// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.data.gpx;

import java.awt.geom.Area;
import java.io.File;
import java.util.Collection;
import java.util.Date;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.Bounds;
import org.openstreetmap.josm.data.Data;
import org.openstreetmap.josm.data.DataSource;
import org.openstreetmap.josm.data.coor.EastNorth;
import org.openstreetmap.josm.tools.Utils;

/**
 * Objects of this class represent a gpx file with tracks, waypoints and routes.
 * It uses GPX v1.1, see <a href="http://www.topografix.com/GPX/1/1/">the spec</a>
 * for details.
 *
 * @author Raphael Mack &lt;ramack@raphael-mack.de&gt;
 */
public class GpxData extends WithAttributes implements Data {

    public File storageFile;
    public boolean fromServer;

    /** Creator (usually software) */
    public String creator;

    /** Tracks */
    public final Collection<GpxTrack> tracks = new LinkedList<>();
    /** Routes */
    public final Collection<GpxRoute> routes = new LinkedList<>();
    /** Waypoints */
    public final Collection<WayPoint> waypoints = new LinkedList<>();

    /**
     * All data sources (bounds of downloaded bounds) of this GpxData.<br>
     * Not part of GPX standard but rather a JOSM extension, needed by the fact that
     * OSM API does not provide {@code <bounds>} element in its GPX reply.
     * @since 7575
     */
    public final Set<DataSource> dataSources = new HashSet<>();

    /**
     * Merges data from another object.
     * @param other existing GPX data
     */
    public void mergeFrom(GpxData other) {
        if (storageFile == null && other.storageFile != null) {
            storageFile = other.storageFile;
        }
        fromServer = fromServer && other.fromServer;

        for (Map.Entry<String, Object> ent : other.attr.entrySet()) {
            // TODO: Detect conflicts.
            String k = ent.getKey();
            if (META_LINKS.equals(k) && attr.containsKey(META_LINKS)) {
                Collection<GpxLink> my = super.<GpxLink>getCollection(META_LINKS);
                @SuppressWarnings("unchecked")
                Collection<GpxLink> their = (Collection<GpxLink>) ent.getValue();
                my.addAll(their);
            } else {
                put(k, ent.getValue());
            }
        }
        tracks.addAll(other.tracks);
        routes.addAll(other.routes);
        waypoints.addAll(other.waypoints);
        dataSources.addAll(other.dataSources);
    }

    /**
     * Determines if this GPX data has one or more track points
     * @return {@code true} if this GPX data has track points, {@code false} otherwise
     */
    public boolean hasTrackPoints() {
        for (GpxTrack trk : tracks) {
            for (GpxTrackSegment trkseg : trk.getSegments()) {
                if (!trkseg.getWayPoints().isEmpty())
                    return true;
            }
        }
        return false;
    }

    /**
     * Determines if this GPX data has one or more route points
     * @return {@code true} if this GPX data has route points, {@code false} otherwise
     */
    public boolean hasRoutePoints() {
        for (GpxRoute rte : routes) {
            if (!rte.routePoints.isEmpty())
                return true;
        }
        return false;
    }

    /**
     * Determines if this GPX data is empty (i.e. does not contain any point)
     * @return {@code true} if this GPX data is empty, {@code false} otherwise
     */
    public boolean isEmpty() {
        return !hasRoutePoints() && !hasTrackPoints() && waypoints.isEmpty();
    }

    /**
     * Returns the bounds defining the extend of this data, as read in metadata, if any.
     * If no bounds is defined in metadata, {@code null} is returned. There is no guarantee
     * that data entirely fit in this bounds, as it is not recalculated. To get recalculated bounds,
     * see {@link #recalculateBounds()}. To get downloaded areas, see {@link #dataSources}.
     * @return the bounds defining the extend of this data, or {@code null}.
     * @see #recalculateBounds()
     * @see #dataSources
     * @since 7575
     */
    public Bounds getMetaBounds() {
        Object value = get(META_BOUNDS);
        if (value instanceof Bounds) {
            return (Bounds) value;
        }
        return null;
    }

    /**
     * Calculates the bounding box of available data and returns it.
     * The bounds are not stored internally, but recalculated every time
     * this function is called.<br>
     * To get bounds as read from metadata, see {@link #getMetaBounds()}.<br>
     * To get downloaded areas, see {@link #dataSources}.<br>
     *
     * FIXME might perhaps use visitor pattern?
     * @return the bounds
     * @see #getMetaBounds()
     * @see #dataSources
     */
    public Bounds recalculateBounds() {
        Bounds bounds = null;
        for (WayPoint wpt : waypoints) {
            if (bounds == null) {
                bounds = new Bounds(wpt.getCoor());
            } else {
                bounds.extend(wpt.getCoor());
            }
        }
        for (GpxRoute rte : routes) {
            for (WayPoint wpt : rte.routePoints) {
                if (bounds == null) {
                    bounds = new Bounds(wpt.getCoor());
                } else {
                    bounds.extend(wpt.getCoor());
                }
            }
        }
        for (GpxTrack trk : tracks) {
            Bounds trkBounds = trk.getBounds();
            if (trkBounds != null) {
                if (bounds == null) {
                    bounds = new Bounds(trkBounds);
                } else {
                    bounds.extend(trkBounds);
                }
            }
        }
        return bounds;
    }

