/* Copyright 2002-2026 CS GROUP
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    * 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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  package org.orekit.propagation.conversion.osc2mean;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.Field;
  import org.orekit.annotation.DefaultDataContext;
  import org.orekit.data.DataContext;
  import org.orekit.frames.Frame;
  import org.orekit.orbits.FieldKeplerianOrbit;
  import org.orekit.orbits.FieldOrbit;
  import org.orekit.orbits.KeplerianOrbit;
  import org.orekit.orbits.Orbit;
  import org.orekit.orbits.OrbitType;
  import org.orekit.propagation.analytical.tle.FieldTLE;
  import org.orekit.propagation.analytical.tle.FieldTLEPropagator;
  import org.orekit.propagation.analytical.tle.TLE;
  import org.orekit.propagation.analytical.tle.TLEConstants;
  import org.orekit.propagation.analytical.tle.TLEPropagator;
  import org.orekit.propagation.analytical.tle.generation.TleGenerationUtil;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.time.TimeScale;
  
  /**
   * TLE, i.e. SGP4/SDP4, theory for osculating to mean orbit conversion.
   *
   * @author Pascal Parraud
   * @since 13.0
   */
  public class TLETheory implements MeanTheory {
  
      /** First line of arbitrary TLE. Should not impact conversion. */
      public static final String TMP_L1 = "1 00000U 00000A   00001.00000000  .00000000  00000+0  00000+0 0    02";
      /** Second line of arbitrary TLE. Should not impact conversion. */
      public static final String TMP_L2 = "2 00000   0.0000   0.0000 0000000   0.0000   0.0000  0.00000000    02";
  
      /** Theory used for converting from osculating to mean orbit. */
      public static final String THEORY = "TLE";
  
      /** Template TLE. */
      private final TLE tmpTle;
  
      /** TEME frame. */
      private final Frame teme;
  
      /**
       * Constructor with default data context and default TLE template.
       */
      @DefaultDataContext
      public TLETheory() {
          this(DataContext.getDefault());
      }
  
      /**
       * Constructor with default data context.
       * @param template template TLE
       */
      @DefaultDataContext
      public TLETheory(final TLE template) {
          this(template, DataContext.getDefault());
      }
  
      /**
       * Constructor with default data context.
       * @param <T> type of the elements
       * @param template template TLE
       */
      @DefaultDataContext
      public <T extends CalculusFieldElement<T>> TLETheory(final FieldTLE<T> template) {
          this(template, DataContext.getDefault());
      }
  
      /**
       * Constructor with default TLE template.
       * @param dataContext data context
       */
      public TLETheory(final DataContext dataContext) {
          this(dataContext.getTimeScales().getUTC(), dataContext.getFrames().getTEME());
      }
  
      /**
       * Constructor.
       * @param utc      UTC scale
       * @param teme     TEME frame scale
       */
     public TLETheory(final TimeScale utc, final Frame teme) {
         this(new TLE(TMP_L1, TMP_L2, utc), teme);
     }
 
     /**
      * Constructor.
      * @param template template TLE
      * @param dataContext data context
      */
     public TLETheory(final TLE template, final DataContext dataContext) {
         this(template, dataContext.getFrames().getTEME());
     }
 
     /**
      * Constructor.
      * @param template template TLE
      * @param teme     TEME frame scale
      */
     public TLETheory(final TLE template, final Frame teme) {
         this.tmpTle = template;
         this.teme   = teme;
     }
 
     /**
      * Constructor.
      * @param <T> type of the elements
      * @param template template TLE
      * @param dataContext data context
      */
     public <T extends CalculusFieldElement<T>> TLETheory(final FieldTLE<T> template, final DataContext dataContext) {
         this(template, dataContext.getTimeScales().getUTC(), dataContext.getFrames().getTEME());
     }
 
     /**
      * Constructor.
      * @param <T> type of the elements
      * @param template template TLE
      * @param utc      UTC scale
      * @param teme     TEME frame scale
      */
     public <T extends CalculusFieldElement<T>> TLETheory(final FieldTLE<T> template, final TimeScale utc, final Frame teme) {
         this.tmpTle = template.toTLE();
         this.teme   = teme;
     }
 
     /** {@inheritDoc} */
     @Override
     public String getTheoryName() {
         return THEORY;
     }
 
     /** {@inheritDoc} */
     @Override
     public double getReferenceRadius() {
         return 1000 * TLEConstants.EARTH_RADIUS;
     }
 
     /** Pre-treatment of the osculating orbit to be converted.
      * <p>The osculating orbit is transformed to TEME frame.</p>
      */
     @Override
     public Orbit preprocessing(final Orbit osculating) {
         return new KeplerianOrbit(osculating.getPVCoordinates(teme), teme, TLEPropagator.getMU());
     }
 
     /** {@inheritDoc} */
     @Override
     public Orbit meanToOsculating(final Orbit mean) {
         // Build TLE from mean and template
         final KeplerianOrbit meanKepl = (KeplerianOrbit) OrbitType.KEPLERIAN.convertType(mean);
         final TLE meanTle = TleGenerationUtil.newTLE(meanKepl, tmpTle);
         final TLEPropagator propagator = TLEPropagator.selectExtrapolator(meanTle, teme);
         return propagator.getInitialState().getOrbit();
     }
 
     /** Post-treatment of the converted mean orbit.
      * <p>The mean orbit returned is a Keplerian orbit in TEME frame.</p>
      */
     @Override
     public Orbit postprocessing(final Orbit osculating, final Orbit mean) {
         return OrbitType.KEPLERIAN.convertType(mean);
     }
 
     /** Pre-treatment of the osculating orbit to be converted.
      * <p>The osculating orbit is transformed to TEME frame.</p>
      */
     @Override
     public <T extends CalculusFieldElement<T>> FieldOrbit<T> preprocessing(final FieldOrbit<T> osculating) {
         final T mu = osculating.getDate().getField().getZero().newInstance(TLEConstants.MU);
         return new FieldKeplerianOrbit<>(osculating.getPVCoordinates(teme), teme, mu);
     }
 
     /** {@inheritDoc} */
     @Override
     public <T extends CalculusFieldElement<T>> FieldOrbit<T> meanToOsculating(final FieldOrbit<T> mean) {
         final FieldAbsoluteDate<T> date = mean.getDate();
         final Field<T> field = date.getField();
         final FieldTLE<T> fieldTmpTle = new FieldTLE<>(field, tmpTle.getLine1(), tmpTle.getLine2(), tmpTle.getUtc());
         // Build TLE from mean and template
         final FieldKeplerianOrbit<T> meanKepl = (FieldKeplerianOrbit<T>) OrbitType.KEPLERIAN.convertType(mean);
         final FieldTLE<T> meanTle = TleGenerationUtil.newTLE(meanKepl, fieldTmpTle);
         final FieldTLEPropagator<T> propagator =
             FieldTLEPropagator.selectExtrapolator(meanTle, teme);
         return propagator.getInitialState().getOrbit();
     }
 
     /** Post-treatment of the converted mean orbit.
      * <p>The mean orbit returned is a Keplerian orbit in TEME frame.</p>
      */
     @Override
     public <T extends CalculusFieldElement<T>> FieldOrbit<T> postprocessing(final FieldOrbit<T> osculating,
                                                                             final FieldOrbit<T> mean) {
         return OrbitType.KEPLERIAN.convertType(mean);
     }
 
 }