path: root/src/Chunk.h

#pragma once

#include "BlockEntities/BlockEntity.h"
#include "ChunkData.h"

#include "Simulator/FireSimulator.h"
#include "Simulator/SandSimulator.h"
#include "Simulator/RedstoneSimulator.h"

#include "ChunkMap.h"





class cWorld;
class cClientHandle;
class cPlayer;
class cChunkMap;
class cBoundingBox;
class cChunkDataCallback;
class cBlockArea;
class cBlockArea;
class cFluidSimulatorData;
class cMobCensus;
class cMobSpawner;

struct SetChunkData;

typedef std::list<cClientHandle *>                cClientHandleList;

// A convenience macro for calling GetChunkAndRelByAbsolute.
#define PREPARE_REL_AND_CHUNK(Position, OriginalChunk) cChunk * Chunk; Vector3i Rel; bool RelSuccess = (OriginalChunk).GetChunkAndRelByAbsolute(Position, &Chunk, Rel)


class cChunk
{
public:

	/** Represents the presence state of the chunk */
	enum ePresence
	{
		cpInvalid,  /**< The chunk is not present at all and is not queued in the loader / generator */
		cpQueued,   /**< The chunk is not present, but is queued for loading / generation */
		cpPresent,  /**< The chunk is present */
	};

	cChunk(
		int a_ChunkX, int a_ChunkZ,   // Chunk coords
		cChunkMap * a_ChunkMap, cWorld * a_World   // Parent objects
	);
	cChunk(const cChunk & Other) = delete;
	~cChunk();

	/** Returns true iff the chunk block data is valid (loaded / generated) */
	bool IsValid(void) const {return (m_Presence == cpPresent); }

	/** Returns true iff the chunk is in the queue for loading / generating */
	bool IsQueued(void) const {return (m_Presence == cpQueued); }

	/** Sets the chunk's presence.
	Wakes up any calls to cChunkMap::GetHeight() when setting to cpPresent. */
	void SetPresence(ePresence a_Presence);

	/** Marks all clients attached to this chunk as wanting this chunk. Also sets presence to cpQueued. */
	void MarkRegenerating(void);

	/** Returns true iff the chunk has changed since it was last saved. */
	bool IsDirty(void) const {return m_IsDirty; }

	bool CanUnload(void) const;

	/** Returns true if the chunk could have been unloaded if it weren't dirty */
	bool CanUnloadAfterSaving(void) const;

	/** Called when the chunkmap unloads unused chunks.
	Notifies contained entities that they are being unloaded and should for example, broadcast a destroy packet.
	Not called during server shutdown; such cleanup during shutdown is unnecessary. */
	void OnUnload();

	bool IsLightValid(void) const {return m_IsLightValid; }

	/*
	To save a chunk, the WSSchema must:
	1. Mark the chunk as being saved (MarkSaving())
	2. Get the chunk's data using GetAllData()
	3. Mark the chunk as saved (MarkSaved())
	If anywhere inside this sequence another thread mmodifies the chunk, the chunk will not get marked as saved in MarkSaved()
	*/
	void MarkSaving(void);  // Marks the chunk as being saved.
	void MarkSaved(void);  // Marks the chunk as saved, if it didn't change from the last call to MarkSaving()
	void MarkLoaded(void);  // Marks the chunk as freshly loaded. Fails if the chunk is already valid

	/** Queues the chunk for generating. */
	void MarkLoadFailed(void);

	/** Gets all chunk data, calls the a_Callback's methods for each data type */
	void GetAllData(cChunkDataCallback & a_Callback) const;

	/** Sets all chunk data as either loaded from the storage or generated.
	BlockLight and BlockSkyLight are optional, if not present, chunk will be marked as unlighted.
	Modifies the BlockEntity list in a_SetChunkData - moves the block entities into the chunk. */
	void SetAllData(SetChunkData && a_SetChunkData);

	void SetLight(
		const cChunkDef::BlockNibbles & a_BlockLight,
		const cChunkDef::BlockNibbles & a_SkyLight
	);

