/*
 * 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_TOPOLOGY_HPP
#define ZT_TOPOLOGY_HPP

#include "Constants.hpp"
#include "Address.hpp"
#include "Identity.hpp"
#include "Peer.hpp"
#include "Path.hpp"
#include "Mutex.hpp"
#include "InetAddress.hpp"
#include "SharedPtr.hpp"
#include "ScopedPtr.hpp"
#include "Fingerprint.hpp"
#include "Blob.hpp"
#include "IdentificationCertificate.hpp"
#include "Containers.hpp"

namespace ZeroTier {

class RuntimeEnvironment;

/**
 * Database of network topology
 */
class Topology
{
public:
	Topology(const RuntimeEnvironment *renv, void *tPtr);

	/**
	 * Add peer to database
	 *
	 * This will not replace existing peers. In that case the existing peer
	 * record is returned.
	 *
	 * @param peer Peer to add
	 * @return New or existing peer (should replace 'peer')
	 */
	SharedPtr< Peer > add(void *tPtr, const SharedPtr< Peer > &peer);

	/**
	 * Get a peer from its address
	 *
	 * @param tPtr Thread pointer to be handed through to any callbacks called as a result of this call
	 * @param zta ZeroTier address of peer
	 * @param loadFromCached If false do not load from cache if not in memory (default: true)
	 * @return Peer or NULL if not found
	 */
	ZT_INLINE SharedPtr< Peer > peer(void *tPtr, const Address &zta, const bool loadFromCached = true)
	{
		{
			RWMutex::RLock l(m_peers_l);
			const SharedPtr< Peer > *const ap = m_peers.get(zta);
			if (likely(ap != nullptr))
				return *ap;
		}
		{
			SharedPtr< Peer > p;
			if (loadFromCached) {
				m_loadCached(tPtr, zta, p);
				if (p) {
					RWMutex::Lock l(m_peers_l);
					SharedPtr< Peer > &hp = m_peers[zta];
					if (hp)
						return hp;
					hp = p;
				}
			}
			return p;
		}
	}

	/**
	 * Get a Path object for a given local and remote physical address, creating if needed
	 *
	 * @param l Local socket
	 * @param r Remote address
	 * @return Pointer to canonicalized Path object or NULL on error
	 */
	ZT_INLINE SharedPtr< Path > path(const int64_t l, const InetAddress &r)
	{
		const uint64_t k = s_getPathKey(l, r);
		{
			RWMutex::RLock lck(m_paths_l);
			SharedPtr< Path > *const p = m_paths.get(k);
			if (likely(p != nullptr))
				return *p;
		}
		{
			SharedPtr< Path > p(new Path(l, r));
			RWMutex::Lock lck(m_paths_l);
			SharedPtr< Path > &p2 = m_paths[k];
			if (p2)
				return p2;
			p2 = p;
			return p;
		}
	}

	/**
	 * @return Current best root server
	 */
	ZT_INLINE SharedPtr< Peer > root() const
	{
		RWMutex::RLock l(m_peers_l);
		if (unlikely(m_rootPeers.empty()))
			return SharedPtr< Peer >();
		return m_rootPeers.front();
	}

	/**
	 * @param id Identity to check
	 * @return True if this identity corresponds to a root
	 */
	ZT_INLINE bool isRoot(const Identity &id) const
	{
		RWMutex::RLock l(m_peers_l);
		return (m_roots.find(id) != m_roots.end());
	}

	/**
	 * Apply a function or function object to all peers
	 *
	 * This locks the peer map during execution, so calls to get() etc. during
	 * eachPeer() will deadlock.
	 *
	 * @param f Function to apply
	 * @tparam F Function or function object type
	 */
	template< typename F >
	ZT_INLINE void eachPeer(F f) const
	{
		RWMutex::RLock l(m_peers_l);
		for (Map< Address, SharedPtr< Peer > >::const_iterator i(m_peers.begin()); i != m_peers.end(); ++i)
			f(i->second);
	}

