Taker.cpp

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2014 Ripple Labs Inc.
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#include <xrpld/app/tx/detail/Taker.h>
 
#include <xrpl/basics/Log.h>
#include <xrpl/basics/contract.h>
 
namespace ripple {
 
static std::string
format_amount(STAmount const& amount)
{
    std::string txt = amount.getText();
    txt += "/";
    txt += to_string(amount.issue().currency);
    return txt;
}
 
BasicTaker::BasicTaker(
    CrossType cross_type,
    AccountID const& account,
    Amounts const& amount,
    Quality const& quality,
    std::uint32_t flags,
    Rate const& rate_in,
    Rate const& rate_out,
    beast::Journal journal)
    : account_(account)
    , quality_(quality)
    , threshold_(quality_)
    , sell_(flags & tfSell)
    , original_(amount)
    , remaining_(amount)
    , issue_in_(remaining_.in.issue())
    , issue_out_(remaining_.out.issue())
    , m_rate_in(rate_in)
    , m_rate_out(rate_out)
    , cross_type_(cross_type)
    , journal_(journal)
{
    XRPL_ASSERT(
        remaining_.in > beast::zero,
        "ripple::BasicTaker::BasicTaker : positive remaining in");
    XRPL_ASSERT(
        remaining_.out > beast::zero,
        "ripple::BasicTaker::BasicTaker : positive remaining out");
 
    XRPL_ASSERT(
        m_rate_in.value, "ripple::BasicTaker::BasicTaker : nonzero rate in");
    XRPL_ASSERT(
        m_rate_out.value, "ripple::BasicTaker::BasicTaker : nonzero rate out");
 
    // If we are dealing with a particular flavor, make sure that it's the
    // flavor we expect:
    XRPL_ASSERT(
        cross_type != CrossType::XrpToIou ||
            (isXRP(issue_in()) && !isXRP(issue_out())),
        "ripple::BasicTaker::BasicTaker : valid cross to IOU");
 
    XRPL_ASSERT(
        cross_type != CrossType::IouToXrp ||
            (!isXRP(issue_in()) && isXRP(issue_out())),
        "ripple::BasicTaker::BasicTaker : valid cross to XRP");
 
    // And make sure we're not crossing XRP for XRP
    XRPL_ASSERT(
        !isXRP(issue_in()) || !isXRP(issue_out()),
        "ripple::BasicTaker::BasicTaker : not crossing XRP for XRP");
 
    // If this is a passive order, we adjust the quality so as to prevent offers
    // at the same quality level from being consumed.
    if (flags & tfPassive)
        ++threshold_;
}
 
Rate
BasicTaker::effective_rate(
    Rate const& rate,
    Issue const& issue,
    AccountID const& from,
    AccountID const& to)
{
    // If there's a transfer rate, the issuer is not involved
    // and the sender isn't the same as the recipient, return
    // the actual transfer rate.
    if (rate != parityRate && from != to && from != issue.account &&
        to != issue.account)
    {
        return rate;
    }
 
    return parityRate;
}
 
bool
BasicTaker::unfunded() const
{
    if (get_funds(account(), remaining_.in) > beast::zero)
        return false;
 
    JLOG(journal_.debug()) << "Unfunded: taker is out of funds.";
    return true;
}
 
bool
BasicTaker::done() const
{
    // We are done if we have consumed all the input currency
    if (remaining_.in <= beast::zero)
    {
        JLOG(journal_.debug())
            << "Done: all the input currency has been consumed.";
        return true;
    }
 
    // We are done if using buy semantics and we received the
    // desired amount of output currency
    if (!sell_ && (remaining_.out <= beast::zero))
    {
        JLOG(journal_.debug()) << "Done: the desired amount has been received.";
        return true;
    }
 
    // We are done if the taker is out of funds
    if (unfunded())
    {
        JLOG(journal_.debug()) << "Done: taker out of funds.";
        return true;
    }
 
    return false;
}
 
Amounts
BasicTaker::remaining_offer() const
{
    // If the taker is done, then there's no offer to place.
    if (done())
        return Amounts(remaining_.in.zeroed(), remaining_.out.zeroed());
 
    // Avoid math altogether if we didn't cross.
    if (original_ == remaining_)
        return original_;
 
    if (sell_)
    {
        XRPL_ASSERT(
            remaining_.in > beast::zero,
            "ripple::BasicTaker::remaining_offer : positive remaining in");
 
