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

import java.awt.Container;
import java.awt.Point;
import java.awt.geom.AffineTransform;
import java.awt.geom.Point2D;
import java.awt.geom.Point2D.Double;

import javax.swing.JComponent;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.Bounds;
import org.openstreetmap.josm.data.ProjectionBounds;
import org.openstreetmap.josm.data.coor.EastNorth;
import org.openstreetmap.josm.data.coor.LatLon;
import org.openstreetmap.josm.data.projection.Projection;
import org.openstreetmap.josm.gui.download.DownloadDialog;

/**
 * This class represents a state of the {@link MapView}.
 * @author Michael Zangl
 * @since 10343
 */
public final class MapViewState {

    private final Projection projection;

    private final int viewWidth;
    private final int viewHeight;

    private final double scale;

    /**
     * Top left {@link EastNorth} coordinate of the view.
     */
    private final EastNorth topLeft;

    private final Point topLeftOnScreen;
    private final Point topLeftInWindow;

    /**
     * Create a new {@link MapViewState}
     * @param projection The projection to use.
     * @param viewWidth The view width
     * @param viewHeight The view height
     * @param scale The scale to use
     * @param topLeft The top left corner in east/north space.
     */
    private MapViewState(Projection projection, int viewWidth, int viewHeight, double scale, EastNorth topLeft) {
        this.projection = projection;
        this.scale = scale;
        this.topLeft = topLeft;

        this.viewWidth = viewWidth;
        this.viewHeight = viewHeight;
        topLeftInWindow = new Point(0, 0);
        topLeftOnScreen = new Point(0, 0);
    }

    private MapViewState(EastNorth topLeft, MapViewState mapViewState) {
        this.projection = mapViewState.projection;
        this.scale = mapViewState.scale;
        this.topLeft = topLeft;

        viewWidth = mapViewState.viewWidth;
        viewHeight = mapViewState.viewHeight;
        topLeftInWindow = mapViewState.topLeftInWindow;
        topLeftOnScreen = mapViewState.topLeftOnScreen;
    }

    private MapViewState(double scale, MapViewState mapViewState) {
        this.projection = mapViewState.projection;
        this.scale = scale;
        this.topLeft = mapViewState.topLeft;

        viewWidth = mapViewState.viewWidth;
        viewHeight = mapViewState.viewHeight;
        topLeftInWindow = mapViewState.topLeftInWindow;
        topLeftOnScreen = mapViewState.topLeftOnScreen;
    }

    private MapViewState(JComponent position, MapViewState mapViewState) {
        this.projection = mapViewState.projection;
        this.scale = mapViewState.scale;
        this.topLeft = mapViewState.topLeft;

        viewWidth = position.getWidth();
        viewHeight = position.getHeight();
        topLeftInWindow = new Point();
        // better than using swing utils, since this allows us to use the mehtod if no screen is present.
        Container component = position;
        while (component != null) {
            topLeftInWindow.x += component.getX();
            topLeftInWindow.y += component.getY();
            component = component.getParent();
        }
        topLeftOnScreen = position.getLocationOnScreen();
    }

    /**
     * The scale in east/north units per pixel.
     * @return The scale.
     */
    public double getScale() {
        return scale;
    }

    /**
     * Gets the MapViewPoint representation for a position in view coordinates.
     * @param x The x coordinate inside the view.
     * @param y The y coordinate inside the view.
     * @return The MapViewPoint.
     */
    public MapViewPoint getForView(double x, double y) {
        return new MapViewViewPoint(x, y);
    }

    /**
     * Gets the {@link MapViewPoint} for the given {@link EastNorth} coordinate.
     * @param eastNorth the position.
     * @return The point for that position.
     */
    public MapViewPoint getPointFor(EastNorth eastNorth) {
        return new MapViewEastNorthPoint(eastNorth);
    }

    /**
     * Gets a rectangle representing the whole view area.
     * @return The rectangle.
     */
    public MapViewRectangle getViewArea() {
        return getForView(0, 0).rectTo(getForView(viewWidth, viewHeight));
    }

    /**
     * Gets the center of the view.
     * @return The center position.
     */
    public MapViewPoint getCenter() {
        return getForView(viewWidth / 2.0, viewHeight / 2.0);
    }

    /**
     * Gets the width of the view on the Screen;
     * @return The width of the view component in screen pixel.
     */
    public double getViewWidth() {
        return viewWidth;
    }

    /**
     * Gets the height of the view on the Screen;
     * @return The height of the view component in screen pixel.
     */
    public double getViewHeight() {
        return viewHeight;
    }

    /**
     * Gets the current projection used for the MapView.
     * @return The projection.
     */
    public Projection getProjection() {
        return projection;
    }

    /**
     * Creates an affine transform that is used to convert the east/north coordinates to view coordinates.
     * @return The affine transform. It should not be changed.
     * @since xxx
     */
    public AffineTransform getAffineTransform() {
        return new AffineTransform(1.0 / scale, 0.0, 0.0, -1.0 / scale, topLeft.east() / scale,
                topLeft.north() / scale);
    }

    /**
     * Creates a new state that is the same as the current state except for that it is using a new center.
     * @param newCenter The new center coordinate.
     * @return The new state.
     * @since xxx
     */
    public MapViewState usingCenter(EastNorth newCenter) {
        return movedTo(getCenter(), newCenter);
    }

    /**
     * @param mapViewPoint The reference point.
     * @param newEastNorthThere The east/north coordinate that should be there.
     * @return The new state.
     * @since xxx
     */
    public MapViewState movedTo(MapViewPoint mapViewPoint, EastNorth newEastNorthThere) {
        EastNorth delta = newEastNorthThere.subtract(mapViewPoint.getEastNorth());
        if (delta.distanceSq(0, 0) < .000001) {
            return this;
        } else {
            return new MapViewState(topLeft.add(delta), this);
        }
    }

