// Copyright (c) 2021-2022 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 <txorphanage.h>

#include <consensus/validation.h>
#include <logging.h>
#include <policy/policy.h>
#include <primitives/transaction.h>
#include <util/time.h>

#include <cassert>

/** Expiration time for orphan transactions */
static constexpr auto ORPHAN_TX_EXPIRE_TIME{20min};
/** Minimum time between orphan transactions expire time checks */
static constexpr auto ORPHAN_TX_EXPIRE_INTERVAL{5min};


bool TxOrphanage::AddTx(const CTransactionRef& tx, NodeId peer)
{
    const Txid& hash = tx->GetHash();
    const Wtxid& wtxid = tx->GetWitnessHash();
    if (m_orphans.count(wtxid))
        return false;

    // Ignore big transactions, to avoid a
    // send-big-orphans memory exhaustion attack. If a peer has a legitimate
    // large transaction with a missing parent then we assume
    // it will rebroadcast it later, after the parent transaction(s)
    // have been mined or received.
    // 100 orphans, each of which is at most 100,000 bytes big is
    // at most 10 megabytes of orphans and somewhat more byprev index (in the worst case):
    unsigned int sz = GetTransactionWeight(*tx);
    if (sz > MAX_STANDARD_TX_WEIGHT)
    {
        LogPrint(BCLog::TXPACKAGES, "ignoring large orphan tx (size: %u, txid: %s, wtxid: %s)\n", sz, hash.ToString(), wtxid.ToString());
        return false;
    }

    auto ret = m_orphans.emplace(wtxid, OrphanTx{tx, peer, Now<NodeSeconds>() + ORPHAN_TX_EXPIRE_TIME, m_orphan_list.size()});
    assert(ret.second);
    m_orphan_list.push_back(ret.first);
    for (const CTxIn& txin : tx->vin) {
        m_outpoint_to_orphan_it[txin.prevout].insert(ret.first);
    }

    LogPrint(BCLog::TXPACKAGES, "stored orphan tx %s (wtxid=%s), weight: %u (mapsz %u outsz %u)\n", hash.ToString(), wtxid.ToString(), sz,
             m_orphans.size(), m_outpoint_to_orphan_it.size());
    return true;
}

int TxOrphanage::EraseTx(const Wtxid& wtxid)
{
    std::map<Wtxid, OrphanTx>::iterator it = m_orphans.find(wtxid);
    if (it == m_orphans.end())
        return 0;
    for (const CTxIn& txin : it->second.tx->vin)
    {
        auto itPrev = m_outpoint_to_orphan_it.find(txin.prevout);
        if (itPrev == m_outpoint_to_orphan_it.end())
            continue;
        itPrev->second.erase(it);
        if (itPrev->second.empty())
            m_outpoint_to_orphan_it.erase(itPrev);
    }

    size_t old_pos = it->second.list_pos;
    assert(m_orphan_list[old_pos] == it);
    if (old_pos + 1 != m_orphan_list.size()) {
        // Unless we're deleting the last entry in m_orphan_list, move the last
        // entry to the position we're deleting.
        auto it_last = m_orphan_list.back();
        m_orphan_list[old_pos] = it_last;
        it_last->second.list_pos = old_pos;
    }
    const auto& txid = it->second.tx->GetHash();
    // Time spent in orphanage = difference between current and entry time.
    // Entry time is equal to ORPHAN_TX_EXPIRE_TIME earlier than entry's expiry.
    LogPrint(BCLog::TXPACKAGES, "   removed orphan tx %s (wtxid=%s) after %ds\n", txid.ToString(), wtxid.ToString(),
             Ticks<std::chrono::seconds>(NodeClock::now() + ORPHAN_TX_EXPIRE_TIME - it->second.nTimeExpire));
    m_orphan_list.pop_back();

    m_orphans.erase(it);
    return 1;
}

void TxOrphanage::EraseForPeer(NodeId peer)
{
    m_peer_work_set.erase(peer);

