
#pragma once

/*
// Needed Fwds: cPath
enum class ePathFinderStatus;
class cPath;
*/

#include "../FastRandom.h"
#ifdef COMPILING_PATHFIND_DEBUGGER
	/* Note: the COMPILING_PATHFIND_DEBUGGER flag is used by Native / WiseOldMan95 to debug
	this class outside of MCServer. This preprocessor flag is never set when compiling MCServer. */
	#include "PathFinderIrrlicht_Head.h"
#endif

#include <unordered_map>

//fwd: ../Chunk.h
class cChunk;

/* Various little structs and classes */
enum class ePathFinderStatus {CALCULATING,  PATH_FOUND,  PATH_NOT_FOUND, NEARBY_FOUND};
enum class eCellStatus {OPENLIST,  CLOSEDLIST,  NOLIST};
struct cPathCell
{
	Vector3i m_Location;   // Location of the cell in the world.
	int m_F, m_G, m_H;  // F, G, H as defined in regular A*.
	eCellStatus m_Status;  // Which list is the cell in? Either non, open, or closed.
	cPathCell * m_Parent;  // Cell's parent, as defined in regular A*.
	bool m_IsSolid;	   // Is the cell an air or a solid? Partial solids are currently considered solids.
};





class compareHeuristics
{
public:
	bool operator()(cPathCell * & a_V1,  cPathCell * &  a_V2);
};





class cPath
{
public:
	/** Creates a pathfinder instance. A Mob will probably need a single pathfinder instance for its entire life.

	Note that if you have a man-sized mob (1x1x2, zombies, etc), you are advised to call this function without parameters
	because the declaration might change in later version of the pathFinder, and a parameter-less call always assumes a man-sized mob.

	If your mob is not man-sized, you are advised to use cPath(width, height), this would be compatible with future versions,
	but please be aware that as of now those parameters will be ignored and your mob will be assumed to be man sized.

	@param a_BoundingBoxWidth the character's boundingbox width in blocks. Currently the parameter is ignored and 1 is assumed.
	@param a_BoundingBoxHeight the character's boundingbox width in blocks. Currently the parameter is ignored and 2 is assumed.
	@param a_MaxUp the character's max jump height in blocks. Currently the parameter is ignored and 1 is assumed.
	@param a_MaxDown How far is the character willing to fall? Currently the parameter is ignored and 1 is assumed. */
	/** Attempts to find a path starting from source to destination.
	After calling this, you are expected to call Step() once per tick or once per several ticks until it returns true. You should then call getPath() to obtain the path.
	Calling this before a path is found resets the current path and starts another search.
	@param a_StartingPoint The function expects this position to be the lowest block the mob is in, a rule of thumb: "The block where the Zombie's knees are at".
	@param a_EndingPoint "The block where the Zombie's knees want to be".
	@param a_MaxSteps The maximum steps before giving up. */
	cPath(
		cChunk & a_Chunk,
		const Vector3d & a_StartingPoint, const Vector3d & a_EndingPoint, int a_MaxSteps,
		double a_BoundingBoxWidth, double a_BoundingBoxHeight,
		int a_MaxUp = 1, int a_MaxDown = 1
	);

	/** Destroys the path and frees its memory. */
	~cPath();

	/** Performs part of the path calculation and returns the appropriate status.
	If NEARBY_FOUND is returned, it means that the destination is not reachable, but a nearby destination
	is reachable. If the user likes the alternative destination, they can call AcceptNearbyPath to treat the path as found,
	and to make consequent calls to step return PATH_FOUND*/
	ePathFinderStatus Step(cChunk & a_Chunk);

	/** Called after the PathFinder's step returns NEARBY_FOUND.
	Changes the PathFinder status from NEARBY_FOUND to PATH_FOUND, returns the nearby destination that
	the PathFinder found a path to. */
	Vector3i AcceptNearbyPath();

	/* Point retrieval functions, inlined for performance. */
	/** Returns the next point in the path. */
	inline Vector3d GetNextPoint()
	{
		ASSERT(m_Status == ePathFinderStatus::PATH_FOUND);
		Vector3i Point = m_PathPoints[m_PathPoints.size() - 1 - (++m_CurrentPoint)];
		return Vector3d(Point.x + m_HalfWidth, Point.y, Point.z + m_HalfWidth);
	}
	/** Checks whether this is the last point or not. Never call getnextPoint when this is true. */
	inline bool IsLastPoint()
	{
		ASSERT(m_Status == ePathFinderStatus::PATH_FOUND);
		return (m_CurrentPoint == m_PathPoints.size() - 1);
	}
	inline bool IsFirstPoint()
	{
		ASSERT(m_Status == ePathFinderStatus::PATH_FOUND);
		return (m_CurrentPoint == 0);
	}
	/** Get the point at a_index. Remark: Internally, the indexes are reversed. */
	inline Vector3d GetPoint(size_t a_index)
	{
		ASSERT(m_Status == ePathFinderStatus::PATH_FOUND);
		ASSERT(a_index < m_PathPoints.size());
		Vector3i Point = m_PathPoints[m_PathPoints.size() - 1 - a_index];
		return Vector3d(Point.x + m_HalfWidth, Point.y, Point.z + m_HalfWidth);
	}
	/** Returns the total number of points this path has. */
	inline size_t GetPointCount()
	{
		if (m_Status != ePathFinderStatus::PATH_FOUND)
		{
			return 0;
		}
		return m_PathPoints.size();
	}

private:

	/* General */
	bool IsSolid(const Vector3i & a_Location);  // Query our hosting world and ask it if there's a solid at a_location.
	bool Step_Internal();  // The public version just calls this version * CALCULATIONS_PER_CALL times.
	void FinishCalculation();  // Clears the memory used for calculating the path.
	void FinishCalculation(ePathFinderStatus a_NewStatus);  // Clears the memory used for calculating the path and changes the status.
	void AttemptToFindAlternative();
	void BuildPath();

	/* Openlist and closedlist management */
	void OpenListAdd(cPathCell * a_Cell);
	cPathCell * OpenListPop();
	void ProcessIfWalkable(const Vector3i &a_Location, cPathCell * a_Parent, int a_Cost);

	/* Map management */
	void ProcessCell(cPathCell * a_Cell,  cPathCell * a_Caller,  int a_GDelta);
	cPathCell * GetCell(const Vector3i & a_location);

	/* Pathfinding fields */
	std::priority_queue<cPathCell *,  std::vector<cPathCell *>,  compareHeuristics> m_OpenList;
	std::unordered_map<Vector3i, cPathCell, VectorHasher<int>> m_Map;
	Vector3i m_Destination;
	Vector3i m_Source;
	int m_BoundingBoxWidth;
	int m_BoundingBoxHeight;
	double m_HalfWidth;
	int m_StepsLeft;
	cPathCell * m_NearestPointToTarget;
	cFastRandom m_Rand;

	/* Control fields */
	ePathFinderStatus m_Status;

	/* Final path fields */
	size_t m_CurrentPoint;
	std::vector<Vector3i> m_PathPoints;

	/* Interfacing with the world */
	cChunk * m_Chunk;  // Only valid inside Step()!
	bool m_BadChunkFound;
	#ifdef COMPILING_PATHFIND_DEBUGGER
	#include "../path_irrlicht.cpp"
	#endif
};
