PaySteps.cpp

#include <xrpl/basics/contract.h>
#include <xrpl/json/json_writer.h>
#include <xrpl/ledger/ReadView.h>
#include <xrpl/protocol/IOUAmount.h>
#include <xrpl/protocol/XRPAmount.h>
#include <xrpl/tx/paths/detail/Steps.h>
 
#include <algorithm>
 
namespace xrpl {
 
// Check equal with tolerance
bool
checkNear(IOUAmount const& expected, IOUAmount const& actual)
{
    double const ratTol = 0.001;
    if (abs(expected.exponent() - actual.exponent()) > 1)
        return false;
 
    if (actual.exponent() < -20)
        return true;
 
    auto const a =
        (expected.exponent() < actual.exponent()) ? expected.mantissa() / 10 : expected.mantissa();
    auto const b =
        (actual.exponent() < expected.exponent()) ? actual.mantissa() / 10 : actual.mantissa();
    if (a == b)
        return true;
 
    double const diff = std::abs(a - b);
    auto const r = diff / std::max(std::abs(a), std::abs(b));
    return r <= ratTol;
};
 
bool
checkNear(XRPAmount const& expected, XRPAmount const& actual)
{
    return expected == actual;
};
 
static bool
isXRPAccount(STPathElement const& pe)
{
    if (pe.getNodeType() != STPathElement::typeAccount)
        return false;
    return isXRP(pe.getAccountID());
};
 
static std::pair<TER, std::unique_ptr<Step>>
toStep(
    StrandContext const& ctx,
    STPathElement const* e1,
    STPathElement const* e2,
    Issue const& curIssue)
{
    auto& j = ctx.j;
 
    if (ctx.isFirst && e1->isAccount() &&
        ((e1->getNodeType() & STPathElement::typeCurrency) != 0u) && isXRP(e1->getCurrency()))
    {
        return make_XRPEndpointStep(ctx, e1->getAccountID());
    }
 
    if (ctx.isLast && isXRPAccount(*e1) && e2->isAccount())
        return make_XRPEndpointStep(ctx, e2->getAccountID());
 
    if (e1->isAccount() && e2->isAccount())
    {
        return make_DirectStepI(ctx, e1->getAccountID(), e2->getAccountID(), curIssue.currency);
    }
 
    if (e1->isOffer() && e2->isAccount())
    {
        // LCOV_EXCL_START
        // should already be taken care of
        JLOG(j.error()) << "Found offer/account payment step. Aborting payment strand.";
        UNREACHABLE("xrpl::toStep : offer/account payment payment strand");
        return {temBAD_PATH, std::unique_ptr<Step>{}};
        // LCOV_EXCL_STOP
    }
 
    XRPL_ASSERT(
        (e2->getNodeType() & STPathElement::typeCurrency) ||
            (e2->getNodeType() & STPathElement::typeIssuer),
        "xrpl::toStep : currency or issuer");
    auto const outCurrency = ((e2->getNodeType() & STPathElement::typeCurrency) != 0u)
        ? e2->getCurrency()
        : curIssue.currency;
    auto const outIssuer = ((e2->getNodeType() & STPathElement::typeIssuer) != 0u)
        ? e2->getIssuerID()
        : curIssue.account;
 
    if (isXRP(curIssue.currency) && isXRP(outCurrency))
    {
        JLOG(j.info()) << "Found xrp/xrp offer payment step";
        return {temBAD_PATH, std::unique_ptr<Step>{}};
    }
 
