/* Copyright (c) 2012 Jesper Öqvist <jesper@llbit.se>
 *
 * This file is part of Chunky.
 *
 * Chunky is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Chunky 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 General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with Chunky.  If not, see <http://www.gnu.org/licenses/>.
 */
package se.llbit.chunky.model;

import se.llbit.chunky.resources.Texture;
import se.llbit.math.DoubleSidedQuad;
import se.llbit.math.Quad;
import se.llbit.math.QuickMath;
import se.llbit.math.Ray;
import se.llbit.math.Vector3;
import se.llbit.math.Vector4;

/**
 * Minecart rails.
 *
 * @author Jesper Öqvist <jesper@llbit.se>
 */
public class RailModel {
  private static Quad[][] rails = {
      // flat north/south
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(1, 0, 0), new Vector3(0, 0, 1),
          new Vector4(0, 1, 0, 1)),},

      // flat east/west
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(0, 0, 1), new Vector3(1, 0, 0),
          new Vector4(0, 1, 0, 1)),},

      // ascending east
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(0, 0, 1), new Vector3(1, 1, 0),
          new Vector4(0, 1, 0, 1)),},

      // ascending west
      {new DoubleSidedQuad(new Vector3(0, 1, 0), new Vector3(0, 1, 1), new Vector3(1, 0, 0),
          new Vector4(0, 1, 0, 1)),},

      // ascending north
      {new DoubleSidedQuad(new Vector3(0, 1, 0), new Vector3(1, 1, 0), new Vector3(0, 0, 1),
          new Vector4(0, 1, 0, 1)),},

      // ascending south
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(1, 0, 0), new Vector3(0, 1, 1),
          new Vector4(0, 1, 0, 1)),},

      // nw corner
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(1, 0, 0), new Vector3(0, 0, 1),
          new Vector4(0, 1, 1, 0)),},

      // ne corner
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(1, 0, 0), new Vector3(0, 0, 1),
          new Vector4(1, 0, 1, 0)),},

      // se corner
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(1, 0, 0), new Vector3(0, 0, 1),
          new Vector4(1, 0, 0, 1)),},

      // sw corner
      {new DoubleSidedQuad(new Vector3(0, 0, 0), new Vector3(1, 0, 0), new Vector3(0, 0, 1),
          new Vector4(0, 1, 0, 1)),},

  };

  public static boolean intersect(Ray ray, Texture texture, int type) {
    boolean hit = false;
    ray.t = Double.POSITIVE_INFINITY;
    for (Quad quad : rails[type]) {
      if (quad.intersect(ray)) {
        float[] color = texture.getColor(ray.u, ray.v);
        if (color[3] > Ray.EPSILON) {
          ray.color.set(color);
          ray.t = ray.tNext;
          ray.n.set(quad.n);
          ray.n.scale(-QuickMath.signum(ray.d.dot(quad.n)));
          hit = true;
        }
      }
    }
    if (hit) {
      ray.distance += ray.t;
      ray.o.scaleAdd(ray.t, ray.d);
    }
    return hit;
  }
}