIED_FOR_ORBIT_PROPAGATION);
         }
 
         if (!tStart.equals(getInitialState().getDate())) {
             // if propagation start date is not initial date,
             // propagate from initial to start date without event detection
             propagate(tStart, false);
         }
 
         // propagate from start date to end date with event detection
         return propagate(tEnd, true);
 
     }
 
     /** Propagation with or without event detection.
      * @param tEnd target date to which orbit should be propagated
      * @param activateHandlers if true, step and event handlers should be activated
      * @return state at end of propagation
      */
     protected SpacecraftState propagate(final AbsoluteDate tEnd, final boolean activateHandlers) {
         try {
 
             initializePropagation();
 
             if (getInitialState().getDate().equals(tEnd)) {
                 // don't extrapolate
                 return getInitialState();
             }
 
             // space dynamics view
             stateMapper = createMapper(getInitialState().getDate(), stateMapper.getMu(),
                                        stateMapper.getOrbitType(), stateMapper.getPositionAngleType(),
                                        stateMapper.getAttitudeProvider(), getInitialState().getFrame());
 
 
             if (Double.isNaN(getMu())) {
                 setMu(getInitialState().getMu());
             }
 
             if (getInitialState().getMass() <= 0.0) {
                 throw new OrekitException(OrekitMessages.SPACECRAFT_MASS_BECOMES_NEGATIVE,
                                           getInitialState().getMass());
             }
 
             integrator.clearEventHandlers();
 
             // set up events added by user, only if handlers are activated
             if (activateHandlers) {
                 setUpUserEventDetectors();
             }
 
             // convert space flight dynamics API to math API
             final SpacecraftState initialIntegrationState = getInitialIntegrationState();
             final ODEState mathInitialState = createInitialState(initialIntegrationState);
             final ExpandableODE mathODE = createODE(integrator, mathInitialState);
             equationsMapper = mathODE.getMapper();
 
             // initialize mode handler
             if (modeHandler != null) {
                 modeHandler.initialize(activateHandlers, tEnd);
             }
 
             // mathematical integration
             final ODEStateAndDerivative mathFinalState;
             beforeIntegration(initialIntegrationState, tEnd);
             mathFinalState = integrator.integrate(mathODE, mathInitialState,
                                                   tEnd.durationFrom(getInitialState().getDate()));
             afterIntegration();
 
             // get final state
             SpacecraftState finalState =
                             stateMapper.mapArrayToState(stateMapper.mapDoubleToDate(mathFinalState.getTime(),
                                                                                     tEnd),
                                                         mathFinalState.getPrimaryState(),
                                                         mathFinalState.getPrimaryDerivative(),
                                                         propagationType);
 
             finalState = updateAdditionalStates(finalState);
             for (int i = 0; i < additionalEquations.size(); ++i) {
                 final double[] secondary = mathFinalState.getSecondaryState(i + 1);
                 finalState = finalState.addAdditionalState(additionalEquations.get(i).getName(),
                                                            secondary);
             }
             if (resetAtEnd) {
                 resetInitialState(finalState);
                 setStartDate(finalState.getDate());
             }
 
             return finalState;
 
         } catch (MathRuntimeException mre) {
             throw OrekitException.unwrap(mre);
         }
     }
 
     /** Get the initial state for integration.
      * @return initial state for integration
      */
     protected SpacecraftState getInitialIntegrationState() {
         return getInitialState();
     }
 
     /** Create an initial state.
      * @param initialState initial state in flight dynamics world
      * @return initial state in mathematics world
      */
     private ODEState createInitialState(final SpacecraftState initialState) {
 
         // retrieve initial state
         final double[] primary  = new double[getBasicDimension()];
         stateMapper.mapStateToArray(initialState, primary, null);
 
         // secondary part of the ODE
         final double[][] secondary = new double[additionalEquations.size()][];
         for (int i = 0; i < additionalEquations.size(); ++i) {
             final AdditionalEquations additional = additionalEquations.get(i);
             secondary[i] = initialState.getAdditionalState(additional.getName());
         }
 
         return new ODEState(0.0, primary, secondary);
 
     }
 
     /** Create an ODE with all equations.
      * @param integ numerical integrator to use for propagation.
      * @param mathInitialState initial state
      * @return a new ode
      */
     private ExpandableODE createODE(final ODEIntegrator integ,
                                     final ODEState mathInitialState) {
 
         final ExpandableODE ode =
                 new ExpandableODE(new ConvertedMainStateEquations(getMainStateEquations(integ)));
 
