package org.djutils.draw.line;

import org.djutils.draw.Directed;
import org.djutils.draw.DrawRuntimeException;
import org.djutils.draw.Space;
import org.djutils.draw.point.Point;
import org.djutils.exceptions.Throw;

/**
 * A Ray is a half-line; it has one end point with non-infinite coordinates; the other end point is infinitely far away.
 * <p>
 * Copyright (c) 2020-2021 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
 * BSD-style license. See <a href="https://djutils.org/docs/current/djutils/licenses.html">DJUTILS License</a>.
 * </p>
 * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
 * @author <a href="https://www.tudelft.nl/pknoppers">Peter Knoppers</a>
 * @param <R> The Ray type (2d or 3d)
 * @param <P> The Point type (2d, or 3d)
 * @param <S> The Space type
 */
public interface Ray<R extends Ray<R, P, S>, P extends Point<P, S>, S extends Space> extends Directed<R>, Project<P, S>
{
    /**
     * Get the finite end point of this Ray.
     * @return P; the finite end point of this Ray
     */
    P getEndPoint();

    /**
     * Retrieve the angle from the positive X axis direction in radians.
     * @return double; the angle from the positive X axis direction in radians
     */
    double getPhi();

    /**
     * Flip the direction of the Ray (creates and returns a new Ray instance).
     * @return R; Ray at the same location, but with phi incremented by &pi; and theta (in case of a Ray3d) subtracted from &pi;
     */
    R flip();

    /**
     * Get the location at a position on the line, with its direction. Position must be a positive, finite value
     * @param position double; the position on the line for which to calculate the point on the line
     * @return R; a ray with the same direction as this ray (even if the direction of this ray is not normalized)
     * @throws DrawRuntimeException when position less than 0.0, infinite, or NaN.
     */
    default R getLocation(double position) throws DrawRuntimeException
    {
        Throw.when(Double.isNaN(position) || position < 0, DrawRuntimeException.class, "position must be finite and positive");
        return getLocationExtended(position);
    }

    /**
     * Get the location at a position on the line, with its direction. Position must be a positive, finite value
     * @param position double; the position on the line for which to calculate the point on the line
     * @return R; a ray with the same direction as this ray
     * @throws DrawRuntimeException when position infinite, or NaN.
     */
    R getLocationExtended(double position) throws DrawRuntimeException;

    /**
     * Project a Point on a Segment. If the the projected points lies outside the ray, the start point of the ray is returned.
     * Otherwise the closest point on the ray is returned. <br>
     * Adapted from <a href="http://paulbourke.net/geometry/pointlineplane/DistancePoint.java">example code provided by Paul
     * Bourke</a>.
     * @param point P; the point to project onto the segment
     * @return P; either the start point, or the end point of the segment or a Point2d that lies somewhere in between those two.
     * @throws NullPointerException when point is null
     */
    P closestPointOnRay(P point) throws NullPointerException;

}