    XRPL_ASSERT(e2->isOffer(), "xrpl::toStep : is offer");
 
    if (isXRP(outCurrency))
        return make_BookStepIX(ctx, curIssue);
 
    if (isXRP(curIssue.currency))
        return make_BookStepXI(ctx, {outCurrency, outIssuer});
 
    return make_BookStepII(ctx, curIssue, {outCurrency, outIssuer});
}
 
std::pair<TER, Strand>
toStrand(
    ReadView const& view,
    AccountID const& src,
    AccountID const& dst,
    Issue const& deliver,
    std::optional<Quality> const& limitQuality,
    std::optional<Issue> const& sendMaxIssue,
    STPath const& path,
    bool ownerPaysTransferFee,
    OfferCrossing offerCrossing,
    AMMContext& ammContext,
    std::optional<uint256> const& domainID,
    beast::Journal j)
{
    if (isXRP(src) || isXRP(dst) || !isConsistent(deliver) ||
        (sendMaxIssue && !isConsistent(*sendMaxIssue)))
        return {temBAD_PATH, Strand{}};
 
    if ((sendMaxIssue && sendMaxIssue->account == noAccount()) || (src == noAccount()) ||
        (dst == noAccount()) || (deliver.account == noAccount()))
        return {temBAD_PATH, Strand{}};
 
    for (auto const& pe : path)
    {
        auto const t = pe.getNodeType();
 
        if (((t & ~STPathElement::typeAll) != 0u) || (t == 0u))
            return {temBAD_PATH, Strand{}};
 
        bool const hasAccount = (t & STPathElement::typeAccount) != 0u;
        bool const hasIssuer = (t & STPathElement::typeIssuer) != 0u;
        bool const hasCurrency = (t & STPathElement::typeCurrency) != 0u;
 
        if (hasAccount && (hasIssuer || hasCurrency))
            return {temBAD_PATH, Strand{}};
 
        if (hasIssuer && isXRP(pe.getIssuerID()))
            return {temBAD_PATH, Strand{}};
 
        if (hasAccount && isXRP(pe.getAccountID()))
            return {temBAD_PATH, Strand{}};
 
        if (hasCurrency && hasIssuer && isXRP(pe.getCurrency()) != isXRP(pe.getIssuerID()))
            return {temBAD_PATH, Strand{}};
 
        if (hasIssuer && (pe.getIssuerID() == noAccount()))
            return {temBAD_PATH, Strand{}};
 
        if (hasAccount && (pe.getAccountID() == noAccount()))
            return {temBAD_PATH, Strand{}};
    }
 
    Issue curIssue = [&] {
        auto const& currency = sendMaxIssue ? sendMaxIssue->currency : deliver.currency;
        if (isXRP(currency))
            return xrpIssue();
        return Issue{currency, src};
    }();
 
    auto hasCurrency = [](STPathElement const pe) {
        return pe.getNodeType() & STPathElement::typeCurrency;
    };
 
    std::vector<STPathElement> normPath;
    // reserve enough for the path, the implied source, destination,
    // sendmax and deliver.
    normPath.reserve(4 + path.size());
    {
        normPath.emplace_back(STPathElement::typeAll, src, curIssue.currency, curIssue.account);
 
        if (sendMaxIssue && sendMaxIssue->account != src &&
            (path.empty() || !path[0].isAccount() ||
             path[0].getAccountID() != sendMaxIssue->account))
        {
            normPath.emplace_back(sendMaxIssue->account, std::nullopt, std::nullopt);
        }
 
        for (auto const& i : path)
            normPath.push_back(i);
 
        {
            // Note that for offer crossing (only) we do use an offer book
            // even if all that is changing is the Issue.account.
            STPathElement const& lastCurrency =
                *std::find_if(normPath.rbegin(), normPath.rend(), hasCurrency);
            if ((lastCurrency.getCurrency() != deliver.currency) ||
                ((offerCrossing != 0u) && lastCurrency.getIssuerID() != deliver.account))
            {
                normPath.emplace_back(std::nullopt, deliver.currency, deliver.account);
            }
        }
 
        if (!((normPath.back().isAccount() && normPath.back().getAccountID() == deliver.account) ||
              (dst == deliver.account)))
        {
            normPath.emplace_back(deliver.account, std::nullopt, std::nullopt);
        }
 
        if (!normPath.back().isAccount() || normPath.back().getAccountID() != dst)
        {
            normPath.emplace_back(dst, std::nullopt, std::nullopt);
        }
    }
 
    if (normPath.size() < 2)
        return {temBAD_PATH, Strand{}};
 
    auto const strandSrc = normPath.front().getAccountID();
    auto const strandDst = normPath.back().getAccountID();
    bool const isDefaultPath = path.empty();
 