	/**
	 * @param allPeers vector to fill with all current peers
	 */
	ZT_INLINE void getAllPeers(Vector< SharedPtr< Peer > > &allPeers) const
	{
		allPeers.clear();
		RWMutex::RLock l(m_peers_l);
		allPeers.reserve(m_peers.size());
		for (Map< Address, SharedPtr< Peer > >::const_iterator i(m_peers.begin()); i != m_peers.end(); ++i)
			allPeers.push_back(i->second);
	}

	/**
	 * @param allPeers vector to fill with all current peers
	 */
	ZT_INLINE void getAllPeers(Vector< SharedPtr< Peer > > &allPeers, Vector< SharedPtr< Peer > > &rootPeers) const
	{
		allPeers.clear();
		RWMutex::RLock l(m_peers_l);
		allPeers.reserve(m_peers.size());
		for (Map< Address, SharedPtr< Peer > >::const_iterator i(m_peers.begin()); i != m_peers.end(); ++i)
			allPeers.push_back(i->second);
		rootPeers = m_rootPeers;
	}

	/**
	 * Flag a peer as a root, adding the peer if it is not known
	 *
	 * @param tPtr Thread pointer
	 * @param id Root identity (will be locally validated)
	 * @return Root peer or NULL if some problem occurred
	 */
	SharedPtr< Peer > addRoot(void *tPtr, const Identity &id);

	/**
	 * Remove a root server's identity from the root server set
	 *
	 * @param tPtr Thread pointer
	 * @param address Root address
	 * @return True if root found and removed, false if not found
	 */
	bool removeRoot(void *tPtr, Address address);

	/**
	 * Sort roots in ascending order of apparent latency
	 *
	 * @param now Current time
	 */
	void rankRoots();

	/**
	 * Do periodic tasks such as database cleanup
	 */
	void doPeriodicTasks(void *tPtr, int64_t now);

	/**
	 * Save all currently known peers to data store
	 */
	void saveAll(void *tPtr);

private:
	void m_loadCached(void *tPtr, const Address &zta, SharedPtr< Peer > &peer);

	void m_writeRootList(void *tPtr);

	void m_updateRootPeers(void *tPtr);

	// This gets an integer key from an InetAddress for looking up paths.
	static ZT_INLINE uint64_t s_getPathKey(const int64_t l, const InetAddress &r) noexcept
	{
		// SECURITY: these will be used as keys in a Map<> which uses its own hasher that
		// mixes in a per-invocation secret to work against hash collision attacks. See the
		// map hasher in Containers.hpp. Otherwise the point here is really really fast
		// path lookup by address. The number of paths is never likely to be high enough
		// for a collision to be something we worry about. That would require a minimum of
		// millions and millions of paths on a single node.
		if (r.family() == AF_INET) {
			return ((uint64_t)(r.as.sa_in.sin_addr.s_addr) << 32U) ^ ((uint64_t)r.as.sa_in.sin_port << 16U) ^ (uint64_t)l;
		} else if (r.family() == AF_INET6) {
			return Utils::loadAsIsEndian< uint64_t >(r.as.sa_in6.sin6_addr.s6_addr) + Utils::loadAsIsEndian< uint64_t >(r.as.sa_in6.sin6_addr.s6_addr + 8) + (uint64_t)r.as.sa_in6.sin6_port + (uint64_t)l;
		} else {
			// This should never really be used but it's here just in case.
			return (uint64_t)Utils::fnv1a32(reinterpret_cast<const void *>(&r), sizeof(InetAddress)) + (uint64_t)l;
		}
	}

	const RuntimeEnvironment *const RR;
	RWMutex m_paths_l; // locks m_paths
	RWMutex m_peers_l; // locks m_peers, m_roots, and m_rootPeers
	Map< uint64_t, SharedPtr< Path > > m_paths;
	Map< Address, SharedPtr< Peer > > m_peers;
	Map< Identity, Set< IdentificationCertificate > > m_roots;
	Vector< SharedPtr< Peer > > m_rootPeers;
};

} // namespace ZeroTier

#endif