EventState.java

  1. /*
  2.  * Licensed to the Apache Software Foundation (ASF) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * The ASF 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.function.DoubleFunction;

  21. import org.hipparchus.analysis.UnivariateFunction;
  22. import org.hipparchus.analysis.solvers.BracketedUnivariateSolver;
  23. import org.hipparchus.analysis.solvers.BracketedUnivariateSolver.Interval;
  24. import org.hipparchus.analysis.solvers.BracketingNthOrderBrentSolver;
  25. import org.hipparchus.exception.MathRuntimeException;
  26. import org.hipparchus.ode.events.Action;
  27. import org.hipparchus.util.FastMath;
  28. import org.hipparchus.util.Precision;
  29. import org.orekit.errors.OrekitException;
  30. import org.orekit.errors.OrekitInternalError;
  31. import org.orekit.errors.OrekitMessages;
  32. import org.orekit.propagation.SpacecraftState;
  33. import org.orekit.propagation.sampling.OrekitStepInterpolator;
  34. import org.orekit.time.AbsoluteDate;

  36. /** This class handles the state for one {@link EventDetector
  37.  * event detector} during integration steps.
  38.  *
  39.  * <p>This class is heavily based on the class with the same name from the
  40.  * Hipparchus library. The changes performed consist in replacing
  41.  * raw types (double and double arrays) with space dynamics types
  42.  * ({@link AbsoluteDate}, {@link SpacecraftState}).</p>
  43.  * <p>Each time the propagator proposes a step, the event detector
  44.  * should be checked. This class handles the state of one detector
  45.  * during one propagation step, with references to the state at the
  46.  * end of the preceding step. This information is used to determine if
  47.  * the detector should trigger an event or not during the proposed
  48.  * step (and hence the step should be reduced to ensure the event
  49.  * occurs at a bound rather than inside the step).</p>
  50.  * @author Luc Maisonobe
  51.  * @param <T> class type for the generic version
  52.  */
  53. public class EventState<T extends EventDetector> {

  55.     /** Event detector. */
  56.     private T detector;

  58.     /** Time of the previous call to g. */
  59.     private AbsoluteDate lastT;

  61.     /** Value from the previous call to g. */
  62.     private double lastG;

  64.     /** Time at the beginning of the step. */
  65.     private AbsoluteDate t0;

  67.     /** Value of the event detector at the beginning of the step. */
  68.     private double g0;

  70.     /** Simulated sign of g0 (we cheat when crossing events). */
  71.     private boolean g0Positive;

  73.     /** Indicator of event expected during the step. */
  74.     private boolean pendingEvent;

  76.     /** Occurrence time of the pending event. */
  77.     private AbsoluteDate pendingEventTime;

  79.     /**
  80.      * Time to stop propagation if the event is a stop event. Used to enable stopping at
  81.      * an event and then restarting after that event.
  82.      */
  83.     private AbsoluteDate stopTime;

  85.     /** Time after the current event. */
  86.     private AbsoluteDate afterEvent;

  88.     /** Value of the g function after the current event. */
  89.     private double afterG;

  91.     /** The earliest time considered for events. */
  92.     private AbsoluteDate earliestTimeConsidered;

  94.     /** Integration direction. */
  95.     private boolean forward;

  97.     /** Variation direction around pending event.
  98.      *  (this is considered with respect to the integration direction)
  99.      */
  100.     private boolean increasing;

  102.     /** Simple constructor.
  103.      * @param detector monitored event detector
  104.      */
  105.     public EventState(final T detector) {
  106.         this.detector     = detector;

  108.         // some dummy values ...
  109.         lastT                  = AbsoluteDate.PAST_INFINITY;
  110.         lastG                  = Double.NaN;
  111.         t0                     = null;
  112.         g0                     = Double.NaN;
  113.         g0Positive             = true;
  114.         pendingEvent           = false;
  115.         pendingEventTime       = null;
  116.         stopTime               = null;
  117.         increasing             = true;
  118.         earliestTimeConsidered = null;
  119.         afterEvent             = null;
  120.         afterG                 = Double.NaN;

  122.     }

  124.     /** Get the underlying event detector.
  125.      * @return underlying event detector
  126.      */
  127.     public T getEventDetector() {
  128.         return detector;
  129.     }

