/*
Minetest
Copyright (C) 2013 sapier, sapier at gmx dot net
Copyright (C) 2016 est31, <MTest31@outlook.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

/******************************************************************************/
/* Includes                                                                   */
/******************************************************************************/

#include "pathfinder.h"
#include "serverenvironment.h"
#include "server.h"
#include "nodedef.h"

//#define PATHFINDER_DEBUG
//#define PATHFINDER_CALC_TIME

#ifdef PATHFINDER_DEBUG
	#include <string>
#endif
#ifdef PATHFINDER_DEBUG
	#include <iomanip>
#endif
#ifdef PATHFINDER_CALC_TIME
	#include <sys/time.h>
#endif

/******************************************************************************/
/* Typedefs and macros                                                        */
/******************************************************************************/

#define LVL "(" << level << ")" <<

#ifdef PATHFINDER_DEBUG
#define DEBUG_OUT(a)     std::cout << a
#define INFO_TARGET      std::cout
#define VERBOSE_TARGET   std::cout
#define ERROR_TARGET     std::cout
#else
#define DEBUG_OUT(a)     while(0)
#define INFO_TARGET      infostream << "Pathfinder: "
#define VERBOSE_TARGET   verbosestream << "Pathfinder: "
#define ERROR_TARGET     warningstream << "Pathfinder: "
#endif

/******************************************************************************/
/* Class definitions                                                          */
/******************************************************************************/


/** representation of cost in specific direction */
class PathCost {
public:

	/** default constructor */
	PathCost() = default;

	/** copy constructor */
	PathCost(const PathCost &b);

	/** assignment operator */
	PathCost &operator= (const PathCost &b);

	bool valid = false;              /**< movement is possible         */
	int  value = 0;                  /**< cost of movement             */
	int  direction = 0;              /**< y-direction of movement      */
	bool updated = false;            /**< this cost has ben calculated */

};


/** representation of a mapnode to be used for pathfinding */
class PathGridnode {

public:
	/** default constructor */
	PathGridnode() = default;

	/** copy constructor */
	PathGridnode(const PathGridnode &b);

	/**
	 * assignment operator
	 * @param b node to copy
	 */
	PathGridnode &operator= (const PathGridnode &b);

	/**
	 * read cost in a specific direction
	 * @param dir direction of cost to fetch
	 */
	PathCost getCost(v3s16 dir);

	/**
	 * set cost value for movement
	 * @param dir direction to set cost for
	 * @cost cost to set
	 */
	void      setCost(v3s16 dir, const PathCost &cost);

	bool      valid = false;               /**< node is on surface                    */
	bool      target = false;              /**< node is target position               */
	bool      source = false;              /**< node is stating position              */
	int       totalcost = -1;              /**< cost to move here from starting point */
	v3s16     sourcedir;                   /**< origin of movement for current cost   */
	v3s16     pos;                         /**< real position of node                 */
	PathCost directions[4];                /**< cost in different directions          */

	/* debug values */
	bool      is_element = false;          /**< node is element of path detected      */
	char      type = 'u';                  /**< type of node                          */
};

class Pathfinder;

/** Abstract class to manage the map data */
class GridNodeContainer {
public:
	virtual PathGridnode &access(v3s16 p)=0;
	virtual ~GridNodeContainer() = default;

protected:
	Pathfinder *m_pathf;

	void initNode(v3s16 ipos, PathGridnode *p_node);
};

class ArrayGridNodeContainer : public GridNodeContainer {
public:
	virtual ~ArrayGridNodeContainer() = default;

	ArrayGridNodeContainer(Pathfinder *pathf, v3s16 dimensions);
	virtual PathGridnode &access(v3s16 p);
private:
	v3s16 m_dimensions;

	int m_x_stride;
	int m_y_stride;
	std::vector<PathGridnode> m_nodes_array;
};

class MapGridNodeContainer : public GridNodeContainer {
public:
	virtual ~MapGridNodeContainer() = default;

	MapGridNodeContainer(Pathfinder *pathf);
	virtual PathGridnode &access(v3s16 p);
private:
	std::map<v3s16, PathGridnode> m_nodes;
};

