/*
---------------------------------------------------------------------
   Terrain Renderer using texture splatting and geomipmapping
   Copyright (c) 2006 Jelmer Cnossen

   This software is provided 'as-is', without any express or implied
   warranty. In no event will the authors be held liable for any
   damages arising from the use of this software.

   Permission is granted to anyone to use this software for any
   purpose, including commercial applications, and to alter it and
   redistribute it freely, subject to the following restrictions:

   1. The origin of this software must not be misrepresented; you
      must not claim that you wrote the original software. If you use
      this software in a product, an acknowledgment in the product
      documentation would be appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and
      must not be misrepresented as being the original software.

   3. This notice may not be removed or altered from any source
      distribution.

   Jelmer Cnossen
   j.cnossen at gmail dot com
---------------------------------------------------------------------
*/
#ifndef JC_TERRAIN_NODE_H
#define JC_TERRAIN_NODE_H

#include "TerrainVertexBuffer.h"

class Frustum;
struct Sm3VisibilityNode;

namespace terrain
{
	struct int2 { 
		int2(int X,int Y) : x(X),y(Y) {}
		int2() { x=y=0; }
		int x,y; 
	};

	class Camera;
	struct Heightmap;
	struct QuadMap;
	struct IndexTable;
	class QuadRenderData;
	class QuadNormals;
	struct RenderSetupCollection;
	struct IShaderSetup;
	class TerrainTexture;

//-----------------------------------------------------------------------
// Terrain Quadtree Node
//-----------------------------------------------------------------------

	static const int QUAD_W=16;
	static const int VERTC = QUAD_W+1;
	static const int MAX_INDICES=((QUAD_W+1)*(QUAD_W+1)*2*3);
	static const int NUM_VERTICES=((QUAD_W+1)*(QUAD_W+1));

	const float SquareSize=8.0f;
	const float VBufMinDetail=0.25f; // at lod < 0.25f, the vertex buffer is deleted

	const float AREA_TEST_RANGE=0.05f;

	class TQuad
	{
	public:
		TQuad();
		~TQuad();
		bool isLeaf () { return childs[0]==0; }
		// sqStart=start in square coordinates
		// hmStart=start pixel on hm
		void Build (Heightmap *hm, int2 sqStart, int2 hmStart, int2 quadPos, int w, int depth);
		void Draw (IndexTable *indexTable, bool onlyPositions, int lodState);
		bool InFrustum (Frustum *f);
		float CalcLod (const Vector3& campos);
		void CollectNodes(std::vector<TQuad*>& quads);
		void FreeCachedTexture();

		TQuad* FindSmallestContainingQuad2D(const Vector3& pos, float range, int maxlevel);

		int GetVertexSize ();

		// Possible objects linked to this quad, for visibility determination
		std::vector<Sm3VisibilityNode*> nodeLinks;

		TQuad *parent;
		TQuad *childs[4];
		Vector3 start, end;  // quad node bounding box
		int2 qmPos; // Quad map coordinates
		int2 hmPos;
		int2 sqPos; // square position (position on highest detail heightmap)
		int depth, width;
		RenderSetupCollection *textureSetup;
		GLuint cacheTexture;
		float maxLodValue; 		 /** maximum of the LOD values calculated for each render contexts
			 used for determining if the QuadRenderData can be marked as free (see RenderDataManager::FreeUnused) */

		enum DrawState {
			NoDraw, Parent, Queued, Culled
		} drawState;

		QuadNormals *normalData;
		QuadRenderData *renderData;
	};

	// Each render context has a QuadRenderInfo for every quad they have to render
	struct QuadRenderInfo
	{
		int lodState;
		TQuad *quad;
	};

	class RenderContext
	{
	public:
		Camera *cam;
		bool needsTexturing; // contexts like shadow buffers don't need texturing
		bool needsNormalMap;

		std::vector<QuadRenderInfo> quads;
	};

	// renderdata for a visible quad
	class QuadRenderData
	{
	public:
		QuadRenderData();
		~QuadRenderData();

		uint GetDataSize();

		// seems silly yeah, but I use it to set breakpoints in.
		TQuad* GetQuad() { return quad; }
		void SetQuad(TQuad *q) { quad=q; }

		// renderdata: normalmap + vertex buffer
		// normalmap for detail preservation
		GLuint normalMap;
		uint normalMapW, normalMapTexWidth;

		VertexBuffer vertexBuffer;
		int vertexSize;

		int index;
		bool used;
	protected:
		TQuad *quad;
	};

	// Manager for QuadRenderData
	class RenderDataManager {
	public:
		RenderDataManager(Heightmap *roothm, QuadMap *rootqm);
		~RenderDataManager();

		void Free (QuadRenderData *qrd);
		void FreeUnused ();
		void PruneFreeList (int maxFreeRD=0); /// allow the list of free renderdata to be maxFreeRD or lower

		void InitializeNode (TQuad *q);
		void InitializeNodeNormalMap (TQuad *q, int cfgNormalMapLevel);

		void UpdateRect(int sx,int sy,int w,int h);

		void ClearStat () {
			normalDataAllocates=renderDataAllocates=0;
		}

		int normalDataAllocates; // performance statistic
		int renderDataAllocates;

		int QuadRenderDataCount () { return qrd.size(); }

	protected:
		QuadRenderData* Allocate();

		std::vector<QuadRenderData*> qrd;
		std::vector<QuadRenderData*> freeRD;
		Heightmap *roothm;
		QuadMap* rootQMap;
	};

