VaultInvariant.cpp

#include <xrpl/tx/invariants/VaultInvariant.h>
 
#include <xrpl/basics/Log.h>
#include <xrpl/basics/Number.h>
#include <xrpl/beast/utility/Journal.h>
#include <xrpl/beast/utility/instrumentation.h>
#include <xrpl/ledger/ReadView.h>
#include <xrpl/ledger/helpers/AccountRootHelpers.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/protocol/Indexes.h>
#include <xrpl/protocol/Issue.h>
#include <xrpl/protocol/LedgerFormats.h>
#include <xrpl/protocol/Protocol.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/STAmount.h>
#include <xrpl/protocol/STLedgerEntry.h>
#include <xrpl/protocol/STNumber.h>  // IWYU pragma: keep
#include <xrpl/protocol/STTx.h>
#include <xrpl/protocol/TER.h>
#include <xrpl/protocol/TxFormats.h>
#include <xrpl/protocol/XRPAmount.h>
#include <xrpl/tx/invariants/InvariantCheckPrivilege.h>
 
#include <algorithm>
#include <cstdint>
#include <optional>
#include <variant>
#include <vector>
 
namespace xrpl {
 
ValidVault::Vault
ValidVault::Vault::make(SLE const& from)
{
    XRPL_ASSERT(from.getType() == ltVAULT, "ValidVault::Vault::make : from Vault object");
 
    ValidVault::Vault self;
    self.key = from.key();
    self.asset = from.at(sfAsset);
    self.pseudoId = from.getAccountID(sfAccount);
    self.owner = from.at(sfOwner);
    self.shareMPTID = from.getFieldH192(sfShareMPTID);
    self.assetsTotal = from.at(sfAssetsTotal);
    self.assetsAvailable = from.at(sfAssetsAvailable);
    self.assetsMaximum = from.at(sfAssetsMaximum);
    self.lossUnrealized = from.at(sfLossUnrealized);
    return self;
}
 
ValidVault::Shares
ValidVault::Shares::make(SLE const& from)
{
    XRPL_ASSERT(
        from.getType() == ltMPTOKEN_ISSUANCE,
        "ValidVault::Shares::make : from MPTokenIssuance object");
 
    ValidVault::Shares self;
    self.share = MPTIssue(makeMptID(from.getFieldU32(sfSequence), from.getAccountID(sfIssuer)));
    self.sharesTotal = from.at(sfOutstandingAmount);
    self.sharesMaximum = from[~sfMaximumAmount].value_or(kMaxMpTokenAmount);
    return self;
}
 
void
ValidVault::visitEntry(bool isDelete, SLE::const_ref before, SLE::const_ref after)
{
    // If `before` is empty, this means an object is being created, in which
    // case `isDelete` must be false. Otherwise `before` and `after` are set and
    // `isDelete` indicates whether an object is being deleted or modified.
    XRPL_ASSERT(
        after != nullptr && (before != nullptr || !isDelete),
        "xrpl::ValidVault::visitEntry : some object is available");
 
    // Number balanceDelta will capture the difference (delta) between "before"
    // state (zero if created) and "after" state (zero if destroyed), and
    // preserves value scale (exponent) to round values to the same scale during
    // validation. It is used to validate that the change in account
    // balances matches the change in vault balances, stored to deltas_ at the
    // end of this function.
    DeltaInfo balanceDelta{.delta = kNumZero, .scale = std::nullopt};
 
    std::int8_t sign = 0;
    if (before)
    {
        switch (before->getType())
        {
            case ltVAULT:
                beforeVault_.push_back(Vault::make(*before));
                break;
            case ltMPTOKEN_ISSUANCE:
                // At this moment we have no way of telling if this object holds
                // vault shares or something else. Save it for finalize.
                beforeMPTs_.push_back(Shares::make(*before));
                balanceDelta.delta =
                    static_cast<std::int64_t>(before->getFieldU64(sfOutstandingAmount));
                // MPTs are ints, so the scale is always 0.
                balanceDelta.scale = 0;
                sign = 1;
                break;
            case ltMPTOKEN:
                balanceDelta.delta = static_cast<std::int64_t>(before->getFieldU64(sfMPTAmount));
                // MPTs are ints, so the scale is always 0.
                balanceDelta.scale = 0;
                sign = -1;
                break;
            case ltACCOUNT_ROOT:
                balanceDelta.delta = before->getFieldAmount(sfBalance);
                // Account balance is XRP, which is an int, so the scale is
                // always 0.
                balanceDelta.scale = 0;
                sign = -1;
                break;
            case ltRIPPLE_STATE: {
                auto const amount = before->getFieldAmount(sfBalance);
                balanceDelta.delta = amount;
                // Trust Line balances are STAmounts, so we can use the exponent
                // directly to get the scale.
                balanceDelta.scale = amount.exponent();
                sign = -1;
                break;
            }
            default:;
        }
    }
 
