TimeSpanMap.java

  1. /* Copyright 2002-2020 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.utils;

  19. import java.util.Collections;
  20. import java.util.NavigableSet;
  21. import java.util.TreeSet;
  22. import java.util.function.Consumer;

  24. import org.orekit.time.AbsoluteDate;
  25. import org.orekit.time.ChronologicalComparator;
  26. import org.orekit.time.TimeStamped;

  28. /** Container for objects that apply to spans of time.

  30.  * @param <T> Type of the data.

  32.  * @author Luc Maisonobe
  33.  * @since 7.1
  34.  */
  35. public class TimeSpanMap<T> {

  37.     /** Container for the data. */
  38.     private final NavigableSet<Transition<T>> data;

  40.     /** Create a map containing a single object, initially valid throughout the timeline.
  41.      * <p>
  42.      * The real validity of this first entry will be truncated as other
  43.      * entries are either {@link #addValidBefore(Object, AbsoluteDate)
  44.      * added before} it or {@link #addValidAfter(Object, AbsoluteDate)
  45.      * added after} it.
  46.      * </p>
  47.      * @param entry entry (initially valid throughout the timeline)
  48.      */
  49.     public TimeSpanMap(final T entry) {
  50.         data = new TreeSet<Transition<T>>(new ChronologicalComparator());
  51.         data.add(new Transition<T>(AbsoluteDate.ARBITRARY_EPOCH, entry, entry));
  52.     }

  54.     /** Add an entry valid before a limit date.
  55.      * <p>
  56.      * As an entry is valid, it truncates the validity of the neighboring
  57.      * entries already present in the map.
  58.      * </p>
  59.      * <p>
  60.      * The transition dates should be entered only once, either
  61.      * by a call to this method or by a call to {@link #addValidAfter(Object,
  62.      * AbsoluteDate)}. Repeating a transition date will lead to unexpected
  63.      * result and is not supported.
  64.      * </p>
  65.      * <p>
  66.      * Using addValidBefore(entry, t) will make 'entry' valid in ]-∞, t[ (note the open bracket).
  67.      * </p>
  68.      * @param entry entry to add
  69.      * @param latestValidityDate date before which the entry is valid
  70.      * (must be different from <em>all</em> dates already used for transitions)
  71.      */
  72.     public void addValidBefore(final T entry, final AbsoluteDate latestValidityDate) {

  74.         if (data.size() == 1) {
  75.             final Transition<T> single = data.first();
  76.             if (single.getBefore() == single.getAfter()) {
  77.                 // the single entry was a dummy one, without a real transition
  78.                 // we replace it entirely
  79.                 data.clear();
  80.                 data.add(new Transition<T>(latestValidityDate, entry, single.getAfter()));
  81.                 return;
  82.             }
  83.         }

  85.         final Transition<T> previous =
  86.                 data.floor(new Transition<T>(latestValidityDate, entry, null));
  87.         if (previous == null) {
  88.             // the new transition will be the first one
  89.             data.add(new Transition<T>(latestValidityDate, entry, data.first().getBefore()));
  90.         } else {
  91.             // the new transition will be after the previous one
  92.             data.remove(previous);
  93.             data.add(new Transition<T>(previous.date,      previous.getBefore(), entry));
  94.             data.add(new Transition<T>(latestValidityDate, entry,                previous.getAfter()));
  95.         }

  97.     }

  99.     /** Add an entry valid after a limit date.
  100.      * <p>
  101.      * As an entry is valid, it truncates the validity of the neighboring
  102.      * entries already present in the map.
  103.      * </p>
  104.      * <p>
  105.      * The transition dates should be entered only once, either
  106.      * by a call to this method or by a call to {@link #addValidBefore(Object,
  107.      * AbsoluteDate)}. Repeating a transition date will lead to unexpected
  108.      * result and is not supported.
  109.      * </p>
  110.      * <p>
  111.      * Using addValidAfter(entry, t) will make 'entry' valid [t, +∞[ (note the closed bracket).
  112.      * </p>
  113.      * @param entry entry to add
  114.      * @param earliestValidityDate date after which the entry is valid
  115.      * (must be different from <em>all</em> dates already used for transitions)
  116.      */
  117.     public void addValidAfter(final T entry, final AbsoluteDate earliestValidityDate) {

