/* Copyright 2002-2026 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
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  package org.orekit.propagation.analytical.tle;
  
  import java.util.List;
  
  import org.hipparchus.analysis.differentiation.Gradient;
  import org.orekit.attitudes.AttitudeProvider;
  import org.orekit.frames.Frame;
  import org.orekit.propagation.FieldSpacecraftState;
  import org.orekit.propagation.analytical.AbstractAnalyticalGradientConverter;
  import org.orekit.propagation.analytical.tle.generation.TleGenerationAlgorithm;
  import org.orekit.time.TimeScale;
  import org.orekit.utils.ParameterDriver;
  
  /** Converter for TLE propagator.
   * @author Luc Maisonobe
   * @author Bryan Cazabonne
   * @author Thomas Paulet
   * @since 11.0
   */
  class TLEGradientConverter extends AbstractAnalyticalGradientConverter {
  
      /** Fixed dimension of the state. */
      public static final int FREE_STATE_PARAMETERS = 6;
  
      /** Current TLE. */
      private final TLE tle;
  
      /** UTC time scale. */
      private final TimeScale utc;
  
      /** TEME frame. */
      private final Frame teme;
  
      /** Attitude provider. */
      private final AttitudeProvider provider;
  
      /** Propagator. */
      private final TLEPropagator propagator;
  
      /** Simple constructor.
       * @param propagator TLE propagator used to access initial orbit
       */
      TLEGradientConverter(final TLEPropagator propagator) {
          super(propagator, FREE_STATE_PARAMETERS);
          this.tle                 = propagator.getTLE();
          this.teme                = propagator.getFrame();
          this.utc                 = tle.getUtc();
          this.provider            = propagator.getAttitudeProvider();
          this.propagator          = propagator;
      }
  
      /** {@inheritDoc} */
      @Override
      public FieldTLEPropagator<Gradient> getPropagator() {
  
          final FieldSpacecraftState<Gradient> state = getState(this);
          final Gradient[] parameters = getParameters(state, tle);
  
          // Zero
          final Gradient zero = state.getMass().getField().getZero();
  
          // Template TLE
          final int satelliteNumber         = tle.getSatelliteNumber();
          final char classification         = tle.getClassification();
          final int launchYear              = tle.getLaunchYear();
          final int launchNumber            = tle.getLaunchNumber();
          final String launchPiece          = tle.getLaunchPiece();
          final int ephemerisType           = tle.getEphemerisType();
          final int elementNumber           = tle.getElementNumber();
          final int revolutionNumberAtEpoch = tle.getRevolutionNumberAtEpoch();
          final double bStar                = tle.getBStar(state.getDate().toAbsoluteDate());
  
          // Initialize the new TLE
          final FieldTLE<Gradient> templateTLE = new FieldTLE<>(satelliteNumber, classification,
                  launchYear, launchNumber, launchPiece,
                  ephemerisType, elementNumber, state.getDate(),
                  zero, zero, zero, zero, zero, zero, zero, zero,
                  revolutionNumberAtEpoch, bStar, utc);
  
          // TLE
          final TleGenerationAlgorithm algorithm = propagator.getTleGenerationAlgorithm();
          final FieldTLE<Gradient> gTLE = algorithm.generate(state, templateTLE);
  
         // Return the "Field" propagator
         final FieldTLEPropagator<Gradient> fieldPropagator =
             FieldTLEPropagator.selectExtrapolator(gTLE, provider, state.getMass(), teme, parameters);
         fieldPropagator.setTleGenerationAlgorithm(algorithm);
         return fieldPropagator;
     }
 
     /** {@inheritDoc} */
     @Override
     public List<ParameterDriver> getParametersDrivers() {
         return tle.getParametersDrivers();
     }
 
 }