/*
 * CPathfinder.h, part of VCMI engine
 *
 * Authors: listed in file AUTHORS in main folder
 *
 * License: GNU General Public License v2.0 or later
 * Full text of license available in license.txt file, in main folder
 *
 */
#pragma once

#include "VCMI_Lib.h"
#include "IGameCallback.h"
#include "HeroBonus.h"
#include "int3.h"

#include <boost/heap/priority_queue.hpp>

class CGHeroInstance;
class CGObjectInstance;
struct TerrainTile;
class CPathfinderHelper;
class CMap;
class CGWhirlpool;
class CPathfinderHelper;
class CPathfinder;
class CPathfinderConfig;

struct DLL_LINKAGE CGPathNode
{
	typedef EPathfindingLayer ELayer;

	enum ENodeAction : ui8
	{
		UNKNOWN = 0,
		EMBARK = 1,
		DISEMBARK,
		NORMAL,
		BATTLE,
		VISIT,
		BLOCKING_VISIT,
		TELEPORT_NORMAL,
		TELEPORT_BLOCKING_VISIT,
		TELEPORT_BATTLE
	};

	enum EAccessibility : ui8
	{
		NOT_SET = 0,
		ACCESSIBLE = 1, //tile can be entered and passed
		VISITABLE, //tile can be entered as the last tile in path
		BLOCKVIS,  //visitable from neighbouring tile but not passable
		FLYABLE, //can only be accessed in air layer
		BLOCKED //tile can't be entered nor visited
	};

	CGPathNode * theNodeBefore;
	int3 coord; //coordinates
	ui32 moveRemains; //remaining tiles after hero reaches the tile
	ui8 turns; //how many turns we have to wait before reachng the tile - 0 means current turn
	ELayer layer;
	EAccessibility accessible;
	ENodeAction action;
	bool locked;

	CGPathNode();
	void reset();
	void update(const int3 & Coord, const ELayer Layer, const EAccessibility Accessible);
	bool reachable() const;
};

struct DLL_LINKAGE CGPath
{
	std::vector<CGPathNode> nodes; //just get node by node

	int3 startPos() const; // start point
	int3 endPos() const; //destination point
	void convert(ui8 mode); //mode=0 -> from 'manifest' to 'object'
};

struct DLL_LINKAGE CPathsInfo
{
	typedef EPathfindingLayer ELayer;

	mutable boost::mutex pathMx;

	const CGHeroInstance * hero;
	int3 hpos;
	int3 sizes;
	boost::multi_array<CGPathNode, 4> nodes; //[w][h][level][layer]

	CPathsInfo(const int3 & Sizes);
	~CPathsInfo();
	const CGPathNode * getPathInfo(const int3 & tile) const;
	bool getPath(CGPath & out, const int3 & dst) const;
	int getDistance(const int3 & tile) const;
	const CGPathNode * getNode(const int3 & coord) const;

	CGPathNode * getNode(const int3 & coord, const ELayer layer);
};

struct DLL_LINKAGE CPathNodeInfo
{
	CGPathNode * node;
	const CGObjectInstance * nodeObject;
	const TerrainTile * tile;
	int3 coord;
	bool guarded;
	PlayerRelations::PlayerRelations objectRelations;

	CPathNodeInfo();

	virtual void setNode(CGameState * gs, CGPathNode * n, bool excludeTopObject = false);

	bool isNodeObjectVisitable() const;
};

struct DLL_LINKAGE CDestinationNodeInfo : public CPathNodeInfo
{
	CGPathNode::ENodeAction action;
	int turn;
	int movementLeft;
	bool blocked;
	bool isGuardianTile;

