/* Copyright 2022-2026 Thales Alenia Space
    * 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.time.clocks;
  
  import java.util.List;
  import java.util.Map;
  import java.util.stream.Stream;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.Field;
  import org.hipparchus.analysis.differentiation.Gradient;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.utils.ImmutableTimeStampedCache;
  import org.orekit.utils.ParameterDriver;
  
  /** Offset clock model backed up by a sample.
   *
   * @author Luc Maisonobe
   * @since 12.1
   */
  public class SampledClockModel implements ClockModel {
  
      /** sample. */
      private final ImmutableTimeStampedCache<ClockOffset> sample;
  
      /** Simple constructor.
       * @param sample                clock offsets sample
       * @param nbInterpolationPoints number of points to use in interpolation
       */
      public SampledClockModel(final List<ClockOffset> sample, final int nbInterpolationPoints) {
          this.sample = new ImmutableTimeStampedCache<>(nbInterpolationPoints, sample);
      }
  
      /** Get the clock offsets cache.
       * @return clock offsets cache
       */
      public ImmutableTimeStampedCache<ClockOffset> getCache() {
          return sample;
      }
  
      /** {@inheritDoc} */
      @Override
      public AbsoluteDate getValidityStart() {
          return sample.getEarliest().getDate();
      }
  
      /** {@inheritDoc} */
      @Override
      public AbsoluteDate getValidityEnd() {
          return sample.getLatest().getDate();
      }
  
      /** {@inheritDoc} */
      @Override
      public ClockOffset getOffset(final AbsoluteDate date) {
          return new ClockOffsetHermiteInterpolator(sample.getMaxNeighborsSize()).
              interpolate(date, sample.getNeighbors(date));
      }
  
      /** {@inheritDoc} */
      @Override
      public <T extends CalculusFieldElement<T>> FieldClockOffset<T> getFieldOffset(final FieldAbsoluteDate<T> date) {
  
          // convert the neighbors to field
          final Field<T> field = date.getField();
          final T zero = field.getZero();
          final Stream<FieldClockOffset<T>> fieldSample =
              sample.
                  getNeighbors(date.toAbsoluteDate()).
                  map(c -> {
                      final FieldAbsoluteDate<T> dateF = new FieldAbsoluteDate<>(field, c.getDate());
                      final T                    biasF = zero.newInstance(c.getBias());
                      final T rateF;
                      final T accelerationF;
                      if (Double.isNaN(c.getRate())) {
                          // no rate available
                          rateF         = null;
                          accelerationF = null;
                      } else {
                          // rate available
                          rateF = zero.newInstance(c.getRate());
                          accelerationF = Double.isNaN(c.getAcceleration()) ?
                                         null :
                                         zero.newInstance(c.getAcceleration());
                     }
                     return new FieldClockOffset<>(dateF, biasF, rateF, accelerationF);
                 });
 
         // perform interpolation
         final FieldClockOffsetHermiteInterpolator<T> interpolator =
             new FieldClockOffsetHermiteInterpolator<>(sample.getMaxNeighborsSize());
         return interpolator.interpolate(date, fieldSample);
 
     }
 
     /** {@inheritDoc} */
     @Override
     public List<ParameterDriver> getParametersDrivers() {
         throw new OrekitException(OrekitMessages.INTERNAL_ERROR);
     }
 
 
     /** {@inheritDoc} */
     @Override
     public FieldClockModel<Gradient> getFieldModel(final int freeParameters,
             final Map<String, Integer> indices, final AbsoluteDate date) {
         throw new OrekitException(OrekitMessages.INTERNAL_ERROR);
     }
 
 }