// Gravitational Attraction
// The Nature of Code
// The Coding Train / Daniel Shiffman
// https://youtu.be/EpgB3cNhKPM
// https://thecodingtrain.com/learning/nature-of-code/2.5-gravitational-attraction.html
// https://editor.p5js.org/codingtrain/sketches/MkLraatd

class Mover {
  constructor(mass, color_value) {
    this.pos = createVector(Math.random() * width, Math.random()*height);
    this.maxSpeed = 10;
    this.vel = createVector(0, 0);
    this.acc = createVector(0, 0);
    this.mass = mass;
    this.r = sqrt(this.mass) * 1;
    this.col = color(color_value);
  }

  mouse_mass() {
    if (focused) {
      let force = p5.Vector.sub(createVector(mouseX, mouseY), this.pos);
      let distanceSq = constrain(force.magSq(), 10, 1000);
      let G = 3;
      let strength = (G * this.mass * 10) / distanceSq;
      force.setMag(strength);
      this.applyForce(force);

      noStroke();
      fill(100, 255, 100, 100);
      ellipse(mouseX, mouseY, 30);
    }
  }

  attract(other) {
    let force = p5.Vector.sub(this.pos, other.pos);
    let distanceSq = constrain(force.magSq(), 10, 1000);
    let G = 3;
    let strength = (G * this.mass * other.mass) / distanceSq;
    
    force.setMag(strength);
    other.applyForce(force);
  }

  applyForce(force) {
    let f = p5.Vector.div(force, this.mass);
    this.acc.add(f);
  }

  edges() {
    if (this.pos.y >= height - this.r) {
      this.pos.y = height - this.r;
      this.vel.y *= -1;
    } else if (this.pos.y <= this.r) {
      this.pos.y = this.r;
      this.vel.y *= -1;
    }

    if (this.pos.x >= width - this.r) {
      this.pos.x = width - this.r;
      this.vel.x *= -1;
    } else if (this.pos.x <= this.r) {
      this.pos.x = this.r;
      this.vel.x *= -1;
    }
  }

  update() {
    this.vel.add(this.acc);
    this.vel.limit(this.maxSpeed);
    this.pos.add(this.vel);
    this.acc.set(0, 0);
  }

  show() {
    noStroke();
    fill(this.col);
    ellipse(this.pos.x, this.pos.y, this.r * 2);
  }
}