        // We scale the output based on the remaining input:
        return Amounts(
            remaining_.in,
            divRound(remaining_.in, quality_.rate(), issue_out_, true));
    }
 
    XRPL_ASSERT(
        remaining_.out > beast::zero,
        "ripple::BasicTaker::remaining_offer : positive remaining out");
 
    // We scale the input based on the remaining output:
    return Amounts(
        mulRound(remaining_.out, quality_.rate(), issue_in_, true),
        remaining_.out);
}
 
Amounts const&
BasicTaker::original_offer() const
{
    return original_;
}
 
// TODO: the presence of 'output' is an artifact caused by the fact that
// Amounts carry issue information which should be decoupled.
static STAmount
qual_div(STAmount const& amount, Quality const& quality, STAmount const& output)
{
    auto result = divide(amount, quality.rate(), output.issue());
    return std::min(result, output);
}
 
static STAmount
qual_mul(STAmount const& amount, Quality const& quality, STAmount const& output)
{
    auto result = multiply(amount, quality.rate(), output.issue());
    return std::min(result, output);
}
 
void
BasicTaker::log_flow(char const* description, Flow const& flow)
{
    auto stream = journal_.debug();
    if (!stream)
        return;
 
    stream << description;
 
    if (isXRP(issue_in()))
        stream << "   order in: " << format_amount(flow.order.in);
    else
        stream << "   order in: " << format_amount(flow.order.in)
               << " (issuer: " << format_amount(flow.issuers.in) << ")";
 
    if (isXRP(issue_out()))
        stream << "  order out: " << format_amount(flow.order.out);
    else
        stream << "  order out: " << format_amount(flow.order.out)
               << " (issuer: " << format_amount(flow.issuers.out) << ")";
}
 
BasicTaker::Flow
BasicTaker::flow_xrp_to_iou(
    Amounts const& order,
    Quality quality,
    STAmount const& owner_funds,
    STAmount const& taker_funds,
    Rate const& rate_out)
{
    Flow f;
    f.order = order;
    f.issuers.out = multiply(f.order.out, rate_out);
 
    log_flow("flow_xrp_to_iou", f);
 
    // Clamp on owner balance
    if (owner_funds < f.issuers.out)
    {
        f.issuers.out = owner_funds;
        f.order.out = divide(f.issuers.out, rate_out);
        f.order.in = qual_mul(f.order.out, quality, f.order.in);
        log_flow("(clamped on owner balance)", f);
    }
 
    // Clamp if taker wants to limit the output
    if (!sell_ && remaining_.out < f.order.out)
    {
        f.order.out = remaining_.out;
        f.order.in = qual_mul(f.order.out, quality, f.order.in);
        f.issuers.out = multiply(f.order.out, rate_out);
        log_flow("(clamped on taker output)", f);
    }
 
    // Clamp on the taker's funds
    if (taker_funds < f.order.in)
    {
        f.order.in = taker_funds;
        f.order.out = qual_div(f.order.in, quality, f.order.out);
        f.issuers.out = multiply(f.order.out, rate_out);
        log_flow("(clamped on taker funds)", f);
    }
 
    // Clamp on remaining offer if we are not handling the second leg
    // of an autobridge.
    if (cross_type_ == CrossType::XrpToIou && (remaining_.in < f.order.in))
    {
        f.order.in = remaining_.in;
        f.order.out = qual_div(f.order.in, quality, f.order.out);
        f.issuers.out = multiply(f.order.out, rate_out);
        log_flow("(clamped on taker input)", f);
    }
 
    return f;
}
 
BasicTaker::Flow
BasicTaker::flow_iou_to_xrp(
    Amounts const& order,
    Quality quality,
    STAmount const& owner_funds,
    STAmount const& taker_funds,
    Rate const& rate_in)
{
    Flow f;
    f.order = order;
    f.issuers.in = multiply(f.order.in, rate_in);
 
    log_flow("flow_iou_to_xrp", f);
 
    // Clamp on owner's funds
    if (owner_funds < f.order.out)
    {
        f.order.out = owner_funds;
        f.order.in = qual_mul(f.order.out, quality, f.order.in);
        f.issuers.in = multiply(f.order.in, rate_in);
        log_flow("(clamped on owner funds)", f);
    }
 
