//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 Ripple Labs Inc.

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#include <BeastConfig.h>
#include <ripple/app/ledger/LedgerMaster.h>
#include <ripple/app/ledger/InboundLedgers.h>
#include <ripple/app/ledger/OpenLedger.h>
#include <ripple/app/ledger/OrderBookDB.h>
#include <ripple/app/ledger/PendingSaves.h>
#include <ripple/app/tx/apply.h>
#include <ripple/app/main/Application.h>
#include <ripple/app/misc/AmendmentTable.h>
#include <ripple/app/misc/HashRouter.h>
#include <ripple/app/misc/NetworkOPs.h>
#include <ripple/app/misc/SHAMapStore.h>
#include <ripple/app/misc/Transaction.h>
#include <ripple/app/misc/TxQ.h>
#include <ripple/app/misc/Validations.h>
#include <ripple/app/paths/PathRequests.h>
#include <ripple/basics/Log.h>
#include <ripple/basics/TaggedCache.h>
#include <ripple/basics/UptimeTimer.h>
#include <ripple/core/LoadFeeTrack.h>
#include <ripple/core/TimeKeeper.h>
#include <ripple/overlay/Overlay.h>
#include <ripple/overlay/Peer.h>
#include <ripple/protocol/digest.h>
#include <ripple/protocol/HashPrefix.h>
#include <ripple/resource/Fees.h>
#include <algorithm>
#include <cassert>
#include <memory>
#include <vector>

namespace ripple {

using namespace std::chrono_literals;

// 150/256ths of validations of previous ledger
#define MIN_VALIDATION_RATIO    150

// Don't catch up more than 100 ledgers (cannot exceed 256)
#define MAX_LEDGER_GAP          100

// Don't acquire history if ledger is too old
auto constexpr MAX_LEDGER_AGE_ACQUIRE = 1min;

LedgerMaster::LedgerMaster (Application& app, Stopwatch& stopwatch,
    Stoppable& parent,
    beast::insight::Collector::ptr const& collector, beast::Journal journal)
    : Stoppable ("LedgerMaster", parent)
    , app_ (app)
    , m_journal (journal)
    , mLastValidLedger (std::make_pair (uint256(), 0))
    , mLedgerHistory (collector, app)
    , mHeldTransactions (uint256 ())
    , mLedgerCleaner (detail::make_LedgerCleaner (
        app, *this, app_.journal("LedgerCleaner")))
    , mMinValidations (0)
    , mStrictValCount (false)
    , mLastValidateSeq (0)
    , mAdvanceThread (false)
    , mAdvanceWork (false)
    , mFillInProgress (0)
    , mPathFindThread (0)
    , mPathFindNewRequest (false)
    , mPubLedgerClose (0)
    , mPubLedgerSeq (0)
    , mValidLedgerSign (0)
    , mValidLedgerSeq (0)
    , mBuildingLedgerSeq (0)
    , standalone_ (app_.config().RUN_STANDALONE)
    , fetch_depth_ (app_.getSHAMapStore ().clampFetchDepth (
        app_.config().FETCH_DEPTH))
    , ledger_history_ (app_.config().LEDGER_HISTORY)
    , ledger_fetch_size_ (app_.config().getSize (siLedgerFetch))
    , fetch_packs_ ("FetchPack", 65536, 45, stopwatch,
        app_.journal("TaggedCache"))
    , fetch_seq_ (0)
{
}

LedgerIndex
LedgerMaster::getCurrentLedgerIndex ()
{
    return app_.openLedger().current()->info().seq;
}

LedgerIndex
LedgerMaster::getValidLedgerIndex ()
{
    return mValidLedgerSeq;
}

bool
LedgerMaster::isCompatible (Ledger::pointer ledger,
    beast::Journal::Stream s, const char* reason)
{
    if (mStrictValCount)
    {
        // If we're only using validation count, then we can't
        // reject a ledger even if it's incompatible
        return true;
    }

    auto validLedger = getValidatedLedger();

    if (validLedger &&
        ! areCompatible (*validLedger, *ledger, s, reason))
    {
        return false;
    }

    {
        ScopedLockType sl (m_mutex);

        if ((mLastValidLedger.second != 0) &&
            ! areCompatible (mLastValidLedger.first,
                mLastValidLedger.second, *ledger, s, reason))
        {
            return false;
        }
    }

    return true;
}

std::chrono::seconds
LedgerMaster::getPublishedLedgerAge()
{
    std::chrono::seconds pubClose{mPubLedgerClose.load()};
    if (pubClose == 0s)
    {
        JLOG (m_journal.debug) << "No published ledger";
        return weeks{2};
    }

    std::chrono::seconds ret = app_.timeKeeper().closeTime().time_since_epoch();
    ret -= pubClose;
    ret = (ret > 0s) ? ret : 0s;

    JLOG (m_journal.trace) << "Published ledger age is " << ret.count();
    return ret;
}

std::chrono::seconds
LedgerMaster::getValidatedLedgerAge()
{
    std::chrono::seconds valClose{mValidLedgerSign.load()};
    if (valClose == 0s)
    {
        JLOG (m_journal.debug) << "No validated ledger";
        return weeks{2};
    }

    std::chrono::seconds ret = app_.timeKeeper().closeTime().time_since_epoch();
    ret -= valClose;
    ret = (ret > 0s) ? ret : 0s;

    JLOG (m_journal.trace) << "Validated ledger age is " << ret.count();
    return ret;
}

bool
LedgerMaster::isCaughtUp(std::string& reason)
{
    if (getPublishedLedgerAge() > 3min)
    {
        reason = "No recently-published ledger";
        return false;
    }
    std::uint32_t validClose = mValidLedgerSign.load();
    std::uint32_t pubClose = mPubLedgerClose.load();
    if (!validClose || !pubClose)
    {
        reason = "No published ledger";
        return false;
    }
    if (validClose  > (pubClose + 90))
    {
        reason = "Published ledger lags validated ledger";
        return false;
    }
    return true;
}

void
LedgerMaster::setValidLedger(Ledger::ref l)
{
    std::vector <NetClock::time_point> times;
    NetClock::time_point signTime;
    if (! app_.config().RUN_STANDALONE)
        times = app_.getValidations().getValidationTimes(
            l->getHash());
    if (! times.empty () && times.size() >= mMinValidations)
    {
        // Calculate the sample median
        std::sort (times.begin (), times.end ());
        auto const t0 = times[(times.size() - 1) / 2];
        auto const t1 = times[times.size() / 2];
        signTime = t0 + (t1 - t0)/2;
    }
    else
    {
        signTime = l->info().closeTime;
    }

    mValidLedger.set (l);
    mValidLedgerSign = signTime.time_since_epoch().count();
    mValidLedgerSeq = l->info().seq;
    app_.getOPs().updateLocalTx (l);
    app_.getSHAMapStore().onLedgerClosed (getValidatedLedger());
    mLedgerHistory.validatedLedger (l);
    app_.getAmendmentTable().doValidatedLedger (l);
}

void
LedgerMaster::setPubLedger(Ledger::ref l)
{
    mPubLedger = l;
    mPubLedgerClose = l->info().closeTime.time_since_epoch().count();
    mPubLedgerSeq = l->info().seq;
}

void
LedgerMaster::addHeldTransaction (
    std::shared_ptr<Transaction> const& transaction)
{
    // returns true if transaction was added
    ScopedLockType ml (m_mutex);
    mHeldTransactions.insert (transaction->getSTransaction ());
}

void
LedgerMaster::switchLCL (Ledger::pointer lastClosed)
{
    assert (lastClosed);

    lastClosed->setClosed ();

