/* Copyright 2020-2025 Exotrail
    * 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.conversion.averaging;
  
  import org.orekit.forces.gravity.potential.UnnormalizedSphericalHarmonicsProvider;
  import org.orekit.frames.Frame;
  import org.orekit.orbits.EquinoctialOrbit;
  import org.orekit.orbits.Orbit;
  import org.orekit.orbits.OrbitType;
  import org.orekit.orbits.PositionAngleType;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.propagation.semianalytical.dsst.DSSTPropagator;
  import org.orekit.propagation.semianalytical.dsst.forces.DSSTForceModel;
  import org.orekit.propagation.semianalytical.dsst.forces.DSSTZonal;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.propagation.conversion.averaging.elements.AveragedEquinoctialWithMeanAngle;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  
  /**
   * Class representing an averaged orbital state as in the DSST theory using only the first 6 zonal
   * harmonics as perturbations.
   *
   * @author Romain Serra
   * @see AveragedOrbitalState
   * @see DSSTPropagator
   * @see DSSTZonal
   * @since 12.1
   */
  public class DSST6X0OrbitalState extends AbstractHarmonicsBasedOrbitalState {
  
      /** Averaged equinoctial elements. */
      private final AveragedEquinoctialWithMeanAngle averagedElements;
  
      /**
       * Constructor.
       * @param date epoch
       * @param elements averaged orbital elements
       * @param frame reference frame
       * @param harmonicsProvider spherical harmonics provider
       */
      public DSST6X0OrbitalState(final AbsoluteDate date,
                                 final AveragedEquinoctialWithMeanAngle elements,
                                 final Frame frame,
                                 final UnnormalizedSphericalHarmonicsProvider harmonicsProvider) {
          super(date, frame, harmonicsProvider);
          this.averagedElements = elements;
      }
  
      /**
       * Create collection of fist 6 zonal DSST forces.
       * @param provider spherical harmonics provider
       * @return six first zonal forces
       */
      public static Collection<DSSTForceModel> createForces(final UnnormalizedSphericalHarmonicsProvider provider) {
          final List<DSSTForceModel> forceModels = new ArrayList<>();
          final DSSTZonal zonal = new DSSTZonal(provider);
          forceModels.add(zonal);
          return forceModels;
      }
  
      /** {@inheritDoc} */
      @Override
      public OrbitType getOrbitType() {
          return OrbitType.EQUINOCTIAL;
      }
  
      /** {@inheritDoc} */
      @Override
      public PositionAngleType getPositionAngleType() {
          return PositionAngleType.MEAN;
      }
  
      /** {@inheritDoc} */
      @Override
      public AveragedEquinoctialWithMeanAngle getAveragedElements() {
          return averagedElements;
      }
  
      /** {@inheritDoc} */
      @Override
      public Orbit toOsculatingOrbit() {
          final EquinoctialOrbit orekitOrbit = createOrekitOrbit();
         final Collection<DSSTForceModel> forceModels = createForces(getHarmonicsProvider());
         final SpacecraftState osculatingState = DSSTPropagator.computeOsculatingState(
                 new SpacecraftState(orekitOrbit), null, forceModels);
         return osculatingState.getOrbit();
     }
 
     /**
      * Create equinoctial orbit representation of averaged state.
      * @return equinoctial orbit
      */
     private EquinoctialOrbit createOrekitOrbit() {
         return new EquinoctialOrbit(averagedElements.getAveragedSemiMajorAxis(),
                 averagedElements.getAveragedEquinoctialEx(),
                 averagedElements.getAveragedEquinoctialEy(),
                 averagedElements.getAveragedHx(), averagedElements.getAveragedHy(),
                 averagedElements.getAveragedMeanLongitudeArgument(),
                 getPositionAngleType(), getFrame(), getDate(), getMu());
     }
 
 }