         // secondary part of the ODE
         for (int i = 0; i < additionalEquations.size(); ++i) {
             final AdditionalEquations additional = additionalEquations.get(i);
             final SecondaryODE secondary =
                     new ConvertedSecondaryStateEquations(additional,
                                                          mathInitialState.getSecondaryStateDimension(i + 1));
             ode.addSecondaryEquations(secondary);
         }
 
         return ode;
 
     }
 
     /** Method called just before integration.
      * <p>
      * The default implementation does nothing, it may be specialized in subclasses.
      * </p>
      * @param initialState initial state
      * @param tEnd target date at which state should be propagated
      */
     protected void beforeIntegration(final SpacecraftState initialState,
                                      final AbsoluteDate tEnd) {
         // do nothing by default
     }
 
     /** Method called just after integration.
      * <p>
      * The default implementation does nothing, it may be specialized in subclasses.
      * </p>
      */
     protected void afterIntegration() {
         // do nothing by default
     }
 
     /** Get state vector dimension without additional parameters.
      * @return state vector dimension without additional parameters.
      */
     public int getBasicDimension() {
         return 7;
 
     }
 
     /** Get the integrator used by the propagator.
      * @return the integrator.
      */
     protected ODEIntegrator getIntegrator() {
         return integrator;
     }
 
     /** Get a complete state with all additional equations.
      * @param t current value of the independent <I>time</I> variable
      * @param y array containing the current value of the state vector
      * @param yDot array containing the current value of the state vector derivative
      * @return complete state
      */
     private SpacecraftState getCompleteState(final double t, final double[] y, final double[] yDot) {
 
         // main state
         SpacecraftState state = stateMapper.mapArrayToState(t, y, yDot, propagationType);
 
         // pre-integrated additional states
         state = updateAdditionalStates(state);
 
         // additional states integrated here
         if (!additionalEquations.isEmpty()) {
 
             for (int i = 0; i < additionalEquations.size(); ++i) {
                 state = state.addAdditionalState(additionalEquations.get(i).getName(),
                                                  equationsMapper.extractEquationData(i + 1, y));
             }
 
         }
 
         return state;
 
     }
 
     /** Differential equations for the main state (orbit, attitude and mass). */
     public interface MainStateEquations {
 
         /**
          * Initialize the equations at the start of propagation. This method will be
          * called before any calls to {@link #computeDerivatives(SpacecraftState)}.
          *
          * <p> The default implementation of this method does nothing.
          *
          * @param initialState initial state information at the start of propagation.
          * @param target       date of propagation. Not equal to {@code
          *                     initialState.getDate()}.
          */
         default void init(final SpacecraftState initialState, final AbsoluteDate target) {
         }
 
         /** Compute differential equations for main state.
          * @param state current state
          * @return derivatives of main state
          */
         double[] computeDerivatives(SpacecraftState state);
 
     }
 
     /** Differential equations for the main state (orbit, attitude and mass), with converted API. */
     private class ConvertedMainStateEquations implements OrdinaryDifferentialEquation {
 
         /** Main state equations. */
         private final MainStateEquations main;
 
         /** Simple constructor.
          * @param main main state equations
          */
         ConvertedMainStateEquations(final MainStateEquations main) {
             this.main = main;
             calls = 0;
         }
 
         /** {@inheritDoc} */
         public int getDimension() {
             return getBasicDimension();
         }
 
         @Override
         public void init(final double t0, final double[] y0, final double finalTime) {
             // update space dynamics view
             SpacecraftState initialState = stateMapper.mapArrayToState(t0, y0, null, PropagationType.MEAN);
             initialState = updateAdditionalStates(initialState);
             final AbsoluteDate target = stateMapper.mapDoubleToDate(finalTime);
             main.init(initialState, target);
         }
 
         /** {@inheritDoc} */
         public double[] computeDerivatives(final double t, final double[] y) {
 
             // increment calls counter
             ++calls;
 
             // update space dynamics view
             SpacecraftState currentState = stateMapper.mapArrayToState(t, y, null, PropagationType.MEAN);
             currentState = updateAdditionalStates(currentState);
 
             // compute main state differentials
             return main.computeDerivatives(currentState);
 
         }
 
     }
 
     /** Differential equations for the secondary state (Jacobians, user variables ...), with converted API. */
     private class ConvertedSecondaryStateEquations implements SecondaryODE {
 
         /** Additional equations. */
         private final AdditionalEquations equations;
 
