#pragma once

#include <DB/Dictionaries/IDictionarySource.h>
#include <DB/Dictionaries/DictionaryStructure.h>


namespace Poco
{
	namespace Util
	{
		class AbstractConfiguration;
	}
}

namespace mongo
{
	class DBClientConnection;
	class BSONObj;
}


namespace DB
{

/// Allows loading dictionaries from a MongoDB collection
class MongoDBDictionarySource final : public IDictionarySource
{
	MongoDBDictionarySource(
		const DictionaryStructure & dict_struct, const std::string & host, const std::string & port,
		const std::string & user, const std::string & password,
		const std::string & db, const std::string & collection,
		const Block & sample_block);

public:
	MongoDBDictionarySource(
		const DictionaryStructure & dict_struct, const Poco::Util::AbstractConfiguration & config,
		const std::string & config_prefix, Block & sample_block);

	MongoDBDictionarySource(const MongoDBDictionarySource & other);

    ~MongoDBDictionarySource() override;

	BlockInputStreamPtr loadAll() override;

	bool supportsSelectiveLoad() const override { return true; }

	BlockInputStreamPtr loadIds(const std::vector<UInt64> & ids) override;

	BlockInputStreamPtr loadKeys(
		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows) override;

	/// @todo: for MongoDB, modification date can somehow be determined from the `_id` object field
	bool isModified() const override { return false; }

	DictionarySourcePtr clone() const override { return std::make_unique<MongoDBDictionarySource>(*this); }

	std::string toString() const override;

private:
	const DictionaryStructure dict_struct;
	const std::string host;
	const std::string port;
	const std::string user;
	const std::string password;
	const std::string db;
	const std::string collection;
	Block sample_block;

	std::unique_ptr<mongo::DBClientConnection> connection;
	std::unique_ptr<mongo::BSONObj> fields_to_query;
};

}