rippled/src/libxrpl/ledger/PaymentSandbox.cpp

#include <xrpl/ledger/PaymentSandbox.h>

#include <xrpl/basics/base_uint.h>
#include <xrpl/beast/utility/Zero.h>
#include <xrpl/beast/utility/instrumentation.h>
#include <xrpl/ledger/RawView.h>
#include <xrpl/protocol/AccountID.h>
#include <xrpl/protocol/Issue.h>
#include <xrpl/protocol/MPTIssue.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/UintTypes.h>
#include <xrpl/protocol/XRPAmount.h>

#include <algorithm>
#include <cstdint>
#include <map>
#include <optional>
#include <tuple>
#include <utility>

namespace xrpl {

namespace detail {

auto
DeferredCredits::makeKeyIOU(AccountID const& a1, AccountID const& a2, Currency const& c) -> KeyIOU
{
    if (a1 < a2)
    {
        return std::make_tuple(a1, a2, c);
    }

    return std::make_tuple(a2, a1, c);
}

void
DeferredCredits::creditIOU(
    AccountID const& sender,
    AccountID const& receiver,
    STAmount const& amount,
    STAmount const& preCreditSenderBalance)
{
    XRPL_ASSERT(
        sender != receiver, "xrpl::detail::DeferredCredits::creditIOU : sender is not receiver");
    XRPL_ASSERT(!amount.negative(), "xrpl::detail::DeferredCredits::creditIOU : positive amount");
    XRPL_ASSERT(
        amount.holds<Issue>(), "xrpl::detail::DeferredCredits::creditIOU : amount is for Issue");

    auto const k = makeKeyIOU(sender, receiver, amount.get<Issue>().currency);
    auto i = creditsIOU_.find(k);
    if (i == creditsIOU_.end())
    {
        ValueIOU v;

        if (sender < receiver)
        {
            v.lowAcctDebits = amount;
            v.highAcctDebits = amount.zeroed();
            v.lowAcctOrigBalance = preCreditSenderBalance;
        }
        else
        {
            v.lowAcctDebits = amount.zeroed();
            v.highAcctDebits = amount;
            v.lowAcctOrigBalance = -preCreditSenderBalance;
        }

        creditsIOU_[k] = v;
    }
    else
    {
        // only record the balance the first time, do not record it here
        auto& v = i->second;
        if (sender < receiver)
        {
            v.lowAcctDebits += amount;
        }
        else
        {
            v.highAcctDebits += amount;
        }
    }
}

void
DeferredCredits::creditMPT(
    AccountID const& sender,
    AccountID const& receiver,
    STAmount const& amount,
    std::uint64_t preCreditBalanceHolder,
    std::int64_t preCreditBalanceIssuer)
{
    XRPL_ASSERT(
        amount.holds<MPTIssue>(),
        "xrpl::detail::DeferredCredits::creditMPT : amount is for MPTIssue");
    XRPL_ASSERT(!amount.negative(), "xrpl::detail::DeferredCredits::creditMPT : positive amount");
    XRPL_ASSERT(
        sender != receiver, "xrpl::detail::DeferredCredits::creditMPT : sender is not receiver");

    auto const mptAmtVal = amount.mpt().value();
    auto const& issuer = amount.getIssuer();
    auto const& mptIssue = amount.get<MPTIssue>();
    auto const& mptID = mptIssue.getMptID();
    bool const isSenderIssuer = sender == issuer;

    auto i = creditsMPT_.find(mptID);
    if (i == creditsMPT_.end())
    {
        IssuerValueMPT v;
        if (isSenderIssuer)
        {
            v.credit = mptAmtVal;
            v.holders[receiver].origBalance = preCreditBalanceHolder;
        }
        else
        {
            v.holders[sender].debit = mptAmtVal;
            v.holders[sender].origBalance = preCreditBalanceHolder;
        }
        v.origBalance = preCreditBalanceIssuer;
        creditsMPT_.emplace(mptID, std::move(v));
    }
    else
    {
        // only record the balance the first time, do not record it here
        auto& v = i->second;
        if (isSenderIssuer)
        {
            v.credit += mptAmtVal;
            if (!v.holders.contains(receiver))
            {
                v.holders[receiver].origBalance = preCreditBalanceHolder;
            }
        }
        else
        {
            if (!v.holders.contains(sender))
            {
                v.holders[sender].debit = mptAmtVal;
                v.holders[sender].origBalance = preCreditBalanceHolder;
            }
            else
            {
                v.holders[sender].debit += mptAmtVal;
            }
        }
    }
}

void
DeferredCredits::issuerSelfDebitMPT(
    MPTIssue const& issue,
    std::uint64_t amount,
    std::int64_t origBalance)
{
    auto const& mptID = issue.getMptID();
    auto i = creditsMPT_.find(mptID);