	/** Writes the specified cBlockArea at the coords specified. Note that the coords may extend beyond the chunk! */
	void WriteBlockArea(cBlockArea & a_Area, int a_MinBlockX, int a_MinBlockY, int a_MinBlockZ, int a_DataTypes);

	/** Returns true if there is a block entity at the coords specified */
	bool HasBlockEntityAt(Vector3i a_BlockPos);

	/** Sets or resets the internal flag that prevents chunk from being unloaded.
	The flag is cumulative - it can be set multiple times and then needs to be un-set that many times
	before the chunk is unloadable again. */
	void Stay(bool a_Stay = true);

	/** Recence all mobs proximities to players in order to know what to do with them */
	void CollectMobCensus(cMobCensus & toFill);

	/** Try to Spawn Monsters inside chunk */
	void SpawnMobs(cMobSpawner & a_MobSpawner);

	void Tick(std::chrono::milliseconds a_Dt);

	/** Ticks a single block. Used by cWorld::TickQueuedBlocks() to tick the queued blocks */
	void TickBlock(const Vector3i a_RelPos);

	int GetPosX(void) const { return m_PosX; }
	int GetPosZ(void) const { return m_PosZ; }
	cChunkCoords GetPos() const { return {m_PosX, m_PosZ}; }

	cWorld * GetWorld(void) const { return m_World; }

	void SetBlock(Vector3i a_RelBlockPos, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta);
	// SetBlock() does a lot of work (heightmap, tickblocks, blockentities) so a BlockIdx version doesn't make sense

	void FastSetBlock(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType, BLOCKTYPE a_BlockMeta);  // Doesn't force block updates on neighbors, use for simple changes such as grass growing etc.
	void FastSetBlock(Vector3i a_RelPos, BLOCKTYPE a_BlockType, BLOCKTYPE a_BlockMeta)
	{
		FastSetBlock(a_RelPos.x, a_RelPos.y, a_RelPos.z, a_BlockType, a_BlockMeta);
	}

	BLOCKTYPE GetBlock(int a_RelX, int a_RelY, int a_RelZ) const { return m_BlockData.GetBlock({ a_RelX, a_RelY, a_RelZ }); }
	BLOCKTYPE GetBlock(Vector3i a_RelCoords) const { return m_BlockData.GetBlock(a_RelCoords); }

	void GetBlockTypeMeta(Vector3i a_RelPos, BLOCKTYPE & a_BlockType, NIBBLETYPE & a_BlockMeta) const;
	void GetBlockTypeMeta(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE & a_BlockType, NIBBLETYPE & a_BlockMeta) const
	{
		GetBlockTypeMeta({ a_RelX, a_RelY, a_RelZ }, a_BlockType, a_BlockMeta);
	}

	void GetBlockInfo(Vector3i a_RelPos, BLOCKTYPE & a_BlockType, NIBBLETYPE & a_Meta, NIBBLETYPE & a_SkyLight, NIBBLETYPE & a_BlockLight) const;

	/** Convert absolute coordinates into relative coordinates.
	Returns false on failure to obtain a valid chunk. Returns true otherwise.
	@param a_Position The position you'd like to convert, a_Position need not be in the calling chunk and can safely be out
	of its bounds, but for best performance, it should not be too far from the calling chunk.
	@param a_Chunk Returns the chunk in which a_Position is in. If a_Position is within the calling chunk's bounds,
	returns the calling chunk. For best performance, a_Position shouldn't be too far from the calling chunk.
	@param a_Rel Returns the converted relative position. Note that it is relative to the returned a_Chunk.
	The vector will not be modified if the function returns false. */
	bool GetChunkAndRelByAbsolute(const Vector3d & a_Position, cChunk ** a_Chunk, Vector3i & a_Rel);

