/*
---------------------------------------------------------------------
   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
---------------------------------------------------------------------
*/
#include "TerrainNode.h"
#include "Textures.h"

class TdfParser;

namespace terrain {

	struct ShadowMapParams;
	class TQuad;
	struct Heightmap;
	class Lightmap;

//-----------------------------------------------------------------------
// terrain texturing system
//-----------------------------------------------------------------------

	enum VertexDataAttribs
	{
		VRT_Basic = 0,
		VRT_TangentSpaceMatrix = 1, // vertex program needs tangent space matrix (world space -> tangent space)
		VRT_Normal = 2,             // vertex program needs normal (world space)
	};

	struct IShaderSetup
	{
		IShaderSetup () {}
		virtual ~IShaderSetup() {}
		virtual uint GetVertexDataRequirements () { return VRT_Basic; }
		virtual std::string GetDebugDesc () { return std::string();} 

		virtual void BindTSM(Vector3* buf, uint vertexSize) {}
		virtual void UnbindTSM() {}

		virtual void GetTextureUnits(BaseTexture *tex, int& imageUnit, int& coordUnit) {}
	};

	// Helper class to determine how to implement the shader stages (with multipass or multitexturing)
	struct TextureUsage
	{
		std::vector<BaseTexture*> texUnits;
		std::vector<BaseTexture*> coordUnits;

		int AddTextureCoordRead (int maxCoords, BaseTexture *texture); // -1 if failed
		int AddTextureRead (int maxUnits, BaseTexture *texture); // -1 if failed
	};

	class ShaderDef
	{
	public:
		ShaderDef() { hasLighting=useShadowMapping=false; specularExponent = 16.0f; }
		void Parse(const TdfParser& tdf, bool needNormalMap);
		void Optimize(ShaderDef* dst);
		void Output();
		void GetTextureUsage(TextureUsage* tu);
		
		enum StageOp
		{
			Add,
			Mul,
			Alpha,
			Blend
		};

		struct Stage {
			Stage() { source=0; operation=Mul; }

			std::string sourceName; // owned by stage
			BaseTexture *source; // not owned
			StageOp operation;
		};

		std::vector<Stage> normalMapStages;
		std::vector<Stage> stages;
		bool hasLighting, useShadowMapping;
		float specularExponent;

		static void OptimizeStages(std::vector<Stage>& src, std::vector<Stage>& dst);
		static void LoadStages(int numStages, const char *stagename, const TdfParser& tdf, std::vector<Stage>& stages);
	};

	struct NodeSetupParams
	{
		const std::vector<Blendmap*>* blendmaps;
		const std::vector<TiledTexture*>* textures;
		const Vector3* wsLightDir, *wsEyePos;
		int pass;

		ShadowMapParams *shadowMapParams;
	};

	enum PassBlendop
	{
		Pass_Mul, 
		Pass_Add, 
		Pass_Replace,         // color = src
		Pass_Interpolate,      // interpolate dest and src using src alpha
		Pass_MulColor
	};


	struct RenderPass 
	{ // a renderpass
		RenderPass() { shaderSetup=0; depthWrite=false; operation=Pass_Replace; invertAlpha=false;}
		IShaderSetup * shaderSetup; 
		PassBlendop operation;
		bool depthWrite;
		bool invertAlpha; // in case of Pass_Interpolate
	};

	struct RenderSetup
	{
		~RenderSetup ();
		void Clear();
		void DebugOutput();

		std::vector <RenderPass> passes;
		ShaderDef shaderDef;
	};

	struct RenderSetupCollection
	{
		RenderSetupCollection () { sortkey=0;currentShaderSetup=0; }
		~RenderSetupCollection ();

		std::vector <RenderSetup *> renderSetup;

		// nodesetup sorting key, terrain nodes are sorted by this key, to minimize state changes
		uint sortkey;
		uint vertexDataReq; // vertex data requirements, calculated by OR'ing all return values of GetVertexDataRequirements()
		IShaderSetup* currentShaderSetup;
	};