    Strand result;
    result.reserve(2 * normPath.size());
 
    /* A strand may not include the same account node more than once
       in the same currency. In a direct step, an account will show up
       at most twice: once as a src and once as a dst (hence the two element
       array). The strandSrc and strandDst will only show up once each.
    */
    std::array<boost::container::flat_set<Issue>, 2> seenDirectIssues;
    // A strand may not include the same offer book more than once
    boost::container::flat_set<Issue> seenBookOuts;
    seenDirectIssues[0].reserve(normPath.size());
    seenDirectIssues[1].reserve(normPath.size());
    seenBookOuts.reserve(normPath.size());
    auto ctx = [&](bool isLast = false) {
        return StrandContext{
            view,
            result,
            strandSrc,
            strandDst,
            deliver,
            limitQuality,
            isLast,
            ownerPaysTransferFee,
            offerCrossing,
            isDefaultPath,
            seenDirectIssues,
            seenBookOuts,
            ammContext,
            domainID,
            j};
    };
 
    for (std::size_t i = 0; i < normPath.size() - 1; ++i)
    {
        /* Iterate through the path elements considering them in pairs.
           The first element of the pair is `cur` and the second element is
           `next`. When an offer is one of the pairs, the step created will be
           for `next`. This means when `cur` is an offer and `next` is an
           account then no step is created, as a step has already been created
           for that offer.
        */
        std::optional<STPathElement> impliedPE;
        auto cur = &normPath[i];
        auto const next = &normPath[i + 1];
 
        if (cur->isAccount())
        {
            curIssue.account = cur->getAccountID();
        }
        else if (cur->hasIssuer())
        {
            curIssue.account = cur->getIssuerID();
        }
 
        if (cur->hasCurrency())
        {
            curIssue.currency = cur->getCurrency();
            if (isXRP(curIssue.currency))
                curIssue.account = xrpAccount();
        }
 
        if (cur->isAccount() && next->isAccount())
        {
            if (!isXRP(curIssue.currency) && curIssue.account != cur->getAccountID() &&
                curIssue.account != next->getAccountID())
            {
                JLOG(j.trace()) << "Inserting implied account";
                auto msr = make_DirectStepI(
                    ctx(), cur->getAccountID(), curIssue.account, curIssue.currency);
                if (!isTesSuccess(msr.first))
                    return {msr.first, Strand{}};
                result.push_back(std::move(msr.second));
                impliedPE.emplace(
                    STPathElement::typeAccount, curIssue.account, xrpCurrency(), xrpAccount());
                cur = &*impliedPE;
            }
        }
        else if (cur->isAccount() && next->isOffer())
        {
            if (curIssue.account != cur->getAccountID())
            {
                JLOG(j.trace()) << "Inserting implied account before offer";
                auto msr = make_DirectStepI(
                    ctx(), cur->getAccountID(), curIssue.account, curIssue.currency);
                if (!isTesSuccess(msr.first))
                    return {msr.first, Strand{}};
                result.push_back(std::move(msr.second));
                impliedPE.emplace(
                    STPathElement::typeAccount, curIssue.account, xrpCurrency(), xrpAccount());
                cur = &*impliedPE;
            }
        }
        else if (cur->isOffer() && next->isAccount())
        {
            if (curIssue.account != next->getAccountID() && !isXRP(next->getAccountID()))
            {
                if (isXRP(curIssue))
                {
                    if (i != normPath.size() - 2)
                        return {temBAD_PATH, Strand{}};
 
