#include "BvhExporter.h"

using namespace std;

// MAGIC of all bin exports
#ifndef MAGIC 
#define MAGIC 0x827923
#endif

#define BVH_VERSION 2.1

namespace CHCDemoEngine
{

static int currentIdx = 0;


void BvhExporter::SaveNode(BvhNode *node, FILE *fw) 
{
	if (!node) return;
	
	int buffer[4];
	buffer[3] = currentIdx ++;

	if (node->IsVirtualLeaf()) 
	{
		BvhLeaf *leaf = (BvhLeaf*)node;
		
		buffer[0] = mTriangleRangeMap[leaf].first;
		buffer[1] = mTriangleRangeMap[leaf].second;
		buffer[2] = -1;//leaf->GetAxis();
		
		fwrite(buffer, sizeof(int), 4, fw);
	}
	else
	{
		BvhInterior *interior = (BvhInterior *)node;
		
		buffer[0] = interior->mFirst;
		buffer[1] = interior->mLast;
		buffer[2] = 0;//interior->mAxis;

		fwrite(buffer, sizeof(int), 4, fw);
		
		SaveNode(interior->GetFront(), fw);
		SaveNode(interior->GetBack(), fw);
	}
}


void BvhExporter::ConstructTriangleRangeMap(Bvh *bvh, 
											BvhNode *node,
											int &first, 
											int &last)
{
	if (!node->IsVirtualLeaf())
	{
		int m;
		BvhInterior *interior = static_cast<BvhInterior *>(node);

		ConstructTriangleRangeMap(bvh, interior->GetBack(), first, m);
		int newFirst = m + 1;
		ConstructTriangleRangeMap(bvh, interior->GetFront(), newFirst, last);

		mTriangleRangeMap[node] = pair<int, int>(first, last);
	}
	else
	{
		//first = currentIdx;
		last = first + bvh->CountTriangles(node) - 1;
		//cout << "x " << node->GetFirstEntity() << " " << node->GetLastEntity() << " " << first << " " << last << endl;
		//currentIdx = last;
		mTriangleRangeMap[node] = pair<int, int>(first, last);
	}
}


bool BvhExporter::Export(const string &filename, Bvh *bvh)
{
	 cout << "Exporting bvh to file '" << filename.c_str() << "'" << endl;
  
	 FILE *fw = fopen(filename.c_str(), "wb");

	 if (fw == NULL) 
	 {
		 cerr << "Error: Cannot open file for writing" << endl;
		 return false;
	 }

	 int buffer[6];
	 buffer[0] = MAGIC;
	 buffer[1] = BVH_VERSION * 1000;
	 buffer[3] = 0; // construction method
	 buffer[4] = 1; // termination leaves
	 buffer[5] = bvh->CountNumVirtualNodes(bvh->GetStaticRoot());

	 int first = 0, last;
	 ConstructTriangleRangeMap(bvh, bvh->GetStaticRoot(), first, last);

	 BvhNodeContainer nodes;
	 bvh->CollectVirtualLeaves(bvh->GetStaticRoot(), nodes);

	 vector<int> triangles;

	 BvhNodeContainer::const_iterator it, it_end = nodes.end();

	 for (it = nodes.begin(); it != it_end; ++ it)
	 {
		 BvhNode *node = *it;

		 const int f = mTriangleRangeMap[node].first;
		 const int l = mTriangleRangeMap[node].second;

		 for (int i = f; i <= l; ++ i)
			 triangles.push_back(i);
	 }

	 buffer[2] = (int)triangles.size();
	 fwrite(buffer, sizeof(int), 6, fw);

	 cout << "writing " << (int)triangles.size() << " triangle ids ..." << endl;

	 // export sorted triangle IDs
	 for (size_t i = 0; i < triangles.size(); ++ i) 
	 {
		 fwrite(&triangles[i], sizeof(int), 1, fw);
	 }

	 cout << "writing bvh nodes ..." << endl;
	 
	 SaveNode(bvh->GetStaticRoot(), fw);
	 
	 cout << "successfully exported bvh" << endl;
	 fclose(fw);

	 return true;
}


}