  131.     /** Initialize event handler at the start of a propagation.
  132.      * <p>
  133.      * This method is called once at the start of the propagation. It
  134.      * may be used by the event handler to initialize some internal data
  135.      * if needed.
  136.      * </p>
  137.      * @param s0 initial state
  138.      * @param t target time for the integration
  139.      *
  140.      */
  141.     public void init(final SpacecraftState s0,
  142.                      final AbsoluteDate t) {
  143.         detector.init(s0, t);
  144.         lastT = AbsoluteDate.PAST_INFINITY;
  145.         lastG = Double.NaN;
  146.     }

  148.     /** Compute the value of the switching function.
  149.      * This function must be continuous (at least in its roots neighborhood),
  150.      * as the integrator will need to find its roots to locate the events.
  151.      * @param s the current state information: date, kinematics, attitude
  152.      * @return value of the switching function
  153.      */
  154.     private double g(final SpacecraftState s) {
  155.         if (!s.getDate().equals(lastT)) {
  156.             lastG = detector.g(s);
  157.             lastT = s.getDate();
  158.         }
  159.         return lastG;
  160.     }

  162.     /** Reinitialize the beginning of the step.
  163.      * @param interpolator interpolator valid for the current step
  164.      */
  165.     public void reinitializeBegin(final OrekitStepInterpolator interpolator) {
  166.         forward = interpolator.isForward();
  167.         final SpacecraftState s0 = interpolator.getPreviousState();
  168.         this.t0 = s0.getDate();
  169.         g0 = g(s0);
  170.         while (g0 == 0) {
  171.             // extremely rare case: there is a zero EXACTLY at interval start
  172.             // we will use the sign slightly after step beginning to force ignoring this zero
  173.             // try moving forward by half a convergence interval
  174.             final double dt = (forward ? 0.5 : -0.5) * detector.getThreshold();
  175.             AbsoluteDate startDate = t0.shiftedBy(dt);
  176.             // if convergence is too small move an ulp
  177.             if (t0.equals(startDate)) {
  178.                 startDate = nextAfter(startDate);
  179.             }
  180.             t0 = startDate;
  181.             g0 = g(interpolator.getInterpolatedState(t0));
  182.         }
  183.         g0Positive = g0 > 0;
  184.         // "last" event was increasing
  185.         increasing = g0Positive;
  186.     }

  188.     /** Evaluate the impact of the proposed step on the event detector.
  189.      * @param interpolator step interpolator for the proposed step
  190.      * @return true if the event detector triggers an event before
  191.      * the end of the proposed step (this implies the step should be
  192.      * rejected)
  193.      * @exception MathRuntimeException if an event cannot be located
  194.      */
  195.     public boolean evaluateStep(final OrekitStepInterpolator interpolator)
  196.         throws MathRuntimeException {

  198.         forward = interpolator.isForward();
  199.         final SpacecraftState s1 = interpolator.getCurrentState();
  200.         final AbsoluteDate t1 = s1.getDate();
  201.         final double dt = t1.durationFrom(t0);
  202.         if (FastMath.abs(dt) < detector.getThreshold()) {
  203.             // we cannot do anything on such a small step, don't trigger any events
  204.             return false;
  205.         }
  206.         // number of points to check in the current step
  207.         final int n = FastMath.max(1, (int) FastMath.ceil(FastMath.abs(dt) / detector.getMaxCheckInterval()));
  208.         final double h = dt / n;


  211.         AbsoluteDate ta = t0;
  212.         double ga = g0;
  213.         for (int i = 0; i < n; ++i) {

  215.             // evaluate handler value at the end of the substep
  216.             final AbsoluteDate tb = (i == n - 1) ? t1 : t0.shiftedBy((i + 1) * h);
  217.             final double gb = g(interpolator.getInterpolatedState(tb));

  219.             // check events occurrence
  220.             if (gb == 0.0 || (g0Positive ^ (gb > 0))) {
  221.                 // there is a sign change: an event is expected during this step
  222.                 if (findRoot(interpolator, ta, ga, tb, gb)) {
  223.                     return true;
  224.                 }
  225.             } else {
  226.                 // no sign change: there is no event for now
  227.                 ta = tb;
  228.                 ga = gb;
  229.             }

  231.         }

  233.         // no event during the whole step
  234.         pendingEvent     = false;
  235.         pendingEventTime = null;
  236.         return false;

