// Daniel Shiffman

// http://natureofcode.com

​

// A soft pendulum (series of connected springs)

​

class Chain {

  constructor(l, n, r, s, x, y) {

    // This list is redundant since we can ask for physics.particles, but in case we have many of these

    // it's a convenient to keep track of our own list  

    this.particles = [];

​

    // Chain properties

    this.totalLength = l; // How long

    this.numPoints = n; // How many points

    this.radius = r; // Strength of springs

    this.strength = s; // Radius of ball at tail

​

    var len = this.totalLength / this.numPoints;

​

    // Here is the real work, go through and add particles to the chain itself

    for (var i = 0; i < this.numPoints; i++) {

      // Make a new particle with an initial starting location

      var particle = new Particle(x+i*len, y);

​

      // Redundancy, we put the particles both in physics and in our own ArrayList

      physics.addParticle(particle);

      this.particles.push(particle);

​

      // Connect the particles with a Spring (except for the head)

      if (i != 0) {

        var previous = this.particles[i - 1];

        var spring = new VerletSpring2D(particle, previous, len, this.strength);

        // Add the spring to the physics world

        physics.addSpring(spring);

      }

    }

​

    // Keep the top fixed

    // var head = this.particles[0];

    // head.lock();

​

    // Let's keep an extra reference to the tail particle

    // This is just the last particle in the ArrayList

    this.tail = this.particles[this.numPoints - 1];

    this.head = this.particles[0];

    this.head.lock();

    this.head.radius = this.radius;

    this.tail.radius = this.radius;

​

    // Some variables for mouse dragging

    this.offset = createVector();

    this.dragged = false;

  }

​

  // Check if a point is within the ball at the end of the chain

  // If so, set dragged = true;

  // contains(x, y) {

  //   var d = dist(x, y, this.head.x, this.head.y);

  //   if (d < this.radius) {

  //     this.offset.x = this.head.x - x;

  //     this.offset.y = this.head.y - y;

  //     this.head.lock();

  //     this.dragged = true;

  //   }

  // }

​

  // Release the ball

  // release() {

  //   this.head.lock();

  //   this.dragged = false;

  // }

​

  // Update tail location if being dragged

  updateTail(x, y) {

      this.tail.set(x + this.offset.x, y + this.offset.y); 

  }

  updateHead(x, y) {

    //if (this.dragged) {

      this.head.set(x + this.offset.x, y + this.offset.y);

    //}

  }

  isAbove(){

​

  }

​

  // Draw the chain

  display() {

    // Draw line connecting all points

    beginShape();

    stroke(200);

    strokeWeight(2);

    noFill();

    for (var i = 0; i < this.particles.length; i++) {

      vertex(this.particles[i].x, this.particles[i].y);

    }

    endShape();

    this.tail.displayTail();

    // this.head.displayHead();

  }

}