    if (!isDelete && after)
    {
        switch (after->getType())
        {
            case ltVAULT:
                afterVault_.push_back(Vault::make(*after));
                break;
            case ltMPTOKEN_ISSUANCE:
                // At this moment we have no way of telling if this object holds
                // vault shares or something else. Save it for finalize.
                afterMPTs_.push_back(Shares::make(*after));
                balanceDelta.delta -=
                    Number(static_cast<std::int64_t>(after->getFieldU64(sfOutstandingAmount)));
                // MPTs are ints, so the scale is always 0.
                balanceDelta.scale = 0;
                sign = 1;
                break;
            case ltMPTOKEN:
                balanceDelta.delta -=
                    Number(static_cast<std::int64_t>(after->getFieldU64(sfMPTAmount)));
                // MPTs are ints, so the scale is always 0.
                balanceDelta.scale = 0;
                sign = -1;
                break;
            case ltACCOUNT_ROOT:
                balanceDelta.delta -= Number(after->getFieldAmount(sfBalance));
                // Account balance is XRP, which is an int, so the scale is
                // always 0.
                balanceDelta.scale = 0;
                sign = -1;
                break;
            case ltRIPPLE_STATE: {
                auto const amount = after->getFieldAmount(sfBalance);
                balanceDelta.delta -= Number(amount);
                // Trust Line balances are STAmounts, so we can use the exponent
                // directly to get the scale.
                if (amount.exponent() > balanceDelta.scale)
                    balanceDelta.scale = amount.exponent();
                sign = -1;
                break;
            }
            default:;
        }
    }
 
    uint256 const key = (before ? before->key() : after->key());
    // Append to deltas if sign is non-zero, i.e. an object of an interesting
    // type has been updated. A transaction may update an object even when
    // its balance has not changed, e.g. transaction fee equals the amount
    // transferred to the account. We intentionally do not compare balanceDelta
    // against zero, to avoid missing such updates.
    if (sign != 0)
    {
        XRPL_ASSERT_PARTS(balanceDelta.scale, "xrpl::ValidVault::visitEntry", "scale initialized");
        balanceDelta.delta *= sign;
        deltas_[key] = balanceDelta;
    }
}
 
std::optional<ValidVault::DeltaInfo>
ValidVault::deltaAssets(AccountID const& id) const
{
    auto const& vaultAsset = afterVault_[0].asset;
    auto const lookup = [&](uint256 const& key) -> std::optional<DeltaInfo> {
        auto const it = deltas_.find(key);
        if (it == deltas_.end())
            return std::nullopt;
        return it->second;
    };
 
    return std::visit(
        [&]<typename TIss>(TIss const& issue) -> std::optional<DeltaInfo> {
            if constexpr (std::is_same_v<TIss, Issue>)
            {
                if (isXRP(issue))
                    return lookup(keylet::account(id).key);
                auto result = lookup(keylet::trustLine(id, issue).key);
                // Trust-line balance is stored from the low-account's perspective;
                // negate if id is the high account so the delta is in id's terms.
                if (result && id > issue.getIssuer())
                    result->delta = -result->delta;
                return result;
            }
            else if constexpr (std::is_same_v<TIss, MPTIssue>)
            {
                return lookup(keylet::mptoken(issue.getMptID(), id).key);
            }
        },
        vaultAsset.value());
}
 
std::optional<ValidVault::DeltaInfo>
ValidVault::deltaAssetsTxAccount(STTx const& tx, XRPAmount fee) const
{
    auto const& vaultAsset = afterVault_[0].asset;
    auto ret = deltaAssets(tx[sfAccount]);
    if (!ret.has_value() || !vaultAsset.native())
        return ret;
 
    if (auto const delegate = tx[~sfDelegate]; delegate.has_value() && *delegate != tx[sfAccount])
        return ret;
 
    ret->delta += fee.drops();
    if (ret->delta == kZero)
        return std::nullopt;
 
    return ret;
}
 
std::optional<ValidVault::DeltaInfo>
ValidVault::deltaShares(AccountID const& id) const
{
    auto const& afterVault = afterVault_[0];
    auto const it = [&]() {
        if (id == afterVault.pseudoId)
            return deltas_.find(keylet::mptokenIssuance(afterVault.shareMPTID).key);
        return deltas_.find(keylet::mptoken(afterVault.shareMPTID, id).key);
    }();
 
    return it != deltas_.end() ? std::optional<DeltaInfo>(it->second) : std::nullopt;
}
 
bool
ValidVault::isVaultEmpty(Vault const& vault)
{
    return vault.assetsAvailable == 0 && vault.assetsTotal == 0;
}
 
