DateDetector.java

  1. /* Copyright 2002-2024 CS GROUP
  2.  * Licensed to CS GROUP (CS) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * CS licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *   http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.orekit.propagation.events;

  19. import java.util.ArrayList;
  20. import java.util.Collections;
  21. import java.util.List;

  23. import org.hipparchus.ode.events.Action;
  24. import org.orekit.errors.OrekitIllegalArgumentException;
  25. import org.orekit.errors.OrekitMessages;
  26. import org.orekit.propagation.SpacecraftState;
  27. import org.orekit.propagation.events.handlers.EventHandler;
  28. import org.orekit.propagation.events.handlers.StopOnEvent;
  29. import org.orekit.time.AbsoluteDate;
  30. import org.orekit.time.TimeStamped;

  32. /** Finder for date events.
  33.  * <p>This class finds date events (i.e. occurrence of some predefined dates).</p>
  34.  * <p>As of version 5.1, it is an enhanced date detector:</p>
  35.  * <ul>
  36.  *   <li>it can be defined without prior date ({@link #DateDetector(TimeStamped...)})</li>
  37.  *   <li>several dates can be added ({@link #addEventDate(AbsoluteDate)})</li>
  38.  * </ul>
  39.  * <p>The gap between the added dates must be more than the minGap.</p>
  40.  * <p>The default implementation behavior is to {@link Action#STOP stop}
  41.  * propagation at the first event date occurrence. This can be changed by calling
  42.  * {@link #withHandler(EventHandler)} after construction.</p>
  43.  * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
  44.  * @author Luc Maisonobe
  45.  * @author Pascal Parraud
  46.  */
  47. public class DateDetector extends AbstractDetector<DateDetector> implements TimeStamped {

  49.     /** Default value for max check.
  50.      * @since 12.0
  51.      */
  52.     public static final double DEFAULT_MAX_CHECK = 1.0e10;

  54.     /** Default value for minimum gap between added dates.
  55.      * @since 12.0
  56.      */
  57.     public static final double DEFAULT_MIN_GAP = 1.0;

  59.     /** Default value for convergence threshold.
  60.      * @since 12.0
  61.      */
  62.     public static final double DEFAULT_THRESHOLD = 1.0e-13;

  64.     /** Minimum gap between added dates.
  65.      * @since 12.0
  66.      */
  67.     private final double minGap;

  69.     /** Last date for g computation. */
  70.     private AbsoluteDate gDate;

  72.     /** List of event dates. */
  73.     private final ArrayList<EventDate> eventDateList;

  75.     /** Current event date. */
  76.     private int currentIndex;

  78.     /** Build a new instance.
  79.      * <p>First event dates are set here, but others can be
  80.      * added later with {@link #addEventDate(AbsoluteDate)}.</p>
  81.      * @param dates list of event dates
  82.      * @see #addEventDate(AbsoluteDate)
  83.      * @since 12.0
  84.      */
  85.     public DateDetector(final TimeStamped... dates) {
  86.         this(s -> DEFAULT_MAX_CHECK, DEFAULT_THRESHOLD, DEFAULT_MAX_ITER, new StopOnEvent(), DEFAULT_MIN_GAP, dates);
  87.     }

  89.     /** Protected constructor with full parameters.
  90.      * <p>
  91.      * This constructor is not public as users are expected to use the builder
  92.      * API with the various {@code withXxx()} methods to set up the instance
  93.      * in a readable manner without using a huge amount of parameters.
  94.      * </p>
  95.      * @param maxCheck maximum checking interval
  96.      * @param threshold convergence threshold (s)
  97.      * @param maxIter maximum number of iterations in the event time search
  98.      * @param handler event handler to call at event occurrences
  99.      * @param minGap minimum gap between added dates (s)
  100.      * @param dates list of event dates
  101.      * @since 12.0
  102.      */
  103.     protected DateDetector(final AdaptableInterval maxCheck, final double threshold, final int maxIter,
  104.                            final EventHandler handler, final double minGap, final TimeStamped... dates) {
  105.         super(maxCheck, threshold, maxIter, handler);
  106.         this.currentIndex  = -1;
  107.         this.gDate         = null;
  108.         this.eventDateList = new ArrayList<DateDetector.EventDate>(dates.length);
  109.         for (final TimeStamped ts : dates) {
  110.             addEventDate(ts.getDate());
  111.         }
  112.         this.minGap        = minGap;
  113.     }

  115.     /**
  116.      * Setup minimum gap between added dates.
  117.      * @param newMinGap new minimum gap between added dates
  118.      * @return a new detector with updated configuration (the instance is not changed)
  119.      * @since 12.0
  120.      */
  121.     public DateDetector withMinGap(final double newMinGap) {
  122.         return new DateDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(),
  123.                                 getHandler(), newMinGap,
  124.                                 eventDateList.toArray(new EventDate[eventDateList.size()]));
  125.     }

  127.     /** {@inheritDoc} */
  128.     @Override
  129.     protected DateDetector create(final AdaptableInterval newMaxCheck, final double newThreshold,
  130.                                   final int newMaxIter, final EventHandler newHandler) {
  131.         return new DateDetector(newMaxCheck, newThreshold, newMaxIter, newHandler, minGap,
  132.                                 eventDateList.toArray(new EventDate[eventDateList.size()]));
  133.     }

