/*************************************************************************
 * Copyright (C) 2010-2012 Tavian Barnes <tavianator@tavianator.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/>.                                       *
 *************************************************************************/

/**
 * @file
 * Constructive solid geometry.
 */

#include "dimension-internal.h"
#include <stdlib.h>

/*
 * Unions
 */

/** CSG union intersection callback. */
static bool
dmnsn_csg_union_intersection_fn(const dmnsn_object *csg,
                                dmnsn_line line,
                                dmnsn_intersection *intersection)
{
  dmnsn_bvh *bvh = csg->ptr;
  return dmnsn_bvh_intersection(bvh, line, intersection, true);
}

/** CSG union inside callback. */
static bool
dmnsn_csg_union_inside_fn(const dmnsn_object *csg, dmnsn_vector point)
{
  dmnsn_bvh *bvh = csg->ptr;
  return dmnsn_bvh_inside(bvh, point);
}

/** CSG union initialization callback. */
static void
dmnsn_csg_union_initialize_fn(dmnsn_object *csg)
{
  csg->trans = dmnsn_identity_matrix();

  dmnsn_bvh *bvh = dmnsn_new_bvh(csg->children, DMNSN_BVH_PRTREE);
  csg->ptr = bvh;
  csg->bounding_box = dmnsn_bvh_bounding_box(bvh);
}

/** CSG union destruction callback. */
static void
dmnsn_csg_union_free_fn(void *ptr)
{
  dmnsn_delete_bvh(ptr);
}

/* Bulk-load a union */
dmnsn_object *
dmnsn_new_csg_union(const dmnsn_array *objects)
{
  dmnsn_object *csg = dmnsn_new_object();

  DMNSN_ARRAY_FOREACH (dmnsn_object **, object, objects) {
    dmnsn_array_push(csg->children, object);
  }
  csg->split_children  = true;
  csg->ptr             = NULL;
  csg->intersection_fn = dmnsn_csg_union_intersection_fn;
  csg->inside_fn       = dmnsn_csg_union_inside_fn;
  csg->initialize_fn   = dmnsn_csg_union_initialize_fn;
  csg->free_fn         = dmnsn_csg_union_free_fn;

  return csg;
}

/**
 * Generic CSG intersection callback.
 * @param[in]  csg           The CSG object.
 * @param[in]  line          The intersection ray.
 * @param[out] intersection  The intersection data.
 * @param[in]  inside1       Whether the first object is allowed inside the
 *                           second object.
 * @param[in]  inside2       Whether the second object is allowed inside the
 *                           first object.
 * @return Whether \p line intersected \p csg.
 */
static bool
dmnsn_csg_intersection_fn(const dmnsn_object *csg, dmnsn_line line,
                          dmnsn_intersection *intersection,
                          bool inside1, bool inside2)
{
  const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
  const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);

  dmnsn_intersection i1, i2;
  bool is_i1 = dmnsn_object_intersection(A, line, &i1);
  bool is_i2 = dmnsn_object_intersection(B, line, &i2);

  double oldt = 0.0;
  while (is_i1) {
    i1.ray = line;
    i1.t += oldt;
    oldt = i1.t + dmnsn_epsilon;

    dmnsn_vector point = dmnsn_line_point(i1.ray, i1.t);
    if (inside2 ^ dmnsn_object_inside(B, point)) {
      dmnsn_line newline = line;
      newline.x0 = dmnsn_line_point(line, i1.t);
      newline    = dmnsn_line_add_epsilon(newline);
      is_i1 = dmnsn_object_intersection(A, newline, &i1);
    } else {
      break;
    }
  }

  oldt = 0.0;
  while (is_i2) {
    i2.ray = line;
    i2.t += oldt;
    oldt = i2.t + dmnsn_epsilon;

    dmnsn_vector point = dmnsn_line_point(i2.ray, i2.t);
    if (inside1 ^ dmnsn_object_inside(A, point)) {
      dmnsn_line newline = line;
      newline.x0 = dmnsn_line_point(line, i2.t);
      newline    = dmnsn_line_add_epsilon(newline);
      is_i2 = dmnsn_object_intersection(B, newline, &i2);
    } else {
      break;
    }
  }

  if (is_i1 && is_i2) {
    if (i1.t < i2.t) {
      *intersection = i1;
    } else {
      *intersection = i2;
    }
  } else if (is_i1) {
    *intersection = i1;
  } else if (is_i2) {
    *intersection = i2;
  } else {
    return false;
  }

  return true;
}

/*
 * Intersections
 */

/** CSG intersection intersection callback. */
static bool
dmnsn_csg_intersection_intersection_fn(const dmnsn_object *csg,
                                       dmnsn_line line,
                                       dmnsn_intersection *intersection)
{
  return dmnsn_csg_intersection_fn(csg, line, intersection, true, true);
}

