// Copyright (c) 2021-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <netgroup.h>

#include <hash.h>

#include <uint256.h>

#include <util/asmap.h>

#include <util/log.h>

#include <cassert>

#include <cstddef>

#include <utility>

NetGroupManager::NetGroupManager(std::span<const std::byte> embedded_asmap, std::vector<std::byte>&& loaded_asmap)

    : m_asmap{embedded_asmap},

      m_loaded_asmap{std::move(loaded_asmap)},

      m_asmap_version{AsmapVersion(m_asmap)}

{

    assert(m_loaded_asmap.empty() || m_asmap.data() == m_loaded_asmap.data());

}

uint256 NetGroupManager::GetAsmapVersion() const

{

    return m_asmap_version;

}

std::vector<unsigned char> NetGroupManager::GetGroup(const CNetAddr& address) const

{

    std::vector<unsigned char> vchRet;

    // If non-empty asmap is supplied and the address is IPv4/IPv6,

    // return ASN to be used for bucketing.

    uint32_t asn = GetMappedAS(address);

    if (asn != 0) { // Either asmap was empty, or address has non-asmappable net class (e.g. TOR).

        vchRet.push_back(NET_IPV6); // IPv4 and IPv6 with same ASN should be in the same bucket

        for (int i = 0; i < 4; i++) {

            vchRet.push_back((asn >> (8 * i)) & 0xFF);

        }

        return vchRet;

    }

    vchRet.push_back(address.GetNetClass());

    int nStartByte{0};

    int nBits{0};

    if (address.IsLocal()) {

        // all local addresses belong to the same group

    } else if (address.IsInternal()) {

        // All internal-usage addresses get their own group.

        // Skip over the INTERNAL_IN_IPV6_PREFIX returned by CAddress::GetAddrBytes().

        nStartByte = INTERNAL_IN_IPV6_PREFIX.size();

        nBits = ADDR_INTERNAL_SIZE * 8;

    } else if (!address.IsRoutable()) {

        // all other unroutable addresses belong to the same group

    } else if (address.HasLinkedIPv4()) {

        // IPv4 addresses (and mapped IPv4 addresses) use /16 groups

        uint32_t ipv4 = address.GetLinkedIPv4();

        vchRet.push_back((ipv4 >> 24) & 0xFF);

        vchRet.push_back((ipv4 >> 16) & 0xFF);

        return vchRet;

    } else if (address.IsTor() || address.IsI2P()) {

        nBits = 4;

    } else if (address.IsCJDNS()) {

        // Treat in the same way as Tor and I2P because the address in all of

        // them is "random" bytes (derived from a public key). However in CJDNS

        // the first byte is a constant (see CJDNS_PREFIX), so the random bytes

        // come after it. Thus skip the constant 8 bits at the start.

        nBits = 12;

    } else if (address.IsHeNet()) {

        // for he.net, use /36 groups

        nBits = 36;

    } else {

        // for the rest of the IPv6 network, use /32 groups

        nBits = 32;

    }

    // Push our address onto vchRet.

    auto addr_bytes = address.GetAddrBytes();

    const size_t num_bytes = nBits / 8;

    vchRet.insert(vchRet.end(), addr_bytes.begin() + nStartByte, addr_bytes.begin() + nStartByte + num_bytes);

    nBits %= 8;

    // ...for the last byte, push nBits and for the rest of the byte push 1's

    if (nBits > 0) {

        assert(num_bytes < addr_bytes.size());

        vchRet.push_back(addr_bytes[num_bytes + nStartByte] | ((1 << (8 - nBits)) - 1));

    }

    return vchRet;

}

uint32_t NetGroupManager::GetMappedAS(const CNetAddr& address) const

{

    uint32_t net_class = address.GetNetClass();

    if (m_asmap.empty() || (net_class != NET_IPV4 && net_class != NET_IPV6)) {

        return 0; // Indicates not found, safe because AS0 is reserved per RFC7607.

    }

    std::vector<std::byte> ip_bytes(16);

    if (address.HasLinkedIPv4()) {

        // For lookup, treat as if it was just an IPv4 address (IPV4_IN_IPV6_PREFIX + IPv4 bits)

        std::copy_n(std::as_bytes(std::span{IPV4_IN_IPV6_PREFIX}).begin(),

                    IPV4_IN_IPV6_PREFIX.size(), ip_bytes.begin());

        uint32_t ipv4 = address.GetLinkedIPv4();

        for (int i = 0; i < 4; ++i) {

            ip_bytes[12 + i] = std::byte((ipv4 >> (24 - i * 8)) & 0xFF);

        }

    } else {

        // Use all 128 bits of the IPv6 address otherwise

        assert(address.IsIPv6());

        auto addr_bytes = address.GetAddrBytes();

        assert(addr_bytes.size() == ip_bytes.size());

        std::copy_n(std::as_bytes(std::span{addr_bytes}).begin(),

                    addr_bytes.size(), ip_bytes.begin());

    }

    uint32_t mapped_as = Interpret(m_asmap, ip_bytes);

    return mapped_as;

}

void NetGroupManager::ASMapHealthCheck(const std::vector<CNetAddr>& clearnet_addrs) const {

    std::set<uint32_t> clearnet_asns{};

    int unmapped_count{0};

    for (const auto& addr : clearnet_addrs) {

        uint32_t asn = GetMappedAS(addr);

        if (asn == 0) {

            ++unmapped_count;

            continue;

        }

        clearnet_asns.insert(asn);

    }

    LogInfo("ASMap Health Check: %i clearnet peers are mapped to %i ASNs with %i peers being unmapped\n", clearnet_addrs.size(), clearnet_asns.size(), unmapped_count);

}

bool NetGroupManager::UsingASMap() const {

    return m_asmap.size() > 0;

}