#ifndef __MESH_H__
#define __MESH_H__

#include "intersect.h"

#define STACK_SIZE 500

/* flattened triangle mesh */
__device__ float3 *g_vertices;
__device__ uint4 *g_triangles;
__device__ unsigned int *g_colors;
__device__ unsigned int g_start_node;
__device__ unsigned int g_first_node;

/* lower/upper bounds for the bounding box associated with each node/leaf */
texture<float4, 1, cudaReadModeElementType> upper_bounds;
texture<float4, 1, cudaReadModeElementType> lower_bounds;

/* map to child nodes/triangles and the number of child nodes/triangles */
texture<unsigned int, 1, cudaReadModeElementType> node_map;
texture<unsigned int, 1, cudaReadModeElementType> node_length;

__device__ float3 make_float3(const float4 &a)
{
	return make_float3(a.x, a.y, a.z);
}

__device__ int convert(int c)
{
	if (c & 0x80)
		return (0xFFFFFF00 | c);
	else
		return c;
}

/* Test the intersection between a ray starting at `origin` traveling in the
   direction `direction` and the bounding box around node `i`. If the ray
   intersects the bounding box return true, else return false. */
__device__ bool intersect_node(const float3 &origin, const float3 &direction, const int &i)
{
	float3 lower_bound = make_float3(tex1Dfetch(lower_bounds, i));
	float3 upper_bound = make_float3(tex1Dfetch(upper_bounds, i));

	return intersect_box(origin, direction, lower_bound, upper_bound);
}

/* Find the intersection between a ray starting at `origin` traveling in the
   direction `direction` and the global mesh texture. If the ray intersects
   the texture return the index of the triangle which the ray intersected,
   else return -1. */
__device__ __noinline__ int intersect_mesh(const float3 &origin, const float3& direction, float &min_distance, int last_hit_triangle = -1)
{
	int triangle_index = -1;

	float distance;

	if (!intersect_node(origin, direction, g_start_node))
		return -1;

	int stack[STACK_SIZE];

	int *head = &stack[0];
	int *node = &stack[1];
	int *tail = &stack[STACK_SIZE-1];
	*node = g_start_node;

	int i;

	do
	{
		int first_child = tex1Dfetch(node_map, *node);
		int child_count = tex1Dfetch(node_length, *node);

		while (*node >= g_first_node && child_count == 1)
		{
			*node = first_child;
			first_child = tex1Dfetch(node_map, *node);
			child_count = tex1Dfetch(node_length, *node);
		}
		
		if (*node >= g_first_node)
		{
			for (i=0; i < child_count; i++)
			{
				if (intersect_node(origin, direction, first_child+i))
				{
					*node = first_child+i;
					node++;
				}
			}

			node--;
		}
		else // node is a leaf
		{
			for (i=0; i < child_count; i++)
			{
				if (last_hit_triangle == first_child+i)
					continue;

				uint4 triangle_data = g_triangles[first_child+i];

				float3 v0 = g_vertices[triangle_data.x];
				float3 v1 = g_vertices[triangle_data.y];
				float3 v2 = g_vertices[triangle_data.z];

				if (intersect_triangle(origin, direction, v0, v1, v2, distance))
				{
					if (triangle_index == -1)
					{
						triangle_index = first_child + i;
						min_distance = distance;
						continue;
					}

					if (distance < min_distance)
					{
						triangle_index = first_child + i;
						min_distance = distance;
					}
				}
			} // triangle loop

			node--;

		} // node is a leaf

	} // while loop
	while (node != head);

	return triangle_index;
}

extern "C"
{

__global__ void set_global_mesh_variables(uint4 *triangles, float3 *vertices, unsigned int *colors, unsigned int start_node, unsigned int first_node)
{
	g_triangles = triangles;
	g_vertices = vertices;
	g_colors = colors;
	g_start_node = start_node;
	g_first_node = first_node;
}

__global__ void set_colors(unsigned int *colors)
{
	g_colors = colors;
}

} // extern "c"

#endif