XRPEndpointStep.cpp

#include <xrpld/app/paths/Credit.h>
#include <xrpld/app/paths/detail/AmountSpec.h>
#include <xrpld/app/paths/detail/StepChecks.h>
#include <xrpld/app/paths/detail/Steps.h>
 
#include <xrpl/basics/Log.h>
#include <xrpl/ledger/PaymentSandbox.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/protocol/IOUAmount.h>
#include <xrpl/protocol/Quality.h>
#include <xrpl/protocol/XRPAmount.h>
 
#include <boost/container/flat_set.hpp>
 
#include <sstream>
 
namespace xrpl {
 
template <class TDerived>
class XRPEndpointStep
    : public StepImp<XRPAmount, XRPAmount, XRPEndpointStep<TDerived>>
{
private:
    AccountID acc_;
    bool const isLast_;
    beast::Journal const j_;
 
    // Since this step will always be an endpoint in a strand
    // (either the first or last step) the same cache is used
    // for cachedIn and cachedOut and only one will ever be used
    std::optional<XRPAmount> cache_;
 
    std::optional<EitherAmount>
    cached() const
    {
        if (!cache_)
            return std::nullopt;
        return EitherAmount(*cache_);
    }
 
public:
    XRPEndpointStep(StrandContext const& ctx, AccountID const& acc)
        : acc_(acc), isLast_(ctx.isLast), j_(ctx.j)
    {
    }
 
    AccountID const&
    acc() const
    {
        return acc_;
    }
 
    std::optional<std::pair<AccountID, AccountID>>
    directStepAccts() const override
    {
        if (isLast_)
            return std::make_pair(xrpAccount(), acc_);
        return std::make_pair(acc_, xrpAccount());
    }
 
    std::optional<EitherAmount>
    cachedIn() const override
    {
        return cached();
    }
 
    std::optional<EitherAmount>
    cachedOut() const override
    {
        return cached();
    }
 
    DebtDirection
    debtDirection(ReadView const& sb, StrandDirection dir) const override
    {
        return DebtDirection::issues;
    }
 
    std::pair<std::optional<Quality>, DebtDirection>
    qualityUpperBound(ReadView const& v, DebtDirection prevStepDir)
        const override;
 
    std::pair<XRPAmount, XRPAmount>
    revImp(
        PaymentSandbox& sb,
        ApplyView& afView,
        boost::container::flat_set<uint256>& ofrsToRm,
        XRPAmount const& out);
 
    std::pair<XRPAmount, XRPAmount>
    fwdImp(
        PaymentSandbox& sb,
        ApplyView& afView,
        boost::container::flat_set<uint256>& ofrsToRm,
        XRPAmount const& in);
 
    std::pair<bool, EitherAmount>
    validFwd(PaymentSandbox& sb, ApplyView& afView, EitherAmount const& in)
        override;
 
    // Check for errors and violations of frozen constraints.
    TER
    check(StrandContext const& ctx) const;
 
protected:
    XRPAmount
    xrpLiquidImpl(ReadView& sb, std::int32_t reserveReduction) const
    {
        return xrpl::xrpLiquid(sb, acc_, reserveReduction, j_);
    }
 
    std::string
    logStringImpl(char const* name) const
    {
        std::ostringstream ostr;
        ostr << name << ": "
             << "\nAcc: " << acc_;
        return ostr.str();
    }
 
private:
    template <class P>
    friend bool
    operator==(XRPEndpointStep<P> const& lhs, XRPEndpointStep<P> const& rhs);
 
    friend bool
    operator!=(XRPEndpointStep const& lhs, XRPEndpointStep const& rhs)
    {
        return !(lhs == rhs);
    }
 
    bool
    equal(Step const& rhs) const override
    {
        if (auto ds = dynamic_cast<XRPEndpointStep const*>(&rhs))
        {
            return *this == *ds;
        }
        return false;
    }
};
 
//------------------------------------------------------------------------------
 
// Flow is used in two different circumstances for transferring funds:
//  o Payments, and
//  o Offer crossing.
// The rules for handling funds in these two cases are almost, but not
// quite, the same.
 
