// PieceGenerator.h

// Declares the cBFSPieceGenerator class and cDFSPieceGenerator class 
// representing base classes for generating structures composed of individual "pieces"

/*
Each uses a slightly different approach to generating:
	- DFS extends pieces one by one until it hits the configured depth (or can't connect another piece anymore),
		then starts looking at adjacent connectors (like depth-first search).
	- BFS keeps a pool of currently-open connectors, chooses one at random and tries to place a piece on it,
		thus possibly extending the pool of open connectors (like breadth-first search).
*/





#pragma once

#include "../Defines.h"
#include "../Cuboid.h"
#include "../Noise.h"





/** Represents a single piece. Can have multiple connectors of different types where other pieces can connect. */
class cPiece
{
public:
	// Force a virtual destructor in all descendants
	virtual ~cPiece() {}
	
	struct cConnector
	{
		/** Position relative to the piece */
		Vector3i m_Pos;
		
		/** Type of the connector. Any arbitrary number; the generator connects only connectors of the same type. */
		int m_Type;
		
		/** Direction in which the connector is facing.
		Will be matched by the opposite direction for the connecting connector. */
		eBlockFace m_Direction;
		
		cConnector(int a_X, int a_Y, int a_Z, int a_Type, eBlockFace a_Direction);
		cConnector(const Vector3i & a_Pos, int a_Type, eBlockFace a_Direction);
	};
	
	typedef std::vector<cConnector> cConnectors;
	
	/** Returns all of the available connectors that the piece has.
	Each connector has a (relative) position in the piece, and a type associated with it. */
	virtual cConnectors GetConnectors(void) const = 0;
	
	/** Returns the dimensions of this piece.
	The dimensions cover the entire piece, there is no block that the piece generates outside of this size. */
	virtual Vector3i GetSize(void) const = 0;
	
	/** Returns the "hitbox" of this piece.
	A hitbox is what is compared and must not intersect other pieces' hitboxes when generating. */
	virtual cCuboid GetHitBox(void) const = 0;
	
	/** Returns true if the piece can be rotated CCW the specific number of 90-degree turns. */
	virtual bool CanRotateCCW(int a_NumRotations) const = 0;
	
	/** Returns a copy of the a_Pos after rotating the piece the specified number of CCW rotations. */
	Vector3i RotatePos(const Vector3i & a_Pos, int a_NumCCWRotations) const;

	/** Returns a copy of the connector that is rotated and then moved by the specified amounts. */
	cConnector RotateMoveConnector(const cConnector & a_Connector, int a_NumCCWRotations, int a_MoveX, int a_MoveY, int a_MoveZ) const;
	
	/** Returns the hitbox after the specified number of rotations and moved so that a_MyConnector is placed at a_ToConnectorPos. */
	cCuboid RotateHitBoxToConnector(const cConnector & a_MyConnector, const Vector3i & a_ToConnectorPos, int a_NumCCWRotations) const;
	
	/** Returns the hitbox after the specified number of CCW rotations and moved by the specified amounts. */
	cCuboid RotateMoveHitBox(int a_NumCCWRotations, int a_MoveX, int a_MoveY, int a_MoveZ) const;
};

typedef std::vector<cPiece *> cPieces;





/** This class is an interface that provides pieces for the generator. It can keep track of what pieces were
placed and adjust the returned piece vectors. */
class cPiecePool
{
public:
	// Force a virtual destructor in all descendants:
	virtual ~cPiecePool() {}
	
	/** Returns a list of pieces that contain the specified connector type.
	The cPiece pointers returned are managed by the pool and the caller doesn't free them. */
	virtual cPieces GetPiecesWithConnector(int a_ConnectorType) = 0;
	
	/** Returns the pieces that should be used as the starting point.
	Multiple starting points are supported, one of the returned piece will be chosen. */
	virtual cPieces GetStartingPieces(void) = 0;
	
	/** Called after a piece is placed, to notify the pool that it has been used.
	The pool may adjust the pieces it will return the next time. */
	virtual void PiecePlaced(const cPiece & a_Piece) = 0;
	
	/** Called when the pool has finished the current structure and should reset any piece-counters it has
	for a new structure. */
	virtual void Reset(void) = 0;
};