	/** Convert absolute coordinates into relative coordinates.
	Returns false on failure to obtain a valid chunk. Returns true otherwise.
	@param a_Position The position you'd like to convert, a_Position need not be in the calling chunk and can safely be out
	of its bounds, but for best performance, it should not be too far from the calling chunk.
	@param a_Chunk Returns the chunk in which a_Position is in. If a_Position is within the calling chunk's bounds,
	returns the calling chunk. For best performance, a_Position shouldn't be too far from the calling chunk.
	@param a_Rel Returns the converted relative position. Note that it is relative to the returned a_Chunk.
	The vector will not be modified if the function returns false. */
	bool GetChunkAndRelByAbsolute(const Vector3i & a_Position, cChunk ** a_Chunk, Vector3i & a_Rel);

	/** Returns the chunk into which the specified block belongs, by walking the neighbors.
	Will return self if appropriate. Returns nullptr if not reachable through neighbors. */
	cChunk * GetNeighborChunk(int a_BlockX, int a_BlockZ);

	/** Returns the chunk into which the relatively-specified block belongs, by walking the neighbors.
	Will return self if appropriate. Returns nullptr if not reachable through neighbors. */
	cChunk * GetRelNeighborChunk(int a_RelX, int a_RelZ);

	/** Returns the chunk into which the relatively-specified block belongs.
	Also modifies the relative coords from this-relative to return-relative.
	Will return self if appropriate.
	Will try walking the neighbors first; if that fails, will query the chunkmap. */
	cChunk * GetRelNeighborChunkAdjustCoords(Vector3i & a_RelPos) const;

	EMCSBiome GetBiomeAt(int a_RelX, int a_RelZ) const {return cChunkDef::GetBiome(m_BiomeMap, a_RelX, a_RelZ); }

	/** Sets the biome at the specified relative coords.
	Doesn't resend the chunk to clients. */
	void SetBiomeAt(int a_RelX, int a_RelZ, EMCSBiome a_Biome);

	/** Sets the biome in the specified relative coords area. All the coords are inclusive.
	Sends the chunk to all relevant clients. */
	void SetAreaBiome(int a_MinRelX, int a_MaxRelX, int a_MinRelZ, int a_MaxRelZ, EMCSBiome a_Biome);

	int GetHeight( int a_X, int a_Z) const;

	/** Returns true if it is sunny at the specified location. This takes into account biomes. */
	bool IsWeatherSunnyAt(int a_RelX, int a_RelZ) const;

	/** Returns true if it is raining or storming at the specified location, taking into account biomes. */
	bool IsWeatherWetAt(int a_RelX, int a_RelZ) const;

	/** Returns true if it is raining or storming at the specified location,
	and the rain reaches (the bottom of) the specified block position. */
	bool IsWeatherWetAt(Vector3i a_Position) const;

	void SendBlockTo(int a_RelX, int a_RelY, int a_RelZ, cClientHandle * a_Client);

	/** Adds a client to the chunk; returns true if added, false if already there */
	bool AddClient(cClientHandle * a_Client);

	/** Removes the specified client from the chunk; ignored if client not in chunk. */
	void RemoveClient(cClientHandle * a_Client);

	/** Returns true if the specified client is present in this chunk. */
	bool HasClient(cClientHandle * a_Client);

	/** Returns true if theres any client in the chunk; false otherwise */
	bool HasAnyClients(void) const;

	void AddEntity(OwnedEntity a_Entity);

	/** Releases ownership of the given entity if it was found in this chunk.
	Returns an owning reference to the found entity. */
	OwnedEntity RemoveEntity(cEntity & a_Entity);

	bool HasEntity(UInt32 a_EntityID) const;

	/** Calls the callback for each entity; returns true if all entities processed, false if the callback aborted by returning true */
	bool ForEachEntity(cEntityCallback a_Callback) const;  // Lua-accessible

	/** Calls the callback for each entity that has a nonempty intersection with the specified boundingbox.
	Returns true if all entities processed, false if the callback aborted by returning true. */
	bool ForEachEntityInBox(const cBoundingBox & a_Box, cEntityCallback a_Callback) const;  // Lua-accessible