  238.     }

  240.     /**
  241.      * Find a root in a bracketing interval.
  242.      *
  243.      * <p> When calling this method one of the following must be true. Either ga == 0, gb
  244.      * == 0, (ga < 0  and gb > 0), or (ga > 0 and gb < 0).
  245.      *
  246.      * @param interpolator that covers the interval.
  247.      * @param ta           earliest possible time for root.
  248.      * @param ga           g(ta).
  249.      * @param tb           latest possible time for root.
  250.      * @param gb           g(tb).
  251.      * @return if a zero crossing was found.
  252.      */
  253.     private boolean findRoot(final OrekitStepInterpolator interpolator,
  254.                              final AbsoluteDate ta, final double ga,
  255.                              final AbsoluteDate tb, final double gb) {
  256.         // check there appears to be a root in [ta, tb]
  257.         check(ga == 0.0 || gb == 0.0 || ga > 0.0 && gb < 0.0 || ga < 0.0 && gb > 0.0);

  259.         final double convergence = detector.getThreshold();
  260.         final int maxIterationCount = detector.getMaxIterationCount();
  261.         final BracketedUnivariateSolver<UnivariateFunction> solver =
  262.                 new BracketingNthOrderBrentSolver(0, convergence, 0, 5);

  264.         // prepare loop below
  265.         AbsoluteDate loopT = ta;
  266.         double loopG = ga;

  268.         // event time, just at or before the actual root.
  269.         AbsoluteDate beforeRootT = null;
  270.         double beforeRootG = Double.NaN;
  271.         // time on the other side of the root.
  272.         // Initialized the the loop below executes once.
  273.         AbsoluteDate afterRootT = ta;
  274.         double afterRootG = 0.0;

  276.         // check for some conditions that the root finders don't like
  277.         // these conditions cannot not happen in the loop below
  278.         // the ga == 0.0 case is handled by the loop below
  279.         if (ta.equals(tb)) {
  280.             // both non-zero but times are the same. Probably due to reset state
  281.             beforeRootT = ta;
  282.             beforeRootG = ga;
  283.             afterRootT = shiftedBy(beforeRootT, convergence);
  284.             afterRootG = g(interpolator.getInterpolatedState(afterRootT));
  285.         } else if (ga != 0.0 && gb == 0.0) {
  286.             // hard: ga != 0.0 and gb == 0.0
  287.             // look past gb by up to convergence to find next sign
  288.             // throw an exception if g(t) = 0.0 in [tb, tb + convergence]
  289.             beforeRootT = tb;
  290.             beforeRootG = gb;
  291.             afterRootT = shiftedBy(beforeRootT, convergence);
  292.             afterRootG = g(interpolator.getInterpolatedState(afterRootT));
  293.         } else if (ga != 0.0) {
  294.             final double newGa = g(interpolator.getInterpolatedState(ta));
  295.             if (ga > 0 != newGa > 0) {
  296.                 // both non-zero, step sign change at ta, possibly due to reset state
  297.                 final AbsoluteDate nextT = minTime(shiftedBy(ta, convergence), tb);
  298.                 final double       nextG = g(interpolator.getInterpolatedState(nextT));
  299.                 if (nextG > 0.0 == g0Positive) {
  300.                     // the sign change between ga and newGa just moved the root less than one convergence
  301.                     // threshold later, we are still in a regular search for another root before tb,
  302.                     // we just need to fix the bracketing interval
  303.                     // (see issue https://github.com/Hipparchus-Math/hipparchus/issues/184)
  304.                     loopT = nextT;
  305.                     loopG = nextG;
  306.                 } else {
  307.                     beforeRootT = ta;
  308.                     beforeRootG = newGa;
  309.                     afterRootT  = nextT;
  310.                     afterRootG  = nextG;
  311.                 }
  312.             }
  313.         }

