package org.djutils.draw.point;

import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import org.djutils.draw.DrawRuntimeException;
import org.djutils.draw.Drawable2d;
import org.djutils.draw.Space2d;
import org.djutils.draw.bounds.Bounds2d;
import org.djutils.draw.line.Ray2d;
import org.djutils.exceptions.Throw;

/**
 * A Point2d is an immutable Point with an x and y coordinate, stored with double precision. It differs from many Point
 * implementations by being immutable.
 * <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>
 */
public class Point2d implements Drawable2d, Point<Point2d, Space2d>
{
    /** */
    private static final long serialVersionUID = 20201201L;

    /** The x-coordinate. */
    @SuppressWarnings("checkstyle:visibilitymodifier")
    public final double x;

    /** The y-coordinate. */
    @SuppressWarnings("checkstyle:visibilitymodifier")
    public final double y;

    /**
     * Create a new Point with just an x and y coordinate, stored with double precision.
     * @param x double; the x coordinate
     * @param y double; the y coordinate
     * @throws IllegalArgumentException when x or y is NaN
     */
    public Point2d(final double x, final double y) throws IllegalArgumentException
    {
        Throw.when(Double.isNaN(x) || Double.isNaN(y), IllegalArgumentException.class, "Coordinate must be a number (not NaN)");
        this.x = x;
        this.y = y;
    }

    /**
     * Create a new Point with just an x and y coordinate, stored with double precision.
     * @param xy double[]; the x and y coordinate
     * @throws NullPointerException when xy is null
     * @throws IllegalArgumentException when the dimension of xy is not 2, or a coordinate is NaN
     */
    public Point2d(final double[] xy) throws NullPointerException, IllegalArgumentException
    {
        this(checkLengthIsTwo(Throw.whenNull(xy, "xy-point cannot be null"))[0], xy[1]);
    }

    /**
     * Create an immutable point with just two values, x and y, stored with double precision from an AWT Point2D.
     * @param point Point2D; an AWT Point2D
     * @throws NullPointerException when point is null
     * @throws IllegalArgumentException when point has a NaN coordinate
     */
    public Point2d(final Point2D point) throws NullPointerException, IllegalArgumentException
    {
        Throw.whenNull(point, "point cannot be null");
        Throw.when(Double.isNaN(point.getX()) || Double.isNaN(point.getY()), IllegalArgumentException.class,
                "Coordinate must be a number (not NaN)");
        this.x = point.getX();
        this.y = point.getY();
    }

    /**
     * Throw an IllegalArgumentException if the length of the provided array is not two.
     * @param xy double[]; the provided array
     * @return double[]; the provided array
     * @throws IllegalArgumentException when length of xy is not two
     */
    private static double[] checkLengthIsTwo(final double[] xy) throws IllegalArgumentException
    {
        Throw.when(xy.length != 2, IllegalArgumentException.class, "Length of xy-array must be 2");
        return xy;
    }

    /** {@inheritDoc} */
    @Override
    public final double getX()
    {
        return this.x;
    }

    /** {@inheritDoc} */
    @Override
    public final double getY()
    {
        return this.y;
    }

    /** {@inheritDoc} */
    @Override
    public double distance(final Point2d otherPoint)
    {
        Throw.whenNull(otherPoint, "point cannot be null");
        return Math.hypot(otherPoint.x - this.x, otherPoint.y - this.y);
    }

    /** {@inheritDoc} */
    @Override
    public double distanceSquared(final Point2d otherPoint) throws NullPointerException
    {
        Throw.whenNull(otherPoint, "point cannot be null");
        double dx = getX() - otherPoint.x;
        double dy = getY() - otherPoint.y;
        return dx * dx + dy * dy;
    }

    /** {@inheritDoc} */
    @Override
    public int size()
    {
        return 1;
    }

    /** {@inheritDoc} */
    @Override
    public Iterator<? extends Point2d> getPoints()
    {
        return Arrays.stream(new Point2d[] { this }).iterator();
    }

    /**
     * Return a new Point with a translation by the provided dx and dy.
     * @param dx double; the horizontal translation
     * @param dy double; the vertical translation
     * @return P; a new point with the translated coordinates
     * @throws IllegalArgumentException when dx, or dy is NaN
     */
    public Point2d translate(final double dx, final double dy)
    {
        Throw.when(Double.isNaN(dx) || Double.isNaN(dy), IllegalArgumentException.class, "translation may not be NaN");
        return new Point2d(getX() + dx, getY() + dy);
    }