    {
        ScopedLockType ml (m_mutex);

        mClosedLedger.set (lastClosed);
    }

    if (standalone_)
    {
        setFullLedger (lastClosed, true, false);
        tryAdvance();
    }
    else
    {
        checkAccept (lastClosed);
    }
}

bool
LedgerMaster::fixIndex (LedgerIndex ledgerIndex, LedgerHash const& ledgerHash)
{
    return mLedgerHistory.fixIndex (ledgerIndex, ledgerHash);
}

bool
LedgerMaster::storeLedger (Ledger::pointer ledger)
{
    // Returns true if we already had the ledger
    return mLedgerHistory.addLedger (ledger, false);
}

void
LedgerMaster::forceValid (Ledger::pointer ledger)
{
    ledger->setValidated();
    setFullLedger(ledger, true, false);
}

/** Apply held transactions to the open ledger
    This is normally called as we close the ledger.
    The open ledger remains open to handle new transactions
    until a new open ledger is built.
*/
void
LedgerMaster::applyHeldTransactions ()
{
    ScopedLockType sl (m_mutex);

    app_.openLedger().modify(
        [&](OpenView& view, beast::Journal j)
        {
            bool any = false;
            for (auto const& it : mHeldTransactions)
            {
                ApplyFlags flags = tapNONE;
                auto const result = app_.getTxQ().apply(
                    app_, view, it.second, flags, j);
                if (result.second)
                    any = true;
            }
            return any;
        });

    // VFALCO TODO recreate the CanonicalTxSet object instead of resetting
    // it.
    // VFALCO NOTE The hash for an open ledger is undefined so we use
    // something that is a reasonable substitute.
    mHeldTransactions.reset (
        app_.openLedger().current()->info().parentHash);
}

LedgerIndex
LedgerMaster::getBuildingLedger ()
{
    // The ledger we are currently building, 0 of none
    return mBuildingLedgerSeq.load ();
}

void
LedgerMaster::setBuildingLedger (LedgerIndex i)
{
    mBuildingLedgerSeq.store (i);
}

bool
LedgerMaster::haveLedger (std::uint32_t seq)
{
    ScopedLockType sl (mCompleteLock);
    return mCompleteLedgers.hasValue (seq);
}

void
LedgerMaster::clearLedger (std::uint32_t seq)
{
    ScopedLockType sl (mCompleteLock);
    return mCompleteLedgers.clearValue (seq);
}

// returns Ledgers we have all the nodes for
bool
LedgerMaster::getFullValidatedRange (std::uint32_t& minVal, std::uint32_t& maxVal)
{
    // Validated ledger is likely not stored in the DB yet so we use the
    // published ledger which is.
    maxVal = mPubLedgerSeq.load();

    if (!maxVal)
        return false;

    {
        ScopedLockType sl (mCompleteLock);
        minVal = mCompleteLedgers.prevMissing (maxVal);
    }

    if (minVal == RangeSet::absent)
        minVal = maxVal;
    else
        ++minVal;

    return true;
}

// Returns Ledgers we have all the nodes for and are indexed
bool
LedgerMaster::getValidatedRange (std::uint32_t& minVal, std::uint32_t& maxVal)
{
    // Validated ledger is likely not stored in the DB yet so we use the
    // published ledger which is.
    maxVal = mPubLedgerSeq.load();

    if (!maxVal)
        return false;

    {
        ScopedLockType sl (mCompleteLock);
        minVal = mCompleteLedgers.prevMissing (maxVal);
    }

    if (minVal == RangeSet::absent)
        minVal = maxVal;
    else
        ++minVal;

    // Remove from the validated range any ledger sequences that may not be
    // fully updated in the database yet

    auto const pendingSaves =
        app_.pendingSaves().getSnapshot();

    if (!pendingSaves.empty() && ((minVal != 0) || (maxVal != 0)))
    {
        // Ensure we shrink the tips as much as possible. If we have 7-9 and
        // 8,9 are invalid, we don't want to see the 8 and shrink to just 9
        // because then we'll have nothing when we could have 7.
        while (pendingSaves.count(maxVal) > 0)
            --maxVal;
        while (pendingSaves.count(minVal) > 0)
            ++minVal;

        // Best effort for remaining exclusions
        for(auto v : pendingSaves)
        {
            if ((v.first >= minVal) && (v.first <= maxVal))
            {
                if (v.first > ((minVal + maxVal) / 2))
                    maxVal = v.first - 1;
                else
                    minVal = v.first + 1;
            }
        }

        if (minVal > maxVal)
            minVal = maxVal = 0;
    }

    return true;
}

// Get the earliest ledger we will let peers fetch
std::uint32_t
LedgerMaster::getEarliestFetch ()
{
    // The earliest ledger we will let people fetch is ledger zero,
    // unless that creates a larger range than allowed
    std::uint32_t e = getClosedLedger()->info().seq;

    if (e > fetch_depth_)
        e -= fetch_depth_;
    else
        e = 0;
    return e;
}

void
LedgerMaster::tryFill (Job& job, Ledger::pointer ledger)
{
    std::uint32_t seq = ledger->info().seq;
    uint256 prevHash = ledger->info().parentHash;

    std::map< std::uint32_t, std::pair<uint256, uint256> > ledgerHashes;

    std::uint32_t minHas = ledger->info().seq;
    std::uint32_t maxHas = ledger->info().seq;

    while (! job.shouldCancel() && seq > 0)
    {
        {
            ScopedLockType ml (m_mutex);
            minHas = seq;
            --seq;

            if (haveLedger (seq))
                break;
        }

        auto it (ledgerHashes.find (seq));

        if (it == ledgerHashes.end ())
        {
            if (app_.isShutdown ())
                return;

