// Copyright (c) 2021 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 <cassert>

/** Minimum time between orphan transactions expire time checks in seconds */
static constexpr int64_t ORPHAN_TX_EXPIRE_INTERVAL = 5 * 60;

RecursiveMutex g_cs_orphans;

std::map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(g_cs_orphans);
std::map<uint256, std::map<uint256, COrphanTx>::iterator> g_orphans_by_wtxid GUARDED_BY(g_cs_orphans);

    std::map<COutPoint, std::set<std::map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(g_cs_orphans);

    std::vector<std::map<uint256, COrphanTx>::iterator> g_orphan_list GUARDED_BY(g_cs_orphans);

int EraseOrphanTx(uint256 hash)
{
    std::map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
    if (it == mapOrphanTransactions.end())
        return 0;
    for (const CTxIn& txin : it->second.tx->vin)
    {
        auto itPrev = mapOrphanTransactionsByPrev.find(txin.prevout);
        if (itPrev == mapOrphanTransactionsByPrev.end())
            continue;
        itPrev->second.erase(it);
        if (itPrev->second.empty())
            mapOrphanTransactionsByPrev.erase(itPrev);
    }

    size_t old_pos = it->second.list_pos;
    assert(g_orphan_list[old_pos] == it);
    if (old_pos + 1 != g_orphan_list.size()) {
        // Unless we're deleting the last entry in g_orphan_list, move the last
        // entry to the position we're deleting.
        auto it_last = g_orphan_list.back();
        g_orphan_list[old_pos] = it_last;
        it_last->second.list_pos = old_pos;
    }
    g_orphan_list.pop_back();
    g_orphans_by_wtxid.erase(it->second.tx->GetWitnessHash());

    mapOrphanTransactions.erase(it);
    return 1;
}

void EraseOrphansFor(NodeId peer)
{
    LOCK(g_cs_orphans);
    int nErased = 0;
    std::map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
    while (iter != mapOrphanTransactions.end())
    {
        std::map<uint256, COrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
        if (maybeErase->second.fromPeer == peer)
        {
            nErased += EraseOrphanTx(maybeErase->second.tx->GetHash());
        }
    }
    if (nErased > 0) LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx from peer=%d\n", nErased, peer);
}

unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
{
    LOCK(g_cs_orphans);

    unsigned int nEvicted = 0;
    static int64_t nNextSweep;
    int64_t nNow = GetTime();
    if (nNextSweep <= nNow) {
        // Sweep out expired orphan pool entries:
        int nErased = 0;
        int64_t nMinExpTime = nNow + ORPHAN_TX_EXPIRE_TIME - ORPHAN_TX_EXPIRE_INTERVAL;
        std::map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
        while (iter != mapOrphanTransactions.end())
        {
            std::map<uint256, COrphanTx>::iterator maybeErase = iter++;
            if (maybeErase->second.nTimeExpire <= nNow) {
                nErased += EraseOrphanTx(maybeErase->second.tx->GetHash());
            } 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.
        nNextSweep = nMinExpTime + ORPHAN_TX_EXPIRE_INTERVAL;
        if (nErased > 0) LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx due to expiration\n", nErased);
    }
    FastRandomContext rng;
    while (mapOrphanTransactions.size() > nMaxOrphans)
    {
        // Evict a random orphan:
        size_t randompos = rng.randrange(g_orphan_list.size());
        EraseOrphanTx(g_orphan_list[randompos]->first);
        ++nEvicted;
    }
    return nEvicted;
}