/*
 *   __               .__       .__  ._____.           
 * _/  |_  _______  __|__| ____ |  | |__\_ |__   ______
 * \   __\/  _ \  \/  /  |/ ___\|  | |  || __ \ /  ___/
 *  |  | (  <_> >    <|  \  \___|  |_|  || \_\ \\___ \ 
 *  |__|  \____/__/\_ \__|\___  >____/__||___  /____  >
 *                   \/       \/             \/     \/ 
 *
 * Copyright (c) 2006-2011 Karsten Schmidt
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * http://creativecommons.org/licenses/LGPL/2.1/
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
package toxi.physics2d.behaviors;

import java.util.List;

import toxi.geom.SpatialIndex;
import toxi.geom.Vec2D;
import toxi.physics2d.VerletParticle2D;

/**
 *
 * @author tux
 */
public class AttractionBehavior2D implements ParticleBehavior2D {

  /**
   *
   */
  protected Vec2D attractor;

  /**
   *
   */
  protected float attrStrength;

  protected float radius,
    /**
     *
     */
    /**
     *
     */
    radiusSquared;

  /**
   *
   */
  protected float strength;

  /**
   *
   */
  protected float jitter;

  /**
   *
   */
  protected float timeStep;

  /**
   *
   * @param attractor
   * @param radius
   * @param strength
   */
  public AttractionBehavior2D(Vec2D attractor, float radius, float strength) {
    this(attractor, radius, strength, 0);
  }

  /**
   *
   * @param attractor
   * @param radius
   * @param strength
   * @param jitter
   */
  public AttractionBehavior2D(Vec2D attractor, float radius, float strength,
    float jitter) {
    this.attractor = attractor;
    this.strength = strength;
    this.jitter = jitter;
    setRadius(radius);
  }

  @Override
  public void apply(VerletParticle2D p) {
    Vec2D delta = attractor.sub(p);
    float dist = delta.magSquared();
    if (dist < radiusSquared) {
      Vec2D f = delta.normalizeTo((1.0f - dist / radiusSquared))
        .jitter(jitter).scaleSelf(attrStrength);
      p.addForce(f);
    }
  }

  /**
   *
   * @param spaceHash
   */
  @Override
  public void applyWithIndex(SpatialIndex<Vec2D> spaceHash) {
    List<Vec2D> selection = spaceHash.itemsWithinRadius(attractor, radius,
      null);
    final Vec2D temp = new Vec2D();
    if (selection != null) {
      selection.stream().map((p) -> {
        temp.set(p);
        return p;
      }).map((p) -> {
        apply((VerletParticle2D) p);
        return p;
      }).forEachOrdered((p) -> {
        spaceHash.reindex(temp, p);
      });
    }
  }

  /**
   *
   * @param timeStep
   */
  @Override
  public void configure(float timeStep) {
    this.timeStep = timeStep;
    setStrength(strength);
  }

  /**
   * @return the attractor
   */
  public Vec2D getAttractor() {
    return attractor;
  }

  /**
   * @return the jitter
   */
  public float getJitter() {
    return jitter;
  }

  /**
   * @return the radius
   */
  public float getRadius() {
    return radius;
  }

  /**
   * @return the strength
   */
  public float getStrength() {
    return strength;
  }

  /**
   * @param attractor the attractor to set
   */
  public void setAttractor(Vec2D attractor) {
    this.attractor = attractor;
  }

  /**
   * @param jitter the jitter to set
   */
  public void setJitter(float jitter) {
    this.jitter = jitter;
  }

  /**
   *
   * @param r
   */
  public final void setRadius(float r) {
    this.radius = r;
    this.radiusSquared = r * r;
  }

  /**
   * @param strength the strength to set
   */
  public void setStrength(float strength) {
    this.strength = strength;
    this.attrStrength = strength * timeStep;
  }

  /**
   *
   * @return
   */
  @Override
  public boolean supportsSpatialIndex() {
    return true;
  }

}