romgrk-2d-geometry/src/classes/Point.ts

Javascript library for 2d geometry

import Errors from "../utils/errors";
import {convertToString} from "../utils/attributes";
import * as Distance from '../algorithms/distance';
import * as Utils from "../utils/utils";
import * as geom from './index'
import {Shape} from "./Shape";

/**
 * Class representing a point
 * @type {Point}
 */
export class Point extends Shape<Point> {
    static EMPTY = Object.freeze(new Point(0, 0));

    /** x-coordinate (float number) */
    x: number
    /** y-coordinate (float number) */
    y: number

    /**
     * Point may be constructed by two numbers, or by array of two numbers
     * @param {number} x - x-coordinate (float number)
     * @param {number} y - y-coordinate (float number)
     */
    constructor(...args) {
        super()
        this.x = 0;
        this.y = 0;

        if (args.length === 0) {
            return;
        }

        if (args.length === 1 && args[0] instanceof Array && args[0].length === 2) {
            let arr = args[0];
            if (typeof (arr[0]) == "number" && typeof (arr[1]) == "number") {
                this.x = arr[0];
                this.y = arr[1];
                return;
            }
        }

        if (args.length === 1 && args[0] instanceof Object) {
            let { x, y } = args[0];
            this.x = x;
            this.y = y;
            return;
        }

        if (args.length === 2) {
            if (typeof (args[0]) == "number" && typeof (args[1]) == "number") {
                this.x = args[0];
                this.y = args[1];
                return;
            }
        }
        throw Errors.ILLEGAL_PARAMETERS;
    }

    /**
     * Returns bounding box of a point
     * @returns {Box}
     */
    get box() {
        return new geom.Box(this.x, this.y, this.x, this.y);
    }

    /**
     * Return new cloned instance of point
     * @returns {Point}
     */
    clone() {
        return new Point(this.x, this.y);
    }

    get vertices() {
        return [this.clone()];
    }

    /**
     * Returns true if points are equal up to [Utils.DP_TOL]{@link DP_TOL} tolerance
     * @param {Point} pt Query point
     * @returns {boolean}
     */
    equalTo(pt) {
        return Utils.EQ(this.x, pt.x) && Utils.EQ(this.y, pt.y);
    }

    /**
     * Defines predicate "less than" between points. Returns true if the point is less than query points, false otherwise <br/>
     * By definition point1 < point2 if {point1.y < point2.y || point1.y == point2.y && point1.x < point2.x <br/>
     * Numeric values compared with [Utils.DP_TOL]{@link DP_TOL} tolerance
     * @param {Point} pt Query point
     * @returns {boolean}
     */
    lessThan(pt) {
        if (Utils.LT(this.y, pt.y))
            return true;
        if (Utils.EQ(this.y, pt.y) && Utils.LT(this.x, pt.x))
            return true;
        return false;
    }

    /**
     * Return new point transformed by affine transformation matrix
     * @param {Matrix} m - affine transformation matrix (a,b,c,d,tx,ty)
     * @returns {Point}
     */
    transform(m) {
        return new Point(m.transform([this.x, this.y]))
    }

    /**
     * Returns projection point on given line
     * @param {Line} line Line this point be projected on
     * @returns {Point}
     */
    projectionOn(line) {
        if (this.equalTo(line.pt))                   // this point equal to line anchor point
            return this.clone();

        let vec = new geom.Vector(this, line.pt);
        if (Utils.EQ_0(vec.cross(line.norm)))    // vector to point from anchor point collinear to normal vector
            return line.pt.clone();

        let dist = vec.dot(line.norm);             // signed distance
        let proj_vec = line.norm.multiply(dist);
        return this.translate(proj_vec);
    }

    /**
     * Returns true if point belongs to the "left" semi-plane, which means, point belongs to the same semi plane where line normal vector points to
     * Return false if point belongs to the "right" semi-plane or to the line itself
     * @param {Line} line Query line
     * @returns {boolean}
     */
    leftTo(line) {
        let vec = new geom.Vector(line.pt, this);
        let onLeftSemiPlane = Utils.GT(vec.dot(line.norm), 0);
        return onLeftSemiPlane;
    }

    /**
     * Snap the point to a grid.
     */
    snapToGrid(grid: number);
    snapToGrid(xGrid: number, yGrid: number);
    snapToGrid(a: number = 1, b?: unknown) {
        const xGrid = a
        const yGrid = b === undefined ? a : b as number
        return new Point(
            Math.round(this.x / xGrid) * xGrid,
            Math.round(this.y / yGrid) * yGrid,
        )
    }

    /**
     * Calculate distance and shortest segment from point to shape and return as array [distance, shortest segment]
     * @param {Shape} shape Shape of the one of supported types Point, Line, Circle, Segment, Arc, Polygon or Planar Set
     * @returns {number} distance from point to shape
     * @returns {Segment} shortest segment between point and shape (started at point, ended at shape)
     */
    distanceTo(shape) {
        if (shape instanceof Point) {
            let dx = shape.x - this.x;
            let dy = shape.y - this.y;
            return [Math.sqrt(dx * dx + dy * dy), new geom.Segment(this, shape)];
        }

        if (shape instanceof geom.Line) {
            return Distance.point2line(this, shape);
        }

        if (shape instanceof geom.Circle) {
            return Distance.point2circle(this, shape);
        }

        if (shape instanceof geom.Segment) {
            return Distance.point2segment(this, shape);
        }

        if (shape instanceof geom.Arc) {
            return Distance.point2arc(this, shape);
        }

        if (shape instanceof geom.Polygon) {
            return Distance.point2polygon(this, shape);
        }

        // TODO: enable
        // if (shape instanceof PlanarSet) {
        //     return Distance.shape2planarSet(this, shape);
        // }
    }

    /**
     * Returns true if point is on a shape, false otherwise
     * @param {Shape} shape Shape of the one of supported types Point, Line, Circle, Segment, Arc, Polygon
     * @returns {boolean}
     */
    on(shape) {
        if (shape instanceof geom.Point) {
            return this.equalTo(shape);
        }

        if (shape instanceof geom.Line) {
            return shape.contains(this);
        }

        if (shape instanceof geom.Ray) {
            return shape.contains(this)
        }

        if (shape instanceof geom.Circle) {
            return shape.contains(this);
        }

        if (shape instanceof geom.Segment) {
            return shape.contains(this);
        }

        if (shape instanceof geom.Arc) {
            return shape.contains(this);
        }

        if (shape instanceof geom.Polygon) {
            return shape.contains(this);
        }
    }

    get name() {
        return "point"
    }

    /**
     * Return string to draw point in svg as circle with radius "r" <br/>
     * Accept any valid attributes of svg elements as svg object
     * Defaults attribues are: <br/>
     * {
     *    r:"3",
     *    stroke:"black",
     *    strokeWidth:"1",
     *    fill:"red"
     * }
     * @param attrs - Any valid attributes of svg circle element, like "r", "stroke", "strokeWidth", "fill"
     */
    svg(attrs: Record<string, string> = {}): string {
        const r = attrs.r ?? 3            // default radius - 3
        return `\n<circle cx="${this.x}" cy="${this.y}" r="${r}"
            ${convertToString({fill: "red", ...attrs})} />`;
    }
}

export const point = (...args) => new Point(...args);