    int nErased = 0;
    std::map<Wtxid, OrphanTx>::iterator iter = m_orphans.begin();
    while (iter != m_orphans.end())
    {
        // increment to avoid iterator becoming invalid after erasure
        const auto& [wtxid, orphan] = *iter++;
        if (orphan.fromPeer == peer) {
            nErased += EraseTx(wtxid);
        }
    }
    if (nErased > 0) LogPrint(BCLog::TXPACKAGES, "Erased %d orphan transaction(s) from peer=%d\n", nErased, peer);
}

void TxOrphanage::LimitOrphans(unsigned int max_orphans, FastRandomContext& rng)
{
    unsigned int nEvicted = 0;
    auto nNow{Now<NodeSeconds>()};
    if (m_next_sweep <= nNow) {
        // Sweep out expired orphan pool entries:
        int nErased = 0;
        auto nMinExpTime{nNow + ORPHAN_TX_EXPIRE_TIME - ORPHAN_TX_EXPIRE_INTERVAL};
        std::map<Wtxid, OrphanTx>::iterator iter = m_orphans.begin();
        while (iter != m_orphans.end())
        {
            std::map<Wtxid, OrphanTx>::iterator maybeErase = iter++;
            if (maybeErase->second.nTimeExpire <= nNow) {
                nErased += EraseTx(maybeErase->second.tx->GetWitnessHash());
            } else {
                nMinExpTime = std::min(maybeErase->second.nTimeExpire, nMinExpTime);
            }
        }
        // Sweep again 5 minutes after the next entry that expires in order to batch the linear scan.
        m_next_sweep = nMinExpTime + ORPHAN_TX_EXPIRE_INTERVAL;
        if (nErased > 0) LogPrint(BCLog::TXPACKAGES, "Erased %d orphan tx due to expiration\n", nErased);
    }
    while (m_orphans.size() > max_orphans)
    {
        // Evict a random orphan:
        size_t randompos = rng.randrange(m_orphan_list.size());
        EraseTx(m_orphan_list[randompos]->second.tx->GetWitnessHash());
        ++nEvicted;
    }
    if (nEvicted > 0) LogPrint(BCLog::TXPACKAGES, "orphanage overflow, removed %u tx\n", nEvicted);
}

void TxOrphanage::AddChildrenToWorkSet(const CTransaction& tx)
{
    for (unsigned int i = 0; i < tx.vout.size(); i++) {
        const auto it_by_prev = m_outpoint_to_orphan_it.find(COutPoint(tx.GetHash(), i));
        if (it_by_prev != m_outpoint_to_orphan_it.end()) {
            for (const auto& elem : it_by_prev->second) {
                // Get this source peer's work set, emplacing an empty set if it didn't exist
                // (note: if this peer wasn't still connected, we would have removed the orphan tx already)
                std::set<Wtxid>& orphan_work_set = m_peer_work_set.try_emplace(elem->second.fromPeer).first->second;
                // Add this tx to the work set
                orphan_work_set.insert(elem->first);
                LogPrint(BCLog::TXPACKAGES, "added %s (wtxid=%s) to peer %d workset\n",
                         tx.GetHash().ToString(), tx.GetWitnessHash().ToString(), elem->second.fromPeer);
            }
        }
    }
}

bool TxOrphanage::HaveTx(const Wtxid& wtxid) const
{
    return m_orphans.count(wtxid);
}

CTransactionRef TxOrphanage::GetTxToReconsider(NodeId peer)
{
    auto work_set_it = m_peer_work_set.find(peer);
    if (work_set_it != m_peer_work_set.end()) {
        auto& work_set = work_set_it->second;
        while (!work_set.empty()) {
            Wtxid wtxid = *work_set.begin();
            work_set.erase(work_set.begin());

            const auto orphan_it = m_orphans.find(wtxid);
            if (orphan_it != m_orphans.end()) {
                return orphan_it->second.tx;
            }
        }
    }
    return nullptr;
}

bool TxOrphanage::HaveTxToReconsider(NodeId peer)
{
    auto work_set_it = m_peer_work_set.find(peer);
    if (work_set_it != m_peer_work_set.end()) {
        auto& work_set = work_set_it->second;
        return !work_set.empty();
    }
    return false;
}

void TxOrphanage::EraseForBlock(const CBlock& block)
{
    std::vector<Wtxid> vOrphanErase;

    for (const CTransactionRef& ptx : block.vtx) {
        const CTransaction& tx = *ptx;