    if (i == creditsMPT_.end())
    {
        IssuerValueMPT v;
        v.origBalance = origBalance;
        v.selfDebit = amount;
        creditsMPT_.emplace(mptID, std::move(v));
    }
    else
    {
        i->second.selfDebit += amount;
    }
}

void
DeferredCredits::ownerCount(AccountID const& id, std::uint32_t cur, std::uint32_t next)
{
    auto const v = std::max(cur, next);
    auto r = ownerCounts_.emplace(id, v);
    if (!r.second)
    {
        auto& mapVal = r.first->second;
        mapVal = std::max(v, mapVal);
    }
}

std::optional<std::uint32_t>
DeferredCredits::ownerCount(AccountID const& id) const
{
    auto i = ownerCounts_.find(id);
    if (i != ownerCounts_.end())
        return i->second;
    return std::nullopt;
}

// Get the adjustments for the balance between main and other.
auto
DeferredCredits::adjustmentsIOU(
    AccountID const& main,
    AccountID const& other,
    Currency const& currency) const -> std::optional<AdjustmentIOU>
{
    std::optional<AdjustmentIOU> result;

    KeyIOU const k = makeKeyIOU(main, other, currency);
    auto i = creditsIOU_.find(k);
    if (i == creditsIOU_.end())
        return result;

    auto const& v = i->second;

    if (main < other)
    {
        result.emplace(v.lowAcctDebits, v.highAcctDebits, v.lowAcctOrigBalance);
        return result;
    }

    result.emplace(v.highAcctDebits, v.lowAcctDebits, -v.lowAcctOrigBalance);
    return result;
}

auto
DeferredCredits::adjustmentsMPT(xrpl::MPTID const& mptID) const -> std::optional<AdjustmentMPT>
{
    auto i = creditsMPT_.find(mptID);
    if (i == creditsMPT_.end())
        return std::nullopt;
    return i->second;
}

void
DeferredCredits::apply(DeferredCredits& to)
{
    for (auto const& i : creditsIOU_)
    {
        auto r = to.creditsIOU_.emplace(i);
        if (!r.second)
        {
            auto& toVal = r.first->second;
            auto const& fromVal = i.second;
            toVal.lowAcctDebits += fromVal.lowAcctDebits;
            toVal.highAcctDebits += fromVal.highAcctDebits;
            // Do not update the orig balance, it's already correct
        }
    }

    for (auto const& i : creditsMPT_)
    {
        auto r = to.creditsMPT_.emplace(i);
        if (!r.second)
        {
            auto& toVal = r.first->second;
            auto const& fromVal = i.second;
            toVal.credit += fromVal.credit;
            toVal.selfDebit += fromVal.selfDebit;
            for (auto& [k, v] : fromVal.holders)
            {
                if (!toVal.holders.contains(k))
                {
                    toVal.holders[k] = v;
                }
                else
                {
                    toVal.holders[k].debit += v.debit;
                }
            }
            // Do not update the orig balance, it's already correct
        }
    }

    for (auto const& i : ownerCounts_)
    {
        auto r = to.ownerCounts_.emplace(i);
        if (!r.second)
        {
            auto& toVal = r.first->second;
            auto const& fromVal = i.second;
            toVal = std::max(toVal, fromVal);
        }
    }
}

}  // namespace detail

STAmount
PaymentSandbox::balanceHookIOU(
    AccountID const& account,
    AccountID const& issuer,
    STAmount const& amount) const
{
    XRPL_ASSERT(amount.holds<Issue>(), "balanceHookIOU: amount is for Issue");

    /*
    There are two algorithms here. The pre-switchover algorithm takes the
    current amount and subtracts the recorded credits. The post-switchover
    algorithm remembers the original balance, and subtracts the debits. The
    post-switchover algorithm should be more numerically stable. Consider a
    large credit with a small initial balance. The pre-switchover algorithm
    computes (B+C)-C (where B+C will the amount passed in). The
    post-switchover algorithm returns B. When B and C differ by large
    magnitudes, (B+C)-C may not equal B.
    */

    auto const& currency = amount.get<Issue>().currency;

    auto delta = amount.zeroed();
    auto lastBal = amount;
    auto minBal = amount;
    for (auto curSB = this; curSB != nullptr; curSB = curSB->ps_)
    {
        if (auto adj = curSB->tab_.adjustmentsIOU(account, issuer, currency))
        {
            delta += adj->debits;
            lastBal = adj->origBalance;
            if (lastBal < minBal)
                minBal = lastBal;
        }
    }