    // Clamp if taker wants to limit the output and we are not the
    // first leg of an autobridge.
    if (!sell_ && cross_type_ == CrossType::IouToXrp)
    {
        if (remaining_.out < f.order.out)
        {
            f.order.out = remaining_.out;
            f.order.in = qual_mul(f.order.out, quality, f.order.in);
            f.issuers.in = multiply(f.order.in, rate_in);
            log_flow("(clamped on taker output)", f);
        }
    }
 
    // Clamp on the taker's input offer
    if (remaining_.in < f.order.in)
    {
        f.order.in = remaining_.in;
        f.issuers.in = multiply(f.order.in, rate_in);
        f.order.out = qual_div(f.order.in, quality, f.order.out);
        log_flow("(clamped on taker input)", f);
    }
 
    // Clamp on the taker's input balance
    if (taker_funds < f.issuers.in)
    {
        f.issuers.in = taker_funds;
        f.order.in = divide(f.issuers.in, rate_in);
        f.order.out = qual_div(f.order.in, quality, f.order.out);
        log_flow("(clamped on taker funds)", f);
    }
 
    return f;
}
 
BasicTaker::Flow
BasicTaker::flow_iou_to_iou(
    Amounts const& order,
    Quality quality,
    STAmount const& owner_funds,
    STAmount const& taker_funds,
    Rate const& rate_in,
    Rate const& rate_out)
{
    Flow f;
    f.order = order;
    f.issuers.in = multiply(f.order.in, rate_in);
    f.issuers.out = multiply(f.order.out, rate_out);
 
    log_flow("flow_iou_to_iou", f);
 
    // Clamp on owner balance
    if (owner_funds < f.issuers.out)
    {
        f.issuers.out = owner_funds;
        f.order.out = divide(f.issuers.out, rate_out);
        f.order.in = qual_mul(f.order.out, quality, f.order.in);
        f.issuers.in = multiply(f.order.in, rate_in);
        log_flow("(clamped on owner funds)", f);
    }
 
    // Clamp on taker's offer
    if (!sell_ && remaining_.out < f.order.out)
    {
        f.order.out = remaining_.out;
        f.order.in = qual_mul(f.order.out, quality, f.order.in);
        f.issuers.out = multiply(f.order.out, rate_out);
        f.issuers.in = multiply(f.order.in, rate_in);
        log_flow("(clamped on taker output)", f);
    }
 
    // Clamp on the taker's input offer
    if (remaining_.in < f.order.in)
    {
        f.order.in = remaining_.in;
        f.issuers.in = multiply(f.order.in, rate_in);
        f.order.out = qual_div(f.order.in, quality, f.order.out);
        f.issuers.out = multiply(f.order.out, rate_out);
        log_flow("(clamped on taker input)", f);
    }
 
    // Clamp on the taker's input balance
    if (taker_funds < f.issuers.in)
    {
        f.issuers.in = taker_funds;
        f.order.in = divide(f.issuers.in, rate_in);
        f.order.out = qual_div(f.order.in, quality, f.order.out);
        f.issuers.out = multiply(f.order.out, rate_out);
        log_flow("(clamped on taker funds)", f);
    }
 
    return f;
}
 
// Calculates the direct flow through the specified offer
BasicTaker::Flow
BasicTaker::do_cross(Amounts offer, Quality quality, AccountID const& owner)
{
    auto const owner_funds = get_funds(owner, offer.out);
    auto const taker_funds = get_funds(account(), offer.in);
 
    Flow result;
 
    if (cross_type_ == CrossType::XrpToIou)
    {
        result = flow_xrp_to_iou(
            offer,
            quality,
            owner_funds,
            taker_funds,
            out_rate(owner, account()));
    }
    else if (cross_type_ == CrossType::IouToXrp)
    {
        result = flow_iou_to_xrp(
            offer,
            quality,
            owner_funds,
            taker_funds,
            in_rate(owner, account()));
    }
    else
    {
        result = flow_iou_to_iou(
            offer,
            quality,
            owner_funds,
            taker_funds,
            in_rate(owner, account()),
            out_rate(owner, account()));
    }
 
    if (!result.sanity_check())
        Throw<std::logic_error>("Computed flow fails sanity check.");
 
    remaining_.out -= result.order.out;
    remaining_.in -= result.order.in;
 