	// base class for the FragmentProgramHandler (fragment programs) and TexEnvSetupHandler (texture env combine)
	struct ITexShaderHandler
	{
		ITexShaderHandler () {}
		virtual ~ITexShaderHandler() {}

		virtual bool SetupShader (IShaderSetup *shader, NodeSetupParams& params) = 0;// returns false if it doesn't have to be drawn

		virtual void BeginPass (const std::vector<Blendmap*>& blendmaps, const std::vector<TiledTexture*>& textures, int pass) = 0;
		virtual void EndPass () = 0;

		virtual void EndTexturing () {}
		virtual void BeginTexturing () {}

		// true for FragmentProgram, false for TexEnvCombine
		virtual int MaxTextureUnits () = 0;
		virtual int MaxTextureCoords () = 0;

		// Construction
		virtual void BuildNodeSetup (ShaderDef* shaderDef, RenderSetup *rs) = 0;
		virtual void BeginBuild() {}
		virtual void EndBuild() {}
	};

	struct QuadMap;
	struct ILoadCallback;
	struct Config;
	struct IFontRenderer;
	struct LightingInfo;

	class TerrainTexture
	{
	public:
		TerrainTexture();
		~TerrainTexture();

		void Load (const TdfParser *parser, Heightmap *heightmap, TQuad *quadTree, const std::vector<QuadMap*>& qmaps, Config *cfg, ILoadCallback *cb, LightingInfo* li);
		void ReloadShaders (TQuad *quadtree, Config *cfg);

		int NumPasses ();

		void BeginTexturing ();
		void EndTexturing ();

		void BeginPass(int p);
		void EndPass();

		bool SetupNode (TQuad *q, int pass);

		void DebugPrint (IFontRenderer *fr);
		void DebugEvent (const std::string& event);

		void SetShaderParams (const Vector3& lv, const Vector3& eyePos); // world space light vector
		void SetShadowMapParams (const ShadowMapParams *smp);
		
		int debugShader;
	protected:
		// Calculate blending factors for textures with blending defined by terrain properties
		void GenerateBlendmap (Blendmap* bm, Heightmap *heightmap, int level);
		void InstantiateShaders (Config *cfg, ILoadCallback *cb);
		BaseTexture* LoadImageSource(const std::string& texName, const std::string& basepath, Heightmap *heightmap, ILoadCallback *cb, Config *cfg, bool isBumpmap=false);

		bool SetupShading (RenderPass *p, int passIndex);

		struct GenerateInfo;
		void CreateTexProg (TQuad *node, GenerateInfo* gi);
		void ReloadTexProg (TQuad *node, TerrainTexture::GenerateInfo *gi);

		// Calculate sorting key based on current blendmap optimization state (Blendmap::curAreaResult)
		uint CalcBlendmapSortKey (); 

		int heightmapW;
		int blendmapLOD; // lod level from which blendmaps are generated
		bool useBumpMaps;
		float optimizeEpsilon; // epsilon value used for texturing optimization, read from map
		DetailBumpmap detailBumpmap;

		// nearby shader, possibly tangent space bumpmapping
		// far away shader, world space bumpmapping based on heightmap

		struct ShaderDesc
		{
			ShaderDesc() { index=0; }
			ShaderDef def;
			int index;
		};

		ShaderDesc unlitShader;
		ShaderDesc farShader;
		ShaderDesc nearShader;
		std::vector<ShaderDesc*> shaders;

		RenderSetup *currentRenderSetup;

		ITexShaderHandler* shaderHandler;
		Vector3 wsLightDir, wsEyePos;

		std::vector <Blendmap *> blendMaps;
		std::vector <TiledTexture *> textures;

		std::vector <RenderSetupCollection*> texNodeSetup;
		int maxPasses; // the highest number of passes a RenderSetupCollection requires (some nodes might need less passes than this)

		//only valid during loading
		const TdfParser *tdfParser;

		Lightmap *lightmap;
		ShaderDef shaderDef;

		TiledTexture *flatBumpmap;
		ShadowMapParams *shadowMapParams;
	};
	void SetTexGen (float scale);
};