TabulatedLofOffset

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 * this work for additional information regarding copyright ownership.
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 * (the "License"); you may not use this file except in compliance with
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package org.orekit.attitudes;

import java.util.List;
import java.util.stream.Collectors;

import org.hipparchus.CalculusFieldElement;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.frames.FieldTransform;
import org.orekit.frames.Frame;
import org.orekit.frames.LOF;
import org.orekit.frames.Transform;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.time.FieldTimeInterpolator;
import org.orekit.time.TimeInterpolator;
import org.orekit.utils.AngularDerivativesFilter;
import org.orekit.utils.FieldPVCoordinates;
import org.orekit.utils.FieldPVCoordinatesProvider;
import org.orekit.utils.ImmutableTimeStampedCache;
import org.orekit.utils.PVCoordinates;
import org.orekit.utils.PVCoordinatesProvider;
import org.orekit.utils.TimeStampedAngularCoordinates;
import org.orekit.utils.TimeStampedAngularCoordinatesHermiteInterpolator;
import org.orekit.utils.TimeStampedFieldAngularCoordinates;
import org.orekit.utils.TimeStampedFieldAngularCoordinatesHermiteInterpolator;

/**
 * This class handles an attitude provider interpolating from a predefined table
 * containing offsets from a Local Orbital Frame.
 * <p>Instances of this class are guaranteed to be immutable.</p>
 * @see LofOffset
 * @see TabulatedProvider
 * @author Luc Maisonobe
 * @since 7.1
 */
public class TabulatedLofOffset implements BoundedAttitudeProvider {

    /** Inertial frame with respect to which orbit should be computed. */
    private final Frame inertialFrame;

    /** Local Orbital Frame. */
    private final LOF type;

    /** Cached attitude table. */
    private final transient ImmutableTimeStampedCache<? extends TimeStampedAngularCoordinates> table;

    /** Filter for derivatives from the sample to use in interpolation. */
    private final AngularDerivativesFilter filter;

    /** First date of the range. */
    private final AbsoluteDate minDate;

    /** Last date of the range. */
    private final AbsoluteDate maxDate;

    /** Creates new instance.
     * <p>
     * This constructor uses the first and last point samples as the min and max dates.
     * </p>
     * @param inertialFrame inertial frame with respect to which orbit should be computed
     * @param lof local orbital frame
     * @param table tabulated attitudes
     * @param n number of attitude to use for interpolation
     * @param filter filter for derivatives from the sample to use in interpolation
     */
    public TabulatedLofOffset(final Frame inertialFrame, final LOF lof,
                              final List<? extends TimeStampedAngularCoordinates> table,
                              final int n, final AngularDerivativesFilter filter) {
        this(inertialFrame, lof, table, n, filter, table.get(0).getDate(), table.get(table.size() - 1).getDate());
    }

    /** Creates new instance.
     * @param inertialFrame inertial frame with respect to which orbit should be computed
     * @param lof local orbital frame
     * @param table tabulated attitudes
     * @param n number of attitude to use for interpolation
     * @param minDate min date to use
     * @param maxDate max date to use
     * @param filter filter for derivatives from the sample to use in interpolation
     * @since 11.0
     */
    public TabulatedLofOffset(final Frame inertialFrame, final LOF lof,
                              final List<? extends TimeStampedAngularCoordinates> table,
                              final int n, final AngularDerivativesFilter filter,
                              final AbsoluteDate minDate, final AbsoluteDate maxDate) {
        if (!inertialFrame.isPseudoInertial()) {
            throw new OrekitException(OrekitMessages.NON_PSEUDO_INERTIAL_FRAME,
                                      inertialFrame.getName());
        }
        this.inertialFrame = inertialFrame;
        this.type          = lof;
        this.table         = new ImmutableTimeStampedCache<TimeStampedAngularCoordinates>(n, table);
        this.filter        = filter;
        this.minDate       = minDate;
        this.maxDate       = maxDate;
    }

    /** Get an unmodifiable view of the tabulated attitudes.
     * @return unmodifiable view of the tabulated attitudes
     */
    public List<? extends TimeStampedAngularCoordinates> getTable() {
        return table.getAll();
    }

    /** {@inheritDoc} */
    public Attitude getAttitude(final PVCoordinatesProvider pvProv,
                                final AbsoluteDate date, final Frame frame) {

        // get attitudes sample on which interpolation will be performed
        final List<TimeStampedAngularCoordinates> sample = table.getNeighbors(date).collect(Collectors.toList());

        // create interpolator
        final TimeInterpolator<TimeStampedAngularCoordinates> interpolator =
                new TimeStampedAngularCoordinatesHermiteInterpolator(sample.size(), filter);

        // interpolate
        final TimeStampedAngularCoordinates interpolated = interpolator.interpolate(date, sample);

        // construction of the local orbital frame, using PV from inertial frame
        final PVCoordinates pv = pvProv.getPVCoordinates(date, inertialFrame);
        final Transform inertialToLof = type.transformFromInertial(date, pv);

        // take into account the specified start frame (which may not be an inertial one)
        final Transform frameToInertial = frame.getTransformTo(inertialFrame, date);
        final Transform frameToLof      = new Transform(date, frameToInertial, inertialToLof);

        // compose with interpolated rotation
        return new Attitude(date, frame,
                            interpolated.addOffset(frameToLof.getAngular()));
    }

    /** {@inheritDoc} */
    public <T extends CalculusFieldElement<T>> FieldAttitude<T> getAttitude(final FieldPVCoordinatesProvider<T> pvProv,
                                                                        final FieldAbsoluteDate<T> date,
                                                                        final Frame frame) {

        // get attitudes sample on which interpolation will be performed
        final List<TimeStampedFieldAngularCoordinates<T>> sample =
                        table.
                        getNeighbors(date.toAbsoluteDate()).
                        map(ac -> new TimeStampedFieldAngularCoordinates<>(date.getField(), ac)).
                        collect(Collectors.toList());

        // create interpolator
        final FieldTimeInterpolator<TimeStampedFieldAngularCoordinates<T>, T> interpolator =
                new TimeStampedFieldAngularCoordinatesHermiteInterpolator<>(sample.size(), filter);

        // interpolate
        final TimeStampedFieldAngularCoordinates<T> interpolated = interpolator.interpolate(date, sample);

        // construction of the local orbital frame, using PV from inertial frame
        final FieldPVCoordinates<T> pv = pvProv.getPVCoordinates(date, inertialFrame);
        final FieldTransform<T> inertialToLof = type.transformFromInertial(date, pv);

        // take into account the specified start frame (which may not be an inertial one)
        final FieldTransform<T> frameToInertial = frame.getTransformTo(inertialFrame, date);
        final FieldTransform<T> frameToLof      = new FieldTransform<>(date, frameToInertial, inertialToLof);

        // compose with interpolated rotation
        return new FieldAttitude<>(date, frame,
                                   interpolated.addOffset(frameToLof.getAngular()));
    }

    /** {@inheritDoc} */
    public AbsoluteDate getMinDate() {
        return minDate;
    }

    /** {@inheritDoc} */
    public AbsoluteDate getMaxDate() {
        return maxDate;
    }

}