    XRPL_ASSERT(
        remaining_.in >= beast::zero,
        "ripple::BasicTaker::do_cross : minimum remaining in");
 
    return result;
}
 
// Calculates the bridged flow through the specified offers
std::pair<BasicTaker::Flow, BasicTaker::Flow>
BasicTaker::do_cross(
    Amounts offer1,
    Quality quality1,
    AccountID const& owner1,
    Amounts offer2,
    Quality quality2,
    AccountID const& owner2)
{
    XRPL_ASSERT(
        !offer1.in.native(),
        "ripple::BasicTaker::do_cross : offer1 in is not XRP");
    XRPL_ASSERT(
        offer1.out.native(),
        "ripple::BasicTaker::do_cross : offer1 out is XRP");
    XRPL_ASSERT(
        offer2.in.native(), "ripple::BasicTaker::do_cross : offer2 in is XRP");
    XRPL_ASSERT(
        !offer2.out.native(),
        "ripple::BasicTaker::do_cross : offer2 out is not XRP");
 
    // If the taker owns the first leg of the offer, then the taker's available
    // funds aren't the limiting factor for the input - the offer itself is.
    auto leg1_in_funds = get_funds(account(), offer1.in);
 
    if (account() == owner1)
    {
        JLOG(journal_.trace()) << "The taker owns the first leg of a bridge.";
        leg1_in_funds = std::max(leg1_in_funds, offer1.in);
    }
 
    // If the taker owns the second leg of the offer, then the taker's available
    // funds are not the limiting factor for the output - the offer itself is.
    auto leg2_out_funds = get_funds(owner2, offer2.out);
 
    if (account() == owner2)
    {
        JLOG(journal_.trace()) << "The taker owns the second leg of a bridge.";
        leg2_out_funds = std::max(leg2_out_funds, offer2.out);
    }
 
    // The amount available to flow via XRP is the amount that the owner of the
    // first leg of the bridge has, up to the first leg's output.
    //
    // But, when both legs of a bridge are owned by the same person, the amount
    // of XRP that can flow between the two legs is, essentially, infinite
    // since all the owner is doing is taking out XRP of his left pocket
    // and putting it in his right pocket. In that case, we set the available
    // XRP to the largest of the two offers.
    auto xrp_funds = get_funds(owner1, offer1.out);
 
    if (owner1 == owner2)
    {
        JLOG(journal_.trace())
            << "The bridge endpoints are owned by the same account.";
        xrp_funds = std::max(offer1.out, offer2.in);
    }
 
    if (auto stream = journal_.debug())
    {
        stream << "Available bridge funds:";
        stream << "  leg1 in: " << format_amount(leg1_in_funds);
        stream << " leg2 out: " << format_amount(leg2_out_funds);
        stream << "      xrp: " << format_amount(xrp_funds);
    }
 
    auto const leg1_rate = in_rate(owner1, account());
    auto const leg2_rate = out_rate(owner2, account());
 
    // Attempt to determine the maximal flow that can be achieved across each
    // leg independent of the other.
    auto flow1 =
        flow_iou_to_xrp(offer1, quality1, xrp_funds, leg1_in_funds, leg1_rate);
 
    if (!flow1.sanity_check())
        Throw<std::logic_error>("Computed flow1 fails sanity check.");
 
    auto flow2 =
        flow_xrp_to_iou(offer2, quality2, leg2_out_funds, xrp_funds, leg2_rate);
 
    if (!flow2.sanity_check())
        Throw<std::logic_error>("Computed flow2 fails sanity check.");
 
    // We now have the maximal flows across each leg individually. We need to
    // equalize them, so that the amount of XRP that flows out of the first leg
    // is the same as the amount of XRP that flows into the second leg. We take
    // the side which is the limiting factor (if any) and adjust the other.
    if (flow1.order.out < flow2.order.in)
    {
        // Adjust the second leg of the offer down:
        flow2.order.in = flow1.order.out;
        flow2.order.out = qual_div(flow2.order.in, quality2, flow2.order.out);
        flow2.issuers.out = multiply(flow2.order.out, leg2_rate);
        log_flow("Balancing: adjusted second leg down", flow2);
    }
    else if (flow1.order.out > flow2.order.in)
    {
        // Adjust the first leg of the offer down:
        flow1.order.out = flow2.order.in;
        flow1.order.in = qual_mul(flow1.order.out, quality1, flow1.order.in);
        flow1.issuers.in = multiply(flow1.order.in, leg1_rate);
        log_flow("Balancing: adjusted first leg down", flow2);
    }
 
