/*************************************************************************
 * Copyright (C) 2010 Tavian Barnes <tavianator@gmail.com>               *
 *                                                                       *
 * This file is part of The Dimension Library.                           *
 *                                                                       *
 * The Dimension 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 3 of the *
 * License, or (at your option) any later version.                       *
 *                                                                       *
 * The Dimension 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 program.  If not, see                         *
 * <http://www.gnu.org/licenses/>.                                       *
 *************************************************************************/

#include "dimension.h"
#include <stdlib.h> /* For malloc */
#include <math.h>   /* For sqrt   */

/*
 * Cube
 */

/* Cube callbacks */
static dmnsn_intersection *dmnsn_cube_intersection_fn(const dmnsn_object *cube,
                                                      dmnsn_line line);
static int dmnsn_cube_inside_fn(const dmnsn_object *cube,
                                  dmnsn_vector point);

/* Allocate a new cube object */
dmnsn_object *
dmnsn_new_cube()
{
  dmnsn_object *cube = dmnsn_new_object();
  if (cube) {
    cube->intersection_fn = &dmnsn_cube_intersection_fn;
    cube->inside_fn       = &dmnsn_cube_inside_fn;
    cube->min             = dmnsn_new_vector(-1.0, -1.0, -1.0);
    cube->max             = dmnsn_new_vector(1.0, 1.0, 1.0);
  }
  return cube;
}

/* Intersections callback for a cube */
static dmnsn_intersection *
dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
{
  double t = -1.0, t_temp;
  dmnsn_vector p, normal;
  dmnsn_intersection *intersection = NULL;

  /* Six ray-plane intersection tests (x, y, z) = +/- 1.0 */

  if (line.n.x != 0.0) {
    /* x = -1.0 */
    t_temp = (-1.0 - line.x0.x)/line.n.x;
    p = dmnsn_line_point(line, t_temp);
    if (p.y >= -1.0 && p.y <= 1.0 && p.z >= -1.0 && p.z <= 1.0
        && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
    {
      t = t_temp;
      normal = dmnsn_new_vector(-copysign(1.0, line.n.x), 0.0, 0.0);
    }

    /* x = 1.0 */
    t_temp = (1.0 - line.x0.x)/line.n.x;
    p = dmnsn_line_point(line, t_temp);
    if (p.y >= -1.0 && p.y <= 1.0 && p.z >= -1.0 && p.z <= 1.0
        && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
    {
      t = t_temp;
      normal = dmnsn_new_vector(-copysign(1.0, line.n.x), 0.0, 0.0);
    }
  }

  if (line.n.y != 0.0) {
    /* y = -1.0 */
    t_temp = (-1.0 - line.x0.y)/line.n.y;
    p = dmnsn_line_point(line, t_temp);
    if (p.x >= -1.0 && p.x <= 1.0 && p.z >= -1.0 && p.z <= 1.0
        && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
    {
      t = t_temp;
      normal = dmnsn_new_vector(0.0, -copysign(1.0, line.n.y), 0.0);
    }

    /* y = 1.0 */
    t_temp = (1.0 - line.x0.y)/line.n.y;
    p = dmnsn_line_point(line, t_temp);
    if (p.x >= -1.0 && p.x <= 1.0 && p.z >= -1.0 && p.z <= 1.0
        && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
    {
      t = t_temp;
      normal = dmnsn_new_vector(0.0, -copysign(1.0, line.n.y), 0.0);
    }
  }

  if (line.n.z != 0.0) {
    /* z = -1.0 */
    t_temp = (-1.0 - line.x0.z)/line.n.z;
    p = dmnsn_line_point(line, t_temp);
    if (p.x >= -1.0 && p.x <= 1.0 && p.y >= -1.0 && p.y <= 1.0
        && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
    {
      t = t_temp;
      normal = dmnsn_new_vector(0.0, 0.0, -copysign(1.0, line.n.z));
    }

    /* z = 1.0 */
    t_temp = (1.0 - line.x0.z)/line.n.z;
    p = dmnsn_line_point(line, t_temp);
    if (p.x >= -1.0 && p.x <= 1.0 && p.y >= -1.0 && p.y <= 1.0
        && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
    {
      t = t_temp;
      normal = dmnsn_new_vector(0.0, 0.0, -copysign(1.0, line.n.z));
    }
  }

  if (t >= 0.0) {
    intersection = dmnsn_new_intersection();
    intersection->ray     = line;
    intersection->t       = t;
    intersection->normal  = normal;
    intersection->texture = cube->texture;
  }

  return intersection;
}

/* Inside callback for a cube */
static int
dmnsn_cube_inside_fn(const dmnsn_object *cube, dmnsn_vector point)
{
  return point.x > -1.0 && point.x < 1.0
      && point.y > -1.0 && point.y < 1.0
      && point.z > -1.0 && point.z < 1.0;
}