/*

Copyright (c) 2006-2008, 2010, 2014-2019, Arvid Norberg
Copyright (c) 2014-2015, 2017, Steven Siloti
Copyright (c) 2015, Thomas Yuan
Copyright (c) 2015-2017, Alden Torres
Copyright (c) 2020, Fonic
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.

*/

#ifndef TORRENT_DHT_TRACKER
#define TORRENT_DHT_TRACKER

#include <functional>

#include <libtorrent/kademlia/node.hpp>
#include <libtorrent/kademlia/dos_blocker.hpp>
#include <libtorrent/kademlia/dht_state.hpp>

#include <libtorrent/aux_/listen_socket_handle.hpp>
#include <libtorrent/socket.hpp>
#include <libtorrent/deadline_timer.hpp>
#include <libtorrent/span.hpp>
#include <libtorrent/io_context.hpp>
#include <libtorrent/udp_socket.hpp>
#include <libtorrent/entry.hpp>

namespace libtorrent {

	struct counters;
#if TORRENT_ABI_VERSION == 1
	struct session_status;
#endif
namespace aux {
	struct session_settings;
}
}

namespace libtorrent {
namespace dht {

	struct TORRENT_EXTRA_EXPORT dht_tracker final
		: socket_manager
		, std::enable_shared_from_this<dht_tracker>
	{
		using send_fun_t = std::function<void(
			aux::listen_socket_handle const&, udp::endpoint const&
			, span<char const>, error_code&, udp_send_flags_t)>;

		dht_tracker(dht_observer* observer
			, io_context& ios
			, send_fun_t send_fun
			, aux::session_settings const& settings
			, counters& cnt
			, dht_storage_interface& storage
			, dht_state&& state);

		// the dht_state must be moved in!
		dht_tracker(dht_observer* observer
			, io_context& ios
			, send_fun_t const& send_fun
			, aux::session_settings const& settings
			, counters& cnt
			, dht_storage_interface& storage
			, dht_state const& state) = delete;

#if defined(_MSC_VER) && _MSC_VER < 1910
		// workaround for a bug in msvc 14.0
		// it attempts to generate a copy constructor for some strange reason
		// and fails because tracker_node is not copyable
		dht_tracker(dht_tracker const&) = delete;
#endif

		void start(find_data::nodes_callback const& f);
		void stop();

		// tell the node to recalculate its node id based on the current
		// understanding of its external address (which may have changed)
		void update_node_id(aux::listen_socket_handle const& s);

		void new_socket(aux::listen_socket_handle const& s);
		void delete_socket(aux::listen_socket_handle const& s);

		void add_node(udp::endpoint const& node);
		void add_router_node(udp::endpoint const& node);

		dht_state state() const;

		void get_peers(sha1_hash const& ih
			, std::function<void(std::vector<tcp::endpoint> const&)> f);
		void announce(sha1_hash const& ih, int listen_port, announce_flags_t flags
			, std::function<void(std::vector<tcp::endpoint> const&)> f);

		void sample_infohashes(udp::endpoint const& ep, sha1_hash const& target
			, std::function<void(node_id
				, time_duration
				, int, std::vector<sha1_hash>
				, std::vector<std::pair<sha1_hash, udp::endpoint>>)> f);

		void get_item(sha1_hash const& target
			, std::function<void(item const&)> cb);

		// key is a 32-byte binary string, the public key to look up.
		// the salt is optional
		void get_item(public_key const& key
			, std::function<void(item const&, bool)> cb
			, std::string salt = std::string());

		// for immutable_item.
		// the callback function will be called when put operation is done.
		// the int parameter indicates the success numbers of put operation.
		void put_item(entry const& data
			, std::function<void(int)> cb);

		// for mutable_item.
		// the data_cb will be called when we get authoritative mutable_item,
		// the cb is same as put immutable_item.
		void put_item(public_key const& key
			, std::function<void(item const&, int)> cb
			, std::function<void(item&)> data_cb, std::string salt = std::string());

		// send an arbitrary DHT request directly to a node
		void direct_request(udp::endpoint const& ep, entry& e
			, std::function<void(msg const&)> f);

#if TORRENT_ABI_VERSION == 1
		void dht_status(session_status& s);
#endif
		std::vector<lt::dht::dht_status> dht_status() const;
		void update_stats_counters(counters& c) const;

		void incoming_error(error_code const& ec, udp::endpoint const& ep);
		bool incoming_packet(aux::listen_socket_handle const& s
			, udp::endpoint const& ep, span<char const> buf);

		std::vector<std::pair<node_id, udp::endpoint>> live_nodes(node_id const& nid);

	private:
		struct tracker_node
		{
			tracker_node(io_context& ios
				, aux::listen_socket_handle const& s, socket_manager* sock
				, aux::session_settings const& settings
				, node_id const& nid
				, dht_observer* observer, counters& cnt
				, get_foreign_node_t get_foreign_node
				, dht_storage_interface& storage);
			tracker_node(tracker_node const&) = delete;
			tracker_node(tracker_node&&) = delete;

			node dht;
			deadline_timer connection_timer;
		};
		using tracker_nodes_t = std::map<aux::listen_socket_handle, tracker_node>;

		std::shared_ptr<dht_tracker> self()
		{ return shared_from_this(); }

		void connection_timeout(aux::listen_socket_handle const& s, error_code const& e);
		void refresh_timeout(error_code const& e);
		void refresh_key(error_code const& e);
		void update_storage_node_ids();
		node* get_node(node_id const& id, std::string const& family_name);

		// implements socket_manager
		bool has_quota() override;
		bool send_packet(aux::listen_socket_handle const& s, entry& e, udp::endpoint const& addr) override;

		// this is the bdecode_node DHT messages are parsed into. It's a member
		// in order to avoid having to deallocate and re-allocate it for every
		// message.
		bdecode_node m_msg;

		counters& m_counters;
		dht_storage_interface& m_storage;
		dht_state m_state; // to be used only once
		tracker_nodes_t m_nodes;
		send_fun_t m_send_fun;
		dht_observer* m_log;

		std::vector<char> m_send_buf;
		dos_blocker m_blocker;

		deadline_timer m_key_refresh_timer;
		deadline_timer m_refresh_timer;
		aux::session_settings const& m_settings;

		bool m_running;

		// used to resolve hostnames for nodes
		udp::resolver m_host_resolver;

		// state for the send rate limit
		int m_send_quota;
		time_point m_last_tick;

		io_context& m_ioc;
	};
} // namespace dht
} // namespace libtorrent

#endif
