/*
 * This file is part of the Flowee project
 * Copyright (C) 2020-2024 Tom Zander <tom@flowee.org>
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef FLOWEE_PEERADDRESSDB_H
#define FLOWEE_PEERADDRESSDB_H

#include <NetworkEndPoint.h>

#include <boost/filesystem.hpp>

#include <map>
#include <mutex>

class PeerAddressDB;
class Message;
class ConnectionManager;

// this is the cut-off punishment score that makes a peer get
// insta disconnected.
constexpr int PUNISHMENT_MAX = 1000;

/**
 * Represents a single peer we could or have connected to.
 */
class PeerAddress
{
public:
    /// returns the internet address over which the peer can be reached
    const EndPoint &peerAddress() const;

    /**
     * Calling this updates the peer database to register that we have successfully connected to this peer.
     * @param the services that the remote peer advertised in the version handshake.
     */
    void successfullyConnected(uint64_t services);
    /**
     * Calling this updates the database to register that we received good headers.
     */
    void gotGoodHeaders();
    /**
     * Register a punishment for this peer.
     * This is used to keep track of how much this peer misbehaves. 1000 points means they are banned.
     */
    short punishPeer(short amount);
    /**
     * Current level of punishment.
     */
    short punishment() const;
    /**
     * Reset the punishment.
     */
    void resetPunishment();
    /**
     * Returns simply if this instance represents an actual entry in the peer adddress DB.
     */
    bool isValid() const;

    /// Returns true if an p2p message for addresses was received.
    bool askedAddresses() const;
    /// Register if we asked for adddresses.
    void setAskedAddresses(bool on);
    /**
     * Returns true if we have ever made a full connection to this peer.
     * Notice that connecting to a peer on a different chain still may return true here.
     * @see successfullyConnected()
     */
    bool hasEverConnected() const;
    /**
     * Return a unit timestamp (sec since epoch) when we received good headers from this peer.
     * Or 0 if the peer never did.
     */
    uint32_t lastReceivedGoodHeaders() const;

    /**
     * THe PrivacySegment ID that this peer is associated with.
     * For privacy reasons we only allow this peer to see this privacy segments bloom filter.
     */
    uint16_t segment() const;
    /**
     * Set the privacy segment ID.
     */
    void setSegment(uint16_t segment);

    /**
     * Register on the peerAddressDB (non persistent) that this peer is being used.
     * This typically menas we are connecting or connected to the peer.
     */
    void setInUse(bool on);

    /**
     * Remember which services the peer announces.
     * @see Peer::services()
     */
    void setServices(uint64_t services);

    /**
     * Return the unix date (sec since epoch) when we last made a successsful full connection.
     */
    uint32_t lastConnected() const;

    /// \internal This returns the peerAddressDB internal ID for this specific peer.
    int id() const;

protected:
    friend class PeerAddressDB;
    explicit PeerAddress(PeerAddressDB *parent, int peerId);

private:
    PeerAddressDB *d;
    int m_id;
};

struct AddressDBStats
{
    int count;          ///< Total count of IPs known by the DB
    int banned;         ///< The number of IPs that have higher/equal PUNISHMENT_MAX punishment
    int partialBanned;  ///< Number with > 500 punishment (includes the 'banned' ones)
    int ipv6Addresses;  ///< Number IPs using ipv6 addressing scheme
    int everConnected;  ///< Number of peers that were ever connected to.
    bool usesIPv4;
    bool usesIPv6;
};

/**
 * The addresses database to collect and manage all the peeer addresses we learned about.
 * In the p2p net, peers notify each other about peers they recently successsfully connected to.
 * We store and score and manage those addresses for ourselves.
 *
 * This is backed by the on-disk file 'peers.dat'
 */
class PeerAddressDB
{
public:
    PeerAddressDB(ConnectionManager *parent);

    /**
     * Try to find a (semi)random peer that has good specs to connect to.
     * The peer returned will have a good score (low punishment) and not already in use.
     *
     * \param required services. A mask of services that a peer must have.
     *
     * \param segment The segment (privacySegment ID) is matched or a peer with no segment is returned,
     * we guarentee this method never returns a match that has a different segment.
     *
     * Please note that the PeerAddressDB instance has to outlive the PeerAddress instance.
     */
    PeerAddress findBest(uint64_t requiredServices = 0, uint16_t segment = 0);

    /**
     * Reset all properties on our list of addresses.
     */
    void resetAllStats();

    /// return number of peers this DB holds.
    int peerCount() const;

    void processAddressMessage(const Message &message, int sourcePeerId);

    /**
     * Try to add a peer to the DB.
     * Duplicates are Ok, we notice them and decrese their punishment if multiple sources repeat it.
     */
    void addOne(const EndPoint &endPoint);

    /// \internal
    inline PeerAddress peer(int id) {
        assert(0 <= id);
        return PeerAddress(this, id);
    }

    void saveDatabase(const boost::filesystem::path &basedir);
    void loadDatabase(const boost::filesystem::path &basedir);

    /// return the current network's default port number for peers that don't supply one.
    int defaultPortNr() const;
    /**
     * Peers that we get from DNS do not have a port number, this is used to store
     * the current network's default port number for those peers.
     */
    void setDefaultPortNr(int defaultPortNr);

    /**
     * This checks all known data and returns basic statistics.
     */
    AddressDBStats createStats() const;

    /**
     * If true, findBest() will include IPv4 options in its reply.
     */
    bool supportIPv4Net() const;
    void setSupportIPv4Net(bool on);

    /**
     * If true, findBest() will include IPv6 options in its reply.
     */
    bool supportIPv6Net() const;
    void setSupportIPv6Net(bool on);

private:
    friend class PeerAddress;
    struct PeerInfo {
        EndPoint address;
        uint64_t services = 0;
        uint32_t lastConnected = 0;
        uint32_t lastReceivedGoodHeaders = 0;
        short punishment = 0;
        uint16_t segment = 0;
        bool everConnected = false; // if false, lastConnected comes from untrusted peers

        // Not persisted properties.
        bool inUse = false;
        bool askedAddr = false;
    };
    void insert(PeerInfo &pi);

    mutable std::mutex m_lock;
    std::map<int, PeerInfo> m_peers;
    int m_nextPeerId = 0;
    int m_disabledPeerCount = 0; // amount of peers with punishment >= 1000
    int m_defaultPortNr = 8333;
    bool m_needsSave = false;
    bool m_supportIPv4Net = true;
    bool m_supportIPv6Net = false;

    ConnectionManager *m_parent;
};

inline Log::Item operator<<(Log::Item item, const PeerAddress &pa) {
    if (item.isEnabled()) {
        const bool old = item.useSpace();
        item.nospace() << pa.id() << "-{";
        const EndPoint &ep = pa.peerAddress();
        if (ep.ipAddress.is_unspecified())
            item << ep.hostname;
        else
            item << ep.ipAddress.to_string().c_str();
        if (ep.announcePort != 8333 && ep.announcePort != 28333)
            item << ':' << ep.announcePort;
        item << '}';
        if (old)
            return item.space();
    }
    return item;
}
inline Log::SilentItem operator<<(Log::SilentItem item, const PeerAddress&) { return item; }

#endif