// The Nature of Code
// <http://www.shiffman.net/teaching/nature>
// Spring 2010
// PBox2D example

// A rectangular box

class Box {

  // We need to keep track of a Body and a width and height
  Body body;
  float w;
  float h;

  // Constructor
  Box(float x_, float y_) {
    float x = x_;
    float y = y_;
    w = 24;
    h = 24;
    // Add the box to the box2d world
    makeBody(new Vec2(x,y),w,h);
    body.setUserData(this);
  }

  // This function removes the particle from the box2d world
  void killBody() {
    box2d.destroyBody(body);
  }

  boolean contains(float x, float y) {
    Vec2 worldPoint = box2d.screenToWorld(x, y);
    Shape s = body.getShapeList();
    boolean inside = s.testPoint(body.getMemberXForm(),worldPoint);
    return inside;
  }

  // Drawing the box
  void display() {
    // We look at each body and get its screen position
    Vec2 pos = box2d.getScreenPos(body);
    // Get its angle of rotation
    float a = body.getAngle();

    rectMode(PConstants.CENTER);
    pushMatrix();
    translate(pos.x,pos.y);
    rotate(a);
    fill(175);
    stroke(0);
    rect(0,0,w,h);
    popMatrix();
  }

  // This function adds the rectangle to the box2d world
  void makeBody(Vec2 center, float w_, float h_) {
    // Define and create the body
    BodyDef bd = new BodyDef();
    bd.position.set(box2d.screenToWorld(center));
    body = box2d.createBody(bd);

    // Define the shape -- a polygon (this is what we use for a rectangle)
    PolygonDef sd = new PolygonDef();
    float box2dW = box2d.scaleScreenToWorld(w_/2);
    float box2dH = box2d.scaleScreenToWorld(h_/2);
    sd.setAsBox(box2dW, box2dH);
    // Parameters that affect physics
    sd.density = 1.0f;
    sd.friction = 0.3f;
    sd.restitution = 0.5f;

    // Attach that shape to our body!
    body.createShape(sd);
    body.setMassFromShapes();

    // Give it some initial random velocity
    body.setLinearVelocity(new Vec2(random(-5,5),random(2,5)));
    body.setAngularVelocity(random(-5,5));
  }

}