//-----------------------------------------------------------------------
// Heightmap
//-----------------------------------------------------------------------
	struct Heightmap {
		Heightmap ();
		~Heightmap ();

		void Alloc (int W,int H);
		void LodScaleDown (Heightmap * dst);
		void FindMinMax (int2 st, int2 size, float& minH, float& maxH);
		Heightmap *CreateLowDetailHM ();
		void GenerateNormals ();
		void UpdateLower (int sx,int sy,int w,int h);
		Heightmap *GetLevel (int level); // level > 0 returns a high detail HM
										// level < 0 returns a lower detail HM

		float& at(int x,int y) { return data[y*w+x]; }
		uchar* GetNormal(int x,int y) { return &normalData[3*(y*w+x)]; }
		float HeightAt(int x,int y) { return data[y*w+x]; }// * scale + offset; }

		int w,h;
		float *data;
		//float scale, offset;
		float squareSize;

        uchar *normalData; // optional heightmap normals, stored as compressed vectors (3 bytes per normal)

		Heightmap *lowDetail, *highDetail; // geomipmap chain links
	};

//-----------------------------------------------------------------------
// Quad map - stores a 2D map of the quad nodes, 
//            for quick access of nabours
//-----------------------------------------------------------------------
	struct QuadMap 
	{
		QuadMap () {
			w = 0;
			map = 0;
			highDetail=lowDetail=0;
		}
		~QuadMap () {
			delete[] map;
		}

		void Alloc (int W);
		void Fill (TQuad *root);
		TQuad*& At (int x,int y) { return map[y*w+x]; }

		int w;
		TQuad **map;

		QuadMap *highDetail;
		QuadMap *lowDetail;
	};

	
	// Applies a "sobel" filter to the heightmap to find the slope in X and Z(Y in heightmap) direction
	inline void CalculateTangents (Heightmap *hm, int x, int y, Vector3& tangent, Vector3& binormal)
	{
		int xp = (x < hm->w-1) ? x+1 : x;
		int xm = (x > 0) ? x-1 : x;
		int yp = (y < hm->h-1) ? y+1 : y;
		int ym = (y > 0) ? y-1 : y;

		//X filter:
		//-1 0 1
		//-2 0 2
		//-1 0 1
		/*float dhdx = -hm->HeightAt (xm,ym) + hm->HeightAt (xp, ym);
		dhdx += 2.0f * (-hm->HeightAt (xm,y) + hm->HeightAt (xp, y));
		dhdx += -hm->HeightAt (xm,yp) + hm->HeightAt (xp, yp);
		dhdx *= 0.25f;*/

		int dhdx = int(-hm->at (xm,ym) + hm->at (xp, ym));
		dhdx += int(2 * (-hm->at (xm,y) + hm->at (xp, y)));
		dhdx += int(-hm->at (xm,yp) + hm->at (xp, yp));

		// 
		//Z filter:
		//-1 -2 -1
		//0  0  0
		//1  2  1
		//
		/*float dhdz = hm->HeightAt (xm, yp) + 2.0f * hm->HeightAt (x, yp) + hm->HeightAt (xp, yp);
		dhdz -= hm->HeightAt (xm, ym) + 2.0f * hm->HeightAt (x, ym) + hm->HeightAt (xp, ym);
		dhdz *= 0.25f;*/
		int dhdz = int(hm->at (xm, yp) + 2 * hm->at (x, yp) + hm->at (xp, yp));
		dhdz -= int(hm->at (xm, ym) + 2 * hm->at (x, ym) + hm->at (xp, ym));

		tangent = Vector3(hm->squareSize * 2.0f, /*hm->scale * */ dhdx * 0.25f, 0.0f);
		binormal = Vector3(0.0f, dhdz * /*hm->scale * */ 0.25f, hm->squareSize * 2.0f);

//		tangent.set (vdif * 2.0f, dhdx, 0.0f);
//		binormal.set (0.0f, dhdz, vdif * 2.0f);
	}


//-----------------------------------------------------------------------
// IndexTable
//    generates index buffers for the 16 different LOD configurations a quad can be in.
//-----------------------------------------------------------------------
#define NUM_TABLES 16

	// flags that determine if a specific quad side has lower res
#define up_bit 1    // x=0 y=-1
#define left_bit 2  // x=-1 y=0
#define right_bit 4 // x=1 y=0
#define down_bit 8  // x=0 y=1

	// table of precomputed indices
	struct IndexTable
	{
		typedef unsigned short index_t;
		IndexTable ();

		GLenum IndexType() { return GL_UNSIGNED_SHORT; }

		int size[NUM_TABLES];
		IndexBuffer buffers[NUM_TABLES];

		void Calculate (int sides);
	};

};


#endif