/* Copyright 2002-2024 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,
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   * See the License for the specific language governing permissions and
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  package org.orekit.propagation.analytical;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import org.hipparchus.analysis.differentiation.Gradient;
  import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  import org.hipparchus.geometry.euclidean.threed.Vector3D;
  import org.orekit.attitudes.AttitudeProvider;
  import org.orekit.attitudes.FieldAttitude;
  import org.orekit.orbits.FieldCartesianOrbit;
  import org.orekit.orbits.FieldOrbit;
  import org.orekit.propagation.FieldSpacecraftState;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.propagation.integration.AbstractGradientConverter;
  import org.orekit.utils.FieldAngularCoordinates;
  import org.orekit.utils.FieldPVCoordinates;
  import org.orekit.utils.ParameterDriver;
  import org.orekit.utils.ParameterDriversProvider;
  import org.orekit.utils.TimeStampedFieldAngularCoordinates;
  import org.orekit.utils.TimeStampedFieldPVCoordinates;
  
  /**
   * Converter for analytical orbit propagator.
   *
   * @author Bryan Cazabonne
   * @since 11.1
   */
  public abstract class AbstractAnalyticalGradientConverter extends AbstractGradientConverter implements ParameterDriversProvider {
  
      /** Attitude provider. */
      private final AttitudeProvider provider;
  
      /** States with various number of additional propagation parameters. */
      private final List<FieldSpacecraftState<Gradient>> gStates;
  
      /**
       * Constructor.
       * @param propagator analytical orbit propagator
       * @param mu central attraction coefficient
       * @param freeStateParameters number of free parameters
       */
      protected AbstractAnalyticalGradientConverter(final AbstractAnalyticalPropagator propagator,
                                                    final double mu,
                                                    final int freeStateParameters) {
          super(freeStateParameters);
  
          // Attitude provider
          this.provider = propagator.getAttitudeProvider();
  
          // Spacecraft state
          final SpacecraftState state = propagator.getInitialState();
  
          // Position always has derivatives
          final Vector3D pos = state.getPosition();
          final FieldVector3D<Gradient> posG = new FieldVector3D<>(Gradient.variable(freeStateParameters, 0, pos.getX()),
                                                                   Gradient.variable(freeStateParameters, 1, pos.getY()),
                                                                   Gradient.variable(freeStateParameters, 2, pos.getZ()));
  
          // Velocity may have derivatives or not
          final Vector3D vel = state.getPVCoordinates().getVelocity();
          final FieldVector3D<Gradient> velG = new FieldVector3D<>(Gradient.variable(freeStateParameters, 3, vel.getX()),
                                                                   Gradient.variable(freeStateParameters, 4, vel.getY()),
                                                                   Gradient.variable(freeStateParameters, 5, vel.getZ()));
  
          // Acceleration never has derivatives
          final Vector3D acc = state.getPVCoordinates().getAcceleration();
          final FieldVector3D<Gradient> accG = new FieldVector3D<>(Gradient.constant(freeStateParameters, acc.getX()),
                                                                   Gradient.constant(freeStateParameters, acc.getY()),
                                                                   Gradient.constant(freeStateParameters, acc.getZ()));
  
          // Mass never has derivatives
          final Gradient gM  = Gradient.constant(freeStateParameters, state.getMass());
          final Gradient gMu = Gradient.constant(freeStateParameters, mu);
  
          final FieldOrbit<Gradient> gOrbit =
                          new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(state.getDate(), posG, velG, accG),
                                                    state.getFrame(), gMu);
  
          // Attitude
          final FieldAttitude<Gradient> gAttitude = provider.getAttitude(gOrbit, gOrbit.getDate(), gOrbit.getFrame());
  
          // Initialize the list with the state having 0 force model parameters
         gStates = new ArrayList<>();
         gStates.add(new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
 
     }
 
     /** Get the state with the number of parameters consistent with the propagation model.
      * @return state with the number of parameters consistent with the propagation model
      */
     public FieldSpacecraftState<Gradient> getState() {
 
         // Count the required number of parameters
         int nbParams = 0;
         for (final ParameterDriver driver : getParametersDrivers()) {
             if (driver.isSelected()) {
                 ++nbParams;
             }
         }
 
         // Fill in intermediate slots
         while (gStates.size() < nbParams + 1) {
             gStates.add(null);
         }
 
         if (gStates.get(nbParams) == null) {
             // It is the first time we need this number of parameters
             // We need to create the state
             final int freeParameters = getFreeStateParameters() + nbParams;
             final FieldSpacecraftState<Gradient> s0 = gStates.get(0);
 
             // Orbit
             final FieldPVCoordinates<Gradient> pv0 = s0.getPVCoordinates();
             final FieldOrbit<Gradient> gOrbit =
                             new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(s0.getDate().toAbsoluteDate(),
                                                                                           extend(pv0.getPosition(),     freeParameters),
                                                                                           extend(pv0.getVelocity(),     freeParameters),
                                                                                           extend(pv0.getAcceleration(), freeParameters)),
                                                       s0.getFrame(),
                                                       extend(s0.getMu(), freeParameters));
 
             // Attitude
             final FieldAngularCoordinates<Gradient> ac0 = s0.getAttitude().getOrientation();
             final FieldAttitude<Gradient> gAttitude =
                             new FieldAttitude<>(s0.getAttitude().getReferenceFrame(),
                                                 new TimeStampedFieldAngularCoordinates<>(gOrbit.getDate(),
                                                                                          extend(ac0.getRotation(), freeParameters),
                                                                                          extend(ac0.getRotationRate(), freeParameters),
                                                                                          extend(ac0.getRotationAcceleration(), freeParameters)));
 
             // Mass
             final Gradient gM = extend(s0.getMass(), freeParameters);
 
             gStates.set(nbParams, new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
         }
 
         return gStates.get(nbParams);
     }
 
     /**
      * Get the converted analytical orbit propagator.
      * @param state state as returned by {@link #getState()}
      * @param parameters model parameters
      * @return the converted analytical orbit propagator
      */
     public abstract FieldAbstractAnalyticalPropagator<Gradient> getPropagator(FieldSpacecraftState<Gradient> state,
                                                                               Gradient[] parameters);
 
 }