classes/segment.js

/**
 * Created by Alex Bol on 3/10/2017.
 */


"use strict";
import Flatten from '../flatten';

/**
 * Class representing a segment
 * @type {Segment}
 */
export class Segment {
    /**
     *
     * @param {Point} ps - start point
     * @param {Point} pe - end point
     */
    constructor(...args) {
        /**
         * Start point
         * @type {Point}
         */
        this.ps = new Flatten.Point();
        /**
         * End Point
         * @type {Point}
         */
        this.pe = new Flatten.Point();

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

        if (args.length == 1 && args[0] instanceof Array && args[0].length == 4) {
            let coords = args[0];
            this.ps = new Flatten.Point(coords[0], coords[1]);
            this.pe = new Flatten.Point(coords[2], coords[3]);
            return;
        }

        if (args.length == 1 && args[0] instanceof Object && args[0].name === "segment") {
            let {ps, pe} = args[0];
            this.ps = new Flatten.Point(ps.x, ps.y);
            this.pe = new Flatten.Point(pe.x, pe.y);
            return;
        }

        if (args.length == 2 && args[0] instanceof Flatten.Point && args[1] instanceof Flatten.Point) {
            this.ps = args[0].clone();
            this.pe = args[1].clone();
            return;
        }

        if (args.length == 4) {
            this.ps = new Flatten.Point(args[0], args[1]);
            this.pe = new Flatten.Point(args[2], args[3]);
            return;
        }

        throw Flatten.Errors.ILLEGAL_PARAMETERS;
    }

    /**
     * Method clone copies segment and returns a new instance
     * @returns {Segment}
     */
    clone() {
        return new Flatten.Segment(this.start, this.end);
    }

    /**
     * Start point
     * @returns {Point}
     */
    get start() {
        return this.ps;
    }

    /**
     * End point
     * @returns {Point}
     */
    get end() {
        return this.pe;
    }


    /**
     * Returns array of start and end point
     * @returns [Point,Point]
     */
    get vertices() {
        return [this.ps.clone(), this.pe.clone()];
    }

    /**
     * Length of a segment
     * @returns {number}
     */
    get length() {
        return this.start.distanceTo(this.end)[0];
    }

    /**
     * Slope of the line - angle to axe x in radians from 0 to 2PI
     * @returns {number}
     */
    get slope() {
        let vec = new Flatten.Vector(this.start, this.end);
        return vec.slope;
    }

    /**
     * Bounding box
     * @returns {Box}
     */
    get box() {
        return new Flatten.Box(
            Math.min(this.start.x, this.end.x),
            Math.min(this.start.y, this.end.y),
            Math.max(this.start.x, this.end.x),
            Math.max(this.start.y, this.end.y)
        )
    }

    /**
     * Returns true if equals to query segment, false otherwise
     * @param {Seg} seg - query segment
     * @returns {boolean}
     */
    equalTo(seg) {
        return this.ps.equalTo(seg.ps) && this.pe.equalTo(seg.pe);
    }

    /**
     * Returns true if segment contains point
     * @param {Point} pt Query point
     * @returns {boolean}
     */
    contains(pt) {
        return Flatten.Utils.EQ_0(this.distanceToPoint(pt));
    }

    /**
     * Returns array of intersection points between segment and other shape
     * @param {Shape} shape - Shape of the one of supported types <br/>
     * @returns {Point[]}
     */
    intersect(shape) {
        if (shape instanceof Flatten.Point) {
            return this.contains(shape) ? [shape] : [];
        }

        if (shape instanceof Flatten.Line) {
            return Segment.intersectSegment2Line(this, shape);
        }

        if (shape instanceof Flatten.Segment) {
            return Segment.intersectSegment2Segment(this, shape);
        }

        if (shape instanceof Flatten.Circle) {
            return Segment.intersectSegment2Circle(this, shape);
        }

        if (shape instanceof Flatten.Arc) {
            return Segment.intersectSegment2Arc(this, shape);
        }

        if (shape instanceof Flatten.Polygon) {
            return Flatten.Polygon.intersectShape2Polygon(this, shape);
        }
    }

