#pragma once

#include <thread>
#include <common/MultiVersion.h>
#include <Poco/Event.h>


namespace Poco { class Logger; }

class RegionsHierarchies;
class TechDataHierarchy;
class RegionsNames;


namespace DB
{

class Context;


/// Metrica's Dictionaries which can be used in functions.

class EmbeddedDictionaries
{
private:
	MultiVersion<RegionsHierarchies> regions_hierarchies;
	MultiVersion<TechDataHierarchy> tech_data_hierarchy;
	MultiVersion<RegionsNames> regions_names;

	/// Directories' updating periodicity (in seconds).
	int reload_period;
	int cur_reload_period = 1;
	bool is_fast_start_stage = true;

	std::thread reloading_thread;
	Poco::Event destroy;

	Poco::Logger * log;


	void handleException(const bool throw_on_error) const;

	/// Updates dictionaries.
	bool reloadImpl(const bool throw_on_error);

	/** Updates directories (dictionaries) every reload_period seconds.
	 * If all dictionaries are not loaded at least once, try reload them with exponential delay (1, 2, ... reload_period).
	 * If all dictionaries are loaded, update them using constant reload_period delay.
	 */
	void reloadPeriodically();

	template <typename Dictionary>
	bool reloadDictionary(MultiVersion<Dictionary> & dictionary, const bool throw_on_error);

public:
	/// Every reload_period seconds directories are updated inside a separate thread.
	EmbeddedDictionaries(const bool throw_on_error, const int reload_period_);

	EmbeddedDictionaries(const bool throw_on_error);

	~EmbeddedDictionaries();


	MultiVersion<RegionsHierarchies>::Version getRegionsHierarchies() const
	{
		return regions_hierarchies.get();
	}

	MultiVersion<TechDataHierarchy>::Version getTechDataHierarchy() const
	{
		return tech_data_hierarchy.get();
	}

	MultiVersion<RegionsNames>::Version getRegionsNames() const
	{
		return regions_names.get();
	}
};

}