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src/app/components/line-segment-component/models/line-segment-model.js

/*
 * iGeom by LInE
 * Geometric Object: Segment
 * Manage intersection of Segment with: Sements, Circumference
 * www.matematica.br/igeom
 * .app/components/line-segment-component/models/line-segment-model.js
 * @version 2020/11/02: Implemented Line instersection
 */

import { GeometricObject } from "../../../core/models/objects/geometric-object";
import { IntersectionModel } from "../../intersection-component/models/intersection-model";
import { ELEMENTS_CLASS } from "../../../core/enums/elements-class-enum";

export class LineSegmentModel extends GeometricObject {

  constructor(pointA, pointB, label, id) {
    super(id);
    this.pointA = pointA;
    this.pointB = pointB;
    this.setLabel(label);
    super.setClass(ELEMENTS_CLASS.LINE_SEGMENT);
    this.definitions.push(this.pointA);
    this.definitions.push(this.pointB);
  }

  getStraight() {
    const aX = this.pointA.posX;
    const aY = this.pointA.posY;
    const bX = this.pointB.posX;
    const bY = this.pointB.posY;
    const a = bY - aY;
    const b = aX - bX;
    const c = a * aX + b * aY;
    return [a, b, c];
  }

  // Return [(Bx-Ax, By-Ay)]
  getDirection() {
    const aX = this.pointA.posX;
    const aY = this.pointA.posY;
    const bX = this.pointB.posX;
    const bY = this.pointB.posY;
    const a = bX - aX;
    const b = bY - aY;
    return [a, b];
  }


  getMiddlePoint() {
    const x = (this.pointA.posX + this.pointB.posX) / 2;
    const y = (this.pointA.posY + this.pointB.posY) / 2;
    return { posX: x, posY: y };
  }

  getIntersection(geometricObject) {
    switch (geometricObject.elementClass) {
      case ELEMENTS_CLASS.LINE: // StraightLine
        return geometricObject.getIntersectionWithStraightLine(this); // Delegate to StraightLine
      case ELEMENTS_CLASS.LINE_SEGMENT:
        return this.getIntersectionByLine(geometricObject); //TODO nome deveria especificar SEGMENTO: this.getIntersectionWithSegment
      case ELEMENTS_CLASS.CIRCUMFERENCE:
        return this.getIntersectionWithCircumference(geometricObject);
      default:
        break;
    }
  }

  getDeterminantByLine(lineSegment) {
    const og1 = this.getStraight();
    const og2 = lineSegment.getStraight();
    const a1 = og1[0];
    const b1 = og1[1];
    const a2 = og2[0];
    const b2 = og2[1];
    const determinant = a1 * b2 - a2 * b1;
    return determinant;
  }

  getIntersectionByLine(lineSegment) { //TODO nome deveria especificar SEGMENTO: getIntersectionWithSegment
    const og1 = this.getStraight(); //r
    const og2 = lineSegment.getStraight(); //s
    const a1 = og1[0];
    const b1 = og1[1];
    const c1 = og1[2];
    const a2 = og2[0];
    const b2 = og2[1];
    const c2 = og2[2];
    const determinant = a1 * b2 - a2 * b1;
    if (determinant == 0) {
      return [new IntersectionModel(Number.MAX_SAFE_INTEGER, Number.MAX_SAFE_INTEGER, undefined, this, lineSegment, true, 0)];
    }
    else {
      const x = (b2 * c1 - b1 * c2) / determinant;
      const y = (a1 * c2 - a2 * c1) / determinant;
      return [new IntersectionModel(x, y, undefined, this, lineSegment, true, 0)];
    }
  }