/** CSG intersection inside callback. */
static bool
dmnsn_csg_intersection_inside_fn(const dmnsn_object *csg, dmnsn_vector point)
{
  const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
  const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
  return dmnsn_object_inside(A, point) && dmnsn_object_inside(B, point);
}

/** CSG intersection initialization callback. */
static void
dmnsn_csg_intersection_initialize_fn(dmnsn_object *csg)
{
  dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
  dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);

  csg->trans = dmnsn_identity_matrix();
  csg->bounding_box.min
    = dmnsn_vector_max(A->bounding_box.min, B->bounding_box.min);
  csg->bounding_box.max
    = dmnsn_vector_min(A->bounding_box.max, B->bounding_box.max);
}

dmnsn_object *
dmnsn_new_csg_intersection(dmnsn_object *A, dmnsn_object *B)
{
  dmnsn_object *csg = dmnsn_new_object();

  dmnsn_array_push(csg->children, &A);
  dmnsn_array_push(csg->children, &B);

  csg->intersection_fn = dmnsn_csg_intersection_intersection_fn;
  csg->inside_fn       = dmnsn_csg_intersection_inside_fn;
  csg->initialize_fn   = dmnsn_csg_intersection_initialize_fn;

  return csg;
}

/*
 * Differences
 */

/** CSG difference intersection callback. */
static bool
dmnsn_csg_difference_intersection_fn(const dmnsn_object *csg,
                                     dmnsn_line line,
                                     dmnsn_intersection *intersection)
{
  return dmnsn_csg_intersection_fn(csg, line, intersection, true, false);
}

/** CSG difference inside callback. */
static bool
dmnsn_csg_difference_inside_fn(const dmnsn_object *csg, dmnsn_vector point)
{
  const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
  const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
  return dmnsn_object_inside(A, point)  && !dmnsn_object_inside(B, point);
}

/** CSG difference initialization callback. */
static void
dmnsn_csg_difference_initialize_fn(dmnsn_object *csg)
{
  dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);

  csg->trans = dmnsn_identity_matrix();
  csg->bounding_box = A->bounding_box;
}

dmnsn_object *
dmnsn_new_csg_difference(dmnsn_object *A, dmnsn_object *B)
{
  dmnsn_object *csg = dmnsn_new_object();

  dmnsn_array_push(csg->children, &A);
  dmnsn_array_push(csg->children, &B);

  csg->intersection_fn = dmnsn_csg_difference_intersection_fn;
  csg->inside_fn       = dmnsn_csg_difference_inside_fn;
  csg->initialize_fn   = dmnsn_csg_difference_initialize_fn;

  return csg;
}

/*
 * Merges
 */

/** CSG merge intersection callback. */
static bool
dmnsn_csg_merge_intersection_fn(const dmnsn_object *csg,
                                dmnsn_line line,
                                dmnsn_intersection *intersection)
{
  return dmnsn_csg_intersection_fn(csg, line, intersection, false, false);
}

/** CSG merge inside callback. */
static bool
dmnsn_csg_merge_inside_fn(const dmnsn_object *csg, dmnsn_vector point)
{
  const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
  const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
  return dmnsn_object_inside(A, point) || dmnsn_object_inside(B, point);
}

/** CSG merge initialization callback. */
static void
dmnsn_csg_merge_initialize_fn(dmnsn_object *csg)
{
  dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
  dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);

  csg->trans = dmnsn_identity_matrix();
  csg->bounding_box.min
    = dmnsn_vector_min(A->bounding_box.min, B->bounding_box.min);
  csg->bounding_box.max
    = dmnsn_vector_max(A->bounding_box.max, B->bounding_box.max);
}

dmnsn_object *
dmnsn_new_csg_merge(dmnsn_object *A, dmnsn_object *B)
{
  dmnsn_object *csg = dmnsn_new_object();

  dmnsn_array_push(csg->children, &A);
  dmnsn_array_push(csg->children, &B);

  csg->intersection_fn = dmnsn_csg_merge_intersection_fn;
  csg->inside_fn       = dmnsn_csg_merge_inside_fn;
  csg->initialize_fn   = dmnsn_csg_merge_initialize_fn;

  return csg;
}