/** class doing pathfinding */
class Pathfinder {

public:
	/**
	 * default constructor
	 */
	Pathfinder() = default;

	~Pathfinder();

	/**
	 * path evaluation function
	 * @param env environment to look for path
	 * @param source origin of path
	 * @param destination end position of path
	 * @param searchdistance maximum number of nodes to look in each direction
	 * @param max_jump maximum number of blocks a path may jump up
	 * @param max_drop maximum number of blocks a path may drop
	 * @param algo Algorithm to use for finding a path
	 */
	std::vector<v3s16> getPath(ServerEnvironment *env,
			v3s16 source,
			v3s16 destination,
			unsigned int searchdistance,
			unsigned int max_jump,
			unsigned int max_drop,
			PathAlgorithm algo);

private:
	/* helper functions */

	/**
	 * transform index pos to mappos
	 * @param ipos a index position
	 * @return map position
	 */
	v3s16          getRealPos(v3s16 ipos);

	/**
	 * transform mappos to index pos
	 * @param pos a real pos
	 * @return index position
	 */
	v3s16          getIndexPos(v3s16 pos);

	/**
	 * get gridnode at a specific index position
	 * @param ipos index position
	 * @return gridnode for index
	 */
	PathGridnode &getIndexElement(v3s16 ipos);

	/**
	 * Get gridnode at a specific index position
	 * @return gridnode for index
	 */
	PathGridnode &getIdxElem(s16 x, s16 y, s16 z);

	/**
	 * invert a 3d position
	 * @param pos 3d position
	 * @return pos *-1
	 */
	v3s16          invert(v3s16 pos);

	/**
	 * check if a index is within current search area
	 * @param index position to validate
	 * @return true/false
	 */
	bool           isValidIndex(v3s16 index);

	/**
	 * translate position to float position
	 * @param pos integer position
	 * @return float position
	 */
	v3f            tov3f(v3s16 pos);


	/* algorithm functions */

	/**
	 * calculate 2d manahttan distance to target on the xz plane
	 * @param pos position to calc distance
	 * @return integer distance
	 */
	int           getXZManhattanDist(v3s16 pos);

	/**
	 * get best direction based uppon heuristics
	 * @param directions list of unchecked directions
	 * @param g_pos mapnode to start from
	 * @return direction to check
	 */
	v3s16         getDirHeuristic(std::vector<v3s16> &directions, PathGridnode &g_pos);

	/**
	 * build internal data representation of search area
	 * @return true/false if costmap creation was successfull
	 */
	bool          buildCostmap();

	/**
	 * calculate cost of movement
	 * @param pos real world position to start movement
	 * @param dir direction to move to
	 * @return cost information
	 */
	PathCost     calcCost(v3s16 pos, v3s16 dir);

	/**
	 * recursive update whole search areas total cost information
	 * @param ipos position to check next
	 * @param srcdir positionc checked last time
	 * @param total_cost cost of moving to ipos
	 * @param level current recursion depth
	 * @return true/false path to destination has been found
	 */
	bool          updateAllCosts(v3s16 ipos, v3s16 srcdir, int current_cost, int level);

	/**
	 * recursive try to find a patrh to destionation
	 * @param ipos position to check next
	 * @param srcdir positionc checked last time
	 * @param total_cost cost of moving to ipos
	 * @param level current recursion depth
	 * @return true/false path to destination has been found
	 */
	bool          updateCostHeuristic(v3s16 ipos, v3s16 srcdir, int current_cost, int level);

	/**
	 * recursive build a vector containing all nodes from source to destination
	 * @param path vector to add nodes to
	 * @param pos pos to check next
	 * @param level recursion depth
	 */
	void          buildPath(std::vector<v3s16> &path, v3s16 pos, int level);