    /**
     * calculates the sum of the lengths of all track segments
     * @return the length in meters
     */
    public double length() {
        double result = 0.0; // in meters

        for (GpxTrack trk : tracks) {
            result += trk.length();
        }

        return result;
    }

    /**
     * returns minimum and maximum timestamps in the track
     * @param trk track to analyze
     * @return  minimum and maximum dates in array of 2 elements
     */
    public static Date[] getMinMaxTimeForTrack(GpxTrack trk) {
        WayPoint earliest = null, latest = null;

        for (GpxTrackSegment seg : trk.getSegments()) {
            for (WayPoint pnt : seg.getWayPoints()) {
                if (latest == null) {
                    latest = earliest = pnt;
                } else {
                    if (pnt.compareTo(earliest) < 0) {
                        earliest = pnt;
                    } else {
                        latest = pnt;
                    }
                }
            }
        }
        if (earliest == null || latest == null) return null;
        return new Date[]{earliest.getTime(), latest.getTime()};
    }

    /**
    * Returns minimum and maximum timestamps for all tracks
    * Warning: there are lot of track with broken timestamps,
    * so we just ingore points from future and from year before 1970 in this method
    * works correctly @since 5815
     * @return minimum and maximum dates in array of 2 elements
    */
    public Date[] getMinMaxTimeForAllTracks() {
        double min = 1e100;
        double max = -1e100;
        double now = System.currentTimeMillis()/1000.0;
        for (GpxTrack trk: tracks) {
            for (GpxTrackSegment seg : trk.getSegments()) {
                for (WayPoint pnt : seg.getWayPoints()) {
                    double t = pnt.time;
                    if (t > 0 && t <= now) {
                        if (t > max) max = t;
                        if (t < min) min = t;
                    }
                }
            }
        }
        if (Utils.equalsEpsilon(min, 1e100) || Utils.equalsEpsilon(max, -1e100)) return new Date[0];
        return new Date[]{new Date((long) (min * 1000)), new Date((long) (max * 1000))};
    }

    /**
     * Makes a WayPoint at the projection of point p onto the track providing p is less than
     * tolerance away from the track
     *
     * @param p : the point to determine the projection for
     * @param tolerance : must be no further than this from the track
     * @return the closest point on the track to p, which may be the first or last point if off the
     * end of a segment, or may be null if nothing close enough
     */
    public WayPoint nearestPointOnTrack(EastNorth p, double tolerance) {
        /*
         * assume the coordinates of P are xp,yp, and those of a section of track between two
         * trackpoints are R=xr,yr and S=xs,ys. Let N be the projected point.
         *
         * The equation of RS is Ax + By + C = 0 where A = ys - yr B = xr - xs C = - Axr - Byr
         *
         * Also, note that the distance RS^2 is A^2 + B^2
         *
         * If RS^2 == 0.0 ignore the degenerate section of track
         *
         * PN^2 = (Axp + Byp + C)^2 / RS^2 that is the distance from P to the line
         *
         * so if PN^2 is less than PNmin^2 (initialized to tolerance) we can reject the line
         * otherwise... determine if the projected poijnt lies within the bounds of the line: PR^2 -
         * PN^2 <= RS^2 and PS^2 - PN^2 <= RS^2
         *
         * where PR^2 = (xp - xr)^2 + (yp-yr)^2 and PS^2 = (xp - xs)^2 + (yp-ys)^2
         *
         * If so, calculate N as xn = xr + (RN/RS) B yn = y1 + (RN/RS) A
         *
         * where RN = sqrt(PR^2 - PN^2)
         */