/** Represents a single piece that has been placed to specific coords in the world. */
class cPlacedPiece
{
public:
	cPlacedPiece(const cPlacedPiece * a_Parent, const cPiece & a_Piece, const Vector3i & a_Coords, int a_NumCCWRotations);
	
	const cPiece &   GetPiece          (void) const { return *m_Piece; }
	const Vector3i & GetCoords         (void) const { return m_Coords; }
	int              GetNumCCWRotations(void) const { return m_NumCCWRotations; }
	const cCuboid &  GetHitBox         (void) const { return m_HitBox; }
	int              GetDepth          (void) const { return m_Depth; }
	
protected:
	const cPlacedPiece * m_Parent;
	const cPiece * m_Piece;
	Vector3i m_Coords;
	int m_NumCCWRotations;
	cCuboid m_HitBox;
	int m_Depth;
};

typedef std::vector<cPlacedPiece *> cPlacedPieces;





class cPieceGenerator
{
public:
	cPieceGenerator(cPiecePool & a_PiecePool, int a_Seed);
	
	/** Cleans up all the memory used by the placed pieces.
	Call this utility function instead of freeing the items on your own. */
	static void FreePieces(cPlacedPieces & a_PlacedPieces);
	
protected:
	/** The type used for storing a connection from one piece to another, while building the piece tree. */
	struct cConnection
	{
		cPiece * m_Piece;                  // The piece being connected
		cPiece::cConnector m_Connector;    // The piece's connector being used (relative non-rotated coords)
		int m_NumCCWRotations;             // Number of rotations necessary to match the two connectors
		
		cConnection(cPiece & a_Piece, cPiece::cConnector & a_Connector, int a_NumCCWRotations);
	};
	typedef std::vector<cConnection> cConnections;
	
	/** The type used for storing a pool of connectors that will be attempted to expand by another piece. */
	struct cFreeConnector
	{
		cPlacedPiece * m_Piece;
		cPiece::cConnector m_Connector;
		
		cFreeConnector(cPlacedPiece * a_Piece, const cPiece::cConnector & a_Connector);
	};
	typedef std::vector<cFreeConnector> cFreeConnectors;


	cPiecePool & m_PiecePool;
	cNoise m_Noise;
	int m_Seed;

	
	/** Selects a starting piece and places it, including the rotations.
	Also puts the piece's connectors in a_OutConnectors. */
	cPlacedPiece * PlaceStartingPiece(int a_BlockX, int a_BlockY, int a_BlockZ, cFreeConnectors & a_OutConnectors);
	
	/** Tries to place a new piece at the specified (placed) connector. Returns true if successful. */
	bool TryPlacePieceAtConnector(
		const cPlacedPiece & a_ParentPiece,      // The existing piece to a new piece should be placed
		const cPiece::cConnector & a_Connector,  // The existing connector (world-coords) to which a new piece should be placed
		cPlacedPieces & a_OutPieces,             // Already placed pieces, to be checked for intersections
		cFreeConnectors & a_OutConnectors        // List of free connectors to which the new connectors will be placed
	);

	/** Checks if the specified piece would fit with the already-placed pieces, using the specified connector
	and number of CCW rotations.
	a_ExistingConnector is in world-coords and is already rotated properly
	a_ToPos is the world-coords position on which the new connector should be placed (1 block away from a_ExistingConnector, in its Direction)
	a_NewConnector is in the original (non-rotated) coords.
	Returns true if the piece fits, false if not. */
	bool CheckConnection(
		const cPiece::cConnector & a_ExistingConnector,  // The existing connector
		const Vector3i & a_ToPos,                        // The position on which the new connector should be placed
		const cPiece & a_Piece,                          // The new piece
		const cPiece::cConnector & a_NewConnector,       // The connector of the new piece 
		int a_NumCCWRotations,                           // Number of rotations for the new piece to align the connector
		const cPlacedPieces & a_OutPieces                // All the already-placed pieces to check
	);
	
	/** DEBUG: Outputs all the connectors in the pool into stdout.
	a_NumProcessed signals the number of connectors from the pool that should be considered processed (not listed). */
	void DebugConnectorPool(const cPieceGenerator::cFreeConnectors & a_ConnectorPool, size_t a_NumProcessed);
} ;





class cBFSPieceGenerator :
	public cPieceGenerator
{
	typedef cPieceGenerator super;
	
public:
	cBFSPieceGenerator(cPiecePool & a_PiecePool, int a_Seed);
	
	/** Generates a placement for pieces at the specified coords.
	Caller must free each individual cPlacedPiece in a_OutPieces. */
	void PlacePieces(int a_BlockX, int a_BlockY, int a_BlockZ, int a_MaxDepth, cPlacedPieces & a_OutPieces);
};





class cDFSPieceGenerator :
	public cPieceGenerator
{
public:
	cDFSPieceGenerator(cPiecePool & a_PiecePool, int a_Seed);
	
	/** Generates a placement for pieces at the specified coords.
	Caller must free each individual cPlacedPiece in a_OutPieces. */
	void PlacePieces(int a_BlockX, int a_BlockY, int a_BlockZ, cPlacedPieces & a_OutPieces);
};