std::int32_t
ValidVault::computeVaultMinScale(DeltaInfo const& vaultDelta, Rules const& rules) const
{
    // Returns the posterior `assetsTotal` scale.
    //
    // 1. Because STAmounts are normalized, `assetsTotal` (being >= `assetsAvailable`)
    // safely represents the coarsest exponent needed for both fields.
    //
    // 2. The scale may decrease (withdraw/clawback) or increase (deposit). In both cases
    // we ensure the vault is in a legitimate state in the post-transaction scale.
    auto const& afterVault = afterVault_[0];
    auto const& vaultAsset = afterVault.asset;
    if (rules.enabled(fixCleanup3_2_0))
    {
        NumberRoundModeGuard const roundGuard(Number::RoundingMode::ToNearest);
        return scale(afterVault.assetsTotal, vaultAsset);
    }
 
    auto const& beforeVault = beforeVault_[0];
    auto const totalDelta =
        DeltaInfo::makeDelta(beforeVault.assetsTotal, afterVault.assetsTotal, vaultAsset);
    auto const availableDelta =
        DeltaInfo::makeDelta(beforeVault.assetsAvailable, afterVault.assetsAvailable, vaultAsset);
    return computeCoarsestScale({vaultDelta, totalDelta, availableDelta});
}
 
bool
ValidVault::finalize(
    STTx const& tx,
    TER const ret,
    XRPAmount const fee,
    ReadView const& view,
    beast::Journal const& j)
{
    bool const enforce = view.rules().enabled(featureSingleAssetVault);
 
    if (!isTesSuccess(ret))
        return true;  // Do not perform checks
 
    if (afterVault_.empty() && beforeVault_.empty())
    {
        if (hasPrivilege(tx, MustModifyVault))
        {
            JLOG(j.fatal()) <<  //
                "Invariant failed: vault operation succeeded without modifying "
                "a vault";
            XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : vault noop invariant");
            return !enforce;
        }
 
        return true;  // Not a vault operation
    }
    if (!(hasPrivilege(tx, MustModifyVault) || hasPrivilege(tx, MayModifyVault)))
    {
        JLOG(j.fatal()) <<  //
            "Invariant failed: vault updated by a wrong transaction type";
        XRPL_ASSERT(
            enforce,
            "xrpl::ValidVault::finalize : illegal vault transaction "
            "invariant");
        return !enforce;  // Also not a vault operation
    }
 
    if (beforeVault_.size() > 1 || afterVault_.size() > 1)
    {
        JLOG(j.fatal()) <<  //
            "Invariant failed: vault operation updated more than single vault";
        XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : single vault invariant");
        return !enforce;  // That's all we can do here
    }
 
    auto const txnType = tx.getTxnType();
 
    // We do special handling for ttVAULT_DELETE first, because it's the only
    // vault-modifying transaction without an "after" state of the vault
    if (afterVault_.empty())
    {
        if (txnType != ttVAULT_DELETE)
        {
            JLOG(j.fatal()) <<  //
                "Invariant failed: vault deleted by a wrong transaction type";
            XRPL_ASSERT(
                enforce,
                "xrpl::ValidVault::finalize : illegal vault deletion "
                "invariant");
            return !enforce;  // That's all we can do here
        }
 
        // Note, if afterVault_ is empty then we know that beforeVault_ is not
        // empty, as enforced at the top of this function
        auto const& beforeVault = beforeVault_[0];
 
        // At this moment we only know a vault is being deleted and there
        // might be some MPTokenIssuance objects which are deleted in the
        // same transaction. Find the one matching this vault.
        auto const deletedShares = [&]() -> std::optional<Shares> {
            for (auto const& e : beforeMPTs_)
            {
                if (e.share.getMptID() == beforeVault.shareMPTID)
                    return e;
            }
            return std::nullopt;
        }();
 
        if (!deletedShares)
        {
            JLOG(j.fatal()) << "Invariant failed: deleted vault must also "
                               "delete shares";
            XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : shares deletion invariant");
            return !enforce;  // That's all we can do here
        }
 
        bool result = true;
        if (deletedShares->sharesTotal != 0)
        {
            JLOG(j.fatal()) << "Invariant failed: deleted vault must have no "
                               "shares outstanding";
            result = false;
        }
        if (beforeVault.assetsTotal != kZero)
        {
            JLOG(j.fatal()) << "Invariant failed: deleted vault must have no "
                               "assets outstanding";
            result = false;
        }
        if (beforeVault.assetsAvailable != kZero)
        {
            JLOG(j.fatal()) << "Invariant failed: deleted vault must have no "
                               "assets available";
            result = false;
        }
 
        return result;
    }
    if (txnType == ttVAULT_DELETE)
    {
        JLOG(j.fatal()) << "Invariant failed: vault deletion succeeded without "
                           "deleting a vault";
        XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : vault deletion invariant");
        return !enforce;  // That's all we can do here
    }
 