            {
                ScopedLockType ml (mCompleteLock);
                mCompleteLedgers.setRange (minHas, maxHas);
            }
            maxHas = minHas;
            ledgerHashes = getHashesByIndex ((seq < 500)
                ? 0
                : (seq - 499), seq, app_);
            it = ledgerHashes.find (seq);

            if (it == ledgerHashes.end ())
                break;
        }

        if (it->second.first != prevHash)
            break;

        prevHash = it->second.second;
    }

    {
        ScopedLockType ml (mCompleteLock);
        mCompleteLedgers.setRange (minHas, maxHas);
    }
    {
        ScopedLockType ml (m_mutex);
        mFillInProgress = 0;
        tryAdvance();
    }
}

/** Request a fetch pack to get to the specified ledger
*/
void
LedgerMaster::getFetchPack (LedgerHash missingHash, LedgerIndex missingIndex)
{
    uint256 haveHash = getLedgerHashForHistory (missingIndex + 1);

    if (haveHash.isZero())
    {
        JLOG (m_journal.error) << "No hash for fetch pack";
        return;
    }

    // Select target Peer based on highest score.  The score is randomized
    // but biased in favor of Peers with low latency.
    Peer::ptr target;
    {
        int maxScore = 0;
        auto peerList = app_.overlay ().getActivePeers();
        for (auto const& peer : peerList)
        {
            if (peer->hasRange (missingIndex, missingIndex + 1))
            {
                int score = peer->getScore (true);
                if (! target || (score > maxScore))
                {
                    target = peer;
                    maxScore = score;
                }
            }
        }
    }

    if (target)
    {
        protocol::TMGetObjectByHash tmBH;
        tmBH.set_query (true);
        tmBH.set_type (protocol::TMGetObjectByHash::otFETCH_PACK);
        tmBH.set_ledgerhash (haveHash.begin(), 32);
        auto packet = std::make_shared<Message> (
            tmBH, protocol::mtGET_OBJECTS);

        target->send (packet);
        JLOG (m_journal.trace) << "Requested fetch pack for "
                                            << missingIndex;
    }
    else
        JLOG (m_journal.debug) << "No peer for fetch pack";
}

void
LedgerMaster::fixMismatch (Ledger::ref ledger)
{
    int invalidate = 0;
    boost::optional<uint256> hash;

    for (std::uint32_t lSeq = ledger->info().seq - 1; lSeq > 0; --lSeq)
    {
        if (haveLedger (lSeq))
        {
            try
            {
                hash = hashOfSeq(*ledger, lSeq, m_journal);
            }
            catch (std::exception const&)
            {
                JLOG (m_journal.warning) <<
                    "fixMismatch encounters partial ledger";
                clearLedger(lSeq);
                return;
            }

            if (hash)
            {
                // try to close the seam
                Ledger::pointer otherLedger = getLedgerBySeq (lSeq);

                if (otherLedger && (otherLedger->getHash () == *hash))
                {
                    // we closed the seam
                    CondLog (invalidate != 0, lsWARNING, LedgerMaster) <<
                        "Match at " << lSeq << ", " << invalidate <<
                        " prior ledgers invalidated";
                    return;
                }
            }

            clearLedger (lSeq);
            ++invalidate;
        }
    }

    // all prior ledgers invalidated
    CondLog (invalidate != 0, lsWARNING, LedgerMaster) << "All " <<
        invalidate << " prior ledgers invalidated";
}

void
LedgerMaster::setFullLedger (
    Ledger::pointer ledger, bool isSynchronous, bool isCurrent)
{
    // A new ledger has been accepted as part of the trusted chain
    JLOG (m_journal.debug) << "Ledger " << ledger->info().seq
                            << " accepted :" << ledger->getHash ();
    assert (ledger->stateMap().getHash ().isNonZero ());

    ledger->setValidated();
    ledger->setFull();

    if (isCurrent)
        mLedgerHistory.addLedger(ledger, true);

    {
        // Check the SQL database's entry for the sequence before this
        // ledger, if it's not this ledger's parent, invalidate it
        uint256 prevHash = getHashByIndex (ledger->info().seq - 1, app_);
        if (prevHash.isNonZero () && prevHash != ledger->info().parentHash)
            clearLedger (ledger->info().seq - 1);
    }


    pendSaveValidated (app_, ledger, isSynchronous, isCurrent);

    {

        {
            ScopedLockType ml (mCompleteLock);
            mCompleteLedgers.setValue (ledger->info().seq);
        }

        ScopedLockType ml (m_mutex);

        if (ledger->info().seq > mValidLedgerSeq)
            setValidLedger(ledger);
        if (!mPubLedger)
        {
            setPubLedger(ledger);
            app_.getOrderBookDB().setup(ledger);
        }

        if (ledger->info().seq != 0 && haveLedger (ledger->info().seq - 1))
        {
            // we think we have the previous ledger, double check
            auto prevLedger = getLedgerBySeq (ledger->info().seq - 1);

            if (!prevLedger ||
                (prevLedger->getHash () != ledger->info().parentHash))
            {
                JLOG (m_journal.warning)
                        << "Acquired ledger invalidates previous ledger: "
                        << (prevLedger ? "hashMismatch" : "missingLedger");
                fixMismatch (ledger);
            }
        }
    }
}

void
LedgerMaster::failedSave(std::uint32_t seq, uint256 const& hash)
{
    clearLedger(seq);
    app_.getInboundLedgers().acquire(
        hash, seq, InboundLedger::fcGENERIC);
}

// Check if the specified ledger can become the new last fully-validated
// ledger.
void
LedgerMaster::checkAccept (uint256 const& hash, std::uint32_t seq)
{

    int valCount;

    if (seq != 0)
    {
        // Ledger is too old
        if (seq < mValidLedgerSeq)
            return;

        valCount =
            app_.getValidations().getTrustedValidationCount (hash);

        if (valCount >= mMinValidations)
        {
            ScopedLockType ml (m_mutex);
            if (seq > mLastValidLedger.second)
                mLastValidLedger = std::make_pair (hash, seq);

            if (!mStrictValCount && (mMinValidations < (valCount/2 + 1)))
            {
                mMinValidations = (valCount/2 + 1);
                JLOG (m_journal.info)
                    << "Raising minimum validations to " << mMinValidations;
            }
        }

        if (seq == mValidLedgerSeq)
            return;

        // Ledger could match the ledger we're already building
        if (seq == mBuildingLedgerSeq)
            return;
    }

    Ledger::pointer ledger = mLedgerHistory.getLedgerByHash (hash);

    if (!ledger)
    {
        if ((seq != 0) && (getValidLedgerIndex() == 0))
        {
            // Set peers sane early if we can
            if (valCount >= mMinValidations)
                app_.overlay().checkSanity (seq);
        }

