package seng302.Model;

import seng302.GPSCoordinate;

/**
 * A TrackPoint is a point plotted to display the track a
 * {@link seng302.Model.Boat Boat} has travelled in a race. <br>
 * TrackPoints are displayed on a
 * {@link seng302.Model.ResizableRaceCanvas ResizableRaceCanvas}, via the
 * {@link seng302.Controllers.RaceController RaceController}. <br>
 * Track points can be made visible or hidden via the RaceController's
 * {@link seng302.Model.Annotations Annotations}.
 */
public class TrackPoint {
    private final GPSCoordinate coordinate;
    private final long timeAdded;
    private final long expiry;
    private final double minAlpha;

    /**
     * Creates a new track point with fixed GPS coordinates and time, to reach minimum opacity on expiry.
     *
     * @param coordinate position of point on physical race map
     * @param timeAdded  system clock at time of addition
     * @param expiry     time to minimum opacity after added
     */
    public TrackPoint(GPSCoordinate coordinate, long timeAdded, long expiry) {
        this.coordinate = coordinate;
        this.timeAdded = timeAdded;
        this.expiry = expiry;
        this.minAlpha = 0.1;
    }

    /**
     * Gets the position of the point on physical race map.
     *
     * @return GPS coordinate of point
     */
    public GPSCoordinate getCoordinate() {
        return coordinate;
    }

    /**
     * Gets opacity of point scaled by age in proportion to expiry, between 1 and minimum opacity inclusive.
     *
     * @return greater of minimum opacity and scaled opacity
     */
    public double getAlpha() {
        return Double.max(minAlpha, 1.0 - (double) (System.currentTimeMillis() - timeAdded) / expiry);
    }

    /**
     * Gets time point was added to track.
     *
     * @return system clock at time of addition
     */
    public long getTimeAdded() {
        return timeAdded;
    }
}