// cChunkGenerator.h

// Interfaces to the cChunkGenerator class representing the thread that generates chunks

/*
The object takes requests for generating chunks and processes them in a separate thread one by one.
The requests are not added to the queue if there is already a request with the same coords
Before generating, the thread checks if the chunk hasn't been already generated.
It is theoretically possible to have multiple generator threads by having multiple instances of this object,
but then it MAY happen that the chunk is generated twice.
If the generator queue is overloaded, the generator skips chunks with no clients in them

Generating works by composing several algorithms:
Biome, TerrainHeight, TerrainComposition, Ores, Structures and SmallFoliage
Each algorithm may be chosen from a pool of available algorithms in the same class and combined with others,
based on user's preferences in the world.ini.
See http://forum.mc-server.org/showthread.php?tid=409 for details.
*/





#pragma once

#include "cIsThread.h"
#include "ChunkDef.h"





// fwd:
class cWorld;
class cIniFile;

// TODO: remove this:
class cWorldGenerator;





/** The interface that a biome generator must implement
A biome generator takes chunk coords on input and outputs an array of biome indices for that chunk on output.
The output array is sequenced in the same way as the MapChunk packet's biome data.
*/
class cBiomeGen
{
public:
	virtual ~cBiomeGen() {}  // Force a virtual destructor in descendants
	
	/// Generates biomes for the given chunk
	virtual void GenBiomes(int a_ChunkX, int a_ChunkZ, cChunkDef::BiomeMap & a_BiomeMap) = 0;
} ;





/** The interface that a terrain height generator must implement
A terrain height generator takes chunk coords on input and outputs an array of terrain heights for that chunk.
The output array is sequenced in the same way as the BiomeGen's biome data.
The generator may request biome information from the underlying BiomeGen, it may even request information for
other chunks than the one it's currently generating (possibly neighbors - for averaging)
*/
class cTerrainHeightGen
{
public:
	virtual ~cTerrainHeightGen() {}  // Force a virtual destructor in descendants
	
	/// Generates heightmap for the given chunk
	virtual void GenHeightMap(int a_ChunkX, int a_ChunkZ, cChunkDef::HeightMap & a_HeightMap) = 0;
} ;





/** The interface that a terrain composition generator must implement
Terrain composition takes chunk coords on input and outputs the blockdata for that entire chunk, along with
the list of entities. It is supposed to make use of the underlying TerrainHeightGen and BiomeGen for that purpose,
but it may request information for other chunks than the one it's currently generating from them.
*/
class cTerrainCompositionGen
{
public:
	virtual ~cTerrainCompositionGen() {}  // Force a virtual destructor in descendants
	
	virtual void ComposeTerrain(
		int a_ChunkX, int a_ChunkZ,
		cChunkDef::BlockTypes & a_BlockTypes,      // BlockTypes to be generated (the whole array gets initialized, even air)
		cChunkDef::BlockNibbles & a_BlockMeta,     // BlockMetas to be generated (the whole array gets initialized)
		const cChunkDef::HeightMap & a_HeightMap,  // The height map to fit
		const cChunkDef::BiomeMap & a_BiomeMap,    // Biomes to adhere to
		cEntityList & a_Entities,                  // Entitites may be generated along with the terrain
		cBlockEntityList & a_BlockEntities         // Block entitites may be generated (chests / furnaces / ...)
	) = 0;
} ;





/** The interface that a structure generator must implement
Structures are generated after the terrain composition took place. It should modify the blocktype data to account
for whatever structures the generator is generating.
Note that ores are considered structures too, at least from the interface point of view.
Also note that a worldgenerator may contain multiple structure generators, one for each type of structure
*/
class cStructureGen
{
public:
	virtual ~cStructureGen() {}  // Force a virtual destructor in descendants
	
	virtual void GenStructures(
		int a_ChunkX, int a_ChunkZ,
		cChunkDef::BlockTypes & a_BlockTypes,   // Block types to read and change
		cChunkDef::BlockNibbles & a_BlockMeta,  // Block meta to read and change
		cChunkDef::HeightMap & a_HeightMap,     // Height map to read and change by the current data
		cEntityList & a_Entities,               // Entities may be added or deleted
		cBlockEntityList & a_BlockEntities      // Block entities may be added or deleted
	) = 0;
} ;

typedef std::list<cStructureGen *> cStructureGenList;





/** The interface that a finisher must implement
Finisher implements small additions after all structures have been generated.
*/
class cFinishGen
{
public:
	virtual ~cFinishGen() {}  // Force a virtual destructor in descendants
	
	virtual void GenFinish(
		int a_ChunkX, int a_ChunkZ,
		cChunkDef::BlockTypes & a_BlockTypes,    // Block types to read and change
		cChunkDef::BlockNibbles & a_BlockMeta,   // Block meta to read and change
		cChunkDef::HeightMap & a_HeightMap,      // Height map to read and change by the current data
		const cChunkDef::BiomeMap & a_BiomeMap,  // Biomes to adhere to
		cEntityList & a_Entities,                // Entities may be added or deleted
		cBlockEntityList & a_BlockEntities       // Block entities may be added or deleted
	) = 0;
} ;

typedef std::list<cFinishGen *> cFinishGenList;





/// The chunk generator itself
class cChunkGenerator :
	cIsThread
{
	typedef cIsThread super;
	
public:

	cChunkGenerator (void);
	~cChunkGenerator();

	bool Start(cWorld * a_World, cIniFile & a_IniFile);
	void Stop(void);

	void QueueGenerateChunk(int a_ChunkX, int a_ChunkY, int a_ChunkZ);  // Queues the chunk for generation; removes duplicate requests
	
	/// Generates the biomes for the specified chunk (directly, not in a separate thread)
	void GenerateBiomes(int a_ChunkX, int a_ChunkZ, cChunkDef::BiomeMap & a_BiomeMap);
	
	void WaitForQueueEmpty(void);
	
	int GetQueueLength(void);
	
	int GetSeed(void) const { return m_Seed; }
	
	EMCSBiome GetBiomeAt(int a_BlockX, int a_BlockZ);

private:

	cWorld * m_World;
	
	// The generation composition:
	cBiomeGen *              m_BiomeGen;
	cTerrainHeightGen *      m_HeightGen;
	cTerrainCompositionGen * m_CompositionGen;
	cStructureGenList        m_StructureGens;
	cFinishGenList           m_FinishGens;
	
	int m_Seed;

	cCriticalSection m_CS;
	cChunkCoordsList m_Queue;
	cEvent           m_Event;  // Set when an item is added to the queue or the thread should terminate
	cEvent           m_evtRemoved;  // Set when an item is removed from the queue

	/// Reads the biome gen settings from the ini and initializes m_BiomeGen accordingly
	void InitBiomeGen(cIniFile & a_IniFile);
	
	/// Reads the HeightGen settings from the ini and initializes m_HeightGen accordingly
	void InitHeightGen(cIniFile & a_IniFile);
	
	/// Reads the CompositionGen settings from the ini and initializes m_CompositionGen accordingly
	void InitCompositionGen(cIniFile & a_IniFile);
	
	/// Reads the structures to generate from the ini and initializes m_StructureGens accordingly
	void InitStructureGens(cIniFile & a_IniFile);
	
	/// Reads the finishers from the ini and initializes m_FinishGens accordingly
	void InitFinishGens(cIniFile & a_IniFile);
	
	// cIsThread override:
	virtual void Execute(void) override;

	void DoGenerate(int a_ChunkX, int a_ChunkY, int a_ChunkZ);
};