    if (flow1.order.out != flow2.order.in)
        Throw<std::logic_error>("Bridged flow is out of balance.");
 
    remaining_.out -= flow2.order.out;
    remaining_.in -= flow1.order.in;
 
    return std::make_pair(flow1, flow2);
}
 
//==============================================================================
 
Taker::Taker(
    CrossType cross_type,
    ApplyView& view,
    AccountID const& account,
    Amounts const& offer,
    std::uint32_t flags,
    beast::Journal journal)
    : BasicTaker(
          cross_type,
          account,
          offer,
          Quality(offer),
          flags,
          calculateRate(view, offer.in.getIssuer(), account),
          calculateRate(view, offer.out.getIssuer(), account),
          journal)
    , view_(view)
    , xrp_flow_(0)
    , direct_crossings_(0)
    , bridge_crossings_(0)
{
    XRPL_ASSERT(
        issue_in() == offer.in.issue(),
        "ripple::Taker::Taker : issue in is a match");
    XRPL_ASSERT(
        issue_out() == offer.out.issue(),
        "ripple::Taker::Taker : issue out is a match");
 
    if (auto stream = journal_.debug())
    {
        stream << "Crossing as: " << to_string(account);
 
        if (isXRP(issue_in()))
            stream << "   Offer in: " << format_amount(offer.in);
        else
            stream << "   Offer in: " << format_amount(offer.in)
                   << " (issuer: " << issue_in().account << ")";
 
        if (isXRP(issue_out()))
            stream << "  Offer out: " << format_amount(offer.out);
        else
            stream << "  Offer out: " << format_amount(offer.out)
                   << " (issuer: " << issue_out().account << ")";
 
        stream << "    Balance: "
               << format_amount(get_funds(account, offer.in));
    }
}
 
void
Taker::consume_offer(Offer& offer, Amounts const& order)
{
    if (order.in < beast::zero)
        Throw<std::logic_error>("flow with negative input.");
 
    if (order.out < beast::zero)
        Throw<std::logic_error>("flow with negative output.");
 
    JLOG(journal_.debug()) << "Consuming from offer " << offer;
 
    if (auto stream = journal_.trace())
    {
        auto const& available = offer.amount();
 
        stream << "   in:" << format_amount(available.in);
        stream << "  out:" << format_amount(available.out);
    }
 
    offer.consume(view_, order);
}
 
STAmount
Taker::get_funds(AccountID const& account, STAmount const& amount) const
{
    return accountFunds(view_, account, amount, fhZERO_IF_FROZEN, journal_);
}
 
TER
Taker::transferXRP(
    AccountID const& from,
    AccountID const& to,
    STAmount const& amount)
{
    if (!isXRP(amount))
        Throw<std::logic_error>("Using transferXRP with IOU");
 
    if (from == to)
        return tesSUCCESS;
 
    // Transferring zero is equivalent to not doing a transfer
    if (amount == beast::zero)
        return tesSUCCESS;
 
    return ripple::transferXRP(view_, from, to, amount, journal_);
}
 
TER
Taker::redeemIOU(
    AccountID const& account,
    STAmount const& amount,
    Issue const& issue)
{
    if (isXRP(amount))
        Throw<std::logic_error>("Using redeemIOU with XRP");
 
    if (account == issue.account)
        return tesSUCCESS;
 
    // Transferring zero is equivalent to not doing a transfer
    if (amount == beast::zero)
        return tesSUCCESS;
 
    // If we are trying to redeem some amount, then the account
    // must have a credit balance.
    if (get_funds(account, amount) <= beast::zero)
        Throw<std::logic_error>("redeemIOU has no funds to redeem");
 
    auto ret = ripple::redeemIOU(view_, account, amount, issue, journal_);
 
    if (get_funds(account, amount) < beast::zero)
        Throw<std::logic_error>("redeemIOU redeemed more funds than available");
 
    return ret;
}
 
TER
Taker::issueIOU(
    AccountID const& account,
    STAmount const& amount,
    Issue const& issue)
{
    if (isXRP(amount))
        Throw<std::logic_error>("Using issueIOU with XRP");
 
    if (account == issue.account)
        return tesSUCCESS;
 
    // Transferring zero is equivalent to not doing a transfer
    if (amount == beast::zero)
        return tesSUCCESS;
 
    return ripple::issueIOU(view_, account, amount, issue, journal_);
}
 
// Performs funds transfers to fill the given offer and adjusts offer.
TER
Taker::fill(BasicTaker::Flow const& flow, Offer& offer)
{
    // adjust offer
    consume_offer(offer, flow.order);
 