    /**
     * Return a new Point3d with a translation by the provided delta-x, delta-y and deltaZ.
     * @param dx double; the x translation
     * @param dy double; the y translation
     * @param dz double; the z translation
     * @return Point2d; a new point with the translated coordinates
     * @throws IllegalArgumentException when dx, dy, or dz is NaN
     */
    public Point3d translate(final double dx, final double dy, final double dz)
    {
        Throw.when(Double.isNaN(dx) || Double.isNaN(dy) || Double.isNaN(dz), IllegalArgumentException.class,
                "translation may not be NaN");
        return new Point3d(getX() + dx, getY() + dy, dz);
    }

    /** {@inheritDoc} */
    @Override
    public Point2d scale(final double factor)
    {
        Throw.when(Double.isNaN(factor), IllegalArgumentException.class, "factor must be a number (not NaN)");
        return new Point2d(getX() * factor, getY() * factor);
    }

    /** {@inheritDoc} */
    @Override
    public Point2d neg()
    {
        return scale(-1.0);
    }

    /** {@inheritDoc} */
    @Override
    public Point2d abs()
    {
        return new Point2d(Math.abs(getX()), Math.abs(getY()));
    }

    /** {@inheritDoc} */
    @Override
    public Point2d normalize() throws DrawRuntimeException
    {
        double length = Math.sqrt(getX() * getX() + getY() * getY());
        Throw.when(length == 0.0, DrawRuntimeException.class, "cannot normalize (0.0, 0.0)");
        return this.scale(1.0 / length);
    }

    /** {@inheritDoc} */
    @Override
    public Point2d interpolate(final Point2d point, final double fraction)
    {
        Throw.whenNull(point, "point cannot be null");
        Throw.when(Double.isNaN(fraction), IllegalArgumentException.class, "fraction must be a number (not NaN)");
        return new Point2d((1.0 - fraction) * getX() + fraction * point.x, (1.0 - fraction) * getY() + fraction * point.y);
    }

    /** {@inheritDoc} */
    @Override
    public boolean epsilonEquals(final Point2d other, final double epsilon)
    {
        Throw.whenNull(other, "other point cannot be null");
        if (Math.abs(getX() - other.x) > epsilon)
        {
            return false;
        }
        if (Math.abs(getY() - other.y) > epsilon)
        {
            return false;
        }
        return true;
    }

    /** {@inheritDoc} */
    @Override
    public Bounds2d getBounds()
    {
        return new Bounds2d(this);
    }

    /**
     * Compute the 2D intersection of two lines. Both lines are defined by two points (that should be distinct). The lines are
     * considered to be infinitely long; so unless the lines are parallel; there is an intersection.
     * @param l1P1X double; x-coordinate of start point of line segment 1
     * @param l1P1Y double; y-coordinate of start point of line segment 1
     * @param l1P2X double; x-coordinate of end point of line segment 1
     * @param l1P2Y double; y-coordinate of end point of line segment 1
     * @param l2P1X double; x-coordinate of start point of line segment 2
     * @param l2P1Y double; y-coordinate of start point of line segment 2
     * @param l2P2X double; x-coordinate of end point of line segment 2
     * @param l2P2Y double; y-coordinate of end point of line segment 2
     * @return Point2d; the intersection of the two lines, or null if the lines are (almost) parallel
     */
    @SuppressWarnings("checkstyle:parameternumber")
    public static Point2d intersectionOfLines(final double l1P1X, final double l1P1Y, final double l1P2X, final double l1P2Y,
            final double l2P1X, final double l2P1Y, final double l2P2X, final double l2P2Y)
    {
        double l1DX = l1P2X - l1P1X;
        double l1DY = l1P2Y - l1P1Y;
        double denominator = (l2P2Y - l2P1Y) * l1DX - (l2P2X - l2P1X) * l1DY;
        if (denominator == 0.0)
        {
            return null; // lines are parallel (they might even be on top of each other, but we don't check that)
        }
        double u = ((l2P2X - l2P1X) * (l1P1Y - l2P1Y) - (l2P2Y - l2P1Y) * (l1P1X - l2P1X)) / denominator;
        return new Point2d(l1P1X + u * l1DX, l1P1Y + u * l1DY);
    }

