/*
    Copyright (C) 2014-2021 Carl Hetherington <cth@carlh.net>

    This file is part of DCP-o-matic.

    DCP-o-matic is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    DCP-o-matic is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.

*/


/** @file  src/lib/update_checker.h
 *  @brief UpdateChecker class.
 */


#include "signaller.h"
#include <curl/curl.h>
#include <boost/signals2.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread.hpp>


struct update_checker_test;


/** Class to check for the existence of an update for DCP-o-matic on a remote server */
class UpdateChecker : public Signaller
{
public:
	~UpdateChecker ();

	UpdateChecker (UpdateChecker const &);
	UpdateChecker& operator= (UpdateChecker const &);

	void run ();

	enum class State {
		YES,    ///< there is an update
		FAILED, ///< the check failed, so we don't know
		NO,     ///< there is no update
		NOT_RUN ///< the check has not been run (yet)
	};

	/** @return state of the checker */
	State state () {
		boost::mutex::scoped_lock lm (_data_mutex);
		return _state;
	}

	/** @return new stable version, if there is one */
	boost::optional<std::string> stable () {
		boost::mutex::scoped_lock lm (_data_mutex);
		return _stable;
	}

	/** @return new test version, if there is one */
	boost::optional<std::string> test () {
		boost::mutex::scoped_lock lm (_data_mutex);
		return _test;
	}

	size_t write_callback (void *, size_t, size_t);

	boost::signals2::signal<void (void)> StateChanged;

	static UpdateChecker* instance ();

private:
	friend struct update_checker_test;

	static UpdateChecker* _instance;

	static bool version_less_than (std::string const & a, std::string const & b);

	UpdateChecker ();
	void start ();
	void set_state (State);
	void thread ();

	std::vector<char> _buffer;
	int _offset = 0;
	CURL* _curl = nullptr;

	/** mutex to protect _state, _stable, _test and _emits */
	mutable boost::mutex _data_mutex;
	State _state;
	boost::optional<std::string> _stable;
	boost::optional<std::string> _test;

	boost::thread _thread;
	boost::mutex _process_mutex;
	boost::condition _condition;
	int _to_do = 0;
	bool _terminate = false;
};