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

import static org.openstreetmap.josm.tools.I18n.tr;

import java.awt.HeadlessException;
import java.awt.Toolkit;
import java.util.HashMap;
import java.util.Map;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.Bounds;
import org.openstreetmap.josm.data.coor.LatLon;

public final class OsmUrlToBounds {
    private static final String SHORTLINK_PREFIX = "http://osm.org/go/";

    private OsmUrlToBounds() {
        // Hide default constructor for utils classes
    }

    public static Bounds parse(String url) {
        try {
            // a percent sign indicates an encoded URL (RFC 1738).
            if (url.contains("%")) {
                url = Utils.decodeUrl(url);
            }
        } catch (IllegalArgumentException x) {
            Main.error(x);
        }
        Bounds b = parseShortLink(url);
        if (b != null)
            return b;
        int i = url.indexOf("#map");
        if (i >= 0) {
            // probably it's a URL following the new scheme?
            return parseHashURLs(url);
        }
        i = url.indexOf('?');
        if (i == -1) {
            return null;
        }
        String[] args = url.substring(i+1).split("&");
        Map<String, String> map = new HashMap<>();
        for (String arg : args) {
            int eq = arg.indexOf('=');
            if (eq != -1) {
                map.put(arg.substring(0, eq), arg.substring(eq + 1));
            }
        }

        try {
            if (map.containsKey("bbox")) {
                String[] bbox = map.get("bbox").split(",");
                b = new Bounds(
                        Double.parseDouble(bbox[1]), Double.parseDouble(bbox[0]),
                        Double.parseDouble(bbox[3]), Double.parseDouble(bbox[2]));
            } else if (map.containsKey("minlat")) {
                double minlat = Double.parseDouble(map.get("minlat"));
                double minlon = Double.parseDouble(map.get("minlon"));
                double maxlat = Double.parseDouble(map.get("maxlat"));
                double maxlon = Double.parseDouble(map.get("maxlon"));
                b = new Bounds(minlat, minlon, maxlat, maxlon);
            } else {
                String z = map.get("zoom");
                b = positionToBounds(parseDouble(map, "lat"),
                        parseDouble(map, "lon"),
                        z == null ? 18 : Integer.parseInt(z));
            }
        } catch (NumberFormatException | NullPointerException | ArrayIndexOutOfBoundsException x) {
            Main.error(x);
        }
        return b;
    }

    /**
     * Openstreetmap.org changed it's URL scheme in August 2013, which breaks the URL parsing.
     * The following function, called by the old parse function if necessary, provides parsing new URLs
     * the new URLs follow the scheme https://www.openstreetmap.org/#map=18/51.71873/8.76164&amp;layers=CN
     * @param url string for parsing
     * @return Bounds if hashurl, {@code null} otherwise
     */
    private static Bounds parseHashURLs(String url) {
        int startIndex = url.indexOf("#map=");
        if (startIndex == -1) return null;
        int endIndex = url.indexOf('&', startIndex);
        if (endIndex == -1) endIndex = url.length();
        String coordPart = url.substring(startIndex+5, endIndex);
        String[] parts = coordPart.split("/");
        if (parts.length < 3) {
            Main.warn(tr("URL does not contain {0}/{1}/{2}", tr("zoom"), tr("latitude"), tr("longitude")));
            return null;
        }
        int zoom;
        double lat, lon;
        try {
            zoom = Integer.parseInt(parts[0]);
        } catch (NumberFormatException e) {
            Main.warn(tr("URL does not contain valid {0}", tr("zoom")), e);
            return null;
        }
        try {
            lat = Double.parseDouble(parts[1]);
        } catch (NumberFormatException e) {
            Main.warn(tr("URL does not contain valid {0}", tr("latitude")), e);
            return null;
        }
        try {
            lon = Double.parseDouble(parts[2]);
        } catch (NumberFormatException e) {
            Main.warn(tr("URL does not contain valid {0}", tr("longitude")), e);
            return null;
        }
        return positionToBounds(lat, lon, zoom);
    }

    private static double parseDouble(Map<String, String> map, String key) {
        if (map.containsKey(key))
            return Double.parseDouble(map.get(key));
        return Double.parseDouble(map.get("m"+key));
    }

    private static final char[] SHORTLINK_CHARS = {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
        'w', 'x', 'y', 'z', '0', '1', '2', '3',
        '4', '5', '6', '7', '8', '9', '_', '@'
    };

    /**
     * Parse OSM short link
     *
     * @param url string for parsing
     * @return Bounds if shortlink, null otherwise
     * @see <a href="http://trac.openstreetmap.org/browser/sites/rails_port/lib/short_link.rb">short_link.rb</a>
     */
    private static Bounds parseShortLink(final String url) {
        if (!url.startsWith(SHORTLINK_PREFIX))
            return null;
        final String shortLink = url.substring(SHORTLINK_PREFIX.length());

        final Map<Character, Integer> array = new HashMap<>();

        for (int i = 0; i < SHORTLINK_CHARS.length; ++i) {
            array.put(SHORTLINK_CHARS[i], i);
        }