  // Intersection with circunference
  getIntersectionWithCircumference(circumference) { //TODO Nome? Melhor 'getIntersectionWithCircumference'
    const pointA = this.pointA;
    const pointB = this.pointB;
    const center = circumference.center;
    const radius = circumference.getRadius();

    const dx = pointB.posX - pointA.posX;
    const dy = pointB.posY - pointA.posY;

    const cx = center.posX - pointA.posX;
    const cy = center.posY - pointA.posY;

    const a = dx * dx + dy * dy; // ||B-A||^2 = (B-A)'(B-A)
    const b = dx * cx + dy * cy; // (B-A)'(C-A)
    const c = cx * cx + cy * cy - radius * radius; // ||C-A||^2 - r^2

    const D = b / a; // (B-A)'(C-A) / (B-A)'(B-A)
    const q = c / a; // (||C-A||^2 - r^2) / (B-A)'(B-A)

    const delta = D * D - q;

    const PA = new IntersectionModel(Number.MAX_SAFE_INTEGER, Number.MAX_SAFE_INTEGER, undefined, this, circumference, false, 0);
    const PB = new IntersectionModel(Number.MAX_SAFE_INTEGER, Number.MAX_SAFE_INTEGER, undefined, this, circumference, false, 1);

    if (delta < 0) { //TODO Verificar? No intersection points
      //D console.log("line-segment-model.js: getIntersectionWithCircumference(.): delta<0: " + Number.MAX_SAFE_INTEGER);
      return [PA, PB];
    }

    const deltaSqrt = Math.sqrt(delta);
    const root1 = -D + deltaSqrt;
    const root2 = -D - deltaSqrt;
    const x1 = pointA.posX - dx * root1
    const y1 = pointA.posY - dy * root1;

    if (delta == 0) { //TODO Verificar? Only one point (actually, both with the same coordinates)
      //D console.log("line-segment-model.js: getIntersectionWithCircumference(.): delta==0");
      PA.bind(x1, y1, undefined, this, circumference, true, 0);
      return [PA, PB];
    }

    if (delta == 0) {
      PA.bind(x1, y1, undefined, this, circumference, true, 0);
      return [
        PA,
        PB
      ];
    }

    const x2 = pointA.posX - dx * root2;
    const y2 = pointA.posY - dy * root2;

    PA.bind(x1, y1, undefined, this, circumference, true, 0);
    PB.bind(x2, y2, undefined, this, circumference, true, 1);

    if (!this.insideSegment(PB.posX, PB.posY))
      PB.bind(Number.MAX_SAFE_INTEGER, Number.MAX_SAFE_INTEGER, undefined, this, circumference, false, 1);

    return [PA, PB];
  } // getIntersectionWithCircumference(circumference)


  // Considering de "level set" defined by direction d=B-A and intersection P,
  // if d'P<d'A or d'P>d'B, then intersection is empty
  insideSegment(intersecX, intersecY) {
    //D console.log("line-segment-model.js: insideSegment(.)");
    const valuesR = this.getDirection(); // get d=B-A
    const dirX = valuesR[0]; // Bx-Ax
    const dirY = valuesR[1]; // By-Ay
    const cInterA = dirX * intersecX + dirY * intersecY;

    // comparacao cv do ponto A > cv da intersec =>  vazio
    const cRA = dirX * this.pointA.posX + dirY * this.pointA.posY;

    if (cInterA < cRA) { // d'P < d'A
      return false;
    }

    // comparacao cv do ponto B < cv da intersec =>  vazio
    const cRB = dirX * this.pointB.posX + dirY * this.pointB.posY;

    if (cInterA > cRB) { // d'P > d'B
      this.posX = Number.MAX_SAFE_INTEGER;
      this.posY = Number.MAX_SAFE_INTEGER;
      return false;
    }

    return true;
  }

  static do(map, list) {
    const id = map.get("id");
    const pointAId = map.get("param")[0];
    const pointBId = map.get("param")[1];

    const pointA = list.find(x => x.id === pointAId);
    const pointB = list.find(x => x.id === pointBId);
    const label = map.get("label")[0];
    return new LineSegmentModel(pointA, pointB, label, id);
  }

}