// Manager object for a group of Boid particles

class BoidFlock extends Physics{
  Point center, migration;
  float migrationSpeed = 0.005;
  int count;
  // Constructor
  BoidFlock(){
    super();
    center = new Point();
    migration = new Point();
    count = 0;
  }
  // Add a Boid - in lieu of addParticle so it gets the right object
  Boid addBoid(float x, float y){
    Boid temp = new Boid(x, y, this);
    temp.id = count;
    count++;
    p.add(temp);
    return temp;
  }
  // Move all the boids to their known center
  void group(){
    updateCenter();
    for(int i = 0; i < p.size(); i++){
      Boid temp = (Boid)p.get(i);
      temp.group();
    }
  }
  // Make all the boids avoid each other
  void avoid(){
    for(int i = 0; i < p.size(); i++){
      Boid temp = (Boid)p.get(i);
      temp.avoid();
    }
  }
  // Make all the boids fly in the same direction
  void migrate(){
    updateMigration();
    for(int i = 0; i < p.size(); i++){
      Boid temp = (Boid)p.get(i);
      temp.addVelocity(migration.x * migrationSpeed, migration.y * migrationSpeed);
    }
  }
  // Give all the boids a common goal to fly towards
  void goal(float x, float y){
    for(int i = 0; i < p.size(); i++){
      Boid temp = (Boid)p.get(i);
      temp.goal(x, y);
    }
  }
  // Update the average vector they are all flying in
  void updateMigration(){
    float x = 0;
    float y = 0;
    for(int i = 0; i < p.size(); i++){
      Boid temp = (Boid)p.get(i);
      x += temp.x - temp.px;
      y += temp.y - temp.py;
    }
    migration.x = x / p.size();
    migration.y = y / p.size();
  }
  // Update the current center of the group
  void updateCenter(){
    float x = 0;
    float y = 0;
    for(int i = 0; i < p.size(); i++){
      Boid temp = (Boid)p.get(i);
      x += temp.x;
      y += temp.y;
    }
    center.x = x / p.size();
    center.y = y / p.size();
  }
}