	CDestinationNodeInfo();

	virtual void setNode(CGameState * gs, CGPathNode * n, bool excludeTopObject = false) override;

	virtual bool isBetterWay() const;
};

class IPathfindingRule
{
public:
	virtual void process(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const = 0;
};

class DLL_LINKAGE CMovementCostRule : public IPathfindingRule
{
public:
	virtual void process(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const override;
};

class DLL_LINKAGE CLayerTransitionRule : public IPathfindingRule
{
public:
	virtual void process(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const override;
};

class DLL_LINKAGE CDestinationActionRule : public IPathfindingRule
{
public:
	virtual void process(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const override;
};

class DLL_LINKAGE CPathfinderBlockingRule : public IPathfindingRule
{
public:
	virtual void process(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const override
	{
		auto blockingReason = getBlockingReason(source, destination, pathfinderConfig, pathfinderHelper);

		destination.blocked = blockingReason != BlockingReason::NONE;
	}

protected:
	enum class BlockingReason
	{
		NONE = 0,
		SOURCE_GUARDED = 1,
		DESTINATION_GUARDED = 2,
		SOURCE_BLOCKED = 3,
		DESTINATION_BLOCKED = 4,
		DESTINATION_BLOCKVIS = 5,
		DESTINATION_VISIT = 6
	};

	virtual BlockingReason getBlockingReason(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const = 0;
};

class DLL_LINKAGE CMovementAfterDestinationRule : public CPathfinderBlockingRule
{
public:
	virtual void process(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const override;

protected:
	virtual BlockingReason getBlockingReason(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const override;
};

class DLL_LINKAGE CMovementToDestinationRule : public CPathfinderBlockingRule
{
protected:
	virtual BlockingReason getBlockingReason(
		CPathNodeInfo & source,
		CDestinationNodeInfo & destination,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) const override;
};


class INodeStorage
{
public:
	virtual CGPathNode * getInitialNode() = 0;
	virtual void resetTile(const int3 & tile, EPathfindingLayer layer, CGPathNode::EAccessibility accessibility) = 0;

	virtual std::vector<CGPathNode *> calculateNeighbours(
		CPathNodeInfo & source, 
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) = 0;

	virtual std::vector<CGPathNode *> calculateTeleportations(
		CPathNodeInfo & source, 
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) = 0;

	virtual void commit(CDestinationNodeInfo & destination, CPathNodeInfo & source) = 0;
};

class DLL_LINKAGE CNodeStorage : public INodeStorage
{
private:
	CPathsInfo & out;

public:
	CNodeStorage(CPathsInfo & pathsInfo, const CGHeroInstance * hero);

	CGPathNode * getNode(const int3 & coord, const EPathfindingLayer layer);
	virtual CGPathNode * getInitialNode() override;

	virtual std::vector<CGPathNode *> calculateNeighbours(
		CPathNodeInfo & source,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) override;

	virtual std::vector<CGPathNode *> calculateTeleportations(
		CPathNodeInfo & source,
		CPathfinderConfig * pathfinderConfig,
		CPathfinderHelper * pathfinderHelper) override;

	virtual void resetTile(
		const int3 & tile, 
		EPathfindingLayer layer, 
		CGPathNode::EAccessibility accessibility) override;

	virtual void commit(CDestinationNodeInfo & destination, CPathNodeInfo & source) override;
};

struct DLL_LINKAGE PathfinderOptions
{
	bool useFlying;
	bool useWaterWalking;
	bool useEmbarkAndDisembark;
	bool useTeleportTwoWay; // Two-way monoliths and Subterranean Gate
	bool useTeleportOneWay; // One-way monoliths with one known exit only
	bool useTeleportOneWayRandom; // One-way monoliths with more than one known exit
	bool useTeleportWhirlpool; // Force enabled if hero protected or unaffected (have one stack of one creature)

							   /// TODO: Find out with client and server code, merge with normal teleporters.
							   /// Likely proper implementation would require some refactoring of CGTeleport.
							   /// So for now this is unfinished and disabled by default.
	bool useCastleGate;

