#include <test/jtx.h>
#include <test/jtx/PathSet.h>

#include <xrpld/core/Config.h>

#include <xrpl/basics/contract.h>
#include <xrpl/ledger/PaymentSandbox.h>
#include <xrpl/ledger/Sandbox.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/tx/paths/Flow.h>
#include <xrpl/tx/paths/detail/Steps.h>

namespace xrpl {
namespace test {

bool
getNoRippleFlag(
    jtx::Env const& env,
    jtx::Account const& src,
    jtx::Account const& dst,
    Currency const& cur)
{
    if (auto sle = env.le(keylet::line(src, dst, cur)))
    {
        auto const flag = (src.id() > dst.id()) ? lsfHighNoRipple : lsfLowNoRipple;
        return sle->isFlag(flag);
    }
    Throw<std::runtime_error>("No line in getTrustFlag");
    return false;  // silence warning
}

struct Flow_test : public beast::unit_test::suite
{
    void
    testDirectStep(FeatureBitset features)
    {
        testcase("Direct Step");

        using namespace jtx;
        auto const alice = Account("alice");
        auto const bob = Account("bob");
        auto const carol = Account("carol");
        auto const dan = Account("dan");
        auto const erin = Account("erin");
        auto const USDA = alice["USD"];
        auto const USDB = bob["USD"];
        auto const USDC = carol["USD"];
        auto const USDD = dan["USD"];
        auto const gw = Account("gw");
        auto const USD = gw["USD"];
        {
            // Pay USD, trivial path
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, gw);
            env.close();
            env.trust(USD(1000), alice, bob);
            env(pay(gw, alice, USD(100)));
            env(pay(alice, bob, USD(10)), paths(USD));
            env.require(balance(bob, USD(10)));
        }
        {
            // XRP transfer
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob);
            env.close();
            env(pay(alice, bob, XRP(100)));
            env.require(balance(bob, XRP(10000 + 100)));
            env.require(balance(alice, xrpMinusFee(env, 10000 - 100)));
        }
        {
            // Partial payments
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, gw);
            env.close();
            env.trust(USD(1000), alice, bob);
            env(pay(gw, alice, USD(100)));
            env(pay(alice, bob, USD(110)), paths(USD), ter(tecPATH_PARTIAL));
            env.require(balance(bob, USD(0)));
            env(pay(alice, bob, USD(110)), paths(USD), txflags(tfPartialPayment));
            env.require(balance(bob, USD(100)));
        }
        {
            // Pay by rippling through accounts, use path finder
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, dan);
            env.close();
            env.trust(USDA(10), bob);
            env.trust(USDB(10), carol);
            env.trust(USDC(10), dan);
            env(pay(alice, dan, USDC(10)), paths(USDA));
            env.require(balance(bob, USDA(10)), balance(carol, USDB(10)), balance(dan, USDC(10)));
        }
        {
            // Pay by rippling through accounts, specify path
            // and charge a transfer fee
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, dan);
            env.close();
            env.trust(USDA(10), bob);
            env.trust(USDB(10), alice, carol);
            env.trust(USDC(10), dan);
            env(rate(bob, 1.1));

            // alice will redeem to bob; a transfer fee will be charged
            env(pay(bob, alice, USDB(6)));
            env(pay(alice, dan, USDC(5)),
                path(bob, carol),
                sendmax(USDA(6)),
                txflags(tfNoRippleDirect));
            env.require(balance(dan, USDC(5)));
            env.require(balance(alice, USDB(0.5)));
        }
        {
            // Pay by rippling through accounts, specify path and transfer fee
            // Test that the transfer fee is not charged when alice issues
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, dan);
            env.close();
            env.trust(USDA(10), bob);
            env.trust(USDB(10), alice, carol);
            env.trust(USDC(10), dan);
            env(rate(bob, 1.1));

            env(pay(alice, dan, USDC(5)),
                path(bob, carol),
                sendmax(USDA(6)),
                txflags(tfNoRippleDirect));
            env.require(balance(dan, USDC(5)));
            env.require(balance(bob, USDA(5)));
        }
        {
            // test best quality path is taken
            // Paths: A->B->D->E ; A->C->D->E
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, dan, erin);
            env.close();
            env.trust(USDA(10), bob, carol);
            env.trust(USDB(10), dan);
            env.trust(USDC(10), alice, dan);
            env.trust(USDD(20), erin);
            env(rate(bob, 1));
            env(rate(carol, 1.1));