	/** Calls the callback if the entity with the specified ID is found, with the entity object as the callback param. Returns true if entity found. */
	bool DoWithEntityByID(UInt32 a_EntityID, cEntityCallback a_Callback, bool & a_CallbackResult) const;  // Lua-accessible

	/** Calls the callback for each block entity; returns true if all block entities processed, false if the callback aborted by returning true */
	bool ForEachBlockEntity(cBlockEntityCallback a_Callback);  // Lua-accessible

	/** Calls the callback for the block entity at the specified coords; returns false if there's no block entity at those coords, and whatever the callback returns if found. */
	bool DoWithBlockEntityAt(Vector3i a_Position, cBlockEntityCallback a_Callback);  // Lua-acessible

	/** Use block entity on coordinate.
	returns true if the use was successful, return false to use the block as a "normal" block */
	bool UseBlockEntity(cPlayer * a_Player, int a_X, int a_Y, int a_Z);  // [x, y, z] in world block coords

	void SendBlockEntity             (int a_BlockX, int a_BlockY, int a_BlockZ, cClientHandle & a_Client);

	Vector3i PositionToWorldPosition(Vector3i a_RelPos)
	{
		return PositionToWorldPosition(a_RelPos.x, a_RelPos.y, a_RelPos.z);
	}

	void     PositionToWorldPosition(int a_RelX, int a_RelY, int a_RelZ, int & a_BlockX, int & a_BlockY, int & a_BlockZ);
	Vector3i PositionToWorldPosition(int a_RelX, int a_RelY, int a_RelZ);

	inline void MarkDirty(void)
	{
		m_IsDirty = true;
		m_IsSaving = false;
	}

	/** Causes the specified block to be ticked on the next Tick() call.
	Plugins can use this via the cWorld:SetNextBlockToTick() API.
	Only one block coord per chunk may be set, a second call overwrites the first call */
	inline void SetNextBlockToTick(const Vector3i a_RelPos)
	{
		m_BlockToTick = a_RelPos;
	}

	inline NIBBLETYPE GetMeta(int a_RelX, int a_RelY, int a_RelZ) const
	{
		return m_BlockData.GetMeta({ a_RelX, a_RelY, a_RelZ });
	}

	NIBBLETYPE GetMeta(Vector3i a_RelPos) const { return m_BlockData.GetMeta(a_RelPos); }

	void SetMeta(int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE a_Meta)
	{
		SetMeta({ a_RelX, a_RelY, a_RelZ }, a_Meta);
	}

	inline void SetMeta(Vector3i a_RelPos, NIBBLETYPE a_Meta)
	{
		m_BlockData.SetMeta(a_RelPos, a_Meta);
		MarkDirty();
		m_PendingSendBlocks.emplace_back(m_PosX, m_PosZ, a_RelPos.x, a_RelPos.y, a_RelPos.z, GetBlock(a_RelPos), a_Meta);
	}

	/** Light alterations based on time */
	NIBBLETYPE GetTimeAlteredLight(NIBBLETYPE a_Skylight) const;

	/** Get the level of artificial light illuminating the block (0 - 15) */
	inline NIBBLETYPE GetBlockLight(Vector3i a_RelPos) const { return m_LightData.GetBlockLight(a_RelPos); }
	inline NIBBLETYPE GetBlockLight(int a_RelX, int a_RelY, int a_RelZ) const { return m_LightData.GetBlockLight({ a_RelX, a_RelY, a_RelZ }); }

	/** Get the level of sky light illuminating the block (0 - 15) independent of daytime. */
	inline NIBBLETYPE GetSkyLight(Vector3i a_RelPos) const { return m_LightData.GetSkyLight(a_RelPos); }
	inline NIBBLETYPE GetSkyLight(int a_RelX, int a_RelY, int a_RelZ) const { return m_LightData.GetSkyLight({ a_RelX, a_RelY, a_RelZ }); }

	/** Get the level of sky light illuminating the block (0 - 15), taking daytime into a account. */
	inline NIBBLETYPE GetSkyLightAltered(Vector3i a_RelPos) const { return GetTimeAlteredLight(m_LightData.GetSkyLight(a_RelPos)); }
	inline NIBBLETYPE GetSkyLightAltered(int a_RelX, int a_RelY, int a_RelZ) const { return GetSkyLightAltered({ a_RelX, a_RelY, a_RelZ }); }