    // Note, `afterVault_.empty()` is handled above
    auto const& afterVault = afterVault_[0];
    XRPL_ASSERT(
        beforeVault_.empty() || beforeVault_[0].key == afterVault.key,
        "xrpl::ValidVault::finalize : single vault operation");
 
    auto const updatedShares = [&]() -> std::optional<Shares> {
        // At this moment we only know that a vault is being updated and there
        // might be some MPTokenIssuance objects which are also updated in the
        // same transaction. Find the one matching the shares to this vault.
        // Note, we expect updatedMPTs collection to be extremely small. For
        // such collections linear search is faster than lookup.
        for (auto const& e : afterMPTs_)
        {
            if (e.share.getMptID() == afterVault.shareMPTID)
                return e;
        }
 
        auto const sleShares = view.read(keylet::mptokenIssuance(afterVault.shareMPTID));
 
        return sleShares ? std::optional<Shares>(Shares::make(*sleShares)) : std::nullopt;
    }();
 
    bool result = true;
 
    // Universal transaction checks
    if (!beforeVault_.empty())
    {
        auto const& beforeVault = beforeVault_[0];
        if (afterVault.asset != beforeVault.asset || afterVault.pseudoId != beforeVault.pseudoId ||
            afterVault.shareMPTID != beforeVault.shareMPTID)
        {
            JLOG(j.fatal()) << "Invariant failed: violation of vault immutable data";
            result = false;
        }
    }
 
    if (!updatedShares)
    {
        JLOG(j.fatal()) << "Invariant failed: updated vault must have shares";
        XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : vault has shares invariant");
        return !enforce;  // That's all we can do here
    }
 
    if (updatedShares->sharesTotal == 0)
    {
        if (afterVault.assetsTotal != kZero)
        {
            JLOG(j.fatal()) << "Invariant failed: updated zero sized "
                               "vault must have no assets outstanding";
            result = false;
        }
        if (afterVault.assetsAvailable != kZero)
        {
            JLOG(j.fatal()) << "Invariant failed: updated zero sized "
                               "vault must have no assets available";
            result = false;
        }
    }
    else if (updatedShares->sharesTotal > updatedShares->sharesMaximum)
    {
        JLOG(j.fatal())  //
            << "Invariant failed: updated shares must not exceed maximum "
            << updatedShares->sharesMaximum;
        result = false;
    }
 
    if (afterVault.assetsAvailable < kZero)
    {
        JLOG(j.fatal()) << "Invariant failed: assets available must be positive";
        result = false;
    }
 
    if (afterVault.assetsAvailable > afterVault.assetsTotal)
    {
        JLOG(j.fatal()) << "Invariant failed: assets available must "
                           "not be greater than assets outstanding";
        result = false;
    }
    else if (afterVault.lossUnrealized > afterVault.assetsTotal - afterVault.assetsAvailable)
    {
        JLOG(j.fatal())  //
            << "Invariant failed: loss unrealized must not exceed "
               "the difference between assets outstanding and available";
        result = false;
    }
 
    if (afterVault.assetsTotal < kZero)
    {
        JLOG(j.fatal()) << "Invariant failed: assets outstanding must be positive";
        result = false;
    }
 
    if (afterVault.assetsMaximum < kZero)
    {
        JLOG(j.fatal()) << "Invariant failed: assets maximum must be positive";
        result = false;
    }
 
    // Thanks to this check we can simply do `assert(!beforeVault_.empty()` when
    // enforcing invariants on transaction types other than ttVAULT_CREATE
    if (beforeVault_.empty() && txnType != ttVAULT_CREATE)
    {
        JLOG(j.fatal()) <<  //
            "Invariant failed: vault created by a wrong transaction type";
        XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : vault creation invariant");
        return !enforce;  // That's all we can do here
    }
 
    if (!beforeVault_.empty() && afterVault.lossUnrealized != beforeVault_[0].lossUnrealized &&
        txnType != ttLOAN_MANAGE && txnType != ttLOAN_PAY)
    {
        JLOG(j.fatal()) <<  //
            "Invariant failed: vault transaction must not change loss "
            "unrealized";
        result = false;
    }
 
    auto const beforeShares = [&]() -> std::optional<Shares> {
        if (beforeVault_.empty())
            return std::nullopt;
        auto const& beforeVault = beforeVault_[0];
 
        for (auto const& e : beforeMPTs_)
        {
            if (e.share.getMptID() == beforeVault.shareMPTID)
                return e;
        }
        return std::nullopt;
    }();
 
    if (!beforeShares &&
        (tx.getTxnType() == ttVAULT_DEPOSIT ||   //
         tx.getTxnType() == ttVAULT_WITHDRAW ||  //
         tx.getTxnType() == ttVAULT_CLAWBACK))
    {
        JLOG(j.fatal()) << "Invariant failed: vault operation succeeded "
                           "without updating shares";
        XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : shares noop invariant");
        return !enforce;  // That's all we can do here
    }
 
    auto const& vaultAsset = afterVault.asset;
 