        // FIXME: We may not want to fetch a ledger with just one
        // trusted validation
        ledger = app_.getInboundLedgers().acquire(
            hash, 0, InboundLedger::fcGENERIC);
    }

    if (ledger)
        checkAccept (ledger);
}

/**
    * Determines how many validations are needed to fully-validated a ledger
    *
    * @return Number of validations needed
    */
int
LedgerMaster::getNeededValidations ()
{
    if (standalone_)
        return 0;

    int minVal = mMinValidations;

    if (mLastValidateHash.isNonZero ())
    {
        int val = app_.getValidations ().getTrustedValidationCount (
            mLastValidateHash);
        val *= MIN_VALIDATION_RATIO;
        val /= 256;

        if (val > minVal)
            minVal = val;
    }

    return minVal;
}

void
LedgerMaster::checkAccept (Ledger::ref ledger)
{
    if (ledger->info().seq <= mValidLedgerSeq)
        return;

    // Can we advance the last fully-validated ledger? If so, can we
    // publish?
    ScopedLockType ml (m_mutex);

    if (ledger->info().seq <= mValidLedgerSeq)
        return;

    int minVal = getNeededValidations();
    int tvc = app_.getValidations().getTrustedValidationCount(
        ledger->getHash());
    if (tvc < minVal) // nothing we can do
    {
        JLOG (m_journal.trace)
            << "Only " << tvc << " validations for " << ledger->getHash();
        return;
    }

    JLOG (m_journal.info)
        << "Advancing accepted ledger to " << ledger->info().seq
        << " with >= " << minVal << " validations";

    mLastValidateHash = ledger->getHash();
    mLastValidateSeq = ledger->info().seq;

    ledger->setValidated();
    ledger->setFull();
    setValidLedger(ledger);
    if (!mPubLedger)
    {
        pendSaveValidated(app_, ledger, true, true);
        setPubLedger(ledger);
        app_.getOrderBookDB().setup(ledger);
    }

    std::uint64_t const base = app_.getFeeTrack().getLoadBase();
    auto fees = app_.getValidations().fees (ledger->getHash(), base);
    {
        auto fees2 = app_.getValidations().fees (
            ledger->info(). parentHash, base);
        fees.reserve (fees.size() + fees2.size());
        std::copy (fees2.begin(), fees2.end(), std::back_inserter(fees));
    }
    std::uint64_t fee;
    if (! fees.empty())
    {
        std::sort (fees.begin(), fees.end());
        fee = fees[fees.size() / 2]; // median
    }
    else
    {
        fee = base;
    }

    app_.getFeeTrack().setRemoteFee(fee);

    tryAdvance ();
}

/** Report that the consensus process built a particular ledger */
void
LedgerMaster::consensusBuilt (Ledger::ref ledger, Json::Value consensus)
{

    // Because we just built a ledger, we are no longer building one
    setBuildingLedger (0);

    // No need to process validations in standalone mode
    if (standalone_)
        return;

    if (ledger->info().seq <= mValidLedgerSeq)
    {
        JLOG (app_.journal ("LedgerConsensus").info)
            << "Consensus built old ledger: "
            << ledger->info().seq << " <= " << mValidLedgerSeq;
        return;
    }

    // See if this ledger can be the new fully-validated ledger
    checkAccept (ledger);

    if (ledger->info().seq <= mValidLedgerSeq)
    {
        JLOG (app_.journal ("LedgerConsensus").debug)
            << "Consensus ledger fully validated";
        return;
    }

    // This ledger cannot be the new fully-validated ledger, but
    // maybe we saved up validations for some other ledger that can be

    auto const val =
        app_.getValidations().getCurrentTrustedValidations();

    // Track validation counts with sequence numbers
    class valSeq
    {
        public:

        valSeq () : valCount_ (0), ledgerSeq_ (0) { ; }

        void mergeValidation (LedgerIndex seq)
        {
            valCount_++;

            // If we didn't already know the sequence, now we do
            if (ledgerSeq_ == 0)
                ledgerSeq_ = seq;
        }

        int valCount_;
        LedgerIndex ledgerSeq_;
    };

    // Count the number of current, trusted validations
    hash_map <uint256, valSeq> count;
    for (auto const& v : val)
    {
        valSeq& vs = count[v->getLedgerHash()];
        vs.mergeValidation (v->getFieldU32 (sfLedgerSequence));
    }

    auto neededValidations = getNeededValidations ();
    auto maxSeq = mValidLedgerSeq.load();
    auto maxLedger = ledger->getHash();

    // Of the ledgers with sufficient validations,
    // find the one with the highest sequence
    for (auto& v : count)
        if (v.second.valCount_ > neededValidations)
        {
            // If we still don't know the sequence, get it
            if (v.second.ledgerSeq_ == 0)
            {
                Ledger::pointer ledger = getLedgerByHash (v.first);
                if (ledger)
                    v.second.ledgerSeq_ = ledger->info().seq;
            }

            if (v.second.ledgerSeq_ > maxSeq)
            {
                maxSeq = v.second.ledgerSeq_;
                maxLedger = v.first;
            }
        }

    if (maxSeq > mValidLedgerSeq)
    {
        JLOG (app_.journal ("LedgerConsensus").debug)
            << "Consensus triggered check of ledger";
        checkAccept (maxLedger, maxSeq);
    }

    mLedgerHistory.builtLedger (ledger, std::move (consensus));
}

void
LedgerMaster::advanceThread()
{
    ScopedLockType sl (m_mutex);
    assert (!mValidLedger.empty () && mAdvanceThread);

    JLOG (m_journal.trace) << "advanceThread<";

    try
    {
        doAdvance();
    }
    catch (std::exception const&)
    {
        JLOG (m_journal.fatal) << "doAdvance throws an exception";
    }

    mAdvanceThread = false;
    JLOG (m_journal.trace) << "advanceThread>";
}

// VFALCO NOTE This should return boost::optional<uint256>
LedgerHash
LedgerMaster::getLedgerHashForHistory (LedgerIndex index)
{
    // Try to get the hash of a ledger we need to fetch for history
    boost::optional<LedgerHash> ret;

    if (mHistLedger && (mHistLedger->info().seq >= index))
    {
        ret = hashOfSeq(*mHistLedger, index, m_journal);
        if (! ret)
            ret = walkHashBySeq (index, mHistLedger);
    }

    if (! ret)
        ret = walkHashBySeq (index);

    return *ret;
}

bool
LedgerMaster::shouldFetchPack (std::uint32_t seq) const
{
    return (fetch_seq_ != seq);
}

std::vector<Ledger::pointer>
LedgerMaster::findNewLedgersToPublish ()
{
    std::vector<Ledger::pointer> ret;