            // Pay alice so she redeems to carol and a transfer fee is charged
            env(pay(carol, alice, USDC(10)));
            env(pay(alice, erin, USDD(5)),
                path(carol, dan),
                path(bob, dan),
                txflags(tfNoRippleDirect));

            env.require(balance(erin, USDD(5)));
            env.require(balance(dan, USDB(5)));
            env.require(balance(dan, USDC(0)));
        }
        {
            // Limit quality
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol);
            env.close();
            env.trust(USDA(10), bob);
            env.trust(USDB(10), carol);

            env(pay(alice, carol, USDB(5)),
                sendmax(USDA(4)),
                txflags(tfLimitQuality | tfPartialPayment),
                ter(tecPATH_DRY));
            env.require(balance(carol, USDB(0)));

            env(pay(alice, carol, USDB(5)), sendmax(USDA(4)), txflags(tfPartialPayment));
            env.require(balance(carol, USDB(4)));
        }
    }

    void
    testLineQuality(FeatureBitset features)
    {
        testcase("Line Quality");

        using namespace jtx;
        auto const alice = Account("alice");
        auto const bob = Account("bob");
        auto const carol = Account("carol");
        auto const dan = Account("dan");
        auto const USDA = alice["USD"];
        auto const USDB = bob["USD"];
        auto const USDC = carol["USD"];
        auto const USDD = dan["USD"];

        //   Dan -> Bob -> Alice -> Carol; vary bobDanQIn and bobAliceQOut
        for (auto bobDanQIn : {80, 100, 120})
            for (auto bobAliceQOut : {80, 100, 120})
            {
                Env env(*this, features);
                env.fund(XRP(10000), alice, bob, carol, dan);
                env.close();
                env(trust(bob, USDD(100)), qualityInPercent(bobDanQIn));
                env(trust(bob, USDA(100)), qualityOutPercent(bobAliceQOut));
                env(trust(carol, USDA(100)));

                env(pay(alice, bob, USDA(100)));
                env.require(balance(bob, USDA(100)));
                env(pay(dan, carol, USDA(10)),
                    path(bob),
                    sendmax(USDD(100)),
                    txflags(tfNoRippleDirect));
                env.require(balance(bob, USDA(90)));
                if (bobAliceQOut > bobDanQIn)
                    env.require(
                        balance(bob, USDD(10.0 * double(bobAliceQOut) / double(bobDanQIn))));
                else
                    env.require(balance(bob, USDD(10)));
                env.require(balance(carol, USDA(10)));
            }

        // bob -> alice -> carol; vary carolAliceQIn
        for (auto carolAliceQIn : {80, 100, 120})
        {
            Env env(*this, features);
            env.fund(XRP(10000), alice, bob, carol);
            env.close();

            env(trust(bob, USDA(10)));
            env(trust(carol, USDA(10)), qualityInPercent(carolAliceQIn));

            env(pay(alice, bob, USDA(10)));
            env.require(balance(bob, USDA(10)));
            env(pay(bob, carol, USDA(5)), sendmax(USDA(10)));
            auto const effectiveQ = carolAliceQIn > 100 ? 1.0 : carolAliceQIn / 100.0;
            env.require(balance(bob, USDA(10.0 - 5.0 / effectiveQ)));
        }

        // bob -> alice -> carol; bobAliceQOut varies.
        for (auto bobAliceQOut : {80, 100, 120})
        {
            Env env(*this, features);
            env.fund(XRP(10000), alice, bob, carol);
            env.close();
            env(trust(bob, USDA(10)), qualityOutPercent(bobAliceQOut));
            env(trust(carol, USDA(10)));

            env(pay(alice, bob, USDA(10)));
            env.require(balance(bob, USDA(10)));
            env(pay(bob, carol, USDA(5)), sendmax(USDA(5)));
            env.require(balance(carol, USDA(5)));
            env.require(balance(bob, USDA(10 - 5)));
        }
    }

    void
    testBookStep(FeatureBitset features)
    {
        testcase("Book Step");

        using namespace jtx;

        auto const gw = Account("gateway");
        auto const USD = gw["USD"];
        auto const BTC = gw["BTC"];
        auto const EUR = gw["EUR"];
        Account const alice("alice");
        Account const bob("bob");
        Account const carol("carol");