    /**
     * Calculate distance and shortest segment from segment 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 segment to shape
     * @returns {Segment} shortest segment between segment and shape (started at segment, ended at shape)
     */
    distanceTo(shape) {
        if (shape instanceof Flatten.Point) {
            let [dist, shortest_segment] = Flatten.Distance.point2segment(shape, this);
            shortest_segment = shortest_segment.reverse();
            return [dist, shortest_segment];
        }

        if (shape instanceof Flatten.Circle) {
            let [dist, shortest_segment] = Flatten.Distance.segment2circle(this, shape);
            return [dist, shortest_segment];
        }

        if (shape instanceof Flatten.Line) {
            let [dist, shortest_segment] = Flatten.Distance.segment2line(this, shape);
            return [dist, shortest_segment];
        }

        if (shape instanceof Flatten.Segment) {
            let [dist, shortest_segment] = Flatten.Distance.segment2segment(this, shape);
            return [dist, shortest_segment];
        }

        if (shape instanceof Flatten.Arc) {
            let [dist, shortest_segment] = Flatten.Distance.segment2arc(this, shape);
            return [dist, shortest_segment];
        }

        if (shape instanceof Flatten.Polygon) {
            let [dist, shortest_segment] = Flatten.Distance.shape2polygon(this, shape);
            return [dist, shortest_segment];
        }

        if (shape instanceof Flatten.PlanarSet) {
            let [dist, shortest_segment] = Flatten.Distance.shape2planarSet(this, shape);
            return [dist, shortest_segment];
        }
    }

    /**
     * Returns unit vector in the direction from start to end
     * @returns {Vector}
     */
    tangentInStart() {
        let vec = new Flatten.Vector(this.start, this.end);
        return vec.normalize();
    }

    /**
     * Return unit vector in the direction from end to start
     * @returns {Vector}
     */
    tangentInEnd() {
        let vec = new Flatten.Vector(this.end, this.start);
        return vec.normalize();
    }

    /**
     * Returns new segment with swapped start and end points
     * @returns {Segment}
     */
    reverse() {
        return new Segment(this.end, this.start);
    }

    /**
     * When point belongs to segment, return array of two segments split by given point,
     * if point is inside segment. Returns clone of this segment if query point is incident
     * to start or end point of the segment. Returns empty array if point does not belong to segment
     * @param {Point} pt Query point
     * @returns {Segment[]}
     */
    split(pt) {
        if (!this.contains(pt))
            return [];

        if (this.start.equalTo(this.end))
            return [this.clone()];

        if (this.start.equalTo(pt) || this.end.equalTo(pt))
            return [this];

        return [
            new Flatten.Segment(this.start, pt),
            new Flatten.Segment(pt, this.end)
        ]
    }

    /**
     * Return middle point of the segment
     * @returns {Point}
     */
    middle() {
        return new Flatten.Point((this.start.x + this.end.x) / 2, (this.start.y + this.end.y) / 2);
    }

    distanceToPoint(pt) {
        let [dist, ...rest] = Flatten.Distance.point2segment(pt, this);
        return dist;
    };

    definiteIntegral(ymin = 0.0) {
        let dx = this.end.x - this.start.x;
        let dy1 = this.start.y - ymin;
        let dy2 = this.end.y - ymin;
        return (dx * (dy1 + dy2) / 2);
    }

    /**
     * Returns new segment translated by vector vec
     * @param {Vector} vec
     * @returns {Segment}
     */
    translate(...args) {
        return new Segment(this.ps.translate(...args), this.pe.translate(...args));
    }

    /**
     * Return new segment rotated by given angle around given point
     * If point omitted, rotate around origin (0,0)
     * Positive value of angle defines rotation counter clockwise, negative - clockwise
     * @param {number} angle - rotation angle in radians
     * @param {Point} center - center point, default is (0,0)
     * @returns {Segment}
     */
    rotate(angle = 0, center = new Flatten.Point()) {
        let m = new Flatten.Matrix();
        m = m.translate(center.x, center.y).rotate(angle).translate(-center.x, -center.y);
        return this.transform(m);
    }

    /**
     * Return new segment transformed using affine transformation matrix
     * @param {Matrix} matrix - affine transformation matrix
     * @returns {Segment} - transformed segment
     */
    transform(matrix = new Flatten.Matrix()) {
        return new Segment(this.ps.transform(matrix), this.pe.transform(matrix))
    }

    /**
     * Returns true if segment start is equal to segment end up to DP_TOL
     * @returns {boolean}
     */
    isZeroLength() {
        return this.ps.equalTo(this.pe)
    }

    static intersectSegment2Line(seg, line) {
        let ip = [];

        // Boundary cases
        if (seg.ps.on(line)) {
            ip.push(seg.ps);
        }
        // If both ends lay on line, return two intersection points
        if (seg.pe.on(line) && !seg.isZeroLength()) {
            ip.push(seg.pe);
        }

        if (ip.length > 0) {
            return ip;          // done, intersection found
        }

        // If zero-length segment and nothing found, return no intersections
        if (seg.isZeroLength()) {
            return ip;
        }

        // Not a boundary case, check if both points are on the same side and
        // hence there is no intersection
        if (seg.ps.leftTo(line) && seg.pe.leftTo(line) ||
            !seg.ps.leftTo(line) && !seg.pe.leftTo(line)) {
            return ip;
        }

