rippled/src/libxrpl/tx/transactors/AMM/AMMVote.cpp

#include <xrpl/ledger/Sandbox.h>
#include <xrpl/protocol/AMMCore.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/protocol/TxFlags.h>
#include <xrpl/tx/transactors/AMM/AMMUtils.h>
#include <xrpl/tx/transactors/AMM/AMMVote.h>

namespace xrpl {

bool
AMMVote::checkExtraFeatures(PreflightContext const& ctx)
{
    return ammEnabled(ctx.rules);
}

NotTEC
AMMVote::preflight(PreflightContext const& ctx)
{
    if (auto const res =
            invalidAMMAssetPair(ctx.tx[sfAsset].get<Issue>(), ctx.tx[sfAsset2].get<Issue>()))
    {
        JLOG(ctx.j.debug()) << "AMM Vote: invalid asset pair.";
        return res;
    }

    if (ctx.tx[sfTradingFee] > TRADING_FEE_THRESHOLD)
    {
        JLOG(ctx.j.debug()) << "AMM Vote: invalid trading fee.";
        return temBAD_FEE;
    }

    return tesSUCCESS;
}

TER
AMMVote::preclaim(PreclaimContext const& ctx)
{
    if (auto const ammSle = ctx.view.read(keylet::amm(ctx.tx[sfAsset], ctx.tx[sfAsset2])); !ammSle)
    {
        JLOG(ctx.j.debug()) << "AMM Vote: Invalid asset pair.";
        return terNO_AMM;
    }
    else if (ammSle->getFieldAmount(sfLPTokenBalance) == beast::zero)
        return tecAMM_EMPTY;
    else if (
        auto const lpTokensNew = ammLPHolds(ctx.view, *ammSle, ctx.tx[sfAccount], ctx.j);
        lpTokensNew == beast::zero)
    {
        JLOG(ctx.j.debug()) << "AMM Vote: account is not LP.";
        return tecAMM_INVALID_TOKENS;
    }

    return tesSUCCESS;
}

static std::pair<TER, bool>
applyVote(ApplyContext& ctx_, Sandbox& sb, AccountID const& account_, beast::Journal j_)
{
    auto const feeNew = ctx_.tx[sfTradingFee];
    auto ammSle = sb.peek(keylet::amm(ctx_.tx[sfAsset], ctx_.tx[sfAsset2]));
    if (!ammSle)
        return {tecINTERNAL, false};
    STAmount const lptAMMBalance = (*ammSle)[sfLPTokenBalance];
    auto const lpTokensNew = ammLPHolds(sb, *ammSle, account_, ctx_.journal);
    std::optional<STAmount> minTokens;
    std::size_t minPos{0};
    AccountID minAccount{0};
    std::uint32_t minFee{0};
    STArray updatedVoteSlots;
    Number num{0};
    Number den{0};
    // Account already has vote entry
    bool foundAccount = false;

    // Iterate over the current vote entries and update each entry
    // per current total tokens balance and each LP tokens balance.
    // Find the entry with the least tokens and whether the account
    // has the vote entry.
    for (auto const& entry : ammSle->getFieldArray(sfVoteSlots))
    {
        auto const account = entry[sfAccount];
        auto lpTokens = ammLPHolds(sb, *ammSle, account, ctx_.journal);
        if (lpTokens == beast::zero)
        {
            JLOG(j_.debug()) << "AMMVote::applyVote, account " << account << " is not LP";
            continue;
        }
        auto feeVal = entry[sfTradingFee];
        STObject newEntry = STObject::makeInnerObject(sfVoteEntry);
        // The account already has the vote entry.
        if (account == account_)
        {
            lpTokens = lpTokensNew;
            feeVal = feeNew;
            foundAccount = true;
        }
        // Keep running numerator/denominator to calculate the updated fee.
        num += feeVal * lpTokens;
        den += lpTokens;
        newEntry.setAccountID(sfAccount, account);
        if (feeVal != 0)
            newEntry.setFieldU16(sfTradingFee, feeVal);
        newEntry.setFieldU32(
            sfVoteWeight,
            static_cast<std::int64_t>(Number(lpTokens) * VOTE_WEIGHT_SCALE_FACTOR / lptAMMBalance));