    /**
     * Creates a new state that is the same as the current state except for that it is using a new scale.
     * @param newScale The new scale to use.
     * @return The new state.
     * @since xxx
     */
    public MapViewState usingScale(double newScale) {
        return new MapViewState(newScale, this);
    }

    /**
     * Creates a new state that is the same as the current state except for that it is using the location of the given component.
     * <p>
     * The view is moved so that the center is the same as the old center.
     * @param positon The new location to use.
     * @return The new state.
     * @since xxx
     */
    public MapViewState usingLocation(JComponent positon) {
        EastNorth center = this.getCenter().getEastNorth();
        return new MapViewState(positon, this).usingCenter(center);
    }

    /**
     * Create the default {@link MapViewState} object for the given map view. The screen position won't be set so that this method can be used
     * before the view was added to the hirarchy.
     * @param width The view width
     * @param height The view height
     * @return The state
     * @since xxx
     */
    public static MapViewState createDefaultState(int width, int height) {
        Projection projection = Main.getProjection();
        double scale = projection.getDefaultZoomInPPD();
        MapViewState state = new MapViewState(projection, width, height, scale, new EastNorth(0, 0));
        EastNorth center = calculateDefaultCenter();
        return state.movedTo(state.getCenter(), center);
    }

    private static EastNorth calculateDefaultCenter() {
        Bounds b = DownloadDialog.getSavedDownloadBounds();
        if (b == null) {
            b = Main.getProjection().getWorldBoundsLatLon();
        }
        return Main.getProjection().latlon2eastNorth(b.getCenter());
    }

    /**
     * A class representing a point in the map view. It allows to convert between the different coordinate systems.
     * @author Michael Zangl
     */
    public abstract class MapViewPoint {

        /**
         * Get this point in view coordinates.
         * @return The point in view coordinates.
         */
        public Point2D getInView() {
            return new Point2D.Double(getInViewX(), getInViewY());
        }

        protected abstract double getInViewX();

        protected abstract double getInViewY();

        /**
         * Convert this point to window coordinates.
         * @return The point in window coordinates.
         */
        public Point2D getInWindow() {
            return getUsingCorner(topLeftInWindow);
        }

        /**
         * Convert this point to screen coordinates.
         * @return The point in screen coordinates.
         */
        public Point2D getOnScreen() {
            return getUsingCorner(topLeftOnScreen);
        }

        private Double getUsingCorner(Point corner) {
            return new Point2D.Double(corner.getX() + getInViewX(), corner.getY() + getInViewY());
        }

        /**
         * Gets the {@link EastNorth} coordinate of this point.
         * @return The east/north coordinate.
         */
        public EastNorth getEastNorth() {
            return new EastNorth(topLeft.east() + getInViewX() * scale, topLeft.north() - getInViewY() * scale);
        }

        /**
         * Create a rectangle from this to the other point.
         * @param other The other point. Needs to be of the same {@link MapViewState}
         * @return A rectangle.
         */
        public MapViewRectangle rectTo(MapViewPoint other) {
            return new MapViewRectangle(this, other);
        }

        /**
         * Gets the current position in LatLon coordinates according to the current projection.
         * @return The positon as LatLon.
         */
        public LatLon getLatLon() {
            return projection.eastNorth2latlon(getEastNorth());
        }
    }

    private class MapViewViewPoint extends MapViewPoint {
        private final double x;
        private final double y;

        MapViewViewPoint(double x, double y) {
            this.x = x;
            this.y = y;
        }

        @Override
        protected double getInViewX() {
            return x;
        }

        @Override
        protected double getInViewY() {
            return y;
        }

        @Override
        public String toString() {
            return "MapViewViewPoint [x=" + x + ", y=" + y + "]";
        }
    }

    private class MapViewEastNorthPoint extends MapViewPoint {

        private final EastNorth eastNorth;

        MapViewEastNorthPoint(EastNorth eastNorth) {
            this.eastNorth = eastNorth;
        }

        @Override
        protected double getInViewX() {
            return (eastNorth.east() - topLeft.east()) / scale;
        }

        @Override
        protected double getInViewY() {
            return (topLeft.north() - eastNorth.north()) / scale;
        }

        @Override
        public EastNorth getEastNorth() {
            return eastNorth;
        }

        @Override
        public String toString() {
            return "MapViewEastNorthPoint [eastNorth=" + eastNorth + "]";
        }
    }

    /**
     * A rectangle on the MapView. It is rectangular in screen / EastNorth space.
     * @author Michael Zangl
     */
    public class MapViewRectangle {
        private final MapViewPoint p1;
        private final MapViewPoint p2;

        /**
         * Create a new MapViewRectangle
         * @param p1 The first point to use
         * @param p2 The second point to use.
         */
        MapViewRectangle(MapViewPoint p1, MapViewPoint p2) {
            this.p1 = p1;
            this.p2 = p2;
        }

        /**
         * Gets the projection bounds for this rectangle.
         * @return The projection bounds.
         */
        public ProjectionBounds getProjectionBounds() {
            ProjectionBounds b = new ProjectionBounds(p1.getEastNorth());
            b.extend(p2.getEastNorth());
            return b;
        }

        /**
         * Gets a rough estimate of the bounds by assuming lat/lon are parallel to x/y.
         * @return The bounds computed by converting the corners of this rectangle.
         */
        public Bounds getCornerBounds() {
            Bounds b = new Bounds(p1.getLatLon());
            b.extend(p2.getLatLon());
            return b;
        }
    }

}