	/* variables */
	int m_max_index_x = 0;            /**< max index of search area in x direction  */
	int m_max_index_y = 0;            /**< max index of search area in y direction  */
	int m_max_index_z = 0;            /**< max index of search area in z direction  */


	int m_searchdistance = 0;         /**< max distance to search in each direction */
	int m_maxdrop = 0;                /**< maximum number of blocks a path may drop */
	int m_maxjump = 0;                /**< maximum number of blocks a path may jump */
	int m_min_target_distance = 0;    /**< current smalest path to target           */

	bool m_prefetch = true;              /**< prefetch cost data                       */

	v3s16 m_start;                /**< source position                          */
	v3s16 m_destination;          /**< destination position                     */

	core::aabbox3d<s16> m_limits; /**< position limits in real map coordinates  */

	/** contains all map data already collected and analyzed.
		Access it via the getIndexElement/getIdxElem methods. */
	friend class GridNodeContainer;
	GridNodeContainer *m_nodes_container = nullptr;

	ServerEnvironment *m_env = 0;     /**< minetest environment pointer             */

#ifdef PATHFINDER_DEBUG

	/**
	 * print collected cost information
	 */
	void printCost();

	/**
	 * print collected cost information in a specific direction
	 * @param dir direction to print
	 */
	void printCost(PathDirections dir);

	/**
	 * print type of node as evaluated
	 */
	void printType();

	/**
	 * print pathlenght for all nodes in search area
	 */
	void printPathLen();

	/**
	 * print a path
	 * @param path path to show
	 */
	void printPath(std::vector<v3s16> path);

	/**
	 * print y direction for all movements
	 */
	void printYdir();

	/**
	 * print y direction for moving in a specific direction
	 * @param dir direction to show data
	 */
	void printYdir(PathDirections dir);

	/**
	 * helper function to translate a direction to speaking text
	 * @param dir direction to translate
	 * @return textual name of direction
	 */
	std::string dirToName(PathDirections dir);
#endif
};

/******************************************************************************/
/* implementation                                                             */
/******************************************************************************/

std::vector<v3s16> get_path(ServerEnvironment* env,
							v3s16 source,
							v3s16 destination,
							unsigned int searchdistance,
							unsigned int max_jump,
							unsigned int max_drop,
							PathAlgorithm algo)
{
	Pathfinder searchclass;

	return searchclass.getPath(env,
				source, destination,
				searchdistance, max_jump, max_drop, algo);
}

/******************************************************************************/
PathCost::PathCost(const PathCost &b)
{
	valid     = b.valid;
	direction = b.direction;
	value     = b.value;
	updated   = b.updated;
}

/******************************************************************************/
PathCost &PathCost::operator= (const PathCost &b)
{
	valid     = b.valid;
	direction = b.direction;
	value     = b.value;
	updated   = b.updated;

	return *this;
}

/******************************************************************************/
PathGridnode::PathGridnode(const PathGridnode &b)
:	valid(b.valid),
	target(b.target),
	source(b.source),
	totalcost(b.totalcost),
	sourcedir(b.sourcedir),
	pos(b.pos),
	is_element(b.is_element),
	type(b.type)
{

	directions[DIR_XP] = b.directions[DIR_XP];
	directions[DIR_XM] = b.directions[DIR_XM];
	directions[DIR_ZP] = b.directions[DIR_ZP];
	directions[DIR_ZM] = b.directions[DIR_ZM];
}

/******************************************************************************/
PathGridnode &PathGridnode::operator= (const PathGridnode &b)
{
	valid      = b.valid;
	target     = b.target;
	source     = b.source;
	is_element = b.is_element;
	totalcost  = b.totalcost;
	sourcedir  = b.sourcedir;
	pos        = b.pos;
	type       = b.type;

	directions[DIR_XP] = b.directions[DIR_XP];
	directions[DIR_XM] = b.directions[DIR_XM];
	directions[DIR_ZP] = b.directions[DIR_ZP];
	directions[DIR_ZM] = b.directions[DIR_ZM];

	return *this;
}

/******************************************************************************/
PathCost PathGridnode::getCost(v3s16 dir)
{
	if (dir.X > 0) {
		return directions[DIR_XP];
	}
	if (dir.X < 0) {
		return directions[DIR_XM];
	}
	if (dir.Z > 0) {
		return directions[DIR_ZP];
	}
	if (dir.Z < 0) {
		return directions[DIR_ZM];
	}
	PathCost retval;
	return retval;
}

