/*
   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
   2011, 2012 Her Majesty the Queen in Right of Canada (Communications
   Research Center Canada)

   Copyright (C) 2017
   Matthias P. Braendli, matthias.braendli@mpb.li

    http://www.opendigitalradio.org
   */
/*
   This file is part of ODR-DabMux.

   ODR-DabMux 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 3 of the
   License, or (at your option) any later version.

   ODR-DabMux 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 ODR-DabMux.  If not, see <http://www.gnu.org/licenses/>.
*/

/* The EDI output needs TAI clock, according to ETSI TS 102 693 Annex F
 * "EDI Timestamps". This module can set the local CLOCK_TAI clock by
 * setting the TAI-UTC offset using adjtimex.
 *
 * This functionality requires Linux 3.10 (30 Jun 2013) or newer.
 */

#pragma once

#include <stdint.h>
#include <stdlib.h>
#include <sstream>
#include <chrono>
#include <future>

// EDI needs to know UTC-TAI, but doesn't need the CLOCK_TAI to be set.
// We can keep this code, maybe for future use
#define SUPPORT_SETTING_CLOCK_TAI 0

/* Loads, parses and represents TAI-UTC offset information from the IETF bulletin */
class ClockTAI {
    public:
        // Fetch the bulletin from the IETF website and return the current
        // TAI-UTC offset.
        // Throws runtime_error on failure.
        int get_offset(void);

#if SUPPORT_SETTING_CLOCK_TAI
        // Update the local TAI clock according to the TAI-UTC offset
        // return 0 on success
        int update_local_tai_clock(int offset);
#endif

    private:
        // Either retrieve the bulletin from the cache or if necessarly
        // download it, and calculate the TAI-UTC offset.
        // Returns the offset.
        int get_valid_offset(void);

        // Download of new bulletin is done asynchronously
        std::future<int> m_offset_future;

        // The currently used TAI-UTC offset
        int m_offset;
        int m_offset_valid = false;

        std::stringstream m_bulletin;
        std::chrono::system_clock::time_point m_bulletin_download_time;

        // Load bulletin into m_bulletin from the cache file
        void load_bulletin_from_file(const char* cache_filename);

        // Update the cache file with the current m_bulletin
        void update_cache(const char* cache_filename);

        // Verifies the expiration date in the m_bulletin. Returns
        // true if the bulletin is valid.
        bool bulletin_is_valid(void);

        // Load bulletin into m_bulletin from the URL
        void download_tai_utc_bulletin(const char* url);

        // read TAI offset from m_bulletin in IETF format
        int parse_ietf_bulletin(void);

        // callback that receives data from cURL
        size_t fill_bulletin(char *ptr, size_t size, size_t nmemb);

        // static callback wrapper for cURL
        static size_t fill_bulletin_cb(
                char *ptr, size_t size, size_t nmemb, void *ctx);
};