/* 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.attitudes;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  import org.hipparchus.geometry.euclidean.threed.Vector3D;
  import org.orekit.bodies.BodyShape;
  import org.orekit.bodies.GeodeticPoint;
  import org.orekit.frames.FieldStaticTransform;
  import org.orekit.frames.FieldTransform;
  import org.orekit.frames.Frame;
  import org.orekit.frames.StaticTransform;
  import org.orekit.frames.Transform;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.utils.FieldPVCoordinatesProvider;
  import org.orekit.utils.PVCoordinatesProvider;
  import org.orekit.utils.TimeStampedFieldPVCoordinates;
  import org.orekit.utils.TimeStampedPVCoordinates;
  
  /**
   * This class handles target pointing attitude provider.
  
   * <p>
   * This class represents the attitude provider where the satellite z axis is
   * pointing to a ground point target.</p>
   * <p>
   * The target position is defined in a body frame specified by the user.
   * It is important to make sure this frame is consistent.
   * </p>
   * <p>
   * The object <code>TargetPointing</code> is guaranteed to be immutable.
   * </p>
   * @see     GroundPointing
   * @author V&eacute;ronique Pommier-Maurussane
   */
  public class TargetPointing extends GroundPointing {
  
      /** Target in body frame. */
      private final Vector3D target;
  
      /** Creates a new instance from body frame and target expressed in Cartesian coordinates.
       * @param inertialFrame frame in which orbital velocities are computed
       * @param bodyFrame body frame.
       * @param target target position in body frame
       * @since 7.1
       */
      public TargetPointing(final Frame inertialFrame, final Frame bodyFrame, final Vector3D target) {
          super(inertialFrame, bodyFrame);
          this.target = target;
      }
  
      /** Creates a new instance from body shape and target expressed in geodetic coordinates.
       * @param inertialFrame frame in which orbital velocities are computed
       * @param targetGeo target defined as a geodetic point in body shape frame
       * @param shape body shape
       * @since 7.1
       */
      public TargetPointing(final Frame inertialFrame, final GeodeticPoint targetGeo, final BodyShape shape) {
          super(inertialFrame, shape.getBodyFrame());
          // Transform target from geodetic coordinates to Cartesian coordinates
          target = shape.transform(targetGeo);
      }
  
      /** {@inheritDoc} */
      @Override
      public TimeStampedPVCoordinates getTargetPV(final PVCoordinatesProvider pvProv,
                                                  final AbsoluteDate date, final Frame frame) {
          final Transform t = getBodyFrame().getTransformTo(frame, date);
          final TimeStampedPVCoordinates pv =
                  new TimeStampedPVCoordinates(date, target, Vector3D.ZERO, Vector3D.ZERO);
          return t.transformPVCoordinates(pv);
      }
  
      /** {@inheritDoc} */
      @Override
      protected Vector3D getTargetPosition(final PVCoordinatesProvider pvProv, final AbsoluteDate date, final Frame frame) {
          final StaticTransform staticTransform = getBodyFrame().getStaticTransformTo(frame, date);
          return staticTransform.transformPosition(target);
      }
  
      /** {@inheritDoc} */
      @Override
      public <T extends CalculusFieldElement<T>> TimeStampedFieldPVCoordinates<T> getTargetPV(final FieldPVCoordinatesProvider<T> pvProv,
                                                                                             final FieldAbsoluteDate<T> date, final Frame frame) {
         final FieldTransform<T> t = getBodyFrame().getTransformTo(frame, date);
         final FieldVector3D<T> zero = FieldVector3D.getZero(date.getField());
         final TimeStampedFieldPVCoordinates<T> pv =
                 new TimeStampedFieldPVCoordinates<>(date, new FieldVector3D<>(date.getField(), target), zero, zero);
         return t.transformPVCoordinates(pv);
     }
 
     /** {@inheritDoc} */
     @Override
     protected <T extends CalculusFieldElement<T>> FieldVector3D<T> getTargetPosition(final FieldPVCoordinatesProvider<T> pvProv,
                                                                                      final FieldAbsoluteDate<T> date,
                                                                                      final Frame frame) {
         final FieldStaticTransform<T> staticTransform = getBodyFrame().getStaticTransformTo(frame, date);
         return staticTransform.transformPosition(target);
     }
 }