                    // Last step. insert xrp endpoint step
                    auto msr = make_XRPEndpointStep(ctx(), next->getAccountID());
                    if (!isTesSuccess(msr.first))
                        return {msr.first, Strand{}};
                    result.push_back(std::move(msr.second));
                }
                else
                {
                    JLOG(j.trace()) << "Inserting implied account after offer";
                    auto msr = make_DirectStepI(
                        ctx(), curIssue.account, next->getAccountID(), curIssue.currency);
                    if (!isTesSuccess(msr.first))
                        return {msr.first, Strand{}};
                    result.push_back(std::move(msr.second));
                }
            }
            continue;
        }
 
        if (!next->isOffer() && next->hasCurrency() && next->getCurrency() != curIssue.currency)
        {
            // Should never happen
            // LCOV_EXCL_START
            UNREACHABLE("xrpl::toStrand : offer currency mismatch");
            return {temBAD_PATH, Strand{}};
            // LCOV_EXCL_STOP
        }
 
        auto s = toStep(ctx(/*isLast*/ i == normPath.size() - 2), cur, next, curIssue);
        if (isTesSuccess(s.first))
        {
            result.emplace_back(std::move(s.second));
        }
        else
        {
            JLOG(j.debug()) << "toStep failed: " << s.first;
            return {s.first, Strand{}};
        }
    }
 
    auto checkStrand = [&]() -> bool {
        auto stepAccts = [](Step const& s) -> std::pair<AccountID, AccountID> {
            if (auto r = s.directStepAccts())
                return *r;
            if (auto const r = s.bookStepBook())
                return std::make_pair(r->in.account, r->out.account);
            Throw<FlowException>(tefEXCEPTION, "Step should be either a direct or book step");
            return std::make_pair(xrpAccount(), xrpAccount());
        };
 
        auto curAcc = src;
        auto curIss = [&] {
            auto& currency = sendMaxIssue ? sendMaxIssue->currency : deliver.currency;
            if (isXRP(currency))
                return xrpIssue();
            return Issue{currency, src};
        }();
 
        for (auto const& s : result)
        {
            auto const accts = stepAccts(*s);
            if (accts.first != curAcc)
                return false;
 
            if (auto const b = s->bookStepBook())
            {
                if (curIss != b->in)
                    return false;
                curIss = b->out;
            }
            else
            {
                curIss.account = accts.second;
            }
 
            curAcc = accts.second;
        }
        if (curAcc != dst)
            return false;
        if (curIss.currency != deliver.currency)
            return false;
        if (curIss.account != deliver.account && curIss.account != dst)
            return false;
        return true;
    };
 
    if (!checkStrand())
    {
        // LCOV_EXCL_START
        JLOG(j.warn()) << "Flow check strand failed";
        UNREACHABLE("xrpl::toStrand : invalid strand");
        return {temBAD_PATH, Strand{}};
        // LCOV_EXCL_STOP
    }
 
    return {tesSUCCESS, std::move(result)};
}
 
std::pair<TER, std::vector<Strand>>
toStrands(
    ReadView const& view,
    AccountID const& src,
    AccountID const& dst,
    Issue const& deliver,
    std::optional<Quality> const& limitQuality,
    std::optional<Issue> const& sendMax,
    STPathSet const& paths,
    bool addDefaultPath,
    bool ownerPaysTransferFee,
    OfferCrossing offerCrossing,
    AMMContext& ammContext,
    std::optional<uint256> const& domainID,
    beast::Journal j)
{
    std::vector<Strand> result;
    result.reserve(1 + paths.size());
    // Insert the strand into result if it is not already part of the vector
    auto insert = [&](Strand s) {
        bool const hasStrand = std::find(result.begin(), result.end(), s) != result.end();
 
        if (!hasStrand)
            result.emplace_back(std::move(s));
    };
 
    if (addDefaultPath)
    {
        auto sp = toStrand(
            view,
            src,
            dst,
            deliver,
            limitQuality,
            sendMax,
            STPath(),
            ownerPaysTransferFee,
            offerCrossing,
            ammContext,
            domainID,
            j);
        auto const ter = sp.first;
        auto& strand = sp.second;
 