        // Calculate intersection between lines
        let line1 = new Flatten.Line(seg.ps, seg.pe);
        return line1.intersect(line);
    }

    static intersectSegment2Segment(seg1, seg2) {
        let ip = [];

        // quick reject
        if (seg1.box.not_intersect(seg2.box)) {
            return ip;
        }

        // Special case of seg1 zero length
        if (seg1.isZeroLength()) {
            if (seg1.ps.on(seg2)) {
                ip.push(seg1.ps);
            }
            return ip;
        }

        // Special case of seg2 zero length
        if (seg2.isZeroLength()) {
            if (seg2.ps.on(seg1)) {
                ip.push(seg2.ps);
            }
            return ip;
        }

        // Neither seg1 nor seg2 is zero length
        let line1 = new Flatten.Line(seg1.ps, seg1.pe);
        let line2 = new Flatten.Line(seg2.ps, seg2.pe);

        // Check overlapping between segments in case of incidence
        // If segments touching, add one point. If overlapping, add two points
        if (line1.incidentTo(line2)) {
            if (seg1.ps.on(seg2)) {
                ip.push(seg1.ps);
            }
            if (seg1.pe.on(seg2)) {
                ip.push(seg1.pe);
            }
            if (seg2.ps.on(seg1) && !seg2.ps.equalTo(seg1.ps) && !seg2.ps.equalTo(seg1.pe)) {
                ip.push(seg2.ps);
            }
            if (seg2.pe.on(seg1) && !seg2.pe.equalTo(seg1.ps) && !seg2.pe.equalTo(seg1.pe)) {
                ip.push(seg2.pe);
            }
        } else {                /* not incident - parallel or intersect */
            // Calculate intersection between lines
            let new_ip = line1.intersect(line2);
            if (new_ip.length > 0 && new_ip[0].on(seg1) && new_ip[0].on(seg2)) {
                ip.push(new_ip[0]);
            }
        }

        return ip;
    }

    static intersectSegment2Circle(segment, circle) {
        let ips = [];

        if (segment.box.not_intersect(circle.box)) {
            return ips;
        }

        // Special case of zero length segment
        if (segment.isZeroLength()) {
            let [dist, shortest_segment] = segment.ps.distanceTo(circle.pc);
            if (Flatten.Utils.EQ(dist, circle.r)) {
                ips.push(segment.ps);
            }
            return ips;
        }

        // Non zero-length segment
        let line = new Flatten.Line(segment.ps, segment.pe);

        let ips_tmp = line.intersect(circle);

        for (let ip of ips_tmp) {
            if (ip.on(segment)) {
                ips.push(ip);
            }
        }

        return ips;
    }

    static intersectSegment2Arc(segment, arc) {
        let ip = [];

        if (segment.box.not_intersect(arc.box)) {
            return ip;
        }

        // Special case of zero-length segment
        if (segment.isZeroLength()) {
            if (segment.ps.on(arc)) {
                ip.push(segment.ps);
            }
            return ip;
        }

        // Non-zero length segment
        let line = new Flatten.Line(segment.ps, segment.pe);
        let circle = new Flatten.Circle(arc.pc, arc.r);

        let ip_tmp = line.intersect(circle);

        for (let pt of ip_tmp) {
            if (pt.on(segment) && pt.on(arc)) {
                ip.push(pt);
            }
        }
        return ip;

    }

    /**
     * Return string to draw segment in svg
     * @param {Object} attrs - an object with attributes for svg path element,
     * like "stroke", "strokeWidth" <br/>
     * Defaults are stroke:"black", strokeWidth:"1"
     * @returns {string}
     */
    svg(attrs = {}) {
        let {stroke, strokeWidth, id, className} = attrs;
        // let rest_str = Object.keys(rest).reduce( (acc, key) => acc += ` ${key}="${rest[key]}"`, "");
        let id_str = (id && id.length > 0) ? `id="${id}"` : "";
        let class_str = (className && className.length > 0) ? `class="${className}"` : "";

        return `\n<line x1="${this.start.x}" y1="${this.start.y}" x2="${this.end.x}" y2="${this.end.y}" stroke="${stroke || "black"}" stroke-width="${strokeWidth || 1}" ${id_str} ${class_str} />`;

    }

    /**
     * This method returns an object that defines how data will be
     * serialized when called JSON.stringify() method
     * @returns {Object}
     */
    toJSON() {
        return Object.assign({}, this, {name: "segment"});
    }
};

Flatten.Segment = Segment;
/**
 * Shortcut method to create new segment
 */
export const segment = (...args) => new Flatten.Segment(...args);
Flatten.segment = segment