    TER result = tesSUCCESS;
 
    if (cross_type() != CrossType::XrpToIou)
    {
        XRPL_ASSERT(
            !isXRP(flow.order.in), "ripple::Taker::fill : order in is not XRP");
 
        if (result == tesSUCCESS)
            result =
                redeemIOU(account(), flow.issuers.in, flow.issuers.in.issue());
 
        if (result == tesSUCCESS)
            result =
                issueIOU(offer.owner(), flow.order.in, flow.order.in.issue());
    }
    else
    {
        XRPL_ASSERT(
            isXRP(flow.order.in), "ripple::Taker::fill : order in is XRP");
 
        if (result == tesSUCCESS)
            result = transferXRP(account(), offer.owner(), flow.order.in);
    }
 
    // Now send funds from the account whose offer we're taking
    if (cross_type() != CrossType::IouToXrp)
    {
        XRPL_ASSERT(
            !isXRP(flow.order.out),
            "ripple::Taker::fill : order out is not XRP");
 
        if (result == tesSUCCESS)
            result = redeemIOU(
                offer.owner(), flow.issuers.out, flow.issuers.out.issue());
 
        if (result == tesSUCCESS)
            result =
                issueIOU(account(), flow.order.out, flow.order.out.issue());
    }
    else
    {
        XRPL_ASSERT(
            isXRP(flow.order.out), "ripple::Taker::fill : order out is XRP");
 
        if (result == tesSUCCESS)
            result = transferXRP(offer.owner(), account(), flow.order.out);
    }
 
    if (result == tesSUCCESS)
        direct_crossings_++;
 
    return result;
}
 
// Performs bridged funds transfers to fill the given offers and adjusts offers.
TER
Taker::fill(
    BasicTaker::Flow const& flow1,
    Offer& leg1,
    BasicTaker::Flow const& flow2,
    Offer& leg2)
{
    // Adjust offers accordingly
    consume_offer(leg1, flow1.order);
    consume_offer(leg2, flow2.order);
 
    TER result = tesSUCCESS;
 
    // Taker to leg1: IOU
    if (leg1.owner() != account())
    {
        if (result == tesSUCCESS)
            result = redeemIOU(
                account(), flow1.issuers.in, flow1.issuers.in.issue());
 
        if (result == tesSUCCESS)
            result =
                issueIOU(leg1.owner(), flow1.order.in, flow1.order.in.issue());
    }
 
    // leg1 to leg2: bridging over XRP
    if (result == tesSUCCESS)
        result = transferXRP(leg1.owner(), leg2.owner(), flow1.order.out);
 
    // leg2 to Taker: IOU
    if (leg2.owner() != account())
    {
        if (result == tesSUCCESS)
            result = redeemIOU(
                leg2.owner(), flow2.issuers.out, flow2.issuers.out.issue());
 
        if (result == tesSUCCESS)
            result =
                issueIOU(account(), flow2.order.out, flow2.order.out.issue());
    }
 
    if (result == tesSUCCESS)
    {
        bridge_crossings_++;
        xrp_flow_ += flow1.order.out;
    }
 
    return result;
}
 
TER
Taker::cross(Offer& offer)
{
    // In direct crossings, at least one leg must not be XRP.
    if (isXRP(offer.amount().in) && isXRP(offer.amount().out))
        return tefINTERNAL;
 
    auto const amount =
        do_cross(offer.amount(), offer.quality(), offer.owner());
 
    return fill(amount, offer);
}
 
TER
Taker::cross(Offer& leg1, Offer& leg2)
{
    // In bridged crossings, XRP must can't be the input to the first leg
    // or the output of the second leg.
    if (isXRP(leg1.amount().in) || isXRP(leg2.amount().out))
        return tefINTERNAL;
 
    auto ret = do_cross(
        leg1.amount(),
        leg1.quality(),
        leg1.owner(),
        leg2.amount(),
        leg2.quality(),
        leg2.owner());
 
    return fill(ret.first, leg1, ret.second, leg2);
}
 
Rate
Taker::calculateRate(
    ApplyView const& view,
    AccountID const& issuer,
    AccountID const& account)
{
    return isXRP(issuer) || (account == issuer) ? parityRate
                                                : transferRate(view, issuer);
}
 
}  // namespace ripple