/*
 * AIUtility.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 "../../lib/VCMI_Lib.h"
#include "../../lib/CBuildingHandler.h"
#include "../../lib/CCreatureHandler.h"
#include "../../lib/CTownHandler.h"
#include "../../lib/spells/CSpellHandler.h"
#include "../../lib/CStopWatch.h"
#include "../../lib/mapObjects/CObjectHandler.h"
#include "../../lib/mapObjects/CGHeroInstance.h"
#include "../../lib/CPathfinder.h"
#include <tbb/tbb.h>

using namespace tbb;

class CCallback;
class Nullkiller;
struct creInfo;

typedef const int3 & crint3;
typedef const std::string & crstring;
typedef std::pair<ui32, std::vector<CreatureID>> dwellingContent;

const int GOLD_MINE_PRODUCTION = 1000, WOOD_ORE_MINE_PRODUCTION = 2, RESOURCE_MINE_PRODUCTION = 1;
const int ACTUAL_RESOURCE_COUNT = 7;
const int ALLOWED_ROAMING_HEROES = 8;

//implementation-dependent
extern const float SAFE_ATTACK_CONSTANT;
extern const int GOLD_RESERVE;

enum HeroRole
{
	SCOUT = 0,

	MAIN = 1
};

//provisional class for AI to store a reference to an owned hero object
//checks if it's valid on access, should be used in place of const CGHeroInstance*

struct DLL_EXPORT HeroPtr
{
	const CGHeroInstance * h;
	ObjectInstanceID hid;

public:
	std::string name;


	HeroPtr();
	HeroPtr(const CGHeroInstance * H);
	~HeroPtr();

	operator bool() const
	{
		return validAndSet();
	}

	bool operator<(const HeroPtr & rhs) const;
	const CGHeroInstance * operator->() const;
	const CGHeroInstance * operator*() const; //not that consistent with -> but all interfaces use CGHeroInstance*, so it's convenient
	bool operator==(const HeroPtr & rhs) const;
	bool operator!=(const HeroPtr & rhs) const
	{
		return !(*this == rhs);
	}

	const CGHeroInstance * get(bool doWeExpectNull = false) const;
	const CGHeroInstance * get(CCallback * cb, bool doWeExpectNull = false) const;
	bool validAndSet() const;


	template<typename Handler> void serialize(Handler & h, const int version)
	{
		h & this->h;
		h & hid;
		h & name;
	}
};

enum BattleState
{
	NO_BATTLE,
	UPCOMING_BATTLE,
	ONGOING_BATTLE,
	ENDING_BATTLE
};

// AI lives in a dangerous world. CGObjectInstances under pointer may got deleted/hidden.
// This class stores object id, so we can detect when we lose access to the underlying object.
struct ObjectIdRef
{
	ObjectInstanceID id;

	const CGObjectInstance * operator->() const;
	operator const CGObjectInstance *() const;
	operator bool() const;

	ObjectIdRef(ObjectInstanceID _id);
	ObjectIdRef(const CGObjectInstance * obj);

	bool operator<(const ObjectIdRef & rhs) const;


	template<typename Handler> void serialize(Handler & h, const int version)
	{
		h & id;
	}
};

struct TimeCheck
{
	CStopWatch time;
	std::string txt;
	TimeCheck(crstring TXT)
		: txt(TXT)
	{
	}

	~TimeCheck()
	{
		logAi->trace("Time of %s was %d ms.", txt, time.getDiff());
	}
};

//TODO: replace with vstd::
struct AtScopeExit
{
	std::function<void()> foo;
	AtScopeExit(const std::function<void()> & FOO)
		: foo(FOO)
	{}
	~AtScopeExit()
	{
		foo();
	}
};


class ObjsVector : public std::vector<ObjectIdRef>
{
};

template<int id>
bool objWithID(const CGObjectInstance * obj)
{
	return obj->ID == id;
}

struct creInfo
{
	int count;
	CreatureID creID;
	CCreature * cre;
	int level;
};
creInfo infoFromDC(const dwellingContent & dc);