        {
            // simple IOU/IOU offer
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();
            env.trust(USD(1000), alice, bob, carol);
            env.trust(BTC(1000), alice, bob, carol);

            env(pay(gw, alice, BTC(50)));
            env(pay(gw, bob, USD(50)));

            env(offer(bob, BTC(50), USD(50)));

            env(pay(alice, carol, USD(50)), path(~USD), sendmax(BTC(50)));

            env.require(balance(alice, BTC(0)));
            env.require(balance(bob, BTC(50)));
            env.require(balance(bob, USD(0)));
            env.require(balance(carol, USD(50)));
            BEAST_EXPECT(!isOffer(env, bob, BTC(50), USD(50)));
        }
        {
            // simple IOU/XRP XRP/IOU offer
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();
            env.trust(USD(1000), alice, bob, carol);
            env.trust(BTC(1000), alice, bob, carol);

            env(pay(gw, alice, BTC(50)));
            env(pay(gw, bob, USD(50)));

            env(offer(bob, BTC(50), XRP(50)));
            env(offer(bob, XRP(50), USD(50)));

            env(pay(alice, carol, USD(50)), path(~XRP, ~USD), sendmax(BTC(50)));

            env.require(balance(alice, BTC(0)));
            env.require(balance(bob, BTC(50)));
            env.require(balance(bob, USD(0)));
            env.require(balance(carol, USD(50)));
            BEAST_EXPECT(!isOffer(env, bob, XRP(50), USD(50)));
            BEAST_EXPECT(!isOffer(env, bob, BTC(50), XRP(50)));
        }
        {
            // simple XRP -> USD through offer and sendmax
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();
            env.trust(USD(1000), alice, bob, carol);
            env.trust(BTC(1000), alice, bob, carol);

            env(pay(gw, bob, USD(50)));

            env(offer(bob, XRP(50), USD(50)));

            env(pay(alice, carol, USD(50)), path(~USD), sendmax(XRP(50)));

            env.require(balance(alice, xrpMinusFee(env, 10000 - 50)));
            env.require(balance(bob, xrpMinusFee(env, 10000 + 50)));
            env.require(balance(bob, USD(0)));
            env.require(balance(carol, USD(50)));
            BEAST_EXPECT(!isOffer(env, bob, XRP(50), USD(50)));
        }
        {
            // simple USD -> XRP through offer and sendmax
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();
            env.trust(USD(1000), alice, bob, carol);
            env.trust(BTC(1000), alice, bob, carol);

            env(pay(gw, alice, USD(50)));

            env(offer(bob, USD(50), XRP(50)));

            env(pay(alice, carol, XRP(50)), path(~XRP), sendmax(USD(50)));

            env.require(balance(alice, USD(0)));
            env.require(balance(bob, xrpMinusFee(env, 10000 - 50)));
            env.require(balance(bob, USD(50)));
            env.require(balance(carol, XRP(10000 + 50)));
            BEAST_EXPECT(!isOffer(env, bob, USD(50), XRP(50)));
        }
        {
            // test unfunded offers are removed when payment succeeds
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();
            env.trust(USD(1000), alice, bob, carol);
            env.trust(BTC(1000), alice, bob, carol);
            env.trust(EUR(1000), alice, bob, carol);

            env(pay(gw, alice, BTC(60)));
            env(pay(gw, bob, USD(50)));
            env(pay(gw, bob, EUR(50)));

            env(offer(bob, BTC(50), USD(50)));
            env(offer(bob, BTC(40), EUR(50)));
            env(offer(bob, EUR(50), USD(50)));

            // unfund offer
            env(pay(bob, gw, EUR(50)));
            BEAST_EXPECT(isOffer(env, bob, BTC(50), USD(50)));
            BEAST_EXPECT(isOffer(env, bob, BTC(40), EUR(50)));
            BEAST_EXPECT(isOffer(env, bob, EUR(50), USD(50)));

            env(pay(alice, carol, USD(50)), path(~USD), path(~EUR, ~USD), sendmax(BTC(60)));

