export class MassObject {
  index = undefined;
  mass = 0;
  density = 1;
  position = {x: undefined, y: undefined};
  velocity = {x: 0, y: 0};
  acceleration = {x: 0, y: 0};
  color = {r: undefined, g: undefined, b: undefined};
  created = undefined;
  forces = []; // [{x, y}]

  constructor(x, y, index) {
    this.index = index;
    this.position.x = x;
    this.position.y = y;
    this.color.r = Math.random() * 256;
    this.color.g = Math.random() * 256;
    this.color.b = Math.random() * 256;
    this.created = document.timeline.currentTime;
  }

  get age() {
    return document.timeline.currentTime - this.created;
  }

  get radius() {
    // radius should be proportional to cube root of mass
    return Math.pow(this.mass / this.density, 1/3);
  }

  getAcceleration() {
    let ax = 0;
    let ay = 0;
    for (let {x, y} of this.forces) {
      ax += x;
      ay += y;
    }
    return {
      x: ax / this.mass,
      y: ay / this.mass,
    };
  }
}