	/// If true transition into air layer only possible from initial node.
	/// This is drastically decrease path calculation complexity (and time).
	/// Downside is less MP effective paths calculation.
	///
	/// TODO: If this option end up useful for slow devices it's can be improved:
	/// - Allow transition into air layer not only from initial position, but also from teleporters.
	///   Movement into air can be also allowed when hero disembarked.
	/// - Other idea is to allow transition into air within certain radius of N tiles around hero.
	///   Patrol support need similar functionality so it's won't be ton of useless code.
	///   Such limitation could be useful as it's can be scaled depend on device performance.
	bool lightweightFlyingMode;

	/// This option enable one turn limitation for flying and water walking.
	/// So if we're out of MP while cp is blocked or water tile we won't add dest tile to queue.
	///
	/// Following imitation is default H3 mechanics, but someone may want to disable it in mods.
	/// After all this limit should benefit performance on maps with tons of water or blocked tiles.
	///
	/// TODO:
	/// - Behavior when option is disabled not implemented and will lead to crashes.
	bool oneTurnSpecialLayersLimit;

	/// VCMI have different movement rules to solve flaws original engine has.
	/// If this option enabled you'll able to do following things in fly:
	/// - Move from blocked tiles to visitable one
	/// - Move from guarded tiles to blockvis tiles without being attacked
	/// - Move from guarded tiles to guarded visitable tiles with being attacked after
	/// TODO:
	/// - Option should also allow same tile land <-> air layer transitions.
	///   Current implementation only allow go into (from) air layer only to neighbour tiles.
	///   I find it's reasonable limitation, but it's will make some movements more expensive than in H3.
	bool originalMovementRules;

	PathfinderOptions();
};

class DLL_LINKAGE CPathfinderConfig
{
public:
	std::shared_ptr<INodeStorage> nodeStorage;
	std::vector<std::shared_ptr<IPathfindingRule>> rules;
	PathfinderOptions options;

	CPathfinderConfig(
		std::shared_ptr<INodeStorage> nodeStorage,
		std::vector<std::shared_ptr<IPathfindingRule>> rules);
};

class CPathfinder : private CGameInfoCallback
{
public:
	friend class CPathfinderHelper;

	CPathfinder(CPathsInfo & _out, CGameState * _gs, const CGHeroInstance * _hero);
	CPathfinder(
		CGameState * _gs, 
		const CGHeroInstance * _hero, 
		std::shared_ptr<CPathfinderConfig> config);

	void calculatePaths(); //calculates possible paths for hero, uses current hero position and movement left; returns pointer to newly allocated CPath or nullptr if path does not exists

private:
	typedef EPathfindingLayer ELayer;
	
	const CGHeroInstance * hero;
	const std::vector<std::vector<std::vector<ui8> > > &FoW;
	std::unique_ptr<CPathfinderHelper> hlp;
	std::shared_ptr<CPathfinderConfig> config;

	enum EPatrolState {
		PATROL_NONE = 0,
		PATROL_LOCKED = 1,
		PATROL_RADIUS
	} patrolState;
	std::unordered_set<int3, ShashInt3> patrolTiles;

	struct NodeComparer
	{
		bool operator()(const CGPathNode * lhs, const CGPathNode * rhs) const
		{
			if(rhs->turns > lhs->turns)
				return false;
			else if(rhs->turns == lhs->turns && rhs->moveRemains <= lhs->moveRemains)
				return false;

			return true;
		}
	};
	boost::heap::priority_queue<CGPathNode *, boost::heap::compare<NodeComparer> > pq;

	CPathNodeInfo source; //current (source) path node -> we took it from the queue
	CDestinationNodeInfo destination; //destination node -> it's a neighbour of source that we consider

	bool isHeroPatrolLocked() const;
	bool isPatrolMovementAllowed(const int3 & dst) const;

	bool isLayerTransitionPossible(const ELayer dstLayer) const;
	CGPathNode::ENodeAction getTeleportDestAction() const;

	bool isSourceInitialPosition() const;
	bool isSourceGuarded() const;
	bool isDestinationGuarded() const;
	bool isDestinationGuardian() const;

	void initializePatrol();
	void initializeGraph();

