/* 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.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.function.DoubleFunction;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.analysis.differentiation.Gradient;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.ImmutableTimeStampedCache;
  import org.orekit.utils.drivers.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>> SampledFieldClockModel<T> toField(final DoubleFunction<T> converter) {
          return new SampledFieldClockModel<>(sample.toField(c -> c.toField(converter)).getAll(),
                                              sample.getMaxNeighborsSize());
      }
  
      /** {@inheritDoc} */
      @Override
      public SampledFieldClockModel<Gradient> toGradient(final int freeParameters, final Map<String, Integer> indices) {
          return toField(v -> Gradient.constant(freeParameters, v));
      }
  
      /** {@inheritDoc} */
      @Override
      public List<ParameterDriver> getParametersDrivers() {
          return Collections.emptyList();
      }
  
  }