class Stalk {
  Particle start;
  Particle end;
  Particle [] links;
  final int numLinks = 7;
  
  Stalk(Particle s, Particle e, ParticleSystem ps) {
    start = s;
    end = e;
    links = new Particle[numLinks];
    createSprings(s, e, links, ps);
  }
  
  void draw() {
    stroke(0);
    strokeWeight(3);
    noFill();
    // draw line between each link
    beginShape();  
    vertex(start.position().x(), start.position().y());
    for(int i = 0 ; i < links.length; i++) {
      Particle p = links[i];
      vertex(p.position().x(), p.position().y());
    }
    vertex(end.position().x(), end.position().y());
    endShape();
  }
  
  void createSprings(Particle s, Particle e, Particle [] ls, ParticleSystem ps) {
    // create along line between s and e to minimize entropy
    float dx = s.position().x() - e.position().y();
    float dy = s.position().y() - e.position().x();
    float stepX = dx / ls.length;
    float stepY = dy / ls.length;
    float x = s.position().x();
    float y = s.position().y();
    
    Particle lp = s;
    for(int i = 0; i < ls.length; i++) {
      Particle p = ps.makeParticle(1.0, x, y, 0);
      ls[i] = p;
      createSpring(p, lp, ps);

      lp = p;
      x += stepX;
      y += stepY;
    }
    createSpring(lp, e, ps);    
  }
  
  void createSpring(Particle p0, Particle p1, ParticleSystem ps) {
    ps.makeSpring(p0, p1, 0.3, 0.4, 5);
  }
}