    /**
     * Compute the 2D intersection of two lines. Both lines are defined by two points (that should be distinct). The lines are
     * considered to be infinitely long; so unless the lines are parallel; there is an intersection.
     * @param line1P1 Point2d; first point of line 1
     * @param line1P2 Point2d; second point of line 1
     * @param line2P1 Point2d; first point of line 2
     * @param line2P2 Point2d; second point of line 2
     * @return Point2d; the intersection of the two lines, or null if the lines are (almost) parallel
     */
    public static Point2d intersectionOfLines(final Point2d line1P1, final Point2d line1P2, final Point2d line2P1,
            final Point2d line2P2)
    {
//        double l1p1x = line1P1.x;
//        double l1p1y = line1P1.y;
//        double l1p2x = line1P2.x - l1p1x;
//        double l1p2y = line1P2.y - l1p1y;
//        double l2p1x = line2P1.x - l1p1x;
//        double l2p1y = line2P1.y - l1p1y;
//        double l2p2x = line2P2.x - l1p1x;
//        double l2p2y = line2P2.y - l1p1y;
//        double denominator = (l2p2y - l2p1y) * l1p2x - (l2p2x - l2p1x) * l1p2y;
//        if (denominator == 0.0)
//        {
//            return null; // lines are parallel (they might even be on top of each other, but we don't check that)
//        }
//        double u = ((l2p2x - l2p1x) * (-l2p1y) - (l2p2y - l2p1y) * (-l2p1x)) / denominator;
//        Point2d oldResult = line1P1.interpolate(line1P2, u);
//        Point2d newResult =
//                intersectionOfLines(line1P1.x, line1P1.y, line1P2.x, line1P2.y, line2P1.x, line2P1.y, line2P2.x, line2P2.y);
//        if (oldResult.distance(newResult) > 0.0001)
//        {
//            System.err.println("oops oldResult=" + oldResult + ", newResult=" + newResult);
//        }
//        return newResult;
        return intersectionOfLines(line1P1.x, line1P1.y, line1P2.x, line1P2.y, line2P1.x, line2P1.y, line2P2.x, line2P2.y);
    }

    /**
     * Compute the 2D intersection of two line segments. Both line segments are defined by two points (that should be distinct).
     * @param line1P1 Point2d; first point of line segment 1
     * @param line1P2 Point2d; second point of line segment 1
     * @param line2P1 Point2d; first point of line segment 2
     * @param line2P2 Point2d; second point of line segment 2
     * @return Point2d; the intersection of the two line segments, or null if the lines are (almost) parallel, or do not
     *         intersect
     */
    public static Point2d intersectionOfLineSegments(final Point2d line1P1, final Point2d line1P2, final Point2d line2P1,
            final Point2d line2P2)
    {
        double l1p1x = line1P1.x;
        double l1p1y = line1P1.y;
        double l1p2x = line1P2.x - l1p1x;
        double l1p2y = line1P2.y - l1p1y;
        double l2p1x = line2P1.x - l1p1x;
        double l2p1y = line2P1.y - l1p1y;
        double l2p2x = line2P2.x - l1p1x;
        double l2p2y = line2P2.y - l1p1y;
        double denominator = (l2p2y - l2p1y) * l1p2x - (l2p2x - l2p1x) * l1p2y;
        if (denominator == 0.0)
        {
            return null; // lines are parallel (they might even be on top of each other, but we don't check that)
        }
        double uA = ((l2p2x - l2p1x) * (-l2p1y) - (l2p2y - l2p1y) * (-l2p1x)) / denominator;
        // System.out.println("uA is " + uA);
        if ((uA < 0.0) || (uA > 1.0))
        {
            return null; // intersection outside line 1
        }
        double uB = (l1p2y * l2p1x - l1p2x * l2p1y) / denominator;
        // System.out.println("uB is " + uB);
        if (uB < 0.0 || uB > 1.0)
        {
            return null; // intersection outside line 2
        }
        return line1P1.interpolate(line1P2, uA);
        // return new Point2d(line1P1.x + uA * l1p2x, line1P1.y + uA * l1p2y);
    }

    /** {@inheritDoc} */
    @Override
    public final Point2d closestPointOnSegment(final Point2d segmentPoint1, final Point2d segmentPoint2)
    {
        double dX = segmentPoint2.x - segmentPoint1.x;
        double dY = segmentPoint2.y - segmentPoint1.y;
        if (0 == dX && 0 == dY) // The points may be equal (unlike in Segment2d)
        {
            return segmentPoint1;
        }
        final double u = ((this.x - segmentPoint1.x) * dX + (this.y - segmentPoint1.y) * dY) / (dX * dX + dY * dY);
        if (u < 0)
        {
            return segmentPoint1;
        }
        else if (u > 1)
        {
            return segmentPoint2;
        }
        else
        {
            return segmentPoint1.interpolate(segmentPoint2, u);
        }
    }

    /** {@inheritDoc} */
    @Override
    public final Point2d closestPointOnLine(final Point2d linePoint1, final Point2d linePoint2) throws DrawRuntimeException
    {
        double dX = linePoint2.x - linePoint1.x;
        double dY = linePoint2.y - linePoint1.y;
        Throw.when(dX == 0 && dY == 0, DrawRuntimeException.class, "line points are at same location");
        final double u = ((this.x - linePoint1.x) * dX + (this.y - linePoint1.y) * dY) / (dX * dX + dY * dY);
        return linePoint1.interpolate(linePoint2, u);
    }