  315.         // loop to skip through "fake" roots, i.e. where g(t) = g'(t) = 0.0
  316.         // executed once if we didn't hit a special case above
  317.         while ((afterRootG == 0.0 || afterRootG > 0.0 == g0Positive) &&
  318.                 strictlyAfter(afterRootT, tb)) {
  319.             if (loopG == 0.0) {
  320.                 // ga == 0.0 and gb may or may not be 0.0
  321.                 // handle the root at ta first
  322.                 beforeRootT = loopT;
  323.                 beforeRootG = loopG;
  324.                 afterRootT = minTime(shiftedBy(beforeRootT, convergence), tb);
  325.                 afterRootG = g(interpolator.getInterpolatedState(afterRootT));
  326.             } else {
  327.                 // both non-zero, the usual case, use a root finder.
  328.                 // time zero for evaluating the function f. Needs to be final
  329.                 final AbsoluteDate fT0 = loopT;
  330.                 final double tbDouble = tb.durationFrom(fT0);
  331.                 final double middle = 0.5 * tbDouble;
  332.                 final DoubleFunction<AbsoluteDate> date = dt -> {
  333.                     // use either fT0 or tb as the base time for shifts
  334.                     // in order to ensure we reproduce exactly those times
  335.                     // using only one reference time like fT0 would imply
  336.                     // to use ft0.shiftedBy(tbDouble), which may be different
  337.                     // from tb due to numerical noise (see issue 921)
  338.                     if (forward == dt <= middle) {
  339.                         // use start of interval as reference
  340.                         return fT0.shiftedBy(dt);
  341.                     } else {
  342.                         // use end of interval as reference
  343.                         return tb.shiftedBy(dt - tbDouble);
  344.                     }
  345.                 };
  346.                 final UnivariateFunction f = dt -> g(interpolator.getInterpolatedState(date.apply(dt)));
  347.                 if (forward) {
  348.                     try {
  349.                         final Interval interval =
  350.                                 solver.solveInterval(maxIterationCount, f, 0, tbDouble);
  351.                         beforeRootT = date.apply(interval.getLeftAbscissa());
  352.                         beforeRootG = interval.getLeftValue();
  353.                         afterRootT  = date.apply(interval.getRightAbscissa());
  354.                         afterRootG  = interval.getRightValue();
  355.                         // CHECKSTYLE: stop IllegalCatch check
  356.                     } catch (RuntimeException e) {
  357.                         // CHECKSTYLE: resume IllegalCatch check
  358.                         throw new OrekitException(e, OrekitMessages.FIND_ROOT,
  359.                                 detector, loopT, loopG, tb, gb, lastT, lastG);
  360.                     }
  361.                 } else {
  362.                     try {
  363.                         final Interval interval =
  364.                                 solver.solveInterval(maxIterationCount, f, tbDouble, 0);
  365.                         beforeRootT = date.apply(interval.getRightAbscissa());
  366.                         beforeRootG = interval.getRightValue();
  367.                         afterRootT  = date.apply(interval.getLeftAbscissa());
  368.                         afterRootG  = interval.getLeftValue();
  369.                         // CHECKSTYLE: stop IllegalCatch check
  370.                     } catch (RuntimeException e) {
  371.                         // CHECKSTYLE: resume IllegalCatch check
  372.                         throw new OrekitException(e, OrekitMessages.FIND_ROOT,
  373.                                 detector, tb, gb, loopT, loopG, lastT, lastG);
  374.                     }
  375.                 }
  376.             }
  377.             // tolerance is set to less than 1 ulp
  378.             // assume tolerance is 1 ulp
  379.             if (beforeRootT.equals(afterRootT)) {
  380.                 afterRootT = nextAfter(afterRootT);
  381.                 afterRootG = g(interpolator.getInterpolatedState(afterRootT));
  382.             }
  383.             // check loop is making some progress
  384.             check(forward && afterRootT.compareTo(beforeRootT) > 0 ||
  385.                   !forward && afterRootT.compareTo(beforeRootT) < 0);
  386.             // setup next iteration
  387.             loopT = afterRootT;
  388.             loopG = afterRootG;
  389.         }

  391.         // figure out the result of root finding, and return accordingly
  392.         if (afterRootG == 0.0 || afterRootG > 0.0 == g0Positive) {
  393.             // loop gave up and didn't find any crossing within this step
  394.             return false;
  395.         } else {
  396.             // real crossing
  397.             check(beforeRootT != null && !Double.isNaN(beforeRootG));
  398.             // variation direction, with respect to the integration direction
  399.             increasing = !g0Positive;
  400.             pendingEventTime = beforeRootT;
  401.             stopTime = beforeRootG == 0.0 ? beforeRootT : afterRootT;
  402.             pendingEvent = true;
  403.             afterEvent = afterRootT;
  404.             afterG = afterRootG;

  406.             // check increasing set correctly
  407.             check(afterG > 0 == increasing);
  408.             check(increasing == gb >= ga);