// Payment XRPEndpointStep class (not offer crossing).
class XRPEndpointPaymentStep : public XRPEndpointStep<XRPEndpointPaymentStep>
{
public:
    using XRPEndpointStep<XRPEndpointPaymentStep>::XRPEndpointStep;
 
    XRPAmount
    xrpLiquid(ReadView& sb) const
    {
        return xrpLiquidImpl(sb, 0);
        ;
    }
 
    std::string
    logString() const override
    {
        return logStringImpl("XRPEndpointPaymentStep");
    }
};
 
// Offer crossing XRPEndpointStep class (not a payment).
class XRPEndpointOfferCrossingStep
    : public XRPEndpointStep<XRPEndpointOfferCrossingStep>
{
private:
    // For historical reasons, offer crossing is allowed to dig further
    // into the XRP reserve than an ordinary payment.  (I believe it's
    // because the trust line was created after the XRP was removed.)
    // Return how much the reserve should be reduced.
    //
    // Note that reduced reserve only happens if the trust line does not
    // currently exist.
    static std::int32_t
    computeReserveReduction(StrandContext const& ctx, AccountID const& acc)
    {
        if (ctx.isFirst && !ctx.view.read(keylet::line(acc, ctx.strandDeliver)))
            return -1;
        return 0;
    }
 
public:
    XRPEndpointOfferCrossingStep(StrandContext const& ctx, AccountID const& acc)
        : XRPEndpointStep<XRPEndpointOfferCrossingStep>(ctx, acc)
        , reserveReduction_(computeReserveReduction(ctx, acc))
    {
    }
 
    XRPAmount
    xrpLiquid(ReadView& sb) const
    {
        return xrpLiquidImpl(sb, reserveReduction_);
    }
 
    std::string
    logString() const override
    {
        return logStringImpl("XRPEndpointOfferCrossingStep");
    }
 
private:
    std::int32_t const reserveReduction_;
};
 
//------------------------------------------------------------------------------
 
template <class TDerived>
inline bool
operator==(
    XRPEndpointStep<TDerived> const& lhs,
    XRPEndpointStep<TDerived> const& rhs)
{
    return lhs.acc_ == rhs.acc_ && lhs.isLast_ == rhs.isLast_;
}
 
template <class TDerived>
std::pair<std::optional<Quality>, DebtDirection>
XRPEndpointStep<TDerived>::qualityUpperBound(
    ReadView const& v,
    DebtDirection prevStepDir) const
{
    return {
        Quality{STAmount::uRateOne},
        this->debtDirection(v, StrandDirection::forward)};
}
 
template <class TDerived>
std::pair<XRPAmount, XRPAmount>
XRPEndpointStep<TDerived>::revImp(
    PaymentSandbox& sb,
    ApplyView& afView,
    boost::container::flat_set<uint256>& ofrsToRm,
    XRPAmount const& out)
{
    auto const balance = static_cast<TDerived const*>(this)->xrpLiquid(sb);
 
    auto const result = isLast_ ? out : std::min(balance, out);
 
    auto& sender = isLast_ ? xrpAccount() : acc_;
    auto& receiver = isLast_ ? acc_ : xrpAccount();
    auto ter = accountSend(sb, sender, receiver, toSTAmount(result), j_);
    if (ter != tesSUCCESS)
        return {XRPAmount{beast::zero}, XRPAmount{beast::zero}};
 
    cache_.emplace(result);
    return {result, result};
}
 
template <class TDerived>
std::pair<XRPAmount, XRPAmount>
XRPEndpointStep<TDerived>::fwdImp(
    PaymentSandbox& sb,
    ApplyView& afView,
    boost::container::flat_set<uint256>& ofrsToRm,
    XRPAmount const& in)
{
    XRPL_ASSERT(cache_, "xrpl::XRPEndpointStep::fwdImp : cache is set");
    auto const balance = static_cast<TDerived const*>(this)->xrpLiquid(sb);
 
    auto const result = isLast_ ? in : std::min(balance, in);
 