    JLOG (m_journal.trace) << "findNewLedgersToPublish<";
    if (mValidLedger.empty ())
    {
        // No valid ledger, nothing to do
    }
    else if (! mPubLedger)
    {
        JLOG (m_journal.info) << "First published ledger will be "
                                        << mValidLedgerSeq;
        ret.push_back (mValidLedger.get ());
    }
    else if (mValidLedgerSeq > (mPubLedgerSeq + MAX_LEDGER_GAP))
    {
        JLOG (m_journal.warning)
            << "Gap in validated ledger stream " << mPubLedgerSeq
            << " - " << mValidLedgerSeq - 1;
        Ledger::pointer valLedger = mValidLedger.get ();
        ret.push_back (valLedger);
        setPubLedger (valLedger);
        app_.getOrderBookDB().setup(valLedger);
    }
    else if (mValidLedgerSeq > mPubLedgerSeq)
    {
        int acqCount = 0;

        auto pubSeq = mPubLedgerSeq + 1; // Next sequence to publish
        Ledger::pointer valLedger = mValidLedger.get ();
        std::uint32_t valSeq = valLedger->info().seq;

        ScopedUnlockType sul(m_mutex);
        try
        {
            for (std::uint32_t seq = pubSeq; seq <= valSeq; ++seq)
            {
                JLOG (m_journal.trace)
                    << "Trying to fetch/publish valid ledger " << seq;

                Ledger::pointer ledger;
                // This can throw
                auto hash = hashOfSeq(*valLedger, seq, m_journal);
                // VFALCO TODO Restructure this code so that zero is not
                // used.
                if (! hash)
                    hash = zero; // kludge
                if (seq == valSeq)
                {
                    // We need to publish the ledger we just fully validated
                    ledger = valLedger;
                }
                else if (hash->isZero())
                {
                    JLOG (m_journal.fatal)
                        << "Ledger: " << valSeq
                        << " does not have hash for " << seq;
                    assert (false);
                }
                else
                {
                    ledger = mLedgerHistory.getLedgerByHash (*hash);
                }

                // Can we try to acquire the ledger we need?
                if (! ledger && (++acqCount < 4))
                    ledger = app_.getInboundLedgers ().acquire(
                        *hash, seq, InboundLedger::fcGENERIC);

                // Did we acquire the next ledger we need to publish?
                if (ledger && (ledger->info().seq == pubSeq))
                {
                    ledger->setValidated();
                    ret.push_back (ledger);
                    ++pubSeq;
                }

            }
        }
        catch (std::exception const&)
        {
            JLOG (m_journal.error)
                << "findNewLedgersToPublish catches an exception";
        }
    }

    JLOG (m_journal.trace)
        << "findNewLedgersToPublish> " << ret.size();
    return ret;
}

void
LedgerMaster::tryAdvance()
{
    ScopedLockType ml (m_mutex);

    // Can't advance without at least one fully-valid ledger
    mAdvanceWork = true;
    if (!mAdvanceThread && !mValidLedger.empty ())
    {
        mAdvanceThread = true;
        app_.getJobQueue ().addJob (
            jtADVANCE, "advanceLedger",
            [this] (Job&) { advanceThread(); });
    }
}

// Return the hash of the valid ledger with a particular sequence, given a
// subsequent ledger known valid.
// VFALCO NOTE This should return boost::optional<uint256>
uint256
LedgerMaster::getLedgerHash(std::uint32_t desiredSeq, Ledger::ref knownGoodLedger)
{
    assert(desiredSeq < knownGoodLedger->info().seq);

    auto hash = hashOfSeq(*knownGoodLedger, desiredSeq, m_journal);

    // Not directly in the given ledger
    if (! hash)
    {
        std::uint32_t seq = (desiredSeq + 255) % 256;
        assert(seq < desiredSeq);

        hash = hashOfSeq(*knownGoodLedger, seq, m_journal);
        if (hash)
        {
            auto l = getLedgerByHash(*hash);
            if (l)
            {
                hash = hashOfSeq(*l, desiredSeq, m_journal);
                assert (hash);
            }
        }
        else
        {
            assert(false);
        }
    }

    // VFALCO NOTE This shouldn't be needed, but
    //             preserves original behavior.
    return hash ? *hash : zero; // kludge
}

void
LedgerMaster::updatePaths (Job& job)
{
    {
        ScopedLockType ml (m_mutex);
        if (app_.getOPs().isNeedNetworkLedger())
        {
            --mPathFindThread;
            return;
        }
    }


    while (! job.shouldCancel())
    {
        std::shared_ptr<ReadView const> lastLedger;
        {
            ScopedLockType ml (m_mutex);

            if (!mValidLedger.empty() &&
                (!mPathLedger ||
                    (mPathLedger->info().seq != mValidLedgerSeq)))
            { // We have a new valid ledger since the last full pathfinding
                mPathLedger = mValidLedger.get ();
                lastLedger = mPathLedger;
            }
            else if (mPathFindNewRequest)
            { // We have a new request but no new ledger
                lastLedger = app_.openLedger().current();
            }
            else
            { // Nothing to do
                --mPathFindThread;
                return;
            }
        }

        if (!standalone_)
        { // don't pathfind with a ledger that's more than 60 seconds old
            using namespace std::chrono;
            auto age = time_point_cast<seconds>(app_.timeKeeper().closeTime())
                - lastLedger->info().closeTime;
            if (age > 1min)
            {
                JLOG (m_journal.debug)
                        << "Published ledger too old for updating paths";
                --mPathFindThread;
                return;
            }
        }

        try
        {
            app_.getPathRequests().updateAll(
                lastLedger, job.getCancelCallback());
        }
        catch (SHAMapMissingNode&)
        {
            JLOG (m_journal.info)
                    << "Missing node detected during pathfinding";
            if (lastLedger->info().open)
            {
                // our parent is the problem
                app_.getInboundLedgers().acquire(
                    lastLedger->info().parentHash, lastLedger->info().seq - 1,
                    InboundLedger::fcGENERIC);
            }
            else
            {
                // this ledger is the problem
                app_.getInboundLedgers().acquire(
                    lastLedger->info().hash, lastLedger->info().seq,
                    InboundLedger::fcGENERIC);
                }
        }
    }
}

void
LedgerMaster::newPathRequest ()
{
    ScopedLockType ml (m_mutex);
    mPathFindNewRequest = true;

    newPFWork("pf:newRequest");
}

bool
LedgerMaster::isNewPathRequest ()
{
    ScopedLockType ml (m_mutex);
    if (!mPathFindNewRequest)
        return false;
    mPathFindNewRequest = false;
    return true;
}

// If the order book is radically updated, we need to reprocess all
// pathfinding requests.
void
LedgerMaster::newOrderBookDB ()
{
    ScopedLockType ml (m_mutex);
    mPathLedger.reset();

    newPFWork("pf:newOBDB");
}

/** A thread needs to be dispatched to handle pathfinding work of some kind.
*/
void
LedgerMaster::newPFWork (const char *name)
{
    if (mPathFindThread < 2)
    {
        ++mPathFindThread;
        app_.getJobQueue().addJob (
            jtUPDATE_PF, name,
            [this] (Job& j) { updatePaths(j); });
    }
}

std::recursive_mutex&
LedgerMaster::peekMutex ()
{
    return m_mutex;
}

// The current ledger is the ledger we believe new transactions should go in
std::shared_ptr<ReadView const>
LedgerMaster::getCurrentLedger ()
{
    return app_.openLedger().current();
}

// The finalized ledger is the last closed/accepted ledger
Ledger::pointer
LedgerMaster::getClosedLedger ()
{
    return mClosedLedger.get ();
}

// The validated ledger is the last fully validated ledger
Ledger::pointer
LedgerMaster::getValidatedLedger ()
{
    return mValidLedger.get ();
}

Rules
LedgerMaster::getValidatedRules ()
{
    // Once we have a guarantee that there's always a last validated
    // ledger then we can dispense with the if.

