/*
 * Copyright (c)2013-2020 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2024-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */
/****/

#ifndef ZT_PATH_HPP
#define ZT_PATH_HPP

#include "Constants.hpp"
#include "InetAddress.hpp"
#include "SharedPtr.hpp"
#include "Utils.hpp"
#include "Mutex.hpp"
#include "Meter.hpp"
#include "Containers.hpp"

namespace ZeroTier {

class RuntimeEnvironment;

template<unsigned int MF, unsigned int MFP, unsigned int GCT, unsigned int GCS, typename P>
class Defragmenter;

/**
 * A path across the physical network
 */
class Path
{
	friend class SharedPtr<Path>;

	// Allow defragmenter to access fragment-in-flight info stored in Path for performance reasons.
	template<unsigned int MF, unsigned int MFP, unsigned int GCT, unsigned int GCS, typename P>
	friend
	class Defragmenter;

public:
	ZT_INLINE Path(const int64_t l, const InetAddress &r) noexcept:
		m_localSocket(l),
		m_lastIn(0),
		m_lastOut(0),
		m_latency(-1),
		m_addr(r)
	{
	}

	/**
	 * Send a packet via this path (last out time is also updated)
	 *
	 * @param RR Runtime environment
	 * @param tPtr Thread pointer to be handed through to any callbacks called as a result of this call
	 * @param data Packet data
	 * @param len Packet length
	 * @param now Current time
	 * @return True if transport reported success
	 */
	bool send(const RuntimeEnvironment *RR, void *tPtr, const void *data, unsigned int len, int64_t now) noexcept;

	/**
	 * Explicitly update last sent time
	 *
	 * @param now Time of send
	 * @param bytes Bytes sent
	 */
	ZT_INLINE void sent(const int64_t now, const unsigned int bytes) noexcept
	{
		m_lastOut.store(now);
		m_outMeter.log(now, bytes);
	}

	/**
	 * Called when a packet is received from this remote path, regardless of content
	 *
	 * @param now Time of receive
	 * @param bytes Bytes received
	 */
	ZT_INLINE void received(const int64_t now, const unsigned int bytes) noexcept
	{
		m_lastIn.store(now);
		m_inMeter.log(now, bytes);
	}

	/**
	 * Update latency with a new measurement
	 *
	 * @param newMeasurement New latency measurement in milliseconds
	 */
	ZT_INLINE void updateLatency(const unsigned int newMeasurement) noexcept
	{
		int lat = m_latency;
		if (lat > 0) {
			m_latency = (lat + newMeasurement) / 2;
		} else {
			m_latency = newMeasurement;
		}
	}

	/**
	 * @return Latency in milliseconds or -1 if unknown
	 */
	ZT_INLINE int latency() const noexcept
	{ return m_latency; }

	/**
	 * Check path aliveness
	 *
	 * @param now Current time
	 */
	ZT_INLINE bool alive(const int64_t now) const noexcept
	{ return ((now - m_lastIn.load()) < ZT_PATH_ALIVE_TIMEOUT); }

	/**
	 * @return Physical address
	 */
	ZT_INLINE const InetAddress &address() const noexcept
	{ return m_addr; }

	/**
	 * @return Local socket as specified by external code
	 */
	ZT_INLINE int64_t localSocket() const noexcept
	{ return m_localSocket; }

	/**
	 * @return Last time we received anything
	 */
	ZT_INLINE int64_t lastIn() const noexcept
	{ return m_lastIn.load(); }

	/**
	 * @return Last time we sent something
	 */
	ZT_INLINE int64_t lastOut() const noexcept
	{ return m_lastOut.load(); }

private:
	const int64_t m_localSocket;
	std::atomic<int64_t> m_lastIn;
	std::atomic<int64_t> m_lastOut;
	std::atomic<int> m_latency;
	const InetAddress m_addr;
	Meter<> m_inMeter;
	Meter<> m_outMeter;

	// These fields belong to Defragmenter but are kept in Path for performance
	// as it's much faster this way than having Defragmenter maintain another
	// mapping from paths to inbound message IDs.
	Set<uint64_t> m_inboundFragmentedMessages;
	Mutex m_inboundFragmentedMessages_l;

	std::atomic<int> __refCount;
};

} // namespace ZeroTier

#endif