        // long is necessary (need 32 bit positive value is needed)
        long x = 0;
        long y = 0;
        int zoom = 0;
        int zoomOffset = 0;

        for (final char ch : shortLink.toCharArray()) {
            if (array.containsKey(ch)) {
                int val = array.get(ch);
                for (int i = 0; i < 3; ++i) {
                    x <<= 1;
                    if ((val & 32) != 0) {
                        x |= 1;
                    }
                    val <<= 1;

                    y <<= 1;
                    if ((val & 32) != 0) {
                        y |= 1;
                    }
                    val <<= 1;
                }
                zoom += 3;
            } else {
                zoomOffset--;
            }
        }

        x <<= 32 - zoom;
        y <<= 32 - zoom;

        // 2**32 == 4294967296
        return positionToBounds(y * 180.0 / 4294967296.0 - 90.0,
                x * 360.0 / 4294967296.0 - 180.0,
                // TODO: -2 was not in ruby code
                zoom - 8 - (zoomOffset % 3) - 2);
    }

    /** radius of the earth */
    public static final double R = 6378137.0;

    public static Bounds positionToBounds(final double lat, final double lon, final int zoom) {
        int tileSizeInPixels = 256;
        int height;
        int width;
        try {
            height = Toolkit.getDefaultToolkit().getScreenSize().height;
            width = Toolkit.getDefaultToolkit().getScreenSize().width;
            if (Main.isDisplayingMapView()) {
                height = Main.map.mapView.getHeight();
                width = Main.map.mapView.getWidth();
            }
        } catch (HeadlessException he) {
            // in headless mode, when running tests
            height = 480;
            width = 640;
        }
        double scale = (1 << zoom) * tileSizeInPixels / (2 * Math.PI * R);
        double deltaX = width / 2.0 / scale;
        double deltaY = height / 2.0 / scale;
        double x = Math.toRadians(lon) * R;
        double y = mercatorY(lat);
        return new Bounds(invMercatorY(y - deltaY), Math.toDegrees(x - deltaX) / R, invMercatorY(y + deltaY), Math.toDegrees(x + deltaX) / R);
    }

    public static double mercatorY(double lat) {
        return Math.log(Math.tan(Math.PI/4 + Math.toRadians(lat)/2)) * R;
    }

    public static double invMercatorY(double north) {
        return Math.toDegrees(Math.atan(Math.sinh(north / R)));
    }

    public static Pair<Double, Double> getTileOfLatLon(double lat, double lon, double zoom) {
        double x = Math.floor((lon + 180) / 360 * Math.pow(2.0, zoom));
        double y = Math.floor((1 - Math.log(Math.tan(Math.toRadians(lat)) + 1 / Math.cos(Math.toRadians(lat))) / Math.PI)
                / 2 * Math.pow(2.0, zoom));
        return new Pair<>(x, y);
    }

    public static LatLon getLatLonOfTile(double x, double y, double zoom) {
        double lon = x / Math.pow(2.0, zoom) * 360.0 - 180;
        double lat = Math.toDegrees(Math.atan(Math.sinh(Math.PI - (2.0 * Math.PI * y) / Math.pow(2.0, zoom))));
        return new LatLon(lat, lon);
    }

    /**
     * Return OSM Zoom level for a given area
     *
     * @param b bounds of the area
     * @return matching zoom level for area
     */
    public static int getZoom(Bounds b) {
        // convert to mercator (for calculation of zoom only)
        double latMin = Math.log(Math.tan(Math.PI/4.0+b.getMinLat()/180.0*Math.PI/2.0))*180.0/Math.PI;
        double latMax = Math.log(Math.tan(Math.PI/4.0+b.getMaxLat()/180.0*Math.PI/2.0))*180.0/Math.PI;
        double size = Math.max(Math.abs(latMax-latMin), Math.abs(b.getMaxLon()-b.getMinLon()));
        int zoom = 0;
        while (zoom <= 20) {
            if (size >= 180) {
                break;
            }
            size *= 2;
            zoom++;
        }
        return zoom;
    }

    /**
     * Return OSM URL for given area.
     *
     * @param b bounds of the area
     * @return link to display that area in OSM map
     */
    public static String getURL(Bounds b) {
        return getURL(b.getCenter(), getZoom(b));
    }

    /**
     * Return OSM URL for given position and zoom.
     *
     * @param pos center position of area
     * @param zoom zoom depth of display
     * @return link to display that area in OSM map
     */
    public static String getURL(LatLon pos, int zoom) {
        return getURL(pos.lat(), pos.lon(), zoom);
    }

    /**
     * Return OSM URL for given lat/lon and zoom.
     *
     * @param dlat center latitude of area
     * @param dlon center longitude of area
     * @param zoom zoom depth of display
     * @return link to display that area in OSM map
     *
     * @since 6453
     */
    public static String getURL(double dlat, double dlon, int zoom) {
        // Truncate lat and lon to something more sensible
        int decimals = (int) Math.pow(10, zoom / 3d);
        double lat = Math.round(dlat * decimals);
        lat /= decimals;
        double lon = Math.round(dlon * decimals);
        lon /= decimals;
        return Main.getOSMWebsite() + "/#map="+zoom+"/"+lat+"/"+lon;
    }
}
