FieldTimeStampedCache.java

/* Copyright 2002-2024 CS GROUP
 * 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
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 */
package org.orekit.utils;

import org.hipparchus.CalculusFieldElement;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.time.FieldTimeStamped;

import java.util.stream.Stream;

/**
 * Interface for a data structure that can provide concurrent access to {@link FieldTimeStamped} data surrounding a given
 * date.
 *
 * @param <T> the type of data
 * @param <KK> type of the field element
 *
 * @author Luc Maisonobe
 * @author Evan Ward
 * @author Vincent Cucchietti
 * @see ImmutableFieldTimeStampedCache
 */
public interface FieldTimeStampedCache<T extends FieldTimeStamped<KK>, KK extends CalculusFieldElement<KK>> {

    /**
     * Get the entries surrounding a central date.
     * <p>
     * If the central date is well within covered range, the returned array will be balanced with half the points before
     * central date and half the points after it (depending on n parity, of course). If the central date is near the
     * boundary, then the returned array will be unbalanced and will contain only the n earliest (or latest) entries. A
     * typical example of the later case is leap seconds cache, since the number of leap seconds cannot be arbitrarily
     * increased.
     * <p>
     * This method is safe for multiple threads to execute concurrently.
     *
     * @param central central date
     *
     * @return list of cached entries surrounding the specified date. The size of the list is guaranteed to be
     * {@link #getMaxNeighborsSize()}.
     */
    default Stream<T> getNeighbors(FieldAbsoluteDate<KK> central) {
        return getNeighbors(central, getMaxNeighborsSize());
    }

    /**
     * Get the entries surrounding a central date.
     * <p>
     * If the central date is well within covered range, the returned array will be balanced with half the points before
     * central date and half the points after it (depending on n parity, of course). If the central date is near the
     * boundary, then the returned array will be unbalanced and will contain only the n earliest (or latest) entries. A
     * typical example of the later case is leap seconds cache, since the number of leap seconds cannot be arbitrarily
     * increased.
     * <p>
     * This method is safe for multiple threads to execute concurrently.
     *
     * @param central central date
     * @param n number of neighbors (cannot exceed {@link #getMaxNeighborsSize()})
     *
     * @return list of cached entries surrounding the specified date. The size of the list is guaranteed to be
     * {@link #getMaxNeighborsSize()}.
     * @since 12.1
     */
    Stream<T> getNeighbors(FieldAbsoluteDate<KK> central, int n);

    /**
     * Get the fixed size of the lists returned by {@link #getNeighbors(FieldAbsoluteDate)}.
     *
     * @return size of the list
     */
    int getMaxNeighborsSize();

    /**
     * Get the earliest entry in this cache.
     *
     * @return earliest cached entry
     *
     * @throws IllegalStateException if this cache is empty
     */
    T getEarliest()
            throws IllegalStateException;

    /**
     * Get the latest entry in this cache.
     *
     * @return latest cached entry
     *
     * @throws IllegalStateException if this cache is empty
     */
    T getLatest()
            throws IllegalStateException;
}