    // Technically this does not need to be a lambda, but it's more
    // convenient thanks to early "return false"; the not-so-nice
    // alternatives are several layers of nested if/else or more complex
    // (i.e. brittle) if statements.
    result &= [&]() {
        switch (txnType)
        {
            case ttVAULT_CREATE: {
                bool result = true;
 
                if (!beforeVault_.empty())
                {
                    JLOG(j.fatal())  //
                        << "Invariant failed: create operation must not have "
                           "updated a vault";
                    result = false;
                }
 
                if (afterVault.assetsAvailable != kZero || afterVault.assetsTotal != kZero ||
                    afterVault.lossUnrealized != kZero || updatedShares->sharesTotal != 0)
                {
                    JLOG(j.fatal())  //
                        << "Invariant failed: created vault must be empty";
                    result = false;
                }
 
                if (afterVault.pseudoId != updatedShares->share.getIssuer())
                {
                    JLOG(j.fatal())  //
                        << "Invariant failed: shares issuer and vault "
                           "pseudo-account must be the same";
                    result = false;
                }
 
                auto const sleSharesIssuer =
                    view.read(keylet::account(updatedShares->share.getIssuer()));
                if (!sleSharesIssuer)
                {
                    JLOG(j.fatal())  //
                        << "Invariant failed: shares issuer must exist";
                    return false;
                }
 
                if (!isPseudoAccount(sleSharesIssuer))
                {
                    JLOG(j.fatal())  //
                        << "Invariant failed: shares issuer must be a "
                           "pseudo-account";
                    result = false;
                }
 
                if (auto const vaultId = (*sleSharesIssuer)[~sfVaultID];
                    !vaultId || *vaultId != afterVault.key)
                {
                    JLOG(j.fatal())  //
                        << "Invariant failed: shares issuer pseudo-account "
                           "must point back to the vault";
                    result = false;
                }
 
                return result;
            }
            case ttVAULT_SET: {
                bool result = true;
 
                XRPL_ASSERT(
                    !beforeVault_.empty(), "xrpl::ValidVault::finalize : set updated a vault");
                auto const& beforeVault = beforeVault_[0];
 
                auto const vaultDeltaAssets = deltaAssets(afterVault.pseudoId);
                if (vaultDeltaAssets)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: set must not change vault balance";
                    result = false;
                }
 
                if (beforeVault.assetsTotal != afterVault.assetsTotal)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: set must not change assets "
                        "outstanding";
                    result = false;
                }
 
                if (afterVault.assetsMaximum > kZero &&
                    afterVault.assetsTotal > afterVault.assetsMaximum)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: set assets outstanding must not "
                        "exceed assets maximum";
                    result = false;
                }
 
                if (beforeVault.assetsAvailable != afterVault.assetsAvailable)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: set must not change assets "
                        "available";
                    result = false;
                }
 
                if (beforeShares && updatedShares &&
                    beforeShares->sharesTotal != updatedShares->sharesTotal)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: set must not change shares "
                        "outstanding";
                    result = false;
                }
 
                return result;
            }
            case ttVAULT_DEPOSIT: {
                bool result = true;
 
                XRPL_ASSERT(
                    !beforeVault_.empty(), "xrpl::ValidVault::finalize : deposit updated a vault");
                auto const& beforeVault = beforeVault_[0];
 
                auto const maybeVaultDeltaAssets = deltaAssets(afterVault.pseudoId);
                if (!maybeVaultDeltaAssets)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: deposit must change vault balance";
                    return false;  // That's all we can do
                }
 
                // Get the posterior scale to round calculations to
                auto const minScale = computeVaultMinScale(*maybeVaultDeltaAssets, view.rules());
 
                auto const vaultDeltaAssets =
                    roundToAsset(vaultAsset, maybeVaultDeltaAssets->delta, minScale);
                auto const txAmount = roundToAsset(vaultAsset, tx[sfAmount], minScale);
 
                if (vaultDeltaAssets > txAmount)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: deposit must not change vault "
                        "balance by more than deposited amount";
                    result = false;
                }
 
                if (vaultDeltaAssets <= kZero)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: deposit must increase vault balance";
                    result = false;
                }
 
                // Any payments (including deposits) made by the issuer
                // do not change their balance, but create funds instead.
                bool const issuerDeposit = [&]() -> bool {
                    if (vaultAsset.native())
                        return false;
                    return tx[sfAccount] == vaultAsset.getIssuer();
                }();
 
                if (!issuerDeposit)
                {
                    auto const maybeAccDeltaAssets = deltaAssetsTxAccount(tx, fee);
                    if (!maybeAccDeltaAssets)
                    {
                        JLOG(j.fatal())
                            << "Invariant failed: deposit must change depositor balance";
                        return false;
                    }
                    auto const localMinScale =
                        std::max(minScale, computeCoarsestScale({*maybeAccDeltaAssets}));
 
                    auto const accountDeltaAssets =
                        roundToAsset(vaultAsset, maybeAccDeltaAssets->delta, localMinScale);
                    auto const localVaultDeltaAssets =
                        roundToAsset(vaultAsset, vaultDeltaAssets, localMinScale);
 
