text: /*
  
  Copyright (c) 2015-2018, Arvid Norberg
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:
  
      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in
        the documentation and/or other materials provided with the distribution.
      * Neither the name of the author nor the names of its
        contributors may be used to endorse or promote products derived
        from this software without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.
  
  */
  
  #include "libtorrent/config.hpp"
  #include "libtorrent/announce_entry.hpp"
  #include "libtorrent/string_util.hpp" // for is_space
  #include "libtorrent/aux_/time.hpp"
  #include "libtorrent/aux_/session_settings.hpp"
  #include "libtorrent/aux_/listen_socket_handle.hpp"
  
  namespace libtorrent {
  
  	namespace {
  		// wait at least 5 seconds before retrying a failed tracker
  		seconds32 constexpr tracker_retry_delay_min{5};
  
  		// never wait more than 60 minutes to retry a tracker
  		minutes32 constexpr tracker_retry_delay_max{60};
  	}
  
  	announce_endpoint::announce_endpoint(aux::listen_socket_handle const& s, bool const completed)
  		: local_endpoint(s ? s.get_local_endpoint() : tcp::endpoint())
  		, socket(s)
  		, fails(0)
  		, updating(false)
  		, start_sent(false)
  		, complete_sent(completed)
  		, triggered_manually(false)
  		, enabled(true)
  	{}
  
  	announce_entry::announce_entry(string_view u)
  		: url(u.to_string())
  		, source(0)
  		, verified(false)
  #if TORRENT_ABI_VERSION == 1
  		, fails(0)
  		, send_stats(false)
  		, start_sent(false)
  		, complete_sent(false)
  		, triggered_manually(false)
  		, updating(false)
  #endif
  	{}
  
  	announce_entry::announce_entry()
  		: source(0)
  		, verified(false)
  #if TORRENT_ABI_VERSION == 1
  		, fails(0)
  		, send_stats(false)
  		, start_sent(false)
  		, complete_sent(false)
  		, triggered_manually(false)
  		, updating(false)
  #endif
  	{}
  
  	announce_entry::~announce_entry() = default;
  	announce_entry::announce_entry(announce_entry const&) = default;
  	announce_entry& announce_entry::operator=(announce_entry const&) = default;
  
  	void announce_endpoint::reset()
  	{
  		start_sent = false;
  		next_announce = time_point32::min();
  		min_announce = time_point32::min();
  	}
  
  	void announce_endpoint::failed(int const backoff_ratio, seconds32 const retry_interval)
  	{
  		// fails is only 7 bits
  		if (fails < (1 << 7) - 1) ++fails;
  
  		// the exponential back-off ends up being:
  		// 7, 15, 27, 45, 95, 127, 165, ... seconds
  		// with the default tracker_backoff of 250
  		int const fail_square = int(fails) * int(fails);
  		seconds32 const delay = std::max(retry_interval
  			, std::min(duration_cast<seconds32>(tracker_retry_delay_max)
  				, tracker_retry_delay_min
  					+ fail_square * tracker_retry_delay_min * backoff_ratio / 100
  			));
  		if (!is_working()) next_announce = aux::time_now32() + delay;
  		updating = false;
  	}
  
  	bool announce_endpoint::can_announce(time_point now, bool is_seed, std::uint8_t fail_limit) const
  	{
  		// if we're a seed and we haven't sent a completed
  		// event, we need to let this announce through
  		bool const need_send_complete = is_seed && !complete_sent;
  
  		// add some slack here for rounding errors
  		return now  + seconds(1) >= next_announce
  			&& (now >= min_announce || need_send_complete)
  			&& (fails < fail_limit || fail_limit == 0)
  			&& !updating;
  	}
  
  	void announce_entry::reset()
  	{
  		for (auto& aep : endpoints)
  			aep.reset();
  	}
  
  #if TORRENT_ABI_VERSION == 1
  	bool announce_entry::can_announce(time_point now, bool is_seed) const
  	{
  		return std::any_of(endpoints.begin(), endpoints.end()
  			, [&](announce_endpoint const& aep) { return aep.can_announce(now, is_seed, fail_limit); });
  	}
  
  	bool announce_entry::is_working() const
  	{
  		return std::any_of(endpoints.begin(), endpoints.end()
  			, [](announce_endpoint const& aep) { return aep.is_working(); });
  	}
  #endif
  
  	announce_endpoint* announce_entry::find_endpoint(aux::listen_socket_handle const& s)
  	{
  		auto aep = std::find_if(endpoints.begin(), endpoints.end()
  			, [&](announce_endpoint const& a) { return a.socket == s; });
  		if (aep != endpoints.end()) return &*aep;
  		else return nullptr;
  	}
  
  	void announce_entry::trim()
  	{
  		while (!url.empty() && is_space(url[0]))
  			url.erase(url.begin());
  	}
  
  }
  