  119.         if (data.size() == 1) {
  120.             final Transition<T> single = data.first();
  121.             if (single.getBefore() == single.getAfter()) {
  122.                 // the single entry was a dummy one, without a real transition
  123.                 // we replace it entirely
  124.                 data.clear();
  125.                 data.add(new Transition<T>(earliestValidityDate, single.getBefore(), entry));
  126.                 return;
  127.             }
  128.         }

  130.         final Transition<T> next =
  131.                 data.ceiling(new Transition<T>(earliestValidityDate, entry, null));
  132.         if (next == null) {
  133.             // the new transition will be the last one
  134.             data.add(new Transition<T>(earliestValidityDate, data.last().getAfter(), entry));
  135.         } else {
  136.             // the new transition will be before the next one
  137.             data.remove(next);
  138.             data.add(new Transition<T>(earliestValidityDate, next.getBefore(), entry));
  139.             data.add(new Transition<T>(next.date,            entry,            next.getAfter()));
  140.         }

  142.     }

  144.     /** Get the entry valid at a specified date.
  145.      * @param date date at which the entry must be valid
  146.      * @return valid entry at specified date
  147.      */
  148.     public T get(final AbsoluteDate date) {
  149.         final Transition<T> previous = data.floor(new Transition<T>(date, null, null));
  150.         if (previous == null) {
  151.             // there are no transition before the specified date
  152.             // return the first valid entry
  153.             return data.first().getBefore();
  154.         } else {
  155.             return previous.getAfter();
  156.         }
  157.     }

  159.     /** Get the time span containing a specified date.
  160.      * @param date date belonging to the desired time span
  161.      * @return time span containing the specified date
  162.      * @since 9.3
  163.      */
  164.     public Span<T> getSpan(final AbsoluteDate date) {
  165.         final Transition<T> previous = data.floor(new Transition<T>(date, null, null));
  166.         if (previous == null) {
  167.             // there are no transition before the specified date
  168.             // return the first valid entry
  169.             return new Span<>(data.first().getBefore(),
  170.                               AbsoluteDate.PAST_INFINITY,
  171.                               data.first().getDate());
  172.         } else {
  173.             final Transition<T> next = data.higher(previous);
  174.             return new Span<>(previous.getAfter(),
  175.                               previous.getDate(),
  176.                               next == null ? AbsoluteDate.FUTURE_INFINITY : next.getDate());
  177.         }
  178.     }

  180.     /** Extract a range of the map.
  181.      * <p>
  182.      * The object returned will be a new independent instance that will contain
  183.      * only the transitions that lie in the specified range.
  184.      * </p>
  185.      * <p>
  186.      * Consider for example a map containing objects O₀ valid before t₁, O₁ valid
  187.      * between t₁ and t₂, O₂ valid between t₂ and t₃, O₃ valid between t₃ and t₄,
  188.      * and O₄ valid after t₄. then calling this method with a {@code start}
  189.      * date between t₁ and t₂ and a {@code end} date between t₃ and t₄
  190.      * will result in a new map containing objects O₁ valid before t₂, O₂
  191.      * valid between t₂ and t₃, and O₃ valid after t₃. The validity of O₁
  192.      * is therefore extended in the past, and the validity of O₃ is extended
  193.      * in the future.
  194.      * </p>
  195.      * @param start earliest date at which a transition is included in the range
  196.      * (may be set to {@link AbsoluteDate#PAST_INFINITY} to keep all early transitions)
  197.      * @param end latest date at which a transition is included in the r
  198.      * (may be set to {@link AbsoluteDate#FUTURE_INFINITY} to keep all late transitions)
  199.      * @return a new instance with all transitions restricted to the specified range
  200.      * @since 9.2
  201.      */
  202.     public TimeSpanMap<T> extractRange(final AbsoluteDate start, final AbsoluteDate end) {

  204.         final NavigableSet<Transition<T>> inRange = data.subSet(new Transition<T>(start, null, null), true,
  205.                                                                 new Transition<T>(end,   null, null), true);
  206.         if (inRange.isEmpty()) {
  207.             // there are no transitions at all in the range
  208.             // we need to pick up the only valid object
  209.             return new TimeSpanMap<>(get(start));
  210.         }