    auto& sender = isLast_ ? xrpAccount() : acc_;
    auto& receiver = isLast_ ? acc_ : xrpAccount();
    auto ter = accountSend(sb, sender, receiver, toSTAmount(result), j_);
    if (ter != tesSUCCESS)
        return {XRPAmount{beast::zero}, XRPAmount{beast::zero}};
 
    cache_.emplace(result);
    return {result, result};
}
 
template <class TDerived>
std::pair<bool, EitherAmount>
XRPEndpointStep<TDerived>::validFwd(
    PaymentSandbox& sb,
    ApplyView& afView,
    EitherAmount const& in)
{
    if (!cache_)
    {
        JLOG(j_.error()) << "Expected valid cache in validFwd";
        return {false, EitherAmount(XRPAmount(beast::zero))};
    }
 
    XRPL_ASSERT(in.native, "xrpl::XRPEndpointStep::validFwd : input is XRP");
 
    auto const& xrpIn = in.xrp;
    auto const balance = static_cast<TDerived const*>(this)->xrpLiquid(sb);
 
    if (!isLast_ && balance < xrpIn)
    {
        JLOG(j_.warn()) << "XRPEndpointStep: Strand re-execute check failed."
                        << " Insufficient balance: " << to_string(balance)
                        << " Requested: " << to_string(xrpIn);
        return {false, EitherAmount(balance)};
    }
 
    if (xrpIn != *cache_)
    {
        JLOG(j_.warn()) << "XRPEndpointStep: Strand re-execute check failed."
                        << " ExpectedIn: " << to_string(*cache_)
                        << " CachedIn: " << to_string(xrpIn);
    }
    return {true, in};
}
 
template <class TDerived>
TER
XRPEndpointStep<TDerived>::check(StrandContext const& ctx) const
{
    if (!acc_)
    {
        JLOG(j_.debug()) << "XRPEndpointStep: specified bad account.";
        return temBAD_PATH;
    }
 
    auto sleAcc = ctx.view.read(keylet::account(acc_));
    if (!sleAcc)
    {
        JLOG(j_.warn()) << "XRPEndpointStep: can't send or receive XRP from "
                           "non-existent account: "
                        << acc_;
        return terNO_ACCOUNT;
    }
 
    if (!ctx.isFirst && !ctx.isLast)
    {
        return temBAD_PATH;
    }
 
    auto& src = isLast_ ? xrpAccount() : acc_;
    auto& dst = isLast_ ? acc_ : xrpAccount();
    auto ter = checkFreeze(ctx.view, src, dst, xrpCurrency());
    if (ter != tesSUCCESS)
        return ter;
 
    auto const issuesIndex = isLast_ ? 0 : 1;
    if (!ctx.seenDirectIssues[issuesIndex].insert(xrpIssue()).second)
    {
        JLOG(j_.debug()) << "XRPEndpointStep: loop detected: Index: "
                         << ctx.strandSize << ' ' << *this;
        return temBAD_PATH_LOOP;
    }
 
    return tesSUCCESS;
}
 
//------------------------------------------------------------------------------
 
namespace test {
// Needed for testing
bool
xrpEndpointStepEqual(Step const& step, AccountID const& acc)
{
    if (auto xs =
            dynamic_cast<XRPEndpointStep<XRPEndpointPaymentStep> const*>(&step))
    {
        return xs->acc() == acc;
    }
    return false;
}
}  // namespace test
 
//------------------------------------------------------------------------------
 
std::pair<TER, std::unique_ptr<Step>>
make_XRPEndpointStep(StrandContext const& ctx, AccountID const& acc)
{
    TER ter = tefINTERNAL;
    std::unique_ptr<Step> r;
    if (ctx.offerCrossing)
    {
        auto offerCrossingStep =
            std::make_unique<XRPEndpointOfferCrossingStep>(ctx, acc);
        ter = offerCrossingStep->check(ctx);
        r = std::move(offerCrossingStep);
    }
    else  // payment
    {
        auto paymentStep = std::make_unique<XRPEndpointPaymentStep>(ctx, acc);
        ter = paymentStep->check(ctx);
        r = std::move(paymentStep);
    }
    if (ter != tesSUCCESS)
        return {ter, nullptr};
 
    return {tesSUCCESS, std::move(r)};
}
 
}  // namespace xrpl