	/** Same as GetBlock(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlock(Vector3i a_RelCoords, BLOCKTYPE & a_BlockType, NIBBLETYPE & a_BlockMeta) const;

	/** OBSOLETE, use the Vector3i-based overload.
	Same as GetBlock(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlock(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE & a_BlockType, NIBBLETYPE & a_BlockMeta) const
	{
		return UnboundedRelGetBlock({a_RelX, a_RelY, a_RelZ}, a_BlockType, a_BlockMeta);
	}

	/** Same as GetBlockType(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockType(Vector3i a_RelCoords, BLOCKTYPE & a_BlockType) const;

	/** OBSOLETE, use the Vector3i-based overload.
	Same as GetBlockType(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockType(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE & a_BlockType) const
	{
		return UnboundedRelGetBlockType({a_RelX, a_RelY, a_RelZ}, a_BlockType);
	}

	/** Same as GetBlockMeta(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockMeta(Vector3i a_RelPos, NIBBLETYPE & a_BlockMeta) const;

	/** OBSOLETE, use the Vector3i-based overload.
	Same as GetBlockMeta(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockMeta(int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE & a_BlockMeta) const
	{
		return UnboundedRelGetBlockMeta({a_RelX, a_RelY, a_RelZ}, a_BlockMeta);
	}

	/** Same as GetBlockBlockLight(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockBlockLight(Vector3i a_RelPos, NIBBLETYPE & a_BlockLight) const;

	/** OBSOLETE, use the Vector3i-based overload.
	Same as GetBlockBlockLight(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockBlockLight(int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE & a_BlockLight) const
	{
		return UnboundedRelGetBlockBlockLight({a_RelX, a_RelY, a_RelZ}, a_BlockLight);
	}

	/** Same as GetBlockSkyLight(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockSkyLight(Vector3i a_RelPos, NIBBLETYPE & a_SkyLight) const;

	/** OBSOLETE, use the Vector3i-based overload.
	Same as GetBlockSkyLight(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockSkyLight(int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE & a_SkyLight) const
	{
		return UnboundedRelGetBlockSkyLight({a_RelX, a_RelY, a_RelZ}, a_SkyLight);
	}

	/** Queries both BlockLight and SkyLight, relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockLights(Vector3i a_RelPos, NIBBLETYPE & a_BlockLight, NIBBLETYPE & a_SkyLight) const;

	/** OBSOLETE, use the Vector3i-based overload.
	Queries both BlockLight and SkyLight, relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelGetBlockLights(int a_RelX, int a_RelY, int a_RelZ, NIBBLETYPE & a_BlockLight, NIBBLETYPE & a_SkyLight) const
	{
		return UnboundedRelGetBlockLights({a_RelX, a_RelY, a_RelZ}, a_BlockLight, a_SkyLight);
	}

	/** Same as SetBlock(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelSetBlock(Vector3i a_RelPos, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta);

	/** OBSOLETE, use the Vector3i-based overload.
	Same as SetBlock(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelSetBlock(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta)
	{
		return UnboundedRelSetBlock({a_RelX, a_RelY, a_RelZ}, a_BlockType, a_BlockMeta);
	}

	/** Same as FastSetBlock(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelFastSetBlock(Vector3i a_RelPos, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta);

	/** OBSOLETE, use the Vector3i-based overload.
	Same as FastSetBlock(), but relative coords needn't be in this chunk (uses m_Neighbor-s or m_ChunkMap in such a case)
	Returns true on success, false if queried chunk not loaded. */
	bool UnboundedRelFastSetBlock(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta)
	{
		return UnboundedRelFastSetBlock({a_RelX, a_RelY, a_RelZ}, a_BlockType, a_BlockMeta);
	}