	CGPathNode::EAccessibility evaluateAccessibility(const int3 & pos, const TerrainTile * tinfo, const ELayer layer) const;
};

struct DLL_LINKAGE TurnInfo
{
	/// This is certainly not the best design ever and certainly can be improved
	/// Unfortunately for pathfinder that do hundreds of thousands calls onus system add too big overhead
	struct BonusCache {
		std::vector<bool> noTerrainPenalty;
		bool freeShipBoarding;
		bool flyingMovement;
		int flyingMovementVal;
		bool waterWalking;
		int waterWalkingVal;

		BonusCache(TBonusListPtr bonusList);
	};
	std::unique_ptr<BonusCache> bonusCache;

	const CGHeroInstance * hero;
	TBonusListPtr bonuses;
	mutable int maxMovePointsLand;
	mutable int maxMovePointsWater;
	int nativeTerrain;

	TurnInfo(const CGHeroInstance * Hero, const int Turn = 0);
	bool isLayerAvailable(const EPathfindingLayer layer) const;
	bool hasBonusOfType(const Bonus::BonusType type, const int subtype = -1) const;
	int valOfBonuses(const Bonus::BonusType type, const int subtype = -1) const;
	int getMaxMovePoints(const EPathfindingLayer layer) const;
};

class DLL_LINKAGE CPathfinderHelper : private CGameInfoCallback
{
public:
	int turn;
	const CGHeroInstance * hero;
	std::vector<TurnInfo *> turnsInfo;
	const PathfinderOptions & options;

	CPathfinderHelper(CGameState * gs, const CGHeroInstance * Hero, const PathfinderOptions & Options);
	~CPathfinderHelper();
	void updateTurnInfo(const int turn = 0);
	bool isLayerAvailable(const EPathfindingLayer layer) const;
	const TurnInfo * getTurnInfo() const;
	bool hasBonusOfType(const Bonus::BonusType type, const int subtype = -1) const;
	int getMaxMovePoints(const EPathfindingLayer layer) const;

	std::vector<int3> getCastleGates(CPathNodeInfo & source) const;
	bool isAllowedTeleportEntrance(const CGTeleport * obj) const;
	std::vector<int3> getAllowedTeleportChannelExits(TeleportChannelID channelID) const;
	bool addTeleportTwoWay(const CGTeleport * obj) const;
	bool addTeleportOneWay(const CGTeleport * obj) const;
	bool addTeleportOneWayRandom(const CGTeleport * obj) const;
	bool addTeleportWhirlpool(const CGWhirlpool * obj) const;
	bool canMoveBetween(const int3 & a, const int3 & b) const; //checks only for visitable objects that may make moving between tiles impossible, not other conditions (like tiles itself accessibility)

	std::vector<int3> getNeighbourTiles(CPathNodeInfo & source) const;
	std::vector<int3> getTeleportExits(CPathNodeInfo & source) const;

	void getNeighbours(
		const TerrainTile & srct,
		const int3 & tile, 
		std::vector<int3> & vec, 
		const boost::logic::tribool & onLand, 
		const bool limitCoastSailing) const;
	
	int getMovementCost(
		const int3 & src, 
		const int3 & dst, 
		const TerrainTile * ct,
		const TerrainTile * dt,
		const int remainingMovePoints =- 1, 
		const bool checkLast = true) const;

	int getMovementCost(
		const CPathNodeInfo & src,
		const CPathNodeInfo & dst,
		const int remainingMovePoints = -1,
		const bool checkLast = true) const
	{
		return getMovementCost(
			src.coord,
			dst.coord,
			src.tile,
			dst.tile,
			remainingMovePoints,
			checkLast
		);
	}

	int getHeroMaxMovementPoints(EPathfindingLayer layer) const;
	int movementPointsAfterEmbark(int movement, int cost, int action) const;
	bool passOneTurnLimitCheck(CPathNodeInfo & source) const;
};