/******************************************************************************/
void PathGridnode::setCost(v3s16 dir, const PathCost &cost)
{
	if (dir.X > 0) {
		directions[DIR_XP] = cost;
	}
	if (dir.X < 0) {
		directions[DIR_XM] = cost;
	}
	if (dir.Z > 0) {
		directions[DIR_ZP] = cost;
	}
	if (dir.Z < 0) {
		directions[DIR_ZM] = cost;
	}
}

void GridNodeContainer::initNode(v3s16 ipos, PathGridnode *p_node)
{
	INodeDefManager *ndef = m_pathf->m_env->getGameDef()->ndef();
	PathGridnode &elem = *p_node;

	v3s16 realpos = m_pathf->getRealPos(ipos);

	MapNode current = m_pathf->m_env->getMap().getNodeNoEx(realpos);
	MapNode below   = m_pathf->m_env->getMap().getNodeNoEx(realpos + v3s16(0, -1, 0));


	if ((current.param0 == CONTENT_IGNORE) ||
			(below.param0 == CONTENT_IGNORE)) {
		DEBUG_OUT("Pathfinder: " << PP(realpos) <<
			" current or below is invalid element" << std::endl);
		if (current.param0 == CONTENT_IGNORE) {
			elem.type = 'i';
			DEBUG_OUT(PP(ipos) << ": " << 'i' << std::endl);
		}
		return;
	}

	//don't add anything if it isn't an air node
	if (ndef->get(current).walkable || !ndef->get(below).walkable) {
			DEBUG_OUT("Pathfinder: " << PP(realpos)
				<< " not on surface" << std::endl);
			if (ndef->get(current).walkable) {
				elem.type = 's';
				DEBUG_OUT(PP(ipos) << ": " << 's' << std::endl);
			} else {
				elem.type = '-';
				DEBUG_OUT(PP(ipos) << ": " << '-' << std::endl);
			}
			return;
	}

	elem.valid = true;
	elem.pos   = realpos;
	elem.type  = 'g';
	DEBUG_OUT(PP(ipos) << ": " << 'a' << std::endl);

	if (m_pathf->m_prefetch) {
		elem.directions[DIR_XP] = m_pathf->calcCost(realpos, v3s16( 1, 0, 0));
		elem.directions[DIR_XM] = m_pathf->calcCost(realpos, v3s16(-1, 0, 0));
		elem.directions[DIR_ZP] = m_pathf->calcCost(realpos, v3s16( 0, 0, 1));
		elem.directions[DIR_ZM] = m_pathf->calcCost(realpos, v3s16( 0, 0,-1));
	}
}

ArrayGridNodeContainer::ArrayGridNodeContainer(Pathfinder *pathf, v3s16 dimensions) :
	m_x_stride(dimensions.Y * dimensions.Z),
	m_y_stride(dimensions.Z)
{
	m_pathf = pathf;

	m_nodes_array.resize(dimensions.X * dimensions.Y * dimensions.Z);
	INFO_TARGET << "Pathfinder ArrayGridNodeContainer constructor." << std::endl;
	for (int x = 0; x < dimensions.X; x++) {
		for (int y = 0; y < dimensions.Y; y++) {
			for (int z= 0; z < dimensions.Z; z++) {
				v3s16 ipos(x, y, z);
				initNode(ipos, &access(ipos));
			}
		}
	}
}

PathGridnode &ArrayGridNodeContainer::access(v3s16 p)
{
	return m_nodes_array[p.X * m_x_stride + p.Y * m_y_stride + p.Z];
}

MapGridNodeContainer::MapGridNodeContainer(Pathfinder *pathf)
{
	m_pathf = pathf;
}

PathGridnode &MapGridNodeContainer::access(v3s16 p)
{
	std::map<v3s16, PathGridnode>::iterator it = m_nodes.find(p);
	if (it != m_nodes.end()) {
		return it->second;
	}
	PathGridnode &n = m_nodes[p];
	initNode(p, &n);
	return n;
}