  410.             return true;
  411.         }

  413.     }

  415.     /**
  416.      * Get the next number after the given number in the current propagation direction.
  417.      *
  418.      * @param t input time
  419.      * @return t +/- 1 ulp depending on the direction.
  420.      */
  421.     private AbsoluteDate nextAfter(final AbsoluteDate t) {
  422.         return t.shiftedBy(forward ? +Precision.EPSILON : -Precision.EPSILON);
  423.     }

  425.     /** Get the occurrence time of the event triggered in the current
  426.      * step.
  427.      * @return occurrence time of the event triggered in the current
  428.      * step.
  429.      */
  430.     public AbsoluteDate getEventDate() {
  431.         return pendingEventTime;
  432.     }

  434.     /**
  435.      * Try to accept the current history up to the given time.
  436.      *
  437.      * <p> It is not necessary to call this method before calling {@link
  438.      * #doEvent(SpacecraftState)} with the same state. It is necessary to call this
  439.      * method before you call {@link #doEvent(SpacecraftState)} on some other event
  440.      * detector.
  441.      *
  442.      * @param state        to try to accept.
  443.      * @param interpolator to use to find the new root, if any.
  444.      * @return if the event detector has an event it has not detected before that is on or
  445.      * before the same time as {@code state}. In other words {@code false} means continue
  446.      * on while {@code true} means stop and handle my event first.
  447.      */
  448.     public boolean tryAdvance(final SpacecraftState state,
  449.                               final OrekitStepInterpolator interpolator) {
  450.         final AbsoluteDate t = state.getDate();
  451.         // check this is only called before a pending event.
  452.         check(!pendingEvent || !strictlyAfter(pendingEventTime, t));

  454.         final boolean meFirst;

  456.         if (strictlyAfter(t, earliestTimeConsidered)) {
  457.             // just found an event and we know the next time we want to search again
  458.             meFirst = false;
  459.         } else {
  460.             // check g function to see if there is a new event
  461.             final double g = g(state);
  462.             final boolean positive = g > 0;

  464.             if (positive == g0Positive) {
  465.                 // g function has expected sign
  466.                 g0 = g; // g0Positive is the same
  467.                 meFirst = false;
  468.             } else {
  469.                 // found a root we didn't expect -> find precise location
  470.                 final AbsoluteDate oldPendingEventTime = pendingEventTime;
  471.                 final boolean foundRoot = findRoot(interpolator, t0, g0, t, g);
  472.                 // make sure the new root is not the same as the old root, if one exists
  473.                 meFirst = foundRoot && !pendingEventTime.equals(oldPendingEventTime);
  474.             }
  475.         }

  477.         if (!meFirst) {
  478.             // advance t0 to the current time so we can't find events that occur before t
  479.             t0 = t;
  480.         }

  482.         return meFirst;
  483.     }

  485.     /**
  486.      * Notify the user's listener of the event. The event occurs wholly within this method
  487.      * call including a call to {@link EventDetector#resetState(SpacecraftState)}
  488.      * if necessary.
  489.      *
  490.      * @param state the state at the time of the event. This must be at the same time as
  491.      *              the current value of {@link #getEventDate()}.
  492.      * @return the user's requested action and the new state if the action is {@link
  493.      * Action#RESET_STATE Action.RESET_STATE}.
  494.      * Otherwise the new state is {@code state}. The stop time indicates what time propagation
  495.      * should stop if the action is {@link Action#STOP Action.STOP}.
  496.      * This guarantees the integration will stop on or after the root, so that integration
  497.      * may be restarted safely.
  498.      */
  499.     public EventOccurrence doEvent(final SpacecraftState state) {
  500.         // check event is pending and is at the same time
  501.         check(pendingEvent);
  502.         check(state.getDate().equals(this.pendingEventTime));

  504.         final Action action = detector.eventOccurred(state, increasing == forward);
  505.         final SpacecraftState newState;
  506.         if (action == Action.RESET_STATE) {
  507.             newState = detector.resetState(state);
  508.         } else {
  509.             newState = state;
  510.         }
  511.         // clear pending event
  512.         pendingEvent     = false;
  513.         pendingEventTime = null;
  514.         // setup for next search
  515.         earliestTimeConsidered = afterEvent;
  516.         t0 = afterEvent;
  517.         g0 = afterG;
  518.         g0Positive = increasing;
  519.         // check g0Positive set correctly
  520.         check(g0 == 0.0 || g0Positive == g0 > 0);
  521.         return new EventOccurrence(action, newState, stopTime);
  522.     }