void foreach_tile_pos(std::function<void(const int3 & pos)> foo);
void foreach_tile_pos(CCallback * cbp, std::function<void(CCallback * cbp, const int3 & pos)> foo); // avoid costly retrieval of thread-specific pointer
void foreach_neighbour(const int3 & pos, std::function<void(const int3 & pos)> foo);
void foreach_neighbour(CCallback * cbp, const int3 & pos, std::function<void(CCallback * cbp, const int3 & pos)> foo); // avoid costly retrieval of thread-specific pointer

bool canBeEmbarkmentPoint(const TerrainTile * t, bool fromWater);
bool isObjectPassable(const CGObjectInstance * obj);
bool isObjectPassable(const Nullkiller * ai, const CGObjectInstance * obj);
bool isObjectPassable(const CGObjectInstance * obj, PlayerColor playerColor, PlayerRelations::PlayerRelations objectRelations);
bool isBlockVisitObj(const int3 & pos);

bool isWeeklyRevisitable(const CGObjectInstance * obj);

bool isObjectRemovable(const CGObjectInstance * obj); //FIXME FIXME: move logic to object property!
bool isSafeToVisit(HeroPtr h, uint64_t dangerStrength);
bool isSafeToVisit(HeroPtr h, const CCreatureSet *, uint64_t dangerStrength);

bool compareHeroStrength(HeroPtr h1, HeroPtr h2);
bool compareArmyStrength(const CArmedInstance * a1, const CArmedInstance * a2);
bool compareArtifacts(const CArtifactInstance * a1, const CArtifactInstance * a2);

uint64_t timeElapsed(boost::chrono::time_point<boost::chrono::steady_clock> start);

// todo: move to obj manager
bool shouldVisit(const Nullkiller * ai, const CGHeroInstance * h, const CGObjectInstance * obj);

template<typename TFunc>
void pforeachTilePos(crint3 mapSize, TFunc fn)
{
	parallel_for(blocked_range<size_t>(0, mapSize.x), [&](const blocked_range<size_t>& r)
	{
		int3 pos;

		for(pos.x = r.begin(); pos.x != r.end(); ++pos.x)
		{
			for(pos.y = 0; pos.y < mapSize.y; ++pos.y)
			{
				for(pos.z = 0; pos.z < mapSize.z; ++pos.z)
				{
					fn(pos);
				}
			}
		}
	});
}

class CDistanceSorter
{
	const CGHeroInstance * hero;

public:
	CDistanceSorter(const CGHeroInstance * hero)
		: hero(hero)
	{
	}
	bool operator()(const CGObjectInstance * lhs, const CGObjectInstance * rhs) const;
};

template <class T>
class SharedPool
{
public:
	struct External_Deleter
	{
		explicit External_Deleter(std::weak_ptr<SharedPool<T>* > pool)
			: pool(pool)
		{
		}

		void operator()(T * ptr)
		{
			std::unique_ptr<T> uptr(ptr);

			if(auto pool_ptr = pool.lock())
			{
				(*pool_ptr.get())->add(std::move(uptr));
			}
		}

	private:
		std::weak_ptr<SharedPool<T>* > pool;
	};

public:
	using ptr_type = std::unique_ptr<T, External_Deleter>;

	SharedPool(std::function<std::unique_ptr<T>()> elementFactory)
		: elementFactory(elementFactory), pool(), sync(), instance_tracker(new SharedPool<T>*(this))
	{}
	
	void add(std::unique_ptr<T> t)
	{
		std::lock_guard<std::mutex> lock(sync);
		pool.push_back(std::move(t));
	}

	ptr_type acquire()
	{
		std::lock_guard<std::mutex> lock(sync);
		bool poolIsEmpty = pool.empty();
		T * element = poolIsEmpty
			? elementFactory().release()
			: pool.back().release();

		ptr_type tmp(
			element,
			External_Deleter(std::weak_ptr<SharedPool<T>*>(instance_tracker)));

		if(!poolIsEmpty) pool.pop_back();

		return std::move(tmp);
	}

	bool empty() const
	{
		return pool.empty();
	}

	size_t size() const
	{
		return pool.size();
	}

private:
	std::vector<std::unique_ptr<T>> pool;
	std::function<std::unique_ptr<T>()> elementFactory;
	std::shared_ptr<SharedPool<T> *> instance_tracker;
	std::mutex sync;
};