    // Return the Rules from the last validated ledger.
    if (auto const ledger = getValidatedLedger())
        return ledger->rules();

    return Rules();
}

// This is the last ledger we published to clients and can lag the validated
// ledger.
Ledger::pointer
LedgerMaster::getPublishedLedger ()
{
    ScopedLockType lock(m_mutex);
    return mPubLedger;
}

bool
LedgerMaster::isValidLedger(LedgerInfo const& info)
{
    if (info.validated)
        return true;

    if (info.open)
        return false;

    auto seq = info.seq;
    try
    {
        // Use the skip list in the last validated ledger to see if ledger
        // comes before the last validated ledger (and thus has been
        // validated).
        auto hash = walkHashBySeq (seq);
        if (info.hash != hash)
            return false;
    }
    catch (SHAMapMissingNode const&)
    {
        JLOG (app_.journal ("RPCHandler").warning)
                << "Missing SHANode " << std::to_string (seq);
        return false;
    }

    // Mark ledger as validated to save time if we see it again.
    info.validated = true;
    return true;
}

int
LedgerMaster::getMinValidations ()
{
    return mMinValidations;
}

void
LedgerMaster::setMinValidations (int v, bool strict)
{
    JLOG (m_journal.info) << "Validation quorum: " << v
        << (strict ? " strict" : "");
    mMinValidations = v;
    mStrictValCount = strict;
}

std::string
LedgerMaster::getCompleteLedgers ()
{
    ScopedLockType sl (mCompleteLock);
    return mCompleteLedgers.toString ();
}

boost::optional <NetClock::time_point>
LedgerMaster::getCloseTimeBySeq (LedgerIndex ledgerIndex)
{
    uint256 hash = getHashBySeq (ledgerIndex);
    return hash.isNonZero() ? getCloseTimeByHash (hash) : boost::none;
}

boost::optional <NetClock::time_point>
LedgerMaster::getCloseTimeByHash (LedgerHash const& ledgerHash)
{
    auto node = app_.getNodeStore().fetch (ledgerHash);
    if (node &&
        (node->getData().size() >= 120))
    {
        SerialIter it (node->getData().data(), node->getData().size());
        if (it.get32() == HashPrefix::ledgerMaster)
        {
            it.skip (
                4+8+32+    // seq drops parentHash
                32+32+4);  // txHash acctHash parentClose
            return NetClock::time_point{NetClock::duration{it.get32()}};
        }
    }

    return boost::none;
}

uint256
LedgerMaster::getHashBySeq (std::uint32_t index)
{
    uint256 hash = mLedgerHistory.getLedgerHash (index);

    if (hash.isNonZero ())
        return hash;

    return getHashByIndex (index, app_);
}

// VFALCO NOTE This should return boost::optional<uint256>
uint256
LedgerMaster::walkHashBySeq (std::uint32_t index)
{
    uint256 ledgerHash;
    Ledger::pointer referenceLedger;

    referenceLedger = mValidLedger.get ();
    if (referenceLedger)
        ledgerHash = walkHashBySeq (index, referenceLedger);
    return ledgerHash;
}

/** Walk the chain of ledger hashed to determine the hash of the
    ledger with the specified index. The referenceLedger is used as
    the base of the chain and should be fully validated and must not
    precede the target index. This function may throw if nodes
    from the reference ledger or any prior ledger are not present
    in the node store.
*/
// VFALCO NOTE This should return boost::optional<uint256>
uint256
LedgerMaster::walkHashBySeq (std::uint32_t index, Ledger::ref referenceLedger)
{
    if (!referenceLedger || (referenceLedger->info().seq < index))
    {
        // Nothing we can do. No validated ledger.
        return zero;
    }

    // See if the hash for the ledger we need is in the reference ledger
    auto ledgerHash = hashOfSeq(*referenceLedger, index, m_journal);
    if (ledgerHash)
        return *ledgerHash;

    // The hash is not in the reference ledger. Get another ledger which can
    // be located easily and should contain the hash.
    LedgerIndex refIndex = getCandidateLedger(index);
    auto const refHash = hashOfSeq(*referenceLedger, refIndex, m_journal);
    assert(refHash);
    if (refHash)
    {
        // Try the hash and sequence of a better reference ledger just found
        auto ledger = mLedgerHistory.getLedgerByHash (*refHash);

        if (ledger)
        {
            try
            {
                ledgerHash = hashOfSeq(*ledger, index, m_journal);
            }
            catch(SHAMapMissingNode&)
            {
                ledger.reset();
            }
        }

        // Try to acquire the complete ledger
        if (!ledger)
        {
            auto const ledger = app_.getInboundLedgers().acquire (
                *refHash, refIndex, InboundLedger::fcGENERIC);
            if (ledger)
            {
                ledgerHash = hashOfSeq(*ledger, index, m_journal);
                assert (ledgerHash);
            }
        }
    }
    return ledgerHash ? *ledgerHash : zero; // kludge
}

Ledger::pointer
LedgerMaster::getLedgerBySeq (std::uint32_t index)
{
    if (index <= mValidLedgerSeq)
    {
        // Always prefer a validated ledger
        auto valid = mValidLedger.get ();
        if (valid)
        {
            if (valid->info().seq == index)
                return valid;

            try
            {
                auto const hash = hashOfSeq(*valid, index, m_journal);
                if (hash)
                    return mLedgerHistory.getLedgerByHash (*hash);
            }
            catch (std::exception const&)
            {
                // Missing nodes are already handled
            }
        }
    }