    // The adjusted amount should never be larger than the balance. In
    // some circumstances, it is possible for the deferred credits table
    // to compute usable balance just slightly above what the ledger
    // calculates (but always less than the actual balance).
    auto adjustedAmt = std::min({amount, lastBal - delta, minBal});
    adjustedAmt.get<Issue>().account = amount.getIssuer();

    if (isXRP(issuer) && adjustedAmt < beast::kZero)
    {
        // A calculated negative XRP balance is not an error case. Consider a
        // payment snippet that credits a large XRP amount and then debits the
        // same amount. The credit can't be used, but we subtract the debit and
        // calculate a negative value. It's not an error case.
        adjustedAmt.clear();
    }

    return adjustedAmt;
}

STAmount
PaymentSandbox::balanceHookMPT(AccountID const& account, MPTIssue const& issue, std::int64_t amount)
    const
{
    auto const& issuer = issue.getIssuer();
    bool const accountIsHolder = account != issuer;

    std::int64_t delta = 0;
    std::int64_t lastBal = amount;
    std::int64_t minBal = amount;
    for (auto curSB = this; curSB != nullptr; curSB = curSB->ps_)
    {
        if (auto adj = curSB->tab_.adjustmentsMPT(issue))
        {
            if (accountIsHolder)
            {
                if (auto const i = adj->holders.find(account); i != adj->holders.end())
                {
                    delta += i->second.debit;
                    lastBal = i->second.origBalance;
                }
            }
            else
            {
                delta += adj->credit;
                lastBal = adj->origBalance;
            }
            minBal = std::min(lastBal, minBal);
        }
    }

    // The adjusted amount should never be larger than the balance.

    auto const adjustedAmt = std::min({amount, lastBal - delta, minBal});

    return adjustedAmt > 0 ? STAmount{issue, adjustedAmt} : STAmount{issue};
}

STAmount
PaymentSandbox::balanceHookSelfIssueMPT(xrpl::MPTIssue const& issue, std::int64_t amount) const
{
    std::int64_t selfDebited = 0;
    std::int64_t lastBal = amount;
    for (auto curSB = this; curSB != nullptr; curSB = curSB->ps_)
    {
        if (auto adj = curSB->tab_.adjustmentsMPT(issue))
        {
            selfDebited += adj->selfDebit;
            lastBal = adj->origBalance;
        }
    }

    if (lastBal > selfDebited)
        return STAmount{issue, lastBal - selfDebited};

    return STAmount{issue};
}

std::uint32_t
PaymentSandbox::ownerCountHook(AccountID const& account, std::uint32_t count) const
{
    std::uint32_t result = count;
    for (auto curSB = this; curSB != nullptr; curSB = curSB->ps_)
    {
        if (auto adj = curSB->tab_.ownerCount(account))
            result = std::max(result, *adj);
    }
    return result;
}

void
PaymentSandbox::creditHookIOU(
    AccountID const& from,
    AccountID const& to,
    STAmount const& amount,
    STAmount const& preCreditBalance)
{
    XRPL_ASSERT(amount.holds<Issue>(), "creditHookIOU: amount is for Issue");

    tab_.creditIOU(from, to, amount, preCreditBalance);
}

void
PaymentSandbox::creditHookMPT(
    AccountID const& from,
    AccountID const& to,
    STAmount const& amount,
    std::uint64_t preCreditBalanceHolder,
    std::int64_t preCreditBalanceIssuer)
{
    XRPL_ASSERT(amount.holds<MPTIssue>(), "creditHookMPT: amount is for MPTIssue");

    tab_.creditMPT(from, to, amount, preCreditBalanceHolder, preCreditBalanceIssuer);
}

void
PaymentSandbox::issuerSelfDebitHookMPT(
    MPTIssue const& issue,
    std::uint64_t amount,
    std::int64_t origBalance)
{
    XRPL_ASSERT(amount > 0, "PaymentSandbox::issuerSelfDebitHookMPT: amount must be > 0");

    tab_.issuerSelfDebitMPT(issue, amount, origBalance);
}

void
PaymentSandbox::adjustOwnerCountHook(
    AccountID const& account,
    std::uint32_t cur,
    std::uint32_t next)
{
    tab_.ownerCount(account, cur, next);
}

void
PaymentSandbox::apply(RawView& to)
{
    XRPL_ASSERT(!ps_, "xrpl::PaymentSandbox::apply : non-null sandbox");
    items_.apply(to);
}

void
PaymentSandbox::apply(PaymentSandbox& to)
{
    XRPL_ASSERT(ps_ == &to, "xrpl::PaymentSandbox::apply : matching sandbox");
    items_.apply(to);
    tab_.apply(to.tab_);
}

XRPAmount
PaymentSandbox::xrpDestroyed() const
{
    return items_.dropsDestroyed();
}

}  // namespace xrpl