  212.         final TimeSpanMap<T> range = new TimeSpanMap<>(inRange.first().before);
  213.         for (final Transition<T> transition : inRange) {
  214.             range.addValidAfter(transition.after, transition.getDate());
  215.         }

  217.         return range;

  219.     }

  221.     /** Get an unmodifiable view of the sorted transitions.
  222.      * @return unmodifiable view of the sorted transitions
  223.      */
  224.     public NavigableSet<Transition<T>> getTransitions() {
  225.         return Collections.unmodifiableNavigableSet(data);
  226.     }

  228.     /**
  229.      * Performs an action for each element of map.
  230.      * <p>
  231.      * The action is performed chronologically.
  232.      * </p>
  233.      * @param action action to perform on the elements
  234.      * @since 10.3
  235.      */
  236.     public void forEach(final Consumer<T> action) {
  237.         boolean first = true;
  238.         for (Transition<T> transition : data) {
  239.             if (first) {
  240.                 if (transition.getBefore() != null) {
  241.                     action.accept(transition.getBefore());
  242.                 }
  243.                 first = false;
  244.             }
  245.             if (transition.getAfter() != null) {
  246.                 action.accept(transition.getAfter());
  247.             }
  248.         }
  249.     }

  251.     /** Class holding transition times.
  252.      * <p>
  253.      * This data type is dual to {@link Span}, it is
  254.      * focused one transition date, and gives access to
  255.      * surrounding valid data whereas {@link Span} is focused
  256.      * on one valid data, and gives access to surrounding
  257.      * transition dates.
  258.      * </p>
  259.      * @param <S> Type of the data.
  260.      */
  261.     public static class Transition<S> implements TimeStamped {

  263.         /** Transition date. */
  264.         private final AbsoluteDate date;

  266.         /** Entry valid before the transition. */
  267.         private final S before;

  269.         /** Entry valid after the transition. */
  270.         private final S after;

  272.         /** Simple constructor.
  273.          * @param date transition date
  274.          * @param before entry valid before the transition
  275.          * @param after entry valid after the transition
  276.          */
  277.         private Transition(final AbsoluteDate date, final S before, final S after) {
  278.             this.date   = date;
  279.             this.before = before;
  280.             this.after  = after;
  281.         }

  283.         /** Get the transition date.
  284.          * @return transition date
  285.          */
  286.         @Override
  287.         public AbsoluteDate getDate() {
  288.             return date;
  289.         }

  291.         /** Get the entry valid before transition.
  292.          * @return entry valid before transition
  293.          */
  294.         public S getBefore() {
  295.             return before;
  296.         }

  298.         /** Get the entry valid after transition.
  299.          * @return entry valid after transition
  300.          */
  301.         public S getAfter() {
  302.             return after;
  303.         }

  305.     }

  307.     /** Holder for one time span.
  308.      * <p>
  309.      * This data type is dual to {@link Transition}, it
  310.      * is focused on one valid data, and gives access to
  311.      * surrounding transition dates whereas {@link Transition}
  312.      * is focused on one transition date, and gives access to
  313.      * surrounding valid data.
  314.      * </p>
  315.      * @param <S> Type of the data.
  316.      * @since 9.3
  317.      */
  318.     public static class Span<S> {

  320.         /** Valid data. */
  321.         private final S data;

  323.         /** Start of validity for the data. */
  324.         private final AbsoluteDate start;

  326.         /** End of validity for the data. */
  327.         private final AbsoluteDate end;

  329.         /** Simple constructor.
  330.          * @param data valid data
  331.          * @param start start of validity for the data
  332.          * @param end end of validity for the data
  333.          */
  334.         private Span(final S data, final AbsoluteDate start, final AbsoluteDate end) {
  335.             this.data  = data;
  336.             this.start = start;
  337.             this.end   = end;
  338.         }

  340.         /** Get the data valid during this time span.
  341.          * @return data valid during this time span
  342.          */
  343.         public S getData() {
  344.             return data;
  345.         }

  347.         /** Get the start of this time span.
  348.          * @return start of this time span
  349.          */
  350.         public AbsoluteDate getStart() {
  351.             return start;
  352.         }

  354.         /** Get the end of this time span.
  355.          * @return end of this time span
  356.          */
  357.         public AbsoluteDate getEnd() {
  358.             return end;
  359.         }

  361.     }

  363. }
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