    Ledger::pointer ret = mLedgerHistory.getLedgerBySeq (index);
    if (ret)
        return ret;

    ret = mClosedLedger.get ();
    if (ret && (ret->info().seq == index))
        return ret;

    clearLedger (index);
    return Ledger::pointer();
}

Ledger::pointer
LedgerMaster::getLedgerByHash (uint256 const& hash)
{
    Ledger::pointer ret = mLedgerHistory.getLedgerByHash (hash);
    if (ret)
        return ret;

    ret = mClosedLedger.get ();
    if (ret && (ret->getHash () == hash))
        return ret;

    return Ledger::pointer ();
}

void
LedgerMaster::doLedgerCleaner(Json::Value const& parameters)
{
    mLedgerCleaner->doClean (parameters);
}

void
LedgerMaster::setLedgerRangePresent (std::uint32_t minV, std::uint32_t maxV)
{
    ScopedLockType sl (mCompleteLock);
    mCompleteLedgers.setRange (minV, maxV);
}

void
LedgerMaster::tune (int size, int age)
{
    mLedgerHistory.tune (size, age);
}

void
LedgerMaster::sweep ()
{
    mLedgerHistory.sweep ();
    fetch_packs_.sweep ();
}

float
LedgerMaster::getCacheHitRate ()
{
    return mLedgerHistory.getCacheHitRate ();
}

beast::PropertyStream::Source&
LedgerMaster::getPropertySource ()
{
    return *mLedgerCleaner;
}

void
LedgerMaster::clearPriorLedgers (LedgerIndex seq)
{
    ScopedLockType sl (mCompleteLock);
    for (LedgerIndex i = mCompleteLedgers.getFirst(); i < seq; ++i)
    {
        if (haveLedger (i))
            clearLedger (i);
    }
}

void
LedgerMaster::clearLedgerCachePrior (LedgerIndex seq)
{
    mLedgerHistory.clearLedgerCachePrior (seq);
}

void
LedgerMaster::takeReplay (std::unique_ptr<LedgerReplay> replay)
{
    replayData = std::move (replay);
}

std::unique_ptr<LedgerReplay>
LedgerMaster::releaseReplay ()
{
    return std::move (replayData);
}

bool
LedgerMaster::shouldAcquire (
    std::uint32_t const currentLedger,
    std::uint32_t const ledgerHistory,
    std::uint32_t const ledgerHistoryIndex,
    std::uint32_t const candidateLedger) const
{
    bool ret (candidateLedger >= currentLedger ||
        candidateLedger > ledgerHistoryIndex ||
        (currentLedger - candidateLedger) <= ledgerHistory);

    JLOG (m_journal.trace)
        << "Missing ledger "
        << candidateLedger
        << (ret ? " should" : " should NOT")
        << " be acquired";
    return ret;
}

// Try to publish ledgers, acquire missing ledgers
void LedgerMaster::doAdvance ()
{
    // TODO NIKB: simplify and unindent this a bit!

    do
    {
        mAdvanceWork = false; // If there's work to do, we'll make progress
        bool progress = false;

        auto const pubLedgers = findNewLedgersToPublish ();
        if (pubLedgers.empty())
        {
            if (!standalone_ && !app_.getFeeTrack().isLoadedLocal() &&
                (app_.getJobQueue().getJobCount(jtPUBOLDLEDGER) < 10) &&
                (mValidLedgerSeq == mPubLedgerSeq) &&
                (getValidatedLedgerAge() < MAX_LEDGER_AGE_ACQUIRE))
            { // We are in sync, so can acquire
                std::uint32_t missing;
                {
                    ScopedLockType sl (mCompleteLock);
                    missing = mCompleteLedgers.prevMissing(
                        mPubLedger->info().seq);
                }
                JLOG (m_journal.trace)
                    << "tryAdvance discovered missing " << missing;
                if ((missing != RangeSet::absent) && (missing > 0) &&
                    shouldAcquire (mValidLedgerSeq, ledger_history_,
                        app_.getSHAMapStore ().getCanDelete (), missing) &&
                    ((mFillInProgress == 0) || (missing > mFillInProgress)))
                {
                    JLOG (m_journal.trace)
                        << "advanceThread should acquire";
                    {
                        ScopedUnlockType sl(m_mutex);
                        uint256 hash = getLedgerHashForHistory (missing);
                        if (hash.isNonZero())
                        {
                            Ledger::pointer ledger = getLedgerByHash (hash);
                            if (!ledger)
                            {
                                if (!app_.getInboundLedgers().isFailure (
                                        hash))
                                {
                                    ledger =
                                        app_.getInboundLedgers().acquire(
                                            hash, missing,
                                            InboundLedger::fcHISTORY);
                                    if (! ledger && (missing > 32600) &&
                                        shouldFetchPack (missing))
                                    {
                                        JLOG (m_journal.trace) <<
                                        "tryAdvance want fetch pack " <<
                                        missing;
                                        fetch_seq_ = missing;
                                        getFetchPack(hash, missing);
                                    }
                                    else
                                        JLOG (m_journal.trace) <<
                                        "tryAdvance no fetch pack for " <<
                                        missing;
                                }
                                else
                                    JLOG (m_journal.debug) <<
                                    "tryAdvance found failed acquire";
                            }
                            if (ledger)
                            {
                                auto seq = ledger->info().seq;
                                assert(seq == missing);
                                JLOG (m_journal.trace)
                                        << "tryAdvance acquired "
                                        << ledger->info().seq;
                                setFullLedger(ledger, false, false);
                                auto& parent = ledger->info().parentHash;

                                int fillInProgress;
                                {
                                    ScopedLockType lock(m_mutex);
                                    mHistLedger = ledger;
                                    fillInProgress = mFillInProgress;
                                }

                                if (fillInProgress == 0 &&
                                    getHashByIndex(seq - 1, app_) == parent)
                                {
                                    {
                                        // Previous ledger is in DB
                                        ScopedLockType lock(m_mutex);
                                        mFillInProgress = ledger->info().seq;
                                    }

                                    app_.getJobQueue().addJob(
                                        jtADVANCE, "tryFill",
                                        [this, ledger] (Job& j) {
                                            tryFill(j, ledger);
                                        });
                                }

                                progress = true;
                            }
                            else
                            {
                                try
                                {
                                    for (int i = 0; i < ledger_fetch_size_; ++i)
                                    {
                                        std::uint32_t seq = missing - i;
                                        auto hash =
                                                getLedgerHashForHistory(seq);
                                        if (hash.isNonZero())
                                            app_.getInboundLedgers().acquire
                                                    (hash, seq,
                                                     InboundLedger::fcHISTORY);
                                    }
                                }
                                catch (std::exception const&)
                                {
                                    JLOG (m_journal.warning) <<
                                    "Threw while prefetching";
                                }
                            }
                        }
                        else
                        {
                            JLOG (m_journal.fatal) <<
                                "Can't find ledger following prevMissing " <<
                                missing;
                            JLOG (m_journal.fatal) << "Pub:" <<
                                mPubLedgerSeq << " Val:" << mValidLedgerSeq;
                            JLOG (m_journal.fatal) << "Ledgers: " <<
                                app_.getLedgerMaster().getCompleteLedgers();
                            clearLedger (missing + 1);
                            progress = true;
                        }
                    }
                    if (mValidLedgerSeq != mPubLedgerSeq)
                    {
                        JLOG (m_journal.debug) <<
                            "tryAdvance found last valid changed";
                        progress = true;
                    }
                }
            }
            else
            {
                mHistLedger.reset();
                JLOG (m_journal.trace) <<
                    "tryAdvance not fetching history";
            }
        }
        else
        {
            JLOG (m_journal.trace) <<
                "tryAdvance found " << pubLedgers.size() <<
                " ledgers to publish";
            for(auto ledger : pubLedgers)
            {
                {
                    ScopedUnlockType sul (m_mutex);
                    JLOG (m_journal.debug) <<
                        "tryAdvance publishing seq " << ledger->info().seq;

                    setFullLedger(ledger, true, true);
                }

                setPubLedger(ledger);