                    // For IOUs, if the deposit amount is not-representable at depositor trustline
                    // scale deposit amount could round to zero, giving depositor shares for no
                    // assets. Unlike withdrawal, we do not allow that.
                    if (accountDeltaAssets >= kZero)
                    {
                        JLOG(j.fatal())
                            << "Invariant failed: deposit must decrease depositor balance";
                        result = false;
                    }
 
                    if (localVaultDeltaAssets * -1 != accountDeltaAssets)
                    {
                        JLOG(j.fatal()) << "Invariant failed: " <<  //
                            "deposit must change vault and depositor balance by equal amount";
                        result = false;
                    }
                }
 
                if (afterVault.assetsMaximum > kZero &&
                    afterVault.assetsTotal > afterVault.assetsMaximum)
                {
                    JLOG(j.fatal()) << "Invariant failed: " <<  //
                        "deposit assets outstanding must not exceed assets maximum";
                    result = false;
                }
 
                auto const maybeAccDeltaShares = deltaShares(tx[sfAccount]);
                if (!maybeAccDeltaShares)
                {
                    JLOG(j.fatal()) << "Invariant failed: deposit must change depositor shares";
                    return false;  // That's all we can do
                }
                // We don't round shares, they are integral MPT
                auto const& accountDeltaShares = *maybeAccDeltaShares;
                if (accountDeltaShares.delta <= kZero)
                {
                    JLOG(j.fatal()) << "Invariant failed: deposit must increase depositor shares";
                    result = false;
                }
 
                auto const maybeVaultDeltaShares = deltaShares(afterVault.pseudoId);
                if (!maybeVaultDeltaShares || maybeVaultDeltaShares->delta == kZero)
                {
                    JLOG(j.fatal()) << "Invariant failed: deposit must change vault shares";
                    return false;  // That's all we can do
                }
 
                // We don't round shares, they are integral MPT
                auto const& vaultDeltaShares = *maybeVaultDeltaShares;
                if (vaultDeltaShares.delta * -1 != accountDeltaShares.delta)
                {
                    JLOG(j.fatal()) << "Invariant failed: " <<  //
                        "deposit must change depositor and vault shares by equal amount";
                    result = false;
                }
 
                auto const assetTotalDelta = roundToAsset(
                    vaultAsset, afterVault.assetsTotal - beforeVault.assetsTotal, minScale);
                if (assetTotalDelta != vaultDeltaAssets)
                {
                    JLOG(j.fatal())
                        << "Invariant failed: deposit and assets outstanding must add up";
                    result = false;
                }
 
                auto const assetAvailableDelta = roundToAsset(
                    vaultAsset, afterVault.assetsAvailable - beforeVault.assetsAvailable, minScale);
                if (assetAvailableDelta != vaultDeltaAssets)
                {
                    JLOG(j.fatal()) << "Invariant failed: deposit and assets available must add up";
                    result = false;
                }
 
                return result;
            }
            case ttVAULT_WITHDRAW: {
                bool result = true;
 
                XRPL_ASSERT(
                    !beforeVault_.empty(),
                    "xrpl::ValidVault::finalize : withdrawal updated a vault");
                auto const& beforeVault = beforeVault_[0];
 
                auto const maybeVaultDeltaAssets = deltaAssets(afterVault.pseudoId);
                if (!maybeVaultDeltaAssets)
                {
                    JLOG(j.fatal()) << "Invariant failed: withdrawal must change vault balance";
                    return false;  // That's all we can do
                }
 
                // Get the posterior scale to round calculations to
                auto const minScale = computeVaultMinScale(*maybeVaultDeltaAssets, view.rules());
 
                auto const vaultPseudoDeltaAssets =
                    roundToAsset(vaultAsset, maybeVaultDeltaAssets->delta, minScale);
 
                if (vaultPseudoDeltaAssets >= kZero)
                {
                    JLOG(j.fatal()) << "Invariant failed: withdrawal must decrease vault balance";
                    result = false;
                }
 
                // Any payments (including withdrawal) going to the issuer
                // do not change their balance, but destroy funds instead.
                bool const issuerWithdrawal = [&]() -> bool {
                    if (vaultAsset.native())
                        return false;
                    auto const destination = tx[~sfDestination].value_or(tx[sfAccount]);
                    return destination == vaultAsset.getIssuer();
                }();
 
                if (!issuerWithdrawal)
                {
                    auto const maybeAccDelta = deltaAssetsTxAccount(tx, fee);
                    auto const maybeOtherAccDelta = [&]() -> std::optional<DeltaInfo> {
                        if (auto const destination = tx[~sfDestination];
                            destination && *destination != tx[sfAccount])
                            return deltaAssets(*destination);
                        return std::nullopt;
                    }();
 
                    if (maybeAccDelta.has_value() == maybeOtherAccDelta.has_value())
                    {
                        JLOG(j.fatal()) <<  //
                            "Invariant failed: withdrawal must change one destination balance";
                        return false;
                    }
 
                    auto const destinationDelta =  //
                        maybeAccDelta ? *maybeAccDelta : *maybeOtherAccDelta;
 