/******************************************************************************/
std::vector<v3s16> Pathfinder::getPath(ServerEnvironment *env,
							v3s16 source,
							v3s16 destination,
							unsigned int searchdistance,
							unsigned int max_jump,
							unsigned int max_drop,
							PathAlgorithm algo)
{
#ifdef PATHFINDER_CALC_TIME
	timespec ts;
	clock_gettime(CLOCK_REALTIME, &ts);
#endif
	std::vector<v3s16> retval;

	//check parameters
	if (env == 0) {
		ERROR_TARGET << "missing environment pointer" << std::endl;
		return retval;
	}

	m_searchdistance = searchdistance;
	m_env = env;
	m_maxjump = max_jump;
	m_maxdrop = max_drop;
	m_start       = source;
	m_destination = destination;
	m_min_target_distance = -1;
	m_prefetch = true;

	if (algo == PA_PLAIN_NP) {
		m_prefetch = false;
	}

	int min_x = MYMIN(source.X, destination.X);
	int max_x = MYMAX(source.X, destination.X);

	int min_y = MYMIN(source.Y, destination.Y);
	int max_y = MYMAX(source.Y, destination.Y);

	int min_z = MYMIN(source.Z, destination.Z);
	int max_z = MYMAX(source.Z, destination.Z);

	m_limits.MinEdge.X = min_x - searchdistance;
	m_limits.MinEdge.Y = min_y - searchdistance;
	m_limits.MinEdge.Z = min_z - searchdistance;

	m_limits.MaxEdge.X = max_x + searchdistance;
	m_limits.MaxEdge.Y = max_y + searchdistance;
	m_limits.MaxEdge.Z = max_z + searchdistance;

	v3s16 diff = m_limits.MaxEdge - m_limits.MinEdge;

	m_max_index_x = diff.X;
	m_max_index_y = diff.Y;
	m_max_index_z = diff.Z;

	delete m_nodes_container;
	if (diff.getLength() > 5) {
		m_nodes_container = new MapGridNodeContainer(this);
	} else {
		m_nodes_container = new ArrayGridNodeContainer(this, diff);
	}
#ifdef PATHFINDER_DEBUG
	printType();
	printCost();
	printYdir();
#endif

	//validate and mark start and end pos
	v3s16 StartIndex  = getIndexPos(source);
	v3s16 EndIndex    = getIndexPos(destination);

	PathGridnode &startpos = getIndexElement(StartIndex);
	PathGridnode &endpos   = getIndexElement(EndIndex);

	if (!startpos.valid) {
		VERBOSE_TARGET << "invalid startpos" <<
				"Index: " << PP(StartIndex) <<
				"Realpos: " << PP(getRealPos(StartIndex)) << std::endl;
		return retval;
	}
	if (!endpos.valid) {
		VERBOSE_TARGET << "invalid stoppos" <<
				"Index: " << PP(EndIndex) <<
				"Realpos: " << PP(getRealPos(EndIndex)) << std::endl;
		return retval;
	}

	endpos.target      = true;
	startpos.source    = true;
	startpos.totalcost = 0;

	bool update_cost_retval = false;

	switch (algo) {
		case PA_DIJKSTRA:
			update_cost_retval = updateAllCosts(StartIndex, v3s16(0, 0, 0), 0, 0);
			break;
		case PA_PLAIN_NP:
		case PA_PLAIN:
			update_cost_retval = updateCostHeuristic(StartIndex, v3s16(0, 0, 0), 0, 0);
			break;
		default:
			ERROR_TARGET << "missing PathAlgorithm"<< std::endl;
			break;
	}

	if (update_cost_retval) {

#ifdef PATHFINDER_DEBUG
		std::cout << "Path to target found!" << std::endl;
		printPathLen();
#endif

		//find path
		std::vector<v3s16> path;
		buildPath(path, EndIndex, 0);

#ifdef PATHFINDER_DEBUG
		std::cout << "Full index path:" << std::endl;
		printPath(path);
#endif

		//finalize path
		std::vector<v3s16> full_path;
		for (const v3s16 &i : path) {
			full_path.push_back(getIndexElement(i).pos);
		}