#include <limits.h>

class MQ {

protected:

	std::string name;

	mqd_t handle;

	bool unlinkAfterClose;

	static const size_t MAX_DATA_LENGTH = PATH_MAX; // TODO: maybe more or configurable

	static const __syscall_slong_t MAX_MESSAGES = 10; // TODO: maybe configurable or derived from the process count

public:

	class Message {

	public:

		enum class Type {

			FILENAME,

			END

		};

		Type type;

		size_t dataLength; // TODO: maybe uint16_t from #include <cstdint> would be enough (and shorten the message minimum size from 16 to 4)

		char data[MQ::MAX_DATA_LENGTH];

		void checkDataLength() const {

			if (dataLength > sizeof (data) || dataLength < 0) throw RelpipeWriterException(L"Invalid POSIX MQ message size.");

		}

		size_t getMessageLength() const {

			return sizeof (*this) - sizeof (data) + dataLength;

		}

		std::string getStringData() {

			return std::string(data, dataLength);

		}

		void setStringData(const std::string& s) {

			if (s.size() > sizeof (data)) throw RelpipeWriterException(L"Unable set message data: string too long.");

			::memcpy(data, s.c_str(), s.size());

			dataLength = s.size();

		}

	};

	MQ(const std::string& name, mqd_t handle, bool unlinkAfterClose = false) : name(name), handle(handle), unlinkAfterClose(unlinkAfterClose) {

		if (handle < 0) throw RelpipeWriterException(L"Unable to open POSIX MQ.");

	}

	virtual ~MQ() {

		mq_close(handle);

		if (unlinkAfterClose) mq_unlink(name.c_str());

	}

	MQ(const MQ& other) = delete;

	void operator=(const MQ& right) = delete;

};

class MQReader : public MQ {

public:

	MQReader(std::string name) : MQ(name, mq_open(name.c_str(), O_RDONLY)) {

	}

	void receive(Message* m) {

		int result = mq_receive(handle, (char*) m, sizeof (*m), nullptr);

		if (result < 0) throw RelpipeWriterException(L"Unable to receive POSIX MQ message.");

		m->checkDataLength();

	}

};

class MQWriter : public MQ {

private:

	mq_attr attributes;

	mq_attr* getAttributes() {

		attributes.mq_maxmsg = MQ::MAX_MESSAGES;

		attributes.mq_msgsize = sizeof (Message);

		return &attributes;

	}

public:

	MQWriter(std::string name) : MQ(name, mq_open(name.c_str(), O_RDWR | O_CREAT, S_IRWXU, getAttributes()), true) {

	}

	void send(const Message* m, unsigned int priority = 0) {

		m->checkDataLength();

		int result = mq_send(handle, (const char*) m, m->getMessageLength(), priority);

		if (result) throw RelpipeWriterException(L"Unable to send POSIX MQ message.");

	}

};

class ParallelFilesystemWorker {

};

class ParallelFilesystemProcess {

};

		{ // TODO: demo code – remove:

			std::string queueName = "/relpipe-in-filesystem_parallel_" + std::to_string(getpid());

			MQWriter mqWriter(queueName.c_str());

			MQReader mqReader(queueName.c_str());

			MQ::Message writeBuffer;

			MQ::Message readBuffer;

			// ::memset(&writeBuffer, 0, sizeof (writeBuffer));

			// ::memset(&readBuffer, 0, sizeof (readBuffer));

			writeBuffer.type = MQ::Message::Type::END;

			writeBuffer.setStringData("ahoj");

			mqWriter.send(&writeBuffer);

			mqReader.receive(&readBuffer);

			std::string readData(readBuffer.data, readBuffer.dataLength);

			std::wstring_convert < codecvt_utf8<wchar_t>> convertor;

			std::wcerr << L"Zpráva „" << convertor.from_bytes(readData).c_str() << L"“ typu " << (int) readBuffer.type << L" o celkové délce " << readBuffer.getMessageLength() << L" a délce dat " << readBuffer.dataLength << L" byla přijata." << std::endl;

		}