SampledClockModel.java

/* 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();
    }

}