	// Per-chunk simulator data:
	cFireSimulatorChunkData & GetFireSimulatorData (void) { return m_FireSimulatorData; }
	cFluidSimulatorData * GetWaterSimulatorData(void) const { return m_WaterSimulatorData; }
	cFluidSimulatorData * GetLavaSimulatorData (void) const { return m_LavaSimulatorData; }
	cSandSimulatorChunkData & GetSandSimulatorData (void) { return m_SandSimulatorData; }
	cRedstoneSimulatorChunkData * GetRedstoneSimulatorData(void) const { return m_RedstoneSimulatorData; }

	/** Returns the block entity at the specified (absolute) coords.
	Returns nullptr if no such BE or outside this chunk. */
	cBlockEntity * GetBlockEntity(Vector3i a_AbsPos);

	/** OBSOLETE, use the Vector3i-based overload instead.
	Returns the block entity at the specified (absolute) coords.
	Returns nullptr if no such BE or outside this chunk. */
	cBlockEntity * GetBlockEntity(int a_BlockX, int a_BlockY, int a_BlockZ) { return GetBlockEntity({a_BlockX, a_BlockY, a_BlockZ}); }

	/** Returns the block entity at the specified (relative) coords.
	Returns nullptr if no such BE.
	Asserts that the position is a valid relative position. */
	cBlockEntity * GetBlockEntityRel(Vector3i a_RelPos);

	/** Returns true if the chunk should be ticked in the tick-thread.
	Checks if there are any clients and if the always-tick flag is set */
	bool ShouldBeTicked(void) const;

	/** Increments (a_AlwaysTicked == true) or decrements (false) the m_AlwaysTicked counter.
	If the m_AlwaysTicked counter is greater than zero, the chunk is ticked in the tick-thread regardless of
	whether it has any clients or not. When this is set, the chunk never unloads.
	This function allows nesting and task-concurrency (multiple separate tasks can request ticking and as long
	as at least one requests is active the chunk will be ticked). */
	void SetAlwaysTicked(bool a_AlwaysTicked);

	const auto & GetAllClients(void) const
	{
		return m_LoadedByClient;
	}

	/** Converts the coord relative to this chunk into an absolute coord.
	Doesn't check relative coord validity. */
	Vector3i RelativeToAbsolute(Vector3i a_RelBlockPosition) const
	{
		return cChunkDef::RelativeToAbsolute(a_RelBlockPosition, {m_PosX, m_PosZ});
	}


private:

	friend class cChunkMap;

	struct sSetBlockQueueItem
	{
		Int64 m_Tick;
		int m_RelX, m_RelY, m_RelZ;
		BLOCKTYPE m_BlockType;
		NIBBLETYPE m_BlockMeta;
		BLOCKTYPE m_PreviousType;

		sSetBlockQueueItem(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta, Int64 a_Tick, BLOCKTYPE a_PreviousBlockType) :
			m_Tick(a_Tick), m_RelX(a_RelX), m_RelY(a_RelY), m_RelZ(a_RelZ), m_BlockType(a_BlockType), m_BlockMeta(a_BlockMeta), m_PreviousType(a_PreviousBlockType)
		{
		}
	} ;

	typedef std::vector<sSetBlockQueueItem> sSetBlockQueueVector;


	/** Holds the presence status of the chunk - if it is present, or in the loader / generator queue, or unloaded */
	ePresence m_Presence;

	bool m_IsLightValid;   // True if the blocklight and skylight are calculated
	bool m_IsDirty;        // True if the chunk has changed since it was last saved
	bool m_IsSaving;       // True if the chunk is being saved

	/** Blocks that have changed and need to be sent to all clients.
	The protocol has a provision for coalescing block changes, and this is the buffer.
	It will collect the block changes that occur in a tick, before being flushed in BroadcastPendingSendBlocks. */
	sSetBlockVector m_PendingSendBlocks;

	/** Block entities that have been touched and need to be sent to all clients.
	Because block changes are buffered and we need to happen after them, this buffer exists too.
	Pointers to block entities that were destroyed are guaranteed to be removed from this array by RemoveBlockEntity. */
	std::vector<cBlockEntity *> m_PendingSendBlockEntities;