         /** Dimension of the additional state. */
         private final int dimension;
 
         /** Simple constructor.
          * @param equations additional equations
          * @param dimension dimension of the additional state
          */
         ConvertedSecondaryStateEquations(final AdditionalEquations equations,
                                          final int dimension) {
             this.equations = equations;
             this.dimension = dimension;
         }
 
         /** {@inheritDoc} */
         @Override
         public int getDimension() {
             return dimension;
         }
 
         /** {@inheritDoc} */
         @Override
         public void init(final double t0, final double[] primary0,
                          final double[] secondary0, final double finalTime) {
             // update space dynamics view
             SpacecraftState initialState = stateMapper.mapArrayToState(t0, primary0, null, PropagationType.MEAN);
             initialState = updateAdditionalStates(initialState);
             initialState = initialState.addAdditionalState(equations.getName(), secondary0);
             final AbsoluteDate target = stateMapper.mapDoubleToDate(finalTime);
             equations.init(initialState, target);
 
         }
 
         /** {@inheritDoc} */
         @Override
         public double[] computeDerivatives(final double t, final double[] primary,
                                            final double[] primaryDot, final double[] secondary) {
 
             // update space dynamics view
             SpacecraftState currentState = stateMapper.mapArrayToState(t, primary, primaryDot, PropagationType.MEAN);
             currentState = updateAdditionalStates(currentState);
             currentState = currentState.addAdditionalState(equations.getName(), secondary);
 
             // compute additional derivatives
             final double[] secondaryDot = new double[secondary.length];
             final double[] additionalMainDot =
                             equations.computeDerivatives(currentState, secondaryDot);
             if (additionalMainDot != null) {
                 // the additional equations have an effect on main equations
                 for (int i = 0; i < additionalMainDot.length; ++i) {
                     primaryDot[i] += additionalMainDot[i];
                 }
             }
 
             return secondaryDot;
 
         }
 
     }
 
     /** Adapt an {@link org.orekit.propagation.events.EventDetector}
      * to Hipparchus {@link org.hipparchus.ode.events.ODEEventHandler} interface.
      * @author Fabien Maussion
      */
     private class AdaptedEventDetector implements ODEEventHandler {
 
         /** Underlying event detector. */
         private final EventDetector detector;
 
         /** Time of the previous call to g. */
         private double lastT;
 
         /** Value from the previous call to g. */
         private double lastG;
 
         /** Build a wrapped event detector.
          * @param detector event detector to wrap
         */
         AdaptedEventDetector(final EventDetector detector) {
             this.detector = detector;
             this.lastT    = Double.NaN;
             this.lastG    = Double.NaN;
         }
 
         /** {@inheritDoc} */
         public void init(final ODEStateAndDerivative s0, final double t) {
             detector.init(getCompleteState(s0.getTime(), s0.getCompleteState(), s0.getCompleteDerivative()),
                           stateMapper.mapDoubleToDate(t));
             this.lastT = Double.NaN;
             this.lastG = Double.NaN;
         }
 
         /** {@inheritDoc} */
         public double g(final ODEStateAndDerivative s) {
             if (!Precision.equals(lastT, s.getTime(), 0)) {
                 lastT = s.getTime();
                 lastG = detector.g(getCompleteState(s.getTime(), s.getCompleteState(), s.getCompleteDerivative()));
             }
             return lastG;
         }
 
         /** {@inheritDoc} */
         public Action eventOccurred(final ODEStateAndDerivative s, final boolean increasing) {
             return detector.eventOccurred(
                     getCompleteState(
                             s.getTime(),
                             s.getCompleteState(),
                             s.getCompleteDerivative()),
                     increasing);
         }
 
         /** {@inheritDoc} */
         public ODEState resetState(final ODEStateAndDerivative s) {
 
             final SpacecraftState oldState = getCompleteState(s.getTime(), s.getCompleteState(), s.getCompleteDerivative());
             final SpacecraftState newState = detector.resetState(oldState);
             stateChanged(newState);
 
             // main part
             final double[] primary    = new double[s.getPrimaryStateDimension()];
             stateMapper.mapStateToArray(newState, primary, null);
 
             // secondary part
             final double[][] secondary    = new double[additionalEquations.size()][];
             for (int i = 0; i < additionalEquations.size(); ++i) {
                 secondary[i] = newState.getAdditionalState(additionalEquations.get(i).getName());
             }
 
             return new ODEState(newState.getDate().durationFrom(getStartDate()),
                                 primary, secondary);
 
