AbstractODEDetector

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 * (the "License"); you may not use this file except in compliance with
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 *      https://www.apache.org/licenses/LICENSE-2.0
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package org.hipparchus.ode.events;

import org.hipparchus.analysis.UnivariateFunction;
import org.hipparchus.analysis.solvers.BracketedUnivariateSolver;
import org.hipparchus.analysis.solvers.BracketingNthOrderBrentSolver;
import org.hipparchus.ode.ODEStateAndDerivative;

/** Base class for #@link {@link ODEEventDetector}.
 * @param <T> type of the detector
 * @since 3.0
 */
public abstract class AbstractODEDetector<T extends AbstractODEDetector<T>> implements ODEEventDetector {

    /** Default maximum checking interval (s). */
    public static final double DEFAULT_MAXCHECK = 600;

    /** Default convergence threshold (s). */
    public static final double DEFAULT_THRESHOLD = 1.e-6;

    /** Default maximum number of iterations in the event time search. */
    public static final int DEFAULT_MAX_ITER = 100;

    /** Max check interval. */
    private final AdaptableInterval maxCheck;

    /** Maximum number of iterations in the event time search. */
    private final int maxIter;

    /** Root-finding algorithm to use to detect state events. */
    private final BracketedUnivariateSolver<UnivariateFunction> solver;

    /** Default handler for event overrides. */
    private final ODEEventHandler handler;

    /** Propagation direction. */
    private boolean forward;

    /** Build a new instance.
     * @param maxCheck maximum checking interval, must be strictly positive (s)
     * @param maxIter maximum number of iterations in the event time search
     * @param solver root-finding algorithm to use to detect state events
     * @param handler event handler to call at event occurrences
     */
    protected AbstractODEDetector(final AdaptableInterval maxCheck, final int maxIter,
                                  final BracketedUnivariateSolver<UnivariateFunction> solver,
                                  final ODEEventHandler handler) {
        this.maxCheck  = maxCheck;
        this.maxIter   = maxIter;
        this.solver    = solver;
        this.handler   = handler;
        this.forward   = true;
    }

    /**
     * {@inheritDoc}
     *
     * <p> This implementation sets the direction of integration and initializes the event
     * handler. If a subclass overrides this method it should call {@code
     * super.init(s0, t)}.
     */
    @Override
    public void init(final ODEStateAndDerivative s0, final double t) {
        forward = t >= s0.getTime();
        getHandler().init(s0, t, this);
    }

    /** {@inheritDoc} */
    @Override
    public abstract double g(ODEStateAndDerivative s);

    /** {@inheritDoc} */
    @Override
    public AdaptableInterval getMaxCheckInterval() {
        return maxCheck;
    }

    /** {@inheritDoc} */
    @Override
    public int getMaxIterationCount() {
        return maxIter;
    }

    /** {@inheritDoc} */
    @Override
    public BracketedUnivariateSolver<UnivariateFunction> getSolver() {
        return solver;
    }

    /**
     * Setup the maximum checking interval.
     * <p>
     * This will override a maximum checking interval if it has been configured previously.
     * </p>
     * @param newMaxCheck maximum checking interval
     * @return a new detector with updated configuration (the instance is not changed)
     */
    public T withMaxCheck(final double newMaxCheck) {
        return withMaxCheck(s -> newMaxCheck);
    }

    /**
     * Setup the maximum checking interval.
     * <p>
     * This will override a maximum checking interval if it has been configured previously.
     * </p>
     * @param newMaxCheck maximum checking interval
     * @return a new detector with updated configuration (the instance is not changed)
     * @since 3.0
     */
    public T withMaxCheck(final AdaptableInterval newMaxCheck) {
        return create(newMaxCheck, getMaxIterationCount(), getSolver(), getHandler());
    }

    /**
     * Setup the maximum number of iterations in the event time search.
     * <p>
     * This will override a number of iterations if it has been configured previously.
     * </p>
     * @param newMaxIter maximum number of iterations in the event time search
     * @return a new detector with updated configuration (the instance is not changed)
     */
    public T withMaxIter(final int newMaxIter) {
        return create(getMaxCheckInterval(), newMaxIter, getSolver(), getHandler());
    }

    /**
     * Setup the convergence threshold.
     * <p>
     * This is equivalent to call {@code withSolver(new BracketingNthOrderBrentSolver(0,
     * newThreshold, 0, 5))}, so it will override a solver if one has been configured previously.
     * </p>
     * @param newThreshold convergence threshold
     * @return a new detector with updated configuration (the instance is not changed)
     * @see #withSolver(BracketedUnivariateSolver)
     */
    public T withThreshold(final double newThreshold) {
        return withSolver(new BracketingNthOrderBrentSolver(0, newThreshold, 0, 5));
    }

    /**
     * Setup the root-finding algorithm to use to detect state events.
     * <p>
     * This will override a solver if it has been configured previously.
     * </p>
     * @param newSolver root-finding algorithm to use to detect state events
     * @return a new detector with updated configuration (the instance is not changed)
     * @see #withThreshold(double)
     */
    public T withSolver(final BracketedUnivariateSolver<UnivariateFunction> newSolver) {
        return create(getMaxCheckInterval(), getMaxIterationCount(), newSolver, getHandler());
    }

    /**
     * Setup the event handler to call at event occurrences.
     * <p>
     * This will override a handler if it has been configured previously.
     * </p>
     * @param newHandler event handler to call at event occurrences
     * @return a new detector with updated configuration (the instance is not changed)
     */
    public T withHandler(final ODEEventHandler newHandler) {
        return create(getMaxCheckInterval(), getMaxIterationCount(), getSolver(), newHandler);
    }

    /** {@inheritDoc} */
    @Override
    public ODEEventHandler getHandler() {
        return handler;
    }

    /** Build a new instance.
     * @param newMaxCheck maximum checking interval
     * @param newmaxIter maximum number of iterations in the event time search
     * @param newSolver root-finding algorithm to use to detect state events
     * @param newHandler event handler to call at event occurrences
     * @return a new instance of the appropriate sub-type
     */
    protected abstract T create(AdaptableInterval newMaxCheck, int newmaxIter,
                                BracketedUnivariateSolver<UnivariateFunction> newSolver,
                                ODEEventHandler newHandler);

    /** Check if the current propagation is forward or backward.
     * @return true if the current propagation is forward
     */
    public boolean isForward() {
        return forward;
    }

}