vcmi/lib/CPathfinder.h

#pragma once

#include "VCMI_Lib.h"
#include "mapping/CMap.h"
#include "IGameCallback.h"
#include "int3.h"

#include <boost/heap/priority_queue.hpp>

/*
 * 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
 *
 */

class CGHeroInstance;
class CGObjectInstance;
struct TerrainTile;
class CPathfinderHelper;

struct DLL_LINKAGE CGPathNode
{
	typedef EPathfindingLayer ELayer;

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

	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);
};

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

	CPathfinder(CPathsInfo & _out, CGameState * _gs, const CGHeroInstance * _hero);
	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;

	struct 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.
		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();
	} options;

	CPathsInfo & out;
	const CGHeroInstance * hero;
	unique_ptr<CPathfinderHelper> hlp;

	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;

	std::vector<int3> neighbours;

	CGPathNode * cp; //current (source) path node -> we took it from the queue
	CGPathNode * dp; //destination node -> it's a neighbour of cp that we consider
	const TerrainTile * ct, * dt; //tile info for both nodes
	const CGObjectInstance * ctObj, * dtObj;
	CGPathNode::ENodeAction destAction;

	void addNeighbours();
	void addTeleportExits();

	bool isLayerTransitionPossible() const;
	bool isMovementToDestPossible() const;
	bool isMovementAfterDestPossible() const;
	CGPathNode::ENodeAction getDestAction() const;

	bool isSourceInitialPosition() const;
	bool isSourceVisitableObj() const;
	bool isSourceGuarded() const;
	bool isDestVisitableObj() const;
	bool isDestinationGuarded(const bool ignoreAccessibility = true) const;
	bool isDestinationGuardian() const;

	void initializeGraph();

	CGPathNode::EAccessibility evaluateAccessibility(const int3 & pos, const TerrainTile * tinfo, const ELayer layer) const;
	bool isVisitableObj(const CGObjectInstance * obj, const ELayer layer) const;
	bool canSeeObj(const CGObjectInstance * 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)

	bool isAllowedTeleportEntrance(const CGTeleport * obj) 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;

};

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);
	};
	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
{
public:
	CPathfinderHelper(const CGHeroInstance * Hero, const CPathfinder::PathfinderOptions & Options);
	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;

	static void getNeighbours(const CMap * map, const TerrainTile & srct, const int3 & tile, std::vector<int3> & vec, const boost::logic::tribool & onLand, const bool limitCoastSailing);

	static int getMovementCost(const CGHeroInstance * h, const int3 & src, const int3 & dst, const TerrainTile * ct, const TerrainTile * dt, const int remainingMovePoints =- 1, const TurnInfo * ti = nullptr, const bool checkLast = true);
	static int getMovementCost(const CGHeroInstance * h, const int3 & dst);

private:
	int turn;
	const CGHeroInstance * hero;
	std::vector<TurnInfo *> turnsInfo;
	const CPathfinder::PathfinderOptions & options;
};