        // Which orphan pool entries must we evict?
        for (const auto& txin : tx.vin) {
            auto itByPrev = m_outpoint_to_orphan_it.find(txin.prevout);
            if (itByPrev == m_outpoint_to_orphan_it.end()) continue;
            for (auto mi = itByPrev->second.begin(); mi != itByPrev->second.end(); ++mi) {
                const CTransaction& orphanTx = *(*mi)->second.tx;
                vOrphanErase.push_back(orphanTx.GetWitnessHash());
            }
        }
    }

    // Erase orphan transactions included or precluded by this block
    if (vOrphanErase.size()) {
        int nErased = 0;
        for (const auto& orphanHash : vOrphanErase) {
            nErased += EraseTx(orphanHash);
        }
        LogPrint(BCLog::TXPACKAGES, "Erased %d orphan transaction(s) included or conflicted by block\n", nErased);
    }
}

std::vector<CTransactionRef> TxOrphanage::GetChildrenFromSamePeer(const CTransactionRef& parent, NodeId nodeid) const
{
    // First construct a vector of iterators to ensure we do not return duplicates of the same tx
    // and so we can sort by nTimeExpire.
    std::vector<OrphanMap::iterator> iters;

    // For each output, get all entries spending this prevout, filtering for ones from the specified peer.
    for (unsigned int i = 0; i < parent->vout.size(); i++) {
        const auto it_by_prev = m_outpoint_to_orphan_it.find(COutPoint(parent->GetHash(), i));
        if (it_by_prev != m_outpoint_to_orphan_it.end()) {
            for (const auto& elem : it_by_prev->second) {
                if (elem->second.fromPeer == nodeid) {
                    iters.emplace_back(elem);
                }
            }
        }
    }

    // Sort by address so that duplicates can be deleted. At the same time, sort so that more recent
    // orphans (which expire later) come first.  Break ties based on address, as nTimeExpire is
    // quantified in seconds and it is possible for orphans to have the same expiry.
    std::sort(iters.begin(), iters.end(), [](const auto& lhs, const auto& rhs) {
        if (lhs->second.nTimeExpire == rhs->second.nTimeExpire) {
            return &(*lhs) < &(*rhs);
        } else {
            return lhs->second.nTimeExpire > rhs->second.nTimeExpire;
        }
    });
    // Erase duplicates
    iters.erase(std::unique(iters.begin(), iters.end()), iters.end());

    // Convert to a vector of CTransactionRef
    std::vector<CTransactionRef> children_found;
    children_found.reserve(iters.size());
    for (const auto& child_iter : iters) {
        children_found.emplace_back(child_iter->second.tx);
    }
    return children_found;
}

std::vector<std::pair<CTransactionRef, NodeId>> TxOrphanage::GetChildrenFromDifferentPeer(const CTransactionRef& parent, NodeId nodeid) const
{
    // First construct vector of iterators to ensure we do not return duplicates of the same tx.
    std::vector<OrphanMap::iterator> iters;

    // For each output, get all entries spending this prevout, filtering for ones not from the specified peer.
    for (unsigned int i = 0; i < parent->vout.size(); i++) {
        const auto it_by_prev = m_outpoint_to_orphan_it.find(COutPoint(parent->GetHash(), i));
        if (it_by_prev != m_outpoint_to_orphan_it.end()) {
            for (const auto& elem : it_by_prev->second) {
                if (elem->second.fromPeer != nodeid) {
                    iters.emplace_back(elem);
                }
            }
        }
    }

    // Erase duplicates
    std::sort(iters.begin(), iters.end(), IteratorComparator());
    iters.erase(std::unique(iters.begin(), iters.end()), iters.end());

    // Convert iterators to pair<CTransactionRef, NodeId>
    std::vector<std::pair<CTransactionRef, NodeId>> children_found;
    children_found.reserve(iters.size());
    for (const auto& child_iter : iters) {
        children_found.emplace_back(child_iter->second.tx, child_iter->second.fromPeer);
    }
    return children_found;
}