/* Copyright 2022-2026 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.utils;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.Field;
  import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  import org.hipparchus.geometry.euclidean.threed.Vector3D;
  import org.orekit.frames.Frame;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.FieldAbsoluteDate;
  
  
  /** Fixed-position (in a given frame) provider. The point might be fictitious.
   * @author Romain Serra
   * @since 14.0
   * @see PVCoordinatesProvider
   */
  public class ConstantPositionProvider implements ExtendedPositionProvider {
  
      /** Constant Cartesian position vector. */
      private final Vector3D constantPosition;
  
      /** Reference frame. */
      private final Frame referenceFrame;
  
      /** Simple constructor.
       * @param constantPosition constant position vector in input frame
       * @param referenceFrame frame where constant position is given
       */
      public ConstantPositionProvider(final Vector3D constantPosition, final Frame referenceFrame) {
          this.constantPosition = constantPosition;
          this.referenceFrame = referenceFrame;
      }
  
      /**
       * Getter for constant position in reference frame.
       * @return position in reference frame
       */
      public Vector3D getConstantPosition() {
          return constantPosition;
      }
  
      /** {@inheritDoc} */
      @Override
      public Vector3D getPosition(final AbsoluteDate date, final Frame frame) {
          if (referenceFrame == frame) {
              return constantPosition;
          }
          return referenceFrame.getStaticTransformTo(frame, date).transformPosition(constantPosition);
      }
  
      /** {@inheritDoc} */
      @Override
      public <T extends CalculusFieldElement<T>> FieldVector3D<T> getPosition(final FieldAbsoluteDate<T> date,
                                                                              final Frame frame) {
          if (referenceFrame == frame) {
              return new FieldVector3D<>(date.getField(), constantPosition);
          }
          return referenceFrame.getStaticTransformTo(frame, date).transformPosition(constantPosition);
      }
  
      /** {@inheritDoc} */
      @Override
      public Vector3D getVelocity(final AbsoluteDate date, final Frame frame) {
          if (referenceFrame == frame) {
              return Vector3D.ZERO;
          }
          final PVCoordinates pvCoordinates = new PVCoordinates(constantPosition);
          return referenceFrame.getKinematicTransformTo(frame, date).transformOnlyPV(pvCoordinates).getVelocity();
      }
  
      /** {@inheritDoc} */
      @Override
      public <T extends CalculusFieldElement<T>> FieldVector3D<T> getVelocity(final FieldAbsoluteDate<T> date,
                                                                              final Frame frame) {
          if (referenceFrame == frame) {
              return FieldVector3D.getZero(date.getField());
          }
          final Field<T> field = date.getField();
          final FieldVector3D<T> fieldconstantPosition = new FieldVector3D<>(field, constantPosition);
          final FieldPVCoordinates<T> fieldPVCoordinates = new FieldPVCoordinates<>(fieldconstantPosition, FieldVector3D.getZero(field));
          return referenceFrame.getKinematicTransformTo(frame, date).transformOnlyPV(fieldPVCoordinates).getVelocity();
      }
  
     /** {@inheritDoc} */
     @Override
     public TimeStampedPVCoordinates getPVCoordinates(final AbsoluteDate date, final Frame frame) {
         final TimeStampedPVCoordinates pvCoordinates = new TimeStampedPVCoordinates(date, constantPosition, Vector3D.ZERO);
         if (referenceFrame == frame) {
             return pvCoordinates;
         }
         return referenceFrame.getTransformTo(frame, date).transformPVCoordinates(pvCoordinates);
     }
 
     /** {@inheritDoc} */
     @Override
     public <T extends CalculusFieldElement<T>> TimeStampedFieldPVCoordinates<T> getPVCoordinates(final FieldAbsoluteDate<T> date,
                                                                                                  final Frame frame) {
         final Field<T> field = date.getField();
         final FieldVector3D<T> fieldconstantPosition = new FieldVector3D<>(field, constantPosition);
         final TimeStampedFieldPVCoordinates<T> fieldPVCoordinates = new TimeStampedFieldPVCoordinates<>(date,
                 new FieldPVCoordinates<>(fieldconstantPosition, FieldVector3D.getZero(field)));
         if (referenceFrame == frame) {
             return fieldPVCoordinates;
         }
         return referenceFrame.getTransformTo(frame, date).transformPVCoordinates(fieldPVCoordinates);
     }
 
 }