	/** A queue of relative positions to call cBlockHandler::Check on.
	Processed at the end of each tick by CheckBlocks. */
	std::queue<Vector3i> m_BlocksToCheck;

	// A critical section is not needed, because all chunk access is protected by its parent ChunkMap's csLayers
	std::vector<cClientHandle *> m_LoadedByClient;
	std::vector<OwnedEntity> m_Entities;
	cBlockEntities m_BlockEntities;

	/** Number of times the chunk has been requested to stay (by various cChunkStay objects); if zero, the chunk can be unloaded */
	unsigned m_StayCount;

	int m_PosX, m_PosZ;
	cWorld *    m_World;
	cChunkMap * m_ChunkMap;

	ChunkBlockData m_BlockData;
	ChunkLightData m_LightData;

	cChunkDef::HeightMap m_HeightMap;
	cChunkDef::BiomeMap  m_BiomeMap;

	/** Relative coords of the block to tick first in the next Tick() call.
	Plugins can use this to force a tick in a specific block, using cWorld:SetNextBlockToTick() API. */
	Vector3i m_BlockToTick;

	cChunk * m_NeighborXM;  // Neighbor at [X - 1, Z]
	cChunk * m_NeighborXP;  // Neighbor at [X + 1, Z]
	cChunk * m_NeighborZM;  // Neighbor at [X,     Z - 1]
	cChunk * m_NeighborZP;  // Neighbor at [X,     Z + 1]

	// Per-chunk simulator data:
	cFireSimulatorChunkData m_FireSimulatorData;
	cFluidSimulatorData *   m_WaterSimulatorData;
	cFluidSimulatorData *   m_LavaSimulatorData;
	cSandSimulatorChunkData m_SandSimulatorData;
	cRedstoneSimulatorChunkData * m_RedstoneSimulatorData;

	/** If greater than zero, the chunk is ticked even if it has no clients.
	Manipulated by the SetAlwaysTicked() function, allows for nested calls of the function.
	This is the support for plugin-accessible chunk tick forcing. */
	unsigned m_AlwaysTicked;

	// Pick up a random block of this chunk
	void GetRandomBlockCoords(int & a_X, int & a_Y, int & a_Z);
	void GetThreeRandomNumbers(int & a_X, int & a_Y, int & a_Z, int a_MaxX, int a_MaxY, int a_MaxZ);

	void RemoveBlockEntity(cBlockEntity * a_BlockEntity);
	void AddBlockEntity   (OwnedBlockEntity a_BlockEntity);

	/** Wakes up each simulator for its specific blocks; through all the blocks in the chunk */
	void WakeUpSimulators(void);

	/** Sends m_PendingSendBlocks to all clients */
	void BroadcastPendingBlockChanges(void);

	/** Checks the block scheduled for checking in m_ToTickBlocks[] */
	void CheckBlocks();

	/** Ticks several random blocks in the chunk */
	void TickBlocks(void);

	/** Adds snow to the top of snowy biomes and hydrates farmland / fills cauldrons in rainy biomes */
	void ApplyWeatherToTop(void);

	/** Returns the pickups that would be produced, if the specified block was dug up by a_Digger using a_Tool.
	Doesn't dig the block, only queries the block handlers and then plugins for the pickups. */
	cItems PickupsFromBlock(Vector3i a_RelPos, const cEntity * a_Digger, const cItem * a_Tool);

	/** Grows the plant at the specified position by at most a_NumStages.
	The block's Grow handler is invoked.
	Returns the number of stages the plant has grown, 0 if not a plant. */
	int GrowPlantAt(Vector3i a_RelPos, int a_NumStages = 1);

	/** Called by Tick() when an entity moves out of this chunk into a neighbor; moves the entity and sends spawn / despawn packet to clients */
	void MoveEntityToNewChunk(OwnedEntity a_Entity);

	/** Check m_Entities for cPlayer objects. */
	bool HasPlayerEntities() const;
};