/* 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.cost;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.Field;
  import org.hipparchus.util.FastMath;
  import org.orekit.propagation.events.EventDetectionSettings;
  import org.orekit.propagation.events.FieldEventDetectionSettings;
  import org.orekit.propagation.events.FieldEventDetector;
  
  import java.util.stream.Stream;
  
  /**
   * Class for bounded energy cost with Cartesian coordinates.
   * An energy cost is proportional to the integral over time of the squared Euclidean norm of the control vector, often scaled with 1/2.
   * This type of cost is not optimal in terms of mass consumption, however its solutions showcase a smoother behavior favorable for convergence in shooting techniques.
   * Here, the control vector is chosen as the thrust force divided by the maximum thrust magnitude and expressed in the propagation frame.
   *
   * @param <T> field type
   * @author Romain Serra
   * @see FieldUnboundedCartesianEnergy
   * @see BoundedCartesianEnergy
   * @since 13.0
   */
  public class FieldBoundedCartesianEnergy<T extends CalculusFieldElement<T>> extends FieldCartesianEnergyConsideringMass<T> {
  
      /** Maximum value of thrust force Euclidean norm. */
      private final T maximumThrustMagnitude;
  
      /**
       * Constructor.
       * @param name name
       * @param massFlowRateFactor mass flow rate factor
       * @param maximumThrustMagnitude maximum thrust magnitude
       * @param eventDetectionSettings singularity event detection settings
       */
      public FieldBoundedCartesianEnergy(final String name, final T massFlowRateFactor,
                                         final T maximumThrustMagnitude,
                                         final FieldEventDetectionSettings<T> eventDetectionSettings) {
          super(name, massFlowRateFactor, eventDetectionSettings);
          this.maximumThrustMagnitude = FastMath.abs(maximumThrustMagnitude);
      }
  
      /**
       * Constructor.
       * @param name name
       * @param massFlowRateFactor mass flow rate factor
       * @param maximumThrustMagnitude maximum thrust magnitude
       */
      public FieldBoundedCartesianEnergy(final String name, final T massFlowRateFactor,
                                         final T maximumThrustMagnitude) {
          this(name, massFlowRateFactor, maximumThrustMagnitude, new FieldEventDetectionSettings<>(massFlowRateFactor.getField(),
                  EventDetectionSettings.getDefaultEventDetectionSettings()));
      }
  
      /** Getter for maximum thrust magnitude.
       * @return maximum thrust
       */
      public T getMaximumThrustMagnitude() {
          return maximumThrustMagnitude;
      }
  
      /** {@inheritDoc} */
      @Override
      protected T getFieldThrustForceNorm(final T[] adjointVariables, final T mass) {
          final T adjointVelocityNorm = getFieldAdjointVelocityNorm(adjointVariables);
          T factor = adjointVelocityNorm.divide(mass);
          if (getAdjointDimension() > 6) {
              factor = factor.subtract(adjointVariables[6].multiply(getMassFlowRateFactor()));
          }
          final double factorReal = factor.getReal();
          final T zero = mass.getField().getZero();
          if (factorReal > maximumThrustMagnitude.getReal()) {
              return maximumThrustMagnitude;
          } else if (factorReal < 0.) {
              return zero;
          } else {
              return factor;
          }
      }
  
      /** {@inheritDoc} */
      @Override
      public Stream<FieldEventDetector<T>> getFieldEventDetectors(final Field<T> field) {
         final T zero = field.getZero();
         return Stream.of(new FieldSingularityDetector(getEventDetectionSettings(), zero),
                 new FieldSingularityDetector(getEventDetectionSettings(), maximumThrustMagnitude));
     }
 
     /** {@inheritDoc} */
     @Override
     public BoundedCartesianEnergy toCartesianCost() {
         return new BoundedCartesianEnergy(getAdjointName(), getMassFlowRateFactor().getReal(),
                 maximumThrustMagnitude.getReal(), getEventDetectionSettings().toEventDetectionSettings());
     }
 
 }