                    // the scale of destinationDelta can be coarser than
                    // minScale, so we take that into account when rounding
                    auto const destinationScale = computeCoarsestScale({destinationDelta});
                    auto const localMinScale = std::max(minScale, destinationScale);
 
                    auto const roundedDestinationDelta =
                        roundToAsset(vaultAsset, destinationDelta.delta, localMinScale);
 
                    // Post-fixCleanup3_2_0: Tolerate zero-rounded destination deltas for IOUs only.
                    // If the receiver's trust line sits at a coarser scale, the inflow may
                    // safely round down to zero.
                    //
                    // XRP and MPT remain strict. Because they are integer-exact, a zero
                    // destination delta indicates a true accounting bug, not a rounding artifact.
                    bool const tolerateZeroDelta =
                        view.rules().enabled(fixCleanup3_2_0) && !vaultAsset.integral();
                    auto const invalidBalanceChange = tolerateZeroDelta
                        ? roundedDestinationDelta < kZero
                        : roundedDestinationDelta <= kZero;
                    if (invalidBalanceChange)
                    {
                        JLOG(j.fatal()) <<  //
                            "Invariant failed: withdrawal must increase destination balance";
                        result = false;
                    }
 
                    auto const localPseudoDeltaAssets =
                        roundToAsset(vaultAsset, vaultPseudoDeltaAssets, localMinScale);
                    // For IOU assets near a precision boundary the destination's STAmount
                    // exponent can shift, making part of the sent value unrepresentable at the
                    // receiver's new scale — that portion is irreversibly absorbed by the IOU
                    // rail.  Tolerate the mismatch only when the destroyed amount (vault outflow
                    // minus destination inflow, in Number space) is itself sub-ULP at the
                    // destination's scale.  Floor rounding is used so that values exactly at the
                    // step boundary are not mistakenly dismissed.  Any representable discrepancy
                    // indicates a real accounting bug and must be caught.
                    auto const destroyedIsSubUlp = tolerateZeroDelta &&
                        roundToAsset(
                            vaultAsset,
                            maybeVaultDeltaAssets->delta * -1 - destinationDelta.delta,
                            destinationScale,
                            Number::RoundingMode::Downward) == kZero;
                    if (!destroyedIsSubUlp &&
                        localPseudoDeltaAssets * -1 != roundedDestinationDelta)
                    {
                        JLOG(j.fatal()) << "Invariant failed: " <<  //
                            "withdrawal must change vault and destination balance by equal "
                            "amount";
                        result = false;
                    }
                }
 
                // We don't round shares, they are integral MPT
                auto const accountDeltaShares = deltaShares(tx[sfAccount]);
                if (!accountDeltaShares)
                {
                    JLOG(j.fatal()) << "Invariant failed: withdrawal must change depositor shares";
                    return false;
                }
 
                if (accountDeltaShares->delta >= kZero)
                {
                    JLOG(j.fatal())
                        << "Invariant failed: withdrawal must decrease depositor shares";
                    result = false;
                }
 
                // We don't round shares, they are integral MPT
                auto const vaultDeltaShares = deltaShares(afterVault.pseudoId);
                if (!vaultDeltaShares || vaultDeltaShares->delta == kZero)
                {
                    JLOG(j.fatal()) << "Invariant failed: withdrawal must change vault shares";
                    return false;  // That's all we can do
                }
 
                if (vaultDeltaShares->delta * -1 != accountDeltaShares->delta)
                {
                    JLOG(j.fatal()) << "Invariant failed: " <<  //
                        "withdrawal must change depositor and vault shares by equal amount";
                    result = false;
                }
 
                auto const assetTotalDelta = roundToAsset(
                    vaultAsset, afterVault.assetsTotal - beforeVault.assetsTotal, minScale);
                // Note, vaultBalance is negative (see check above)
                if (assetTotalDelta != vaultPseudoDeltaAssets)
                {
                    JLOG(j.fatal())
                        << "Invariant failed: withdrawal and assets outstanding must add up";
                    result = false;
                }
 
                auto const assetAvailableDelta = roundToAsset(
                    vaultAsset, afterVault.assetsAvailable - beforeVault.assetsAvailable, minScale);
 
                if (assetAvailableDelta != vaultPseudoDeltaAssets)
                {
                    JLOG(j.fatal())
                        << "Invariant failed: withdrawal and assets available must add up";
                    result = false;
                }
 
                return result;
            }
            case ttVAULT_CLAWBACK: {
                bool result = true;
 
