/* 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.signal;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.Field;
  import org.hipparchus.optim.ConvergenceChecker;
  import org.hipparchus.optim.FieldScalarConvergenceCheckerProvider;
  import org.hipparchus.util.FastMath;
  import org.orekit.utils.FieldPVCoordinatesProvider;
  import org.orekit.utils.PVCoordinatesProvider;
  
  /**
   * Full model for signal travel time in vacuum (adjustable receiver/emitter with fixed emission/reception),
   * compatible with Field.
   * @since 14.0
   * @author Romain Serra
   */
  public class SignalTravelTimeModel {
  
      /** Convergence checker for standard values. */
      private final ConvergenceChecker<Double> convergenceChecker;
  
      /** Convergence checker provider for Field values. */
      private final FieldScalarConvergenceCheckerProvider fieldConvergenceCheckerProvider;
  
      /**
       * Constructor.
       * @param convergenceChecker convergence settings for standard values
       * @param fieldConvergenceCheckerProvider convergence settings for Field values
       */
      public SignalTravelTimeModel(final ConvergenceChecker<Double> convergenceChecker,
                                   final FieldScalarConvergenceCheckerProvider fieldConvergenceCheckerProvider) {
          this.convergenceChecker = convergenceChecker;
          this.fieldConvergenceCheckerProvider = fieldConvergenceCheckerProvider;
      }
  
      /**
       * Constructor.
       * @param convergenceChecker convergence settings for standard values
       */
      public SignalTravelTimeModel(final ConvergenceChecker<Double> convergenceChecker) {
          this(convergenceChecker, new FieldScalarConvergenceCheckerProvider() {
              @Override
              public <T extends CalculusFieldElement<T>> ConvergenceChecker<T> getChecker(final Field<T> field) {
                  return (iteration, previous, current) -> iteration != 0 && (iteration > AbstractSignalTravelTime.DEFAULT_MAX_ITER ||
                          (previous.subtract(current)).norm() <= 2 * FastMath.ulp(current).getReal());
              }
          });
      }
  
      /**
       * Constructor.
       */
      public SignalTravelTimeModel() {
          this(AbstractSignalTravelTime.getDefaultConvergenceChecker());
      }
  
      /**
       * Getter for the convergence checker.
       * @return checker
       */
      public ConvergenceChecker<Double> getConvergenceChecker() {
          return convergenceChecker;
      }
  
      /**
       * Getter for the Field convergence checker provider.
       * @return provider
       */
      public FieldScalarConvergenceCheckerProvider getFieldConvergenceCheckerProvider() {
          return fieldConvergenceCheckerProvider;
      }
  
      /**
       * Method returning a model assuming an iteration of the fixed point algorithm has already been performed.
       * @return warmed-up signal model
       */
      public SignalTravelTimeModel getWarmedUpModel() {
          return new SignalTravelTimeModel((iteration, previous, current) -> convergenceChecker.converged(iteration + 1, previous, current),
                  new FieldScalarConvergenceCheckerProvider() {
                      @Override
                      public <T extends CalculusFieldElement<T>> ConvergenceChecker<T> getChecker(final Field<T> field) {
                          return (iteration, previous, current) -> fieldConvergenceCheckerProvider.getChecker(field)
                                  .converged(iteration + 1, previous, current);
                     }
                 });
     }
 
     /**
      * Method constructing a delay computer with input emitter.
      * @param emitter signal emitter
      * @return (positive) time delay
      */
     public AdjustableEmitterSignalTimer getAdjustableEmitterComputer(final PVCoordinatesProvider emitter) {
         return new AdjustableEmitterSignalTimer(emitter, convergenceChecker);
     }
 
     /**
      * Method constructing a delay computer with input receiver.
      * @param receiver signal emitter
      * @return (positive) time delay
      */
     public AdjustableReceiverSignalTimer getAdjustableReceiverComputer(final PVCoordinatesProvider receiver) {
         return new AdjustableReceiverSignalTimer(receiver, convergenceChecker);
     }
 
     /**
      * Method constructing a delay computer with input emitter.
      * @param <T> field type
      * @param field field
      * @param emitter signal emitter
      * @return (positive) time delay
      */
     public <T extends CalculusFieldElement<T>> FieldAdjustableEmitterSignalTimer<T> getFieldAdjustableEmitterComputer(final Field<T> field,
                                                                                                                       final FieldPVCoordinatesProvider<T> emitter) {
         return new FieldAdjustableEmitterSignalTimer<>(emitter, fieldConvergenceCheckerProvider.getChecker(field));
     }
 
     /**
      * Method constructing a delay computer with input receiver.
      * @param <T> field type
      * @param field field
      * @param receiver signal receiver
      * @return (positive) time delay
      */
     public <T extends CalculusFieldElement<T>> FieldAdjustableReceiverSignalTimer<T> getFieldAdjustableReceiverComputer(final Field<T> field,
                                                                                                                         final FieldPVCoordinatesProvider<T> receiver) {
         return new FieldAdjustableReceiverSignalTimer<>(receiver, fieldConvergenceCheckerProvider.getChecker(field));
     }
 }