// This file is part of the 64k demo project.
// It defines the Bounding Volume Hierarchy (BVH) for scene acceleration.

#pragma once

#include "3d/object.h"
#include "util/mini_math.h"
#include <cstdint>
#include <vector>

struct BVHNode {
  float min_x, min_y, min_z;
  int32_t left_idx; // If < 0, this is a leaf node.

  float max_x, max_y, max_z;
  int32_t right_idx; // If leaf, this holds the object_index.
};

struct AABB {
  vec3 min;
  vec3 max;

  AABB() : min(1e10f, 1e10f, 1e10f), max(-1e10f, -1e10f, -1e10f) {
  }
  AABB(vec3 min, vec3 max) : min(min), max(max) {
  }

  void expand(vec3 p) {
    if (p.x < min.x)
      min.x = p.x;
    if (p.y < min.y)
      min.y = p.y;
    if (p.z < min.z)
      min.z = p.z;
    if (p.x > max.x)
      max.x = p.x;
    if (p.y > max.y)
      max.y = p.y;
    if (p.z > max.z)
      max.z = p.z;
  }

  void expand(const AABB& other) {
    expand(other.min);
    expand(other.max);
  }

  bool intersects(const AABB& other) const {
    return (min.x <= other.max.x && max.x >= other.min.x) &&
           (min.y <= other.max.y && max.y >= other.min.y) &&
           (min.z <= other.max.z && max.z >= other.min.z);
  }

  vec3 center() const {
    return (min + max) * 0.5f;
  }
};

class BVH {
 public:
  std::vector<BVHNode> nodes;

  void query(const AABB& box, std::vector<int>& out_indices) const;
};

class BVHBuilder {
 public:
  static void build(BVH& out_bvh, const std::vector<Object3D>& objects);
};