                XRPL_ASSERT(
                    !beforeVault_.empty(), "xrpl::ValidVault::finalize : clawback updated a vault");
                auto const& beforeVault = beforeVault_[0];
 
                if (vaultAsset.native() || vaultAsset.getIssuer() != tx[sfAccount])
                {
                    // The owner can use clawback to force-burn shares when the
                    // vault is empty but there are outstanding shares
                    if (!(beforeShares && beforeShares->sharesTotal > 0 &&
                          isVaultEmpty(beforeVault) && beforeVault.owner == tx[sfAccount]))
                    {
                        JLOG(j.fatal()) << "Invariant failed: " <<  //
                            "clawback may only be performed by the asset issuer, or by the vault "
                            "owner of an empty vault";
                        return false;  // That's all we can do
                    }
                }
 
                auto const maybeVaultDeltaAssets = deltaAssets(afterVault.pseudoId);
                if (maybeVaultDeltaAssets)
                {
                    auto const minScale =
                        computeVaultMinScale(*maybeVaultDeltaAssets, view.rules());
                    auto const vaultDeltaAssets =
                        roundToAsset(vaultAsset, maybeVaultDeltaAssets->delta, minScale);
                    if (vaultDeltaAssets >= kZero)
                    {
                        JLOG(j.fatal()) << "Invariant failed: clawback must decrease vault balance";
                        result = false;
                    }
 
                    auto const assetsTotalDelta = roundToAsset(
                        vaultAsset, afterVault.assetsTotal - beforeVault.assetsTotal, minScale);
                    if (assetsTotalDelta != vaultDeltaAssets)
                    {
                        JLOG(j.fatal()) <<  //
                            "Invariant failed: clawback and assets outstanding must add up";
                        result = false;
                    }
 
                    auto const assetAvailableDelta = roundToAsset(
                        vaultAsset,
                        afterVault.assetsAvailable - beforeVault.assetsAvailable,
                        minScale);
                    if (assetAvailableDelta != vaultDeltaAssets)
                    {
                        JLOG(j.fatal()) <<  //
                            "Invariant failed: clawback and assets available must add up";
                        result = false;
                    }
                }
                else if (!isVaultEmpty(beforeVault))
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: clawback must change vault balance";
                    return false;  // That's all we can do
                }
 
                // We don't need to round shares, they are integral MPT
                auto const maybeAccountDeltaShares = deltaShares(tx[sfHolder]);
                if (!maybeAccountDeltaShares)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: clawback must change holder shares";
                    return false;  // That's all we can do
                }
                if (maybeAccountDeltaShares->delta >= kZero)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: clawback must decrease holder shares";
                    result = false;
                }
 
                // We don't need to round shares, they are integral MPT
                auto const vaultDeltaShares = deltaShares(afterVault.pseudoId);
                if (!vaultDeltaShares || vaultDeltaShares->delta == kZero)
                {
                    JLOG(j.fatal()) <<  //
                        "Invariant failed: clawback must change vault shares";
                    return false;  // That's all we can do
                }
 
                if (vaultDeltaShares->delta * -1 != maybeAccountDeltaShares->delta)
                {
                    JLOG(j.fatal()) << "Invariant failed: " <<  //
                        "clawback must change holder and vault shares by equal amount";
                    result = false;
                }
 
                return result;
            }
 
            case ttLOAN_SET:
            case ttLOAN_MANAGE:
            case ttLOAN_PAY: {
                // TBD
                return true;
            }
 
            default:
                // LCOV_EXCL_START
                UNREACHABLE("xrpl::ValidVault::finalize : unknown transaction type");
                return false;
                // LCOV_EXCL_STOP
        }
    }();
 
    if (!result)
    {
        // The comment at the top of this file starting with "assert(enforce)"
        // explains this assert.
        XRPL_ASSERT(enforce, "xrpl::ValidVault::finalize : vault invariants");
        return !enforce;
    }
 
    return true;
}
 
[[nodiscard]] ValidVault::DeltaInfo
ValidVault::DeltaInfo::makeDelta(Number const& before, Number const& after, Asset const& asset)
{
    return {
        .delta = after - before,
        .scale = std::max(xrpl::scale(after, asset), xrpl::scale(before, asset))};
}
 
[[nodiscard]] std::int32_t
ValidVault::computeCoarsestScale(std::vector<DeltaInfo> const& numbers)
{
    if (numbers.empty())
        return 0;
 
    auto const max = std::ranges::max_element(
        numbers, [](auto const& a, auto const& b) -> bool { return a.scale < b.scale; });
    XRPL_ASSERT_PARTS(
        max->scale, "xrpl::ValidVault::computeCoarsestScale", "scale set for destinationDelta");
    return max->scale.value_or(STAmount::kMaxOffset);
}
 
}  // namespace xrpl