        if (!isTesSuccess(ter))
        {
            JLOG(j.trace()) << "failed to add default path";
            if (isTemMalformed(ter) || paths.empty())
            {
                return {ter, std::vector<Strand>{}};
            }
        }
        else if (strand.empty())
        {
            JLOG(j.trace()) << "toStrand failed";
            Throw<FlowException>(tefEXCEPTION, "toStrand returned tes & empty strand");
        }
        else
        {
            insert(std::move(strand));
        }
    }
    else if (paths.empty())
    {
        JLOG(j.debug()) << "Flow: Invalid transaction: No paths and direct "
                           "ripple not allowed.";
        return {temRIPPLE_EMPTY, std::vector<Strand>{}};
    }
 
    TER lastFailTer = tesSUCCESS;
    for (auto const& p : paths)
    {
        auto sp = toStrand(
            view,
            src,
            dst,
            deliver,
            limitQuality,
            sendMax,
            p,
            ownerPaysTransferFee,
            offerCrossing,
            ammContext,
            domainID,
            j);
        auto ter = sp.first;
        auto& strand = sp.second;
 
        if (!isTesSuccess(ter))
        {
            lastFailTer = ter;
            JLOG(j.trace()) << "failed to add path: ter: " << ter
                            << "path: " << p.getJson(JsonOptions::none);
            if (isTemMalformed(ter))
                return {ter, std::vector<Strand>{}};
        }
        else if (strand.empty())
        {
            JLOG(j.trace()) << "toStrand failed";
            Throw<FlowException>(tefEXCEPTION, "toStrand returned tes & empty strand");
        }
        else
        {
            insert(std::move(strand));
        }
    }
 
    if (result.empty())
        return {lastFailTer, std::move(result)};
 
    return {tesSUCCESS, std::move(result)};
}
 
StrandContext::StrandContext(
    ReadView const& view_,
    std::vector<std::unique_ptr<Step>> const& strand_,
    // A strand may not include an inner node that
    // replicates the source or destination.
    AccountID const& strandSrc_,
    AccountID const& strandDst_,
    Issue const& strandDeliver_,
    std::optional<Quality> const& limitQuality_,
    bool isLast_,
    bool ownerPaysTransferFee_,
    OfferCrossing offerCrossing_,
    bool isDefaultPath_,
    std::array<boost::container::flat_set<Issue>, 2>& seenDirectIssues_,
    boost::container::flat_set<Issue>& seenBookOuts_,
    AMMContext& ammContext_,
    std::optional<uint256> const& domainID_,
    beast::Journal j_)
    : view(view_)
    , strandSrc(strandSrc_)
    , strandDst(strandDst_)
    , strandDeliver(strandDeliver_)
    , limitQuality(limitQuality_)
    , isFirst(strand_.empty())
    , isLast(isLast_)
    , ownerPaysTransferFee(ownerPaysTransferFee_)
    , offerCrossing(offerCrossing_)
    , isDefaultPath(isDefaultPath_)
    , strandSize(strand_.size())
    , prevStep(!strand_.empty() ? strand_.back().get() : nullptr)
    , seenDirectIssues(seenDirectIssues_)
    , seenBookOuts(seenBookOuts_)
    , ammContext(ammContext_)
    , domainID(domainID_)
    , j(j_)
{
}
 
template <class InAmt, class OutAmt>
bool
isDirectXrpToXrp(Strand const& strand)
{
    return false;
}
 
template <>
bool
isDirectXrpToXrp<XRPAmount, XRPAmount>(Strand const& strand)
{
    return (strand.size() == 2);
}
 
template bool
isDirectXrpToXrp<XRPAmount, IOUAmount>(Strand const& strand);
template bool
isDirectXrpToXrp<IOUAmount, XRPAmount>(Strand const& strand);
template bool
isDirectXrpToXrp<IOUAmount, IOUAmount>(Strand const& strand);
 
}  // namespace xrpl