        double pnminsq = tolerance * tolerance;
        EastNorth bestEN = null;
        double bestTime = 0.0;
        double px = p.east();
        double py = p.north();
        double rx = 0.0, ry = 0.0, sx, sy, x, y;
        if (tracks == null)
            return null;
        for (GpxTrack track : tracks) {
            for (GpxTrackSegment seg : track.getSegments()) {
                WayPoint r = null;
                for (WayPoint S : seg.getWayPoints()) {
                    EastNorth en = S.getEastNorth();
                    if (r == null) {
                        r = S;
                        rx = en.east();
                        ry = en.north();
                        x = px - rx;
                        y = py - ry;
                        double pRsq = x * x + y * y;
                        if (pRsq < pnminsq) {
                            pnminsq = pRsq;
                            bestEN = en;
                            bestTime = r.time;
                        }
                    } else {
                        sx = en.east();
                        sy = en.north();
                        double a = sy - ry;
                        double b = rx - sx;
                        double c = -a * rx - b * ry;
                        double rssq = a * a + b * b;
                        if (rssq == 0) {
                            continue;
                        }
                        double pnsq = a * px + b * py + c;
                        pnsq = pnsq * pnsq / rssq;
                        if (pnsq < pnminsq) {
                            x = px - rx;
                            y = py - ry;
                            double prsq = x * x + y * y;
                            x = px - sx;
                            y = py - sy;
                            double pssq = x * x + y * y;
                            if (prsq - pnsq <= rssq && pssq - pnsq <= rssq) {
                                double rnoverRS = Math.sqrt((prsq - pnsq) / rssq);
                                double nx = rx - rnoverRS * b;
                                double ny = ry + rnoverRS * a;
                                bestEN = new EastNorth(nx, ny);
                                bestTime = r.time + rnoverRS * (S.time - r.time);
                                pnminsq = pnsq;
                            }
                        }
                        r = S;
                        rx = sx;
                        ry = sy;
                    }
                }
                if (r != null) {
                    EastNorth c = r.getEastNorth();
                    /* if there is only one point in the seg, it will do this twice, but no matter */
                    rx = c.east();
                    ry = c.north();
                    x = px - rx;
                    y = py - ry;
                    double prsq = x * x + y * y;
                    if (prsq < pnminsq) {
                        pnminsq = prsq;
                        bestEN = c;
                        bestTime = r.time;
                    }
                }
            }
        }
        if (bestEN == null)
            return null;
        WayPoint best = new WayPoint(Main.getProjection().eastNorth2latlon(bestEN));
        best.time = bestTime;
        return best;
    }

    /**
     * Iterate over all track segments and over all routes.
     *
     * @param trackVisibility An array indicating which tracks should be
     * included in the iteration. Can be null, then all tracks are included.
     * @return an Iterable object, which iterates over all track segments and
     * over all routes
     */
    public Iterable<Collection<WayPoint>> getLinesIterable(final boolean[] trackVisibility) {
        return new Iterable<Collection<WayPoint>>() {
            @Override
            public Iterator<Collection<WayPoint>> iterator() {
                return new LinesIterator(GpxData.this, trackVisibility);
            }
        };
    }

    /**
     * Resets the internal caches of east/north coordinates.
     */
    public void resetEastNorthCache() {
        if (waypoints != null) {
            for (WayPoint wp : waypoints) {
                wp.invalidateEastNorthCache();
            }
        }
        if (tracks != null) {
            for (GpxTrack track: tracks) {
                for (GpxTrackSegment segment: track.getSegments()) {
                    for (WayPoint wp: segment.getWayPoints()) {
                        wp.invalidateEastNorthCache();
                    }
                }
            }
        }
        if (routes != null) {
            for (GpxRoute route: routes) {
                if (route.routePoints == null) {
                    continue;
                }
                for (WayPoint wp: route.routePoints) {
                    wp.invalidateEastNorthCache();
                }
            }
        }
    }

    /**
     * Iterates over all track segments and then over all routes.
     */
    public static class LinesIterator implements Iterator<Collection<WayPoint>> {

        private Iterator<GpxTrack> itTracks;
        private int idxTracks;
        private Iterator<GpxTrackSegment> itTrackSegments;
        private final Iterator<GpxRoute> itRoutes;

        private Collection<WayPoint> next;
        private final boolean[] trackVisibility;

        /**
         * Constructs a new {@code LinesIterator}.
         * @param data GPX data
         * @param trackVisibility An array indicating which tracks should be
         * included in the iteration. Can be null, then all tracks are included.
         */
        public LinesIterator(GpxData data, boolean[] trackVisibility) {
            itTracks = data.tracks.iterator();
            idxTracks = -1;
            itRoutes = data.routes.iterator();
            this.trackVisibility = trackVisibility;
            next = getNext();
        }

        @Override
        public boolean hasNext() {
            return next != null;
        }

        @Override
        public Collection<WayPoint> next() {
            if (!hasNext()) {
                throw new NoSuchElementException();
            }
            Collection<WayPoint> current = next;
            next = getNext();
            return current;
        }

        private Collection<WayPoint> getNext() {
            if (itTracks != null) {
                if (itTrackSegments != null && itTrackSegments.hasNext()) {
                    return itTrackSegments.next().getWayPoints();
                } else {
                    while (itTracks.hasNext()) {
                        GpxTrack nxtTrack = itTracks.next();
                        idxTracks++;
                        if (trackVisibility != null && !trackVisibility[idxTracks])
                            continue;
                        itTrackSegments = nxtTrack.getSegments().iterator();
                        if (itTrackSegments.hasNext()) {
                            return itTrackSegments.next().getWayPoints();
                        }
                    }
                    // if we get here, all the Tracks are finished; Continue with Routes
                    itTracks = null;
                }
            }
            if (itRoutes.hasNext()) {
                return itRoutes.next().routePoints;
            }
            return null;
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    @Override
    public Collection<DataSource> getDataSources() {
        return dataSources;
    }

    @Override
    public Area getDataSourceArea() {
        return DataSource.getDataSourceArea(dataSources);
    }

    @Override
    public List<Bounds> getDataSourceBounds() {
        return DataSource.getDataSourceBounds(dataSources);
    }
}