  524.     /**
  525.      * Shift a time value along the current integration direction: {@link #forward}.
  526.      *
  527.      * @param t     the time to shift.
  528.      * @param delta the amount to shift.
  529.      * @return t + delta if forward, else t - delta. If the result has to be rounded it
  530.      * will be rounded to be before the true value of t + delta.
  531.      */
  532.     private AbsoluteDate shiftedBy(final AbsoluteDate t, final double delta) {
  533.         if (forward) {
  534.             final AbsoluteDate ret = t.shiftedBy(delta);
  535.             if (ret.durationFrom(t) > delta) {
  536.                 return ret.shiftedBy(-Precision.EPSILON);
  537.             } else {
  538.                 return ret;
  539.             }
  540.         } else {
  541.             final AbsoluteDate ret = t.shiftedBy(-delta);
  542.             if (t.durationFrom(ret) > delta) {
  543.                 return ret.shiftedBy(+Precision.EPSILON);
  544.             } else {
  545.                 return ret;
  546.             }
  547.         }
  548.     }

  550.     /**
  551.      * Get the time that happens first along the current propagation direction: {@link
  552.      * #forward}.
  553.      *
  554.      * @param a first time
  555.      * @param b second time
  556.      * @return min(a, b) if forward, else max (a, b)
  557.      */
  558.     private AbsoluteDate minTime(final AbsoluteDate a, final AbsoluteDate b) {
  559.         return (forward ^ (a.compareTo(b) > 0)) ? a : b;
  560.     }

  562.     /**
  563.      * Check the ordering of two times.
  564.      *
  565.      * @param t1 the first time.
  566.      * @param t2 the second time.
  567.      * @return true if {@code t2} is strictly after {@code t1} in the propagation
  568.      * direction.
  569.      */
  570.     private boolean strictlyAfter(final AbsoluteDate t1, final AbsoluteDate t2) {
  571.         if (t1 == null || t2 == null) {
  572.             return false;
  573.         } else {
  574.             return forward ? t1.compareTo(t2) < 0 : t2.compareTo(t1) < 0;
  575.         }
  576.     }

  578.     /**
  579.      * Same as keyword assert, but throw a {@link MathRuntimeException}.
  580.      *
  581.      * @param condition to check
  582.      * @throws MathRuntimeException if {@code condition} is false.
  583.      */
  584.     private void check(final boolean condition) throws MathRuntimeException {
  585.         if (!condition) {
  586.             throw new OrekitInternalError(null);
  587.         }
  588.     }

  590.     /**
  591.      * Class to hold the data related to an event occurrence that is needed to decide how
  592.      * to modify integration.
  593.      */
  594.     public static class EventOccurrence {

  596.         /** User requested action. */
  597.         private final Action action;
  598.         /** New state for a reset action. */
  599.         private final SpacecraftState newState;
  600.         /** The time to stop propagation if the action is a stop event. */
  601.         private final AbsoluteDate stopDate;

  603.         /**
  604.          * Create a new occurrence of an event.
  605.          *
  606.          * @param action   the user requested action.
  607.          * @param newState for a reset event. Should be the current state unless the
  608.          *                 action is {@link Action#RESET_STATE}.
  609.          * @param stopDate to stop propagation if the action is {@link Action#STOP}. Used
  610.          *                 to move the stop time to just after the root.
  611.          */
  612.         EventOccurrence(final Action action,
  613.                         final SpacecraftState newState,
  614.                         final AbsoluteDate stopDate) {
  615.             this.action = action;
  616.             this.newState = newState;
  617.             this.stopDate = stopDate;
  618.         }

  620.         /**
  621.          * Get the user requested action.
  622.          *
  623.          * @return the action.
  624.          */
  625.         public Action getAction() {
  626.             return action;
  627.         }

  629.         /**
  630.          * Get the new state for a reset action.
  631.          *
  632.          * @return the new state.
  633.          */
  634.         public SpacecraftState getNewState() {
  635.             return newState;
  636.         }

  638.         /**
  639.          * Get the new time for a stop action.
  640.          *
  641.          * @return when to stop propagation.
  642.          */
  643.         public AbsoluteDate getStopDate() {
  644.             return stopDate;
  645.         }

  647.     }

  649. }
Created with JaCoCo 0.8.8.202204050719