/* Copyright 2022-2025 Romain Serra
    * 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.control.indirect.adjoint;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  import org.hipparchus.geometry.euclidean.threed.Vector3D;
  import org.hipparchus.util.MathArrays;
  import org.orekit.frames.Frame;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.utils.ExtendedPositionProvider;
  
  /**
   * Abstract class defining the contributions of a point-mass, single body gravity in the adjoint equations for Cartesian coordinates.
   * @author Romain Serra
   * @see CartesianAdjointEquationTerm
   * @since 12.2
   */
  public abstract class AbstractCartesianAdjointNonCentralBodyTerm extends AbstractCartesianAdjointNewtonianTerm {
  
      /** Extended position provider for the body. */
      private final ExtendedPositionProvider bodyPositionProvider;
  
      /**
       * Constructor.
       * @param mu body gravitational parameter.
       * @param bodyPositionProvider body position provider
       */
      protected AbstractCartesianAdjointNonCentralBodyTerm(final double mu,
                                                           final ExtendedPositionProvider bodyPositionProvider) {
          super(mu);
          this.bodyPositionProvider = bodyPositionProvider;
      }
  
      /** {@inheritDoc} */
      @Override
      public double[] getPositionAdjointContribution(final AbsoluteDate date, final double[] stateVariables,
                                                     final double[] adjointVariables, final Frame frame) {
          return getNewtonianVelocityAdjointContribution(formRelativePosition(date, stateVariables, frame),
              adjointVariables);
      }
  
      /** {@inheritDoc} */
      @Override
      public <T extends CalculusFieldElement<T>> T[] getPositionAdjointFieldContribution(final FieldAbsoluteDate<T> date,
                                                                                         final T[] stateVariables,
                                                                                         final T[] adjointVariables,
                                                                                         final Frame frame) {
          return getFieldNewtonianVelocityAdjointContribution(formFieldRelativePosition(date, stateVariables, frame),
              adjointVariables);
      }
  
      /**
       * Get body's position.
       * @param date date
       * @param frame frame
       * @return position vector
       */
      protected Vector3D getBodyPosition(final AbsoluteDate date, final Frame frame) {
          return bodyPositionProvider.getPosition(date, frame);
      }
  
      /**
       * Get body's position.
       * @param <T> field type
       * @param date date
       * @param frame frame
       * @return position vector
       */
      protected <T extends CalculusFieldElement<T>> FieldVector3D<T> getFieldBodyPosition(final FieldAbsoluteDate<T> date,
                                                                                          final Frame frame) {
          return bodyPositionProvider.getPosition(date, frame);
      }
  
      /**
       * Form relative position vector w.r.t. body.
       * @param date date
       * @param stateVariables Cartesian variables
       * @param frame frame where Cartesian coordinates apply
       * @return relative position vector as array
       */
      protected double[] formRelativePosition(final AbsoluteDate date, final double[] stateVariables, final Frame frame) {
          final Vector3D bodyPosition = getBodyPosition(date, frame);
          final double x = stateVariables[0] - bodyPosition.getX();
         final double y = stateVariables[1] - bodyPosition.getY();
         final double z = stateVariables[2] - bodyPosition.getZ();
         return new double[] { x, y, z };
     }
 
     /**
      * Form relative position vector w.r.t. body.
      * @param date date
      * @param stateVariables Cartesian variables
      * @param frame frame where Cartesian coordinates apply
      * @param <T> field type
      * @return relative position vector as array
      */
     protected <T extends CalculusFieldElement<T>> T[] formFieldRelativePosition(final FieldAbsoluteDate<T> date,
                                                                               final T[] stateVariables,
                                                                               final Frame frame) {
         final FieldVector3D<T> bodyPosition = getFieldBodyPosition(date, frame);
         final T x = stateVariables[0].subtract(bodyPosition.getX());
         final T y = stateVariables[1].subtract(bodyPosition.getY());
         final T z = stateVariables[2].subtract(bodyPosition.getZ());
         final T[] relativePosition = MathArrays.buildArray(date.getField(), 3);
         relativePosition[0] = x;
         relativePosition[1] = y;
         relativePosition[2] = z;
         return relativePosition;
     }
 }