                {
                    ScopedUnlockType sul(m_mutex);
                    app_.getOPs().pubLedger(ledger);
                }
            }

            progress = true;
            app_.getOPs().clearNeedNetworkLedger();
            newPFWork ("pf:newLedger");
        }
        if (progress)
            mAdvanceWork = true;
    } while (mAdvanceWork);
}

void
LedgerMaster::addFetchPack (
    uint256 const& hash,
    std::shared_ptr< Blob >& data)
{
    fetch_packs_.canonicalize (hash, data);
}

bool
LedgerMaster::getFetchPack (
    uint256 const& hash,
    Blob& data)
{
    if (!fetch_packs_.retrieve (hash, data))
        return false;

    fetch_packs_.del (hash, false);

    return hash == sha512Half(makeSlice(data));
}

void
LedgerMaster::gotFetchPack (
    bool progress,
    std::uint32_t seq)
{
    // FIXME: Calling this function more than once will result in
    // InboundLedgers::gotFetchPack being called more than once
    // which is expensive. A flag should track whether we've already dispatched

    app_.getJobQueue().addJob (
        jtLEDGER_DATA, "gotFetchPack",
        [&] (Job&) { app_.getInboundLedgers().gotFetchPack(); });
}

void
LedgerMaster::makeFetchPack (
    std::weak_ptr<Peer> const& wPeer,
    std::shared_ptr<protocol::TMGetObjectByHash> const& request,
    uint256 haveLedgerHash,
    std::uint32_t uUptime)
{
    if (UptimeTimer::getInstance ().getElapsedSeconds () > (uUptime + 1))
    {
        m_journal.info << "Fetch pack request got stale";
        return;
    }

    if (app_.getFeeTrack ().isLoadedLocal () ||
        (getValidatedLedgerAge() > 40s))
    {
        m_journal.info << "Too busy to make fetch pack";
        return;
    }

    Peer::ptr peer = wPeer.lock ();

    if (!peer)
        return;

    auto haveLedger = getLedgerByHash (haveLedgerHash);

    if (!haveLedger)
    {
        m_journal.info
            << "Peer requests fetch pack for ledger we don't have: "
            << haveLedger;
        peer->charge (Resource::feeRequestNoReply);
        return;
    }

    if (haveLedger->info().open)
    {
        m_journal.warning
            << "Peer requests fetch pack from open ledger: "
            << haveLedger;
        peer->charge (Resource::feeInvalidRequest);
        return;
    }

    if (haveLedger->info().seq < getEarliestFetch())
    {
        m_journal.debug << "Peer requests fetch pack that is too early";
        peer->charge (Resource::feeInvalidRequest);
        return;
    }

    auto wantLedger = getLedgerByHash (haveLedger->info().parentHash);

    if (!wantLedger)
    {
        m_journal.info
            << "Peer requests fetch pack for ledger whose predecessor we "
            << "don't have: " << haveLedger;
        peer->charge (Resource::feeRequestNoReply);
        return;
    }


    auto fpAppender = [](
        protocol::TMGetObjectByHash* reply,
        std::uint32_t ledgerSeq,
        SHAMapHash const& hash,
        const Blob& blob)
    {
        protocol::TMIndexedObject& newObj = * (reply->add_objects ());
        newObj.set_ledgerseq (ledgerSeq);
        newObj.set_hash (hash.as_uint256().begin (), 256 / 8);
        newObj.set_data (&blob[0], blob.size ());
    };

    try
    {
        protocol::TMGetObjectByHash reply;
        reply.set_query (false);

        if (request->has_seq ())
            reply.set_seq (request->seq ());

        reply.set_ledgerhash (request->ledgerhash ());
        reply.set_type (protocol::TMGetObjectByHash::otFETCH_PACK);

        // Building a fetch pack:
        //  1. Add the header for the requested ledger.
        //  2. Add the nodes for the AccountStateMap of that ledger.
        //  3. If there are transactions, add the nodes for the
        //     transactions of the ledger.
        //  4. If the FetchPack now contains greater than or equal to
        //     256 entries then stop.
        //  5. If not very much time has elapsed, then loop back and repeat
        //     the same process adding the previous ledger to the FetchPack.
        do
        {
            std::uint32_t lSeq = wantLedger->info().seq;

            protocol::TMIndexedObject& newObj = *reply.add_objects ();
            newObj.set_hash (wantLedger->getHash ().begin (), 256 / 8);
            Serializer s (256);
            s.add32 (HashPrefix::ledgerMaster);
            wantLedger->addRaw (s);
            newObj.set_data (s.getDataPtr (), s.getLength ());
            newObj.set_ledgerseq (lSeq);

            wantLedger->stateMap().getFetchPack
                (&haveLedger->stateMap(), true, 16384,
                    std::bind (fpAppender, &reply, lSeq, std::placeholders::_1,
                               std::placeholders::_2));

            if (wantLedger->info().txHash.isNonZero ())
                wantLedger->txMap().getFetchPack (
                    nullptr, true, 512,
                    std::bind (fpAppender, &reply, lSeq, std::placeholders::_1,
                               std::placeholders::_2));

            if (reply.objects ().size () >= 512)
                break;

            // move may save a ref/unref
            haveLedger = std::move (wantLedger);
            wantLedger = getLedgerByHash (haveLedger->info().parentHash);
        }
        while (wantLedger &&
               UptimeTimer::getInstance ().getElapsedSeconds () <= uUptime + 1);

        m_journal.info
            << "Built fetch pack with " << reply.objects ().size () << " nodes";
        auto msg = std::make_shared<Message> (reply, protocol::mtGET_OBJECTS);
        peer->send (msg);
    }
    catch (std::exception const&)
    {
        m_journal.warning << "Exception building fetch pach";
    }
}

std::size_t
LedgerMaster::getFetchPackCacheSize () const
{
    return fetch_packs_.getCacheSize ();
}

} // ripple