FieldClockOffset.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.Arrays;
import java.util.List;

import org.hipparchus.CalculusFieldElement;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.time.FieldTimeStamped;

/**
 * Container for time stamped clock offset.
 *
 * @param <T> type of the field elements
 * @author Luc Maisonobe
 * @since 12.1
 */
public class FieldClockOffset<T extends CalculusFieldElement<T>> implements FieldTimeStamped<T> {

    /** Date. */
    private final FieldAbsoluteDate<T> date;

    /** Clock bias. */
    private final T bias;

    /** Clock rate. */
    private final T rate;

    /** Clock acceleration. */
    private final T acceleration;

    /** Simple constructor.
     *
     * @param date         date
     * @param bias         clock bias
     * @param rate         clock rate (can be set to {@code null} if unknown)
     * @param acceleration clock acceleration (can be set to {@code null} if
     *                     unknown)
     */
    public FieldClockOffset(final FieldAbsoluteDate<T> date, final T bias,
            final T rate, final T acceleration) {
        this.date = date;
        this.bias = bias;
        this.rate = rate;
        this.acceleration = acceleration;
    }

    /** Simple constructor.
     *
     * @param date         date
     * @param terms        array of clock terms (bias, rate, acceleration)
     */
    public FieldClockOffset(final FieldAbsoluteDate<T> date, final T[] terms) {
        this(date, Arrays.asList(terms));
    }

    /** Simple constructor.
     *
     * @param date         date
     * @param terms        list of clock terms (bias, rate, acceleration)
     */
    public FieldClockOffset(final FieldAbsoluteDate<T> date, final List<T> terms) {
        this.date = date;

        if (!terms.isEmpty()) {
            this.bias = terms.getFirst();
        } else {
            this.bias = date.getField().getZero();
        }
        if (terms.size() >= 2) {
            this.rate = terms.get(1);
        } else {
            this.rate = date.getField().getZero();
        }
        if (terms.size() == 3) {
            this.acceleration = terms.get(2);
        } else {
            this.acceleration = date.getField().getZero();
        }
        if (terms.size() > 3) {
            throw new OrekitException(OrekitMessages.CANNOT_PARSE_DATA);
        }
    }

    /**
     * Add another offset to the instance.
     * <p>
     * The instance is not modified, a new instance is created
     * </p>
     *
     * @param other offset to add (date part will be ignored)
     * @return instance + other, at instance date
     * @since 14.0
     */
    public FieldClockOffset<T> add(final FieldClockOffset<T> other) {
        return new FieldClockOffset<>(date,
                bias.add(other.bias),
                rate.add(other.rate),
                acceleration.add(other.acceleration));
    }

    /** Subtract another offset from the instance.
     * <p>
     * The instance is not modified, a new instance is created
     * </p>
     *
     * @param other offset to subtract (date part will be ignored)
     * @return instance - other, at instance date
     * @since 14.0
     */
    public FieldClockOffset<T> subtract(final FieldClockOffset<T> other) {
        return new FieldClockOffset<>(date,
                bias.subtract(other.bias),
                rate.subtract(other.rate),
                acceleration.subtract(other.acceleration));
    }

    /** {@inheritDoc} */
    @Override
    public FieldAbsoluteDate<T> getDate() {
        return date;
    }

    /** Get bias.
     * @return bias
     */
    public T getBias() {
        return bias;
    }

    /** Get rate.
     * @return rate ({@code null} if unknown)
     */
    public T getRate() {
        return rate;
    }

    /** Get acceleration.
     * @return acceleration ({@code null} if unknown)
     */
    public T getAcceleration() {
        return acceleration;
    }

    /** Negate instance.
     * <p>
     * The instance is not modified, a new instance is created
     * </p>
     *
     * @return instance - other, at instance date
     * @since 14.0
     */
    public FieldClockOffset<T> negate() {
        return new FieldClockOffset<>(getDate(), bias.negate(), rate.negate(), acceleration.negate());
    }

}