  135.     /** Get all event dates currently managed, in chronological order.
  136.      * @return all event dates currently managed, in chronological order
  137.      * @since 11.1
  138.      */
  139.     public List<TimeStamped> getDates() {
  140.         return Collections.unmodifiableList(eventDateList);
  141.     }

  143.     /** Compute the value of the switching function.
  144.      * This function measures the difference between the current and the target date.
  145.      * @param s the current state information: date, kinematics, attitude
  146.      * @return value of the switching function
  147.      */
  148.     public double g(final SpacecraftState s) {
  149.         gDate = s.getDate();
  150.         if (currentIndex < 0) {
  151.             return -1.0;
  152.         } else {
  153.             final EventDate event = getClosest(gDate);
  154.             return event.isgIncrease() ? gDate.durationFrom(event.getDate()) : event.getDate().durationFrom(gDate);
  155.         }
  156.     }

  158.     /** Get the current event date according to the propagator.
  159.      * @return event date
  160.      */
  161.     public AbsoluteDate getDate() {
  162.         return currentIndex < 0 ? null : eventDateList.get(currentIndex).getDate();
  163.     }

  165.     /** Add an event date.
  166.      * <p>The date to add must be:</p>
  167.      * <ul>
  168.      *   <li>less than the smallest already registered event date minus the maxCheck</li>
  169.      *   <li>or more than the largest already registered event date plus the maxCheck</li>
  170.      * </ul>
  171.      * @param target target date
  172.      * @throws IllegalArgumentException if the date is too close from already defined interval
  173.      * @see #DateDetector(TimeStamped...)
  174.      */
  175.     public void addEventDate(final AbsoluteDate target) throws IllegalArgumentException {
  176.         final boolean increasing;
  177.         if (currentIndex < 0) {
  178.             increasing = (gDate == null) ? true : target.durationFrom(gDate) > 0.0;
  179.             currentIndex = 0;
  180.             eventDateList.add(new EventDate(target, increasing));
  181.         } else {
  182.             final int          lastIndex = eventDateList.size() - 1;
  183.             final AbsoluteDate firstDate = eventDateList.get(0).getDate();
  184.             final AbsoluteDate lastDate  = eventDateList.get(lastIndex).getDate();
  185.             if (firstDate.durationFrom(target) > minGap) {
  186.                 increasing = !eventDateList.get(0).isgIncrease();
  187.                 eventDateList.add(0, new EventDate(target, increasing));
  188.                 currentIndex++;
  189.             } else if (target.durationFrom(lastDate) > minGap) {
  190.                 increasing = !eventDateList.get(lastIndex).isgIncrease();
  191.                 eventDateList.add(new EventDate(target, increasing));
  192.             } else {
  193.                 throw new OrekitIllegalArgumentException(OrekitMessages.EVENT_DATE_TOO_CLOSE,
  194.                                                          target,
  195.                                                          firstDate,
  196.                                                          lastDate,
  197.                                                          minGap,
  198.                                                          firstDate.durationFrom(target),
  199.                                                          target.durationFrom(lastDate));
  200.             }
  201.         }
  202.     }

  204.     /** Get the closest EventDate to the target date.
  205.      * @param target target date
  206.      * @return current EventDate
  207.      */
  208.     private EventDate getClosest(final AbsoluteDate target) {
  209.         final double dt = target.durationFrom(eventDateList.get(currentIndex).getDate());
  210.         if (dt < 0.0 && currentIndex > 0) {
  211.             boolean found = false;
  212.             while (currentIndex > 0 && !found) {
  213.                 if (target.durationFrom(eventDateList.get(currentIndex - 1).getDate()) < eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  214.                     currentIndex--;
  215.                 } else {
  216.                     found = true;
  217.                 }
  218.             }
  219.         } else if (dt > 0.0 && currentIndex < eventDateList.size() - 1) {
  220.             final int maxIndex = eventDateList.size() - 1;
  221.             boolean found = false;
  222.             while (currentIndex < maxIndex && !found) {
  223.                 if (target.durationFrom(eventDateList.get(currentIndex + 1).getDate()) > eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  224.                     currentIndex++;
  225.                 } else {
  226.                     found = true;
  227.                 }
  228.             }
  229.         }
  230.         return eventDateList.get(currentIndex);
  231.     }

  233.     /** Event date specification. */
  234.     private static class EventDate implements TimeStamped {

  236.         /** Event date. */
  237.         private final AbsoluteDate eventDate;

  239.         /** Flag for g function way around event date. */
  240.         private final boolean gIncrease;

  242.         /** Simple constructor.
  243.          * @param date date
  244.          * @param increase if true, g function increases around event date
  245.          */
  246.         EventDate(final AbsoluteDate date, final boolean increase) {
  247.             this.eventDate = date;
  248.             this.gIncrease = increase;
  249.         }

  251.         /** Getter for event date.
  252.          * @return event date
  253.          */
  254.         public AbsoluteDate getDate() {
  255.             return eventDate;
  256.         }

  258.         /** Getter for g function way at event date.
  259.          * @return g function increasing flag
  260.          */
  261.         public boolean isgIncrease() {
  262.             return gIncrease;
  263.         }

  265.     }

  267. }
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