         }
 
     }
 
     /** Adapt an {@link org.orekit.propagation.sampling.OrekitStepHandler}
      * to Hipparchus {@link ODEStepHandler} interface.
      * @author Luc Maisonobe
      */
     private class AdaptedStepHandler implements ODEStepHandler, ModeHandler {
 
         /** Underlying handler. */
         private final OrekitStepHandler handler;
 
         /** Flag for handler . */
         private boolean activate;
 
         /** Build an instance.
          * @param handler underlying handler to wrap
          */
         AdaptedStepHandler(final OrekitStepHandler handler) {
             this.handler = handler;
         }
 
         /** {@inheritDoc} */
         public void initialize(final boolean activateHandlers,
                                final AbsoluteDate targetDate) {
             this.activate = activateHandlers;
         }
 
         /** {@inheritDoc} */
         public void init(final ODEStateAndDerivative s0, final double t) {
             if (activate) {
                 handler.init(getCompleteState(s0.getTime(), s0.getCompleteState(), s0.getCompleteDerivative()),
                              stateMapper.mapDoubleToDate(t));
             }
         }
 
         /** {@inheritDoc} */
         public void handleStep(final ODEStateInterpolator interpolator, final boolean isLast) {
             if (activate) {
                 handler.handleStep(new AdaptedStepInterpolator(interpolator), isLast);
             }
         }
 
     }
 
     /** Adapt an Hipparchus {@link ODEStateInterpolator}
      * to an orekit {@link OrekitStepInterpolator} interface.
      * @author Luc Maisonobe
      */
     private class AdaptedStepInterpolator implements OrekitStepInterpolator {
 
         /** Underlying raw rawInterpolator. */
         private final ODEStateInterpolator mathInterpolator;
 
         /** Simple constructor.
          * @param mathInterpolator underlying raw interpolator
          */
         AdaptedStepInterpolator(final ODEStateInterpolator mathInterpolator) {
             this.mathInterpolator = mathInterpolator;
         }
 
         /** {@inheritDoc}} */
         @Override
         public SpacecraftState getPreviousState() {
             return convert(mathInterpolator.getPreviousState());
         }
 
         /** {@inheritDoc}} */
         @Override
         public boolean isPreviousStateInterpolated() {
             return mathInterpolator.isPreviousStateInterpolated();
         }
 
         /** {@inheritDoc}} */
         @Override
         public SpacecraftState getCurrentState() {
             return convert(mathInterpolator.getCurrentState());
         }
 
         /** {@inheritDoc}} */
         @Override
         public boolean isCurrentStateInterpolated() {
             return mathInterpolator.isCurrentStateInterpolated();
         }
 
         /** {@inheritDoc}} */
         @Override
         public SpacecraftState getInterpolatedState(final AbsoluteDate date) {
             return convert(mathInterpolator.getInterpolatedState(date.durationFrom(stateMapper.getReferenceDate())));
         }
 
         /** Convert a state from mathematical world to space flight dynamics world.
          * @param os mathematical state
          * @return space flight dynamics state
          */
         private SpacecraftState convert(final ODEStateAndDerivative os) {
 
             SpacecraftState s =
                             stateMapper.mapArrayToState(os.getTime(),
                                                         os.getPrimaryState(),
                                                         os.getPrimaryDerivative(),
                                                         propagationType);
             s = updateAdditionalStates(s);
             for (int i = 0; i < additionalEquations.size(); ++i) {
                 final double[] secondary = os.getSecondaryState(i + 1);
                 s = s.addAdditionalState(additionalEquations.get(i).getName(), secondary);
             }
 
             return s;
 
         }
 
         /** Convert a state from space flight dynamics world to mathematical world.
          * @param state space flight dynamics state
          * @return mathematical state
          */
         private ODEStateAndDerivative convert(final SpacecraftState state) {
 
             // retrieve initial state
             final double[] primary    = new double[getBasicDimension()];
             final double[] primaryDot = new double[getBasicDimension()];
             stateMapper.mapStateToArray(state, primary, primaryDot);
 
             // secondary part of the ODE
             final double[][] secondary    = new double[additionalEquations.size()][];
             for (int i = 0; i < additionalEquations.size(); ++i) {
                 final AdditionalEquations additional = additionalEquations.get(i);
                 secondary[i] = state.getAdditionalState(additional.getName());
             }
 
             return new ODEStateAndDerivative(stateMapper.mapDateToDouble(state.getDate()),
                                              primary, primaryDot,
                                              secondary, null);
 