    /**
     * Closest point on a ray.
     * @param ray Ray2d; the ray
     * @return Point2d; the point on the ray that is closest to this
     */
    public final Point2d closestPointOnLine(final Ray2d ray)
    {
        double dX = Math.cos(ray.phi);
        double dY = Math.sin(ray.phi);
        final double u = ((this.x - ray.x) * dX + (this.y - ray.y) * dY) / (dX * dX + dY * dY);
        return ray.interpolate(new Point2d(ray.x + dX, ray.y + dY), Math.max(0, u));
    }

    /**
     * Return the zero, one or two intersections between two circles. The circles must be different. Derived from pseudo code by
     * <a href="http://paulbourke.net/geometry/circlesphere/">Paul Bourke</a> and C implementation by
     * <a href="http://paulbourke.net/geometry/circlesphere/tvoght.c">Tim Voght </a>.
     * @param center1 Point2d; the center of circle 1
     * @param radius1 double; the radius of circle 1
     * @param center2 Point2d; the center of circle 2
     * @param radius2 double; the radius of circle 2
     * @return List&lt;Point2d&gt; a list of zero, one or two points
     * @throws NullPointerException when center1 or center2 is null
     * @throws DrawRuntimeException when the two circles are identical, or radius1 &lt; 0 or radius2 &lt; 0
     */
    public static final List<Point2d> circleIntersections(final Point2d center1, final double radius1, final Point2d center2,
            final double radius2) throws NullPointerException, DrawRuntimeException
    {
        Throw.whenNull(center1, "center1 may not be null");
        Throw.whenNull(center2, "center2 may not be null");
        Throw.when(radius1 < 0 || radius2 < 0, DrawRuntimeException.class, "radius may not be less than 0");
        Throw.when(center1.equals(center2) && radius1 == radius2, DrawRuntimeException.class, "Circles must be different");
        List<Point2d> result = new ArrayList<>();
        // dX,dY is the vector from center1 to center2
        double dX = center2.x - center1.x;
        double dY = center2.y - center1.y;
        double distance = Math.hypot(dX, dY);
        if (distance > radius1 + radius2 || distance < Math.abs(radius1 - radius2))
        {
            return result;
        }
        double a = (radius1 * radius1 - radius2 * radius2 + distance * distance) / (2 * distance);
        // x2,y2 is the point where the line through the circle intersections crosses the line through the circle centers
        double x2 = center1.x + (dX * a / distance);
        double y2 = center1.y + (dY * a / distance);
        // h is distance from x2,y2 to each of the solutions
        double h = Math.sqrt(radius1 * radius1 - a * a);
        // rX, rY is vector from x2,y2 to the first solution
        double rX = -dY * (h / distance);
        double rY = dX * (h / distance);
        result.add(new Point2d(x2 + rX, y2 + rY));
        if (h > 0)
        {
            // Two distinct solutions; add the second one
            result.add(new Point2d(x2 - rX, y2 - rY));
        }
        return result;
    }

    /**
     * Return the direction to another Point2d.
     * @param otherPoint Point2d; the other point
     * @return double; the direction to the other point in Radians (towards infinite X is 0; towards infinite Y is &pi; / 2;
     *         etc.). If the points are identical; this method returns NaN.
     */
    public double directionTo(final Point2d otherPoint)
    {
        return Math.atan2(otherPoint.y - this.y, otherPoint.x - this.x);
    }

    /**
     * Return the coordinates as an AWT Point2D.Double object.
     * @return Point2D; the coordinates as an AWT Point2D.Double object
     */
    public Point2D toPoint2D()
    {
        return new Point2D.Double(getX(), getY());
    }

    /** {@inheritDoc} */
    @Override
    public String toString(final int fractionDigits)
    {
        int digits = fractionDigits < 0 ? 0 : fractionDigits;
        String format = String.format("(%%.%1$df,%%.%1$df)", digits);
        return String.format(format, getX(), getY());
    }

    /** {@inheritDoc} */
    @Override
    public String toString()
    {
        return String.format("(%f,%f)", getX(), getY());
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode()
    {
        final int prime = 31;
        int result = 1;
        long temp;
        temp = Double.doubleToLongBits(this.x);
        result = prime * result + (int) (temp ^ (temp >>> 32));
        temp = Double.doubleToLongBits(this.y);
        result = prime * result + (int) (temp ^ (temp >>> 32));
        return result;
    }

    /** {@inheritDoc} */
    @SuppressWarnings("checkstyle:needbraces")
    @Override
    public boolean equals(final Object obj)
    {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Point2d other = (Point2d) obj;
        if (Double.doubleToLongBits(this.x) != Double.doubleToLongBits(other.x))
            return false;
        if (Double.doubleToLongBits(this.y) != Double.doubleToLongBits(other.y))
            return false;
        return true;
    }

}