/* Copyright 2002-2025 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.events;
  
  import org.hipparchus.util.FastMath;
  import org.junit.jupiter.api.Assertions;
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  import org.orekit.Utils;
  import org.orekit.bodies.CelestialBodyFactory;
  import org.orekit.bodies.OneAxisEllipsoid;
  import org.orekit.frames.Frame;
  import org.orekit.frames.FramesFactory;
  import org.orekit.orbits.KeplerianOrbit;
  import org.orekit.orbits.Orbit;
  import org.orekit.orbits.PositionAngleType;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.propagation.analytical.KeplerianPropagator;
  import org.orekit.propagation.events.handlers.StopOnEvent;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.TimeScalesFactory;
  
  public class AltitudeDetectorTest {
  
      @Test
      public void testBackAndForth() {
  
          final Frame EME2000 = FramesFactory.getEME2000();
          final AbsoluteDate initialDate = new AbsoluteDate(2009, 1, 1, TimeScalesFactory.getUTC());
          final double a = 8000000;
          final double e = 0.1;
          final double earthRadius = 6378137.0;
          final double earthF = 1.0 / 298.257223563;
          final double apogee = a*(1+e);
          final double alt = apogee - earthRadius - 500;
  
  
  
          // initial state is at apogee
          final Orbit initialOrbit = new KeplerianOrbit(a, e, 0, 0, 0, FastMath.PI, PositionAngleType.MEAN, EME2000,
                                                        initialDate, CelestialBodyFactory.getEarth().getGM());
          final SpacecraftState initialState = new SpacecraftState(initialOrbit);
          final KeplerianPropagator kepPropagator = new KeplerianPropagator(initialOrbit);
          final OneAxisEllipsoid earth = new OneAxisEllipsoid(earthRadius, earthF, EME2000);
          final AltitudeDetector altDetector = new AltitudeDetector(alt, earth).
                                               withHandler(new StopOnEvent());
          Assertions.assertEquals(alt, altDetector.getAltitude(), 1.0e-15);
          Assertions.assertSame(earth, altDetector.getBodyShape());
  
          // altitudeDetector should stop propagation upon reaching required altitude
          kepPropagator.addEventDetector(altDetector);
  
          // propagation to the future
          SpacecraftState finalState = kepPropagator.propagate(initialDate.shiftedBy(1000));
          Assertions.assertEquals(finalState.getPosition().getNorm()-earthRadius, alt, 1e-5);
          Assertions.assertEquals(44.079, finalState.getDate().durationFrom(initialDate), 1.0e-3);
  
          // propagation to the past
          kepPropagator.resetInitialState(initialState);
          finalState = kepPropagator.propagate(initialDate.shiftedBy(-1000));
          Assertions.assertEquals(finalState.getPosition().getNorm()-earthRadius, alt, 1e-5);
          Assertions.assertEquals(-44.079, finalState.getDate().durationFrom(initialDate), 1.0e-3);
  
      }
  
      @BeforeEach
      public void setUp() {
          Utils.setDataRoot("regular-data");
      }
  
  }