         }
 
         /** {@inheritDoc}} */
         @Override
         public boolean isForward() {
             return mathInterpolator.isForward();
         }
 
         /** {@inheritDoc}} */
         @Override
         public AdaptedStepInterpolator restrictStep(final SpacecraftState newPreviousState,
                                                     final SpacecraftState newCurrentState) {
             try {
                 final AbstractODEStateInterpolator aosi = (AbstractODEStateInterpolator) mathInterpolator;
                 return new AdaptedStepInterpolator(aosi.restrictStep(convert(newPreviousState),
                                                                      convert(newCurrentState)));
             } catch (ClassCastException cce) {
                 // this should never happen
                 throw new OrekitInternalError(cce);
             }
         }
 
     }
 
     private class EphemerisModeHandler implements ModeHandler, ODEStepHandler {
 
         /** Underlying raw mathematical model. */
         private DenseOutputModel model;
 
         /** Generated ephemeris. */
         private BoundedPropagator ephemeris;
 
         /** Flag for handler . */
         private boolean activate;
 
         /** the user supplied end date. Propagation may not end on this date. */
         private AbsoluteDate endDate;
 
         /** User's integration step handler. May be null. */
         private final AdaptedStepHandler handler;
 
         /** Creates a new instance of EphemerisModeHandler which must be
          *  filled by the propagator.
          */
         EphemerisModeHandler() {
             this.handler = null;
         }
 
         /** Creates a new instance of EphemerisModeHandler which must be
          *  filled by the propagator.
          *  @param handler the handler to notify of every integrator step.
          */
         EphemerisModeHandler(final OrekitStepHandler handler) {
             this.handler = new AdaptedStepHandler(handler);
         }
 
         /** {@inheritDoc} */
         public void initialize(final boolean activateHandlers,
                                final AbsoluteDate targetDate) {
             this.activate = activateHandlers;
             this.model    = new DenseOutputModel();
             this.endDate  = targetDate;
 
             // ephemeris will be generated when last step is processed
             this.ephemeris = null;
             if (this.handler != null) {
                 this.handler.initialize(activateHandlers, targetDate);
             }
         }
 
         /** Get the generated ephemeris.
          * @return a new instance of the generated ephemeris
          */
         public BoundedPropagator getEphemeris() {
             return ephemeris;
         }
 
         /** {@inheritDoc} */
         public void handleStep(final ODEStateInterpolator interpolator, final boolean isLast) {
             if (activate) {
                 if (this.handler != null) {
                     this.handler.handleStep(interpolator, isLast);
                 }
 
                 model.handleStep(interpolator, isLast);
                 if (isLast) {
 
                     // set up the boundary dates
                     final double tI = model.getInitialTime();
                     final double tF = model.getFinalTime();
                     // tI is almost? always zero
                     final AbsoluteDate startDate =
                                     stateMapper.mapDoubleToDate(tI);
                     final AbsoluteDate finalDate =
                                     stateMapper.mapDoubleToDate(tF, this.endDate);
                     final AbsoluteDate minDate;
                     final AbsoluteDate maxDate;
                     if (tF < tI) {
                         minDate = finalDate;
                         maxDate = startDate;
                     } else {
                         minDate = startDate;
                         maxDate = finalDate;
                     }
 
                     // get the initial additional states that are not managed
                     final Map<String, double[]> unmanaged = new HashMap<String, double[]>();
                     for (final Map.Entry<String, double[]> initial : getInitialState().getAdditionalStates().entrySet()) {
                         if (!isAdditionalStateManaged(initial.getKey())) {
                             // this additional state was in the initial state, but is unknown to the propagator
                             // we simply copy its initial value as is
                             unmanaged.put(initial.getKey(), initial.getValue());
                         }
                     }
 
                     // get the names of additional states managed by differential equations
                     final String[] names = new String[additionalEquations.size()];
                     for (int i = 0; i < names.length; ++i) {
                         names[i] = additionalEquations.get(i).getName();
                     }
 
                     // create the ephemeris
                     ephemeris = new IntegratedEphemeris(startDate, minDate, maxDate,
                                                         stateMapper, propagationType, model, unmanaged,
                                                         getAdditionalStateProviders(), names);
 
                 }
             }
 
         }
 
         /** {@inheritDoc} */
         public void init(final ODEStateAndDerivative s0, final double t) {
             model.init(s0, t);
             if (this.handler != null) {
                 this.handler.init(s0, t);
             }
         }
 
     }
 
 }