let vec = p5.Vector


class ConstraintPoint {
  constructor(x, y, size) {
    this.size = size;
    this.pos = new vec(x, y);
    this.forward = new vec(0, 0);
  }

  follow(targetX, targetY, prevForward = null) {
    let target = new vec(targetX, targetY);
    let targetForward = vec.sub(target, this.pos);
    let targetAngle = targetForward.heading();

    

    if (prevForward) {
      let a = targetAngle - prevForward;
      while (a > PI) { a -= TWO_PI; }
      while (a < -PI) { a += TWO_PI; }

      a = constrain(a, -0.3, 0.3);

      targetAngle = prevForward + a;
    }

    this.forward = vec.fromAngle(targetAngle);
    let dir = vec.mult(this.forward, -this.size);
    this.pos = vec.add(target, dir);
  }
  
  getRel(a, dist) {
    return vec.add(this.pos, vec.mult(vec.fromAngle(this.forward.heading() + a), dist));
  }
}

let points = []
let sizes = [60, 55, 50, 40, 45, 47, 50, 47, 45, 42, 39, 35, 30, 25, 22, 17, 13]
function setup() {
  createCanvas(400, 400);
  
  for (let i = 0;i < sizes.length;i++) {
    points.push(new ConstraintPoint(0, 0, 20));
  }
}

function drawPoints(points, sizes) {
  beginShape();
  for (let a = -HALF_PI;a < HALF_PI;a+=0.1) {
    let p = points[0].getRel(a, sizes[0])
    vertex(p.x, p.y);
  }
  for (let i = 0;i < points.length;i++) {
    let p = points[i].getRel(HALF_PI, sizes[i])
    vertex(p.x, p.y);
  }
  
  for (let a = HALF_PI;a < HALF_PI + PI;a+=0.1) {
    let p = points[points.length -1].getRel(a, sizes[points.length -1])
    vertex(p.x, p.y);
  }
  
  for (let i = points.length-1;i >= 0;i--) {
    let p = points[i].getRel(-HALF_PI, sizes[i])
    vertex(p.x, p.y);
  }
  
  endShape();
}


function draw() {
  background(220);
  
  points[0].follow(mouseX, mouseY)
  for (let i = 1;i < sizes.length;i++) {
    let prev = points[i - 1];
    points[i].follow(prev.pos.x, prev.pos.y, prev.forward.heading());
  }

  fill(255)
  drawPoints(points, sizes);
}