        // Find an entry with the least tokens/fee. Make the order deterministic
        // if the tokens/fees are equal.
        if (!minTokens ||
            (lpTokens < *minTokens ||
             (lpTokens == *minTokens &&
              (feeVal < minFee || (feeVal == minFee && account < minAccount)))))
        {
            minTokens = lpTokens;
            minPos = updatedVoteSlots.size();
            minAccount = account;
            minFee = feeVal;
        }
        updatedVoteSlots.push_back(std::move(newEntry));
    }

    // The account doesn't have the vote entry.
    if (!foundAccount)
    {
        auto update = [&](std::optional<std::uint8_t> const& minPos = std::nullopt) {
            STObject newEntry = STObject::makeInnerObject(sfVoteEntry);
            if (feeNew != 0)
                newEntry.setFieldU16(sfTradingFee, feeNew);
            newEntry.setFieldU32(
                sfVoteWeight,
                static_cast<std::int64_t>(
                    Number(lpTokensNew) * VOTE_WEIGHT_SCALE_FACTOR / lptAMMBalance));
            newEntry.setAccountID(sfAccount, account_);
            num += feeNew * lpTokensNew;
            den += lpTokensNew;
            if (minPos)
                *(updatedVoteSlots.begin() + *minPos) = std::move(newEntry);
            else
                updatedVoteSlots.push_back(std::move(newEntry));
        };
        // Add new entry if the number of the vote entries
        // is less than Max.
        if (updatedVoteSlots.size() < VOTE_MAX_SLOTS)
            update();
        // Add the entry if the account has more tokens than
        // the least token holder or same tokens and higher fee.
        else if (lpTokensNew > *minTokens || (lpTokensNew == *minTokens && feeNew > minFee))
        {
            auto const entry = updatedVoteSlots.begin() + minPos;
            // Remove the least token vote entry.
            num -= Number((*entry)[~sfTradingFee].value_or(0)) * *minTokens;
            den -= *minTokens;
            update(minPos);
        }
        // All slots are full and the account does not hold more LPTokens.
        // Update anyway to refresh the slots.
        else
        {
            JLOG(j_.debug()) << "AMMVote::applyVote, insufficient tokens to "
                                "override other votes";
        }
    }

    XRPL_ASSERT(
        !ctx_.view().rules().enabled(fixInnerObjTemplate) || ammSle->isFieldPresent(sfAuctionSlot),
        "xrpl::applyVote : has auction slot");

    // Update the vote entries and the trading/discounted fee.
    ammSle->setFieldArray(sfVoteSlots, updatedVoteSlots);
    if (auto const fee = static_cast<std::int64_t>(num / den))
    {
        ammSle->setFieldU16(sfTradingFee, fee);
        if (ammSle->isFieldPresent(sfAuctionSlot))
        {
            auto& auctionSlot = ammSle->peekFieldObject(sfAuctionSlot);
            if (auto const discountedFee = fee / AUCTION_SLOT_DISCOUNTED_FEE_FRACTION)
                auctionSlot.setFieldU16(sfDiscountedFee, discountedFee);
            else if (auctionSlot.isFieldPresent(sfDiscountedFee))
                auctionSlot.makeFieldAbsent(sfDiscountedFee);
        }
    }
    else
    {
        if (ammSle->isFieldPresent(sfTradingFee))
            ammSle->makeFieldAbsent(sfTradingFee);
        if (ammSle->isFieldPresent(sfAuctionSlot))
        {
            auto& auctionSlot = ammSle->peekFieldObject(sfAuctionSlot);
            if (auctionSlot.isFieldPresent(sfDiscountedFee))
                auctionSlot.makeFieldAbsent(sfDiscountedFee);
        }
    }
    sb.update(ammSle);

    return {tesSUCCESS, true};
}

TER
AMMVote::doApply()
{
    // This is the ledger view that we work against. Transactions are applied
    // as we go on processing transactions.
    Sandbox sb(&ctx_.view());

    auto const result = applyVote(ctx_, sb, account_, j_);
    if (result.second)
        sb.apply(ctx_.rawView());

    return result.first;
}

}  // namespace xrpl