import {
  distance,
  isColinear,
  norm,
  scalar,
  vector,
  plus,
  times,
} from '../maths';

import GraphElement from './GraphElement';
import Line from './Line';
import Point from './Point';

export default class Segment extends GraphElement {
  static type = 'Segment';
  A: Point;
  B: Point;
  constructor(A: Point = new Point(), B: Point = new Point()) {
    super();
    this.A = A;
    this.B = B;
  }

  origin(): Point {
    return this.A;
  }

  destination(): Point {
    return this.B;
  }

  dirVect() {
    return vector(this.origin(), this.destination());
  }

  length() {
    return distance(this.destination(), this.origin());
  }

  isEqual(element: GraphElement): boolean {
    if (!(element instanceof Segment)) return false;
    const o = this.origin();
    const dest = this.destination();
    const oE = element.origin();
    const destE = element.destination();
    return (
      element instanceof Segment &&
      ((o.isEqual(oE) && dest.isEqual(destE)) ||
        (o.isEqual(destE) && dest.isEqual(oE)))
    );
  }

  /** Returns an equivalent line object */
  getLine() {
    const line = new Line(this.origin(), this.destination());
    return line;
  }

  includes(P: Point) {
    const vect = this.dirVect();
    const otherVect = vector(this.origin(), P);
    // The vectors are not even colinear
    if (!isColinear(vect, otherVect)) return false;
    // The point is behind the origin
    else if (scalar(vect, otherVect) < 0) return false;
    // The point is after the destination
    else if (norm(vect) < norm(otherVect)) return false;
    else return true;
  }

  middle() {
    const mid = new Point(
      plus(this.origin().toCoords(), times(this.dirVect(), 0.5)),
    );
    return mid;
  }

  orthoProjection(P: Point) {
    const H = this.getLine().orthoProjection(P);
    const vect = this.dirVect();
    const origin = this.origin().toCoords();
    const destination = this.destination().toCoords();
    const otherVect = vector(this.origin(), H);
    // The point is before the origin
    if (scalar(vect, otherVect) < 0) return new Point(origin);
    // The point is after the destination
    else if (norm(vect) < norm(otherVect)) return new Point(destination);
    // The point is within the segment
    else return H;
  }
}