//
boidFlock flock;

void setup()
{
  size(800,800);
  background(0,166,220);
  flock = new boidFlock(10, new Vector2D(width/2,height/2));
  frameRate(20);
}

void draw()
{
   flock.draw();
   flock.update();
}

class boidFlock
{
  int flockCount;
  boid[] boids;
  boid[] boidnext;
  public boidFlock(int boidcount, Vector2D startpos)
  {
    boids = new boid[boidcount];
    boidnext = new boid[boidcount];
    for(int i = 0; i < boidcount; i++)
    {
      boids[i] = new boid(new Vector2D(startpos.x + random(10),
         startpos.y + random(10)),random(2 * PI), 10);
      boidnext[i] = new boid(new Vector2D(startpos.x + random(10),
         startpos.y + random(10)),1, 10);
    }
  }
  public void draw()
  {
    background(0,166,220);
    for(int i = 0; i < boids.length; i++)
    {
      boids[i].draw();
    }
  }
  public void update()
  {
    for(int i = 0; i < boids.length; i++)
    {
      boidnext[i].update(this, i);
    }
    boid[] temp = boids;
    boids = boidnext;
    boidnext = temp;
  }
}


class boid
{
  Vector2D position;
  float orientation; //z rotation in radians
  float speed;
  public boid(Vector2D initposition, float initorientation,
            float initspeed)
  {
    position = initposition;
    orientation = initorientation;
    speed = initspeed;
  }
  public void draw()
  {
     pushMatrix();
     translate(position.x, position.y);
     fill(255,255,255);
     float coso = cos(orientation);
     float sino = sin(orientation);
     // point b = 5, -10
     // [ sin  cos] [5]  = cos * 5 - sin * -10
     // [ -cos  sin ] [-10]  = sin* 5 + cos* -10
     float bvectx = sino * 5 - coso * 15;
     float bvecty = -coso * 5 - sino * 15;
     float cvectx = -sino * 5 - coso * 15;
     float cvecty =  coso * 5 - sino * 15;
     noStroke();
     triangle(0,0, bvectx, bvecty, cvectx, cvecty);
     popMatrix();
  }
  public void update(boidFlock flock, int me)
  {
      boid oldme = flock.boids[me];
      float coso = cos(oldme.orientation);
      float sino = sin(oldme.orientation);
      float bvectx = coso;
      float bvecty = sino;
      position.x = oldme.position.x + speed * bvectx;
      position.y = oldme.position.y + speed * bvecty;
      orientation = oldme.orientation + PI/12;
  }
}

class Vector2D
{
  public float x;
  public float y;
  public Vector2D(float xcoord, float ycoord)
  {
    x = xcoord;
    y = ycoord;
  }
  public float dot(Vector2D first, Vector2D sec)
  {
    return first.x * sec.x + first.y * sec.y;
  }
  public Vector2D cross(Vector2D first, Vector2D sec)
  {
    return new Vector2D(first.x * sec.y, sec.x* first.y);
  }
}