            env.require(balance(alice, BTC(10)));
            env.require(balance(bob, BTC(50)));
            env.require(balance(bob, USD(0)));
            env.require(balance(bob, EUR(0)));
            env.require(balance(carol, USD(50)));
            // used in the payment
            BEAST_EXPECT(!isOffer(env, bob, BTC(50), USD(50)));
            // found unfunded
            BEAST_EXPECT(!isOffer(env, bob, BTC(40), EUR(50)));
            // unfunded, but should not yet be found unfunded
            BEAST_EXPECT(isOffer(env, bob, EUR(50), USD(50)));
        }
        {
            // test unfunded offers are returned when the payment fails.
            // bob makes two offers: a funded 50 USD for 50 BTC and an unfunded
            // 50 EUR for 60 BTC. alice pays carol 61 USD with 61 BTC. alice
            // only has 60 BTC, so the payment will fail. The payment uses two
            // paths: one through bob's funded offer and one through his
            // unfunded offer. When the payment fails `flow` should return the
            // unfunded offer. This test is intentionally similar to the one
            // that removes unfunded offers when the payment succeeds.
            Env env(*this, features);

            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();
            env.trust(USD(1000), alice, bob, carol);
            env.trust(BTC(1000), alice, bob, carol);
            env.trust(EUR(1000), alice, bob, carol);

            env(pay(gw, alice, BTC(60)));
            env(pay(gw, bob, USD(60)));
            env(pay(gw, bob, EUR(50)));
            env(pay(gw, carol, EUR(1)));

            env(offer(bob, BTC(50), USD(50)));
            env(offer(bob, BTC(60), EUR(50)));
            env(offer(carol, BTC(1000), EUR(1)));
            env(offer(bob, EUR(50), USD(50)));

            // unfund offer
            env(pay(bob, gw, EUR(50)));
            BEAST_EXPECT(isOffer(env, bob, BTC(50), USD(50)));
            BEAST_EXPECT(isOffer(env, bob, BTC(60), EUR(50)));
            BEAST_EXPECT(isOffer(env, carol, BTC(1000), EUR(1)));

            auto flowJournal = env.app().logs().journal("Flow");
            auto const flowResult = [&] {
                STAmount deliver(USD(51));
                STAmount smax(BTC(61));
                PaymentSandbox sb(env.current().get(), tapNONE);
                STPathSet paths;
                auto IPE = [](Issue const& iss) {
                    return STPathElement(
                        STPathElement::typeCurrency | STPathElement::typeIssuer,
                        xrpAccount(),
                        iss.currency,
                        iss.account);
                };
                {
                    // BTC -> USD
                    STPath p1({IPE(USD.issue())});
                    paths.push_back(p1);
                    // BTC -> EUR -> USD
                    STPath p2({IPE(EUR.issue()), IPE(USD.issue())});
                    paths.push_back(p2);
                }

                return flow(
                    sb,
                    deliver,
                    alice,
                    carol,
                    paths,
                    false,
                    false,
                    true,
                    OfferCrossing::no,
                    std::nullopt,
                    smax,
                    std::nullopt,
                    flowJournal);
            }();

            BEAST_EXPECT(flowResult.removableOffers.size() == 1);
            env.app().openLedger().modify([&](OpenView& view, beast::Journal j) {
                if (flowResult.removableOffers.empty())
                    return false;
                Sandbox sb(&view, tapNONE);
                for (auto const& o : flowResult.removableOffers)
                    if (auto ok = sb.peek(keylet::offer(o)))
                        offerDelete(sb, ok, flowJournal);
                sb.apply(view);
                return true;
            });

            // used in payment, but since payment failed should be untouched
            BEAST_EXPECT(isOffer(env, bob, BTC(50), USD(50)));
            BEAST_EXPECT(isOffer(env, carol, BTC(1000), EUR(1)));
            // found unfunded
            BEAST_EXPECT(!isOffer(env, bob, BTC(60), EUR(50)));
        }
        {
            // Do not produce more in the forward pass than the reverse pass
            // This test uses a path that whose reverse pass will compute a
            // 0.5 USD input required for a 1 EUR output. It sets a sendmax of
            // 0.4 USD, so the payment engine will need to do a forward pass.
            // Without limits, the 0.4 USD would produce 1000 EUR in the forward
            // pass. This test checks that the payment produces 1 EUR, as
            // expected.
            Env env(*this, features);
            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();

            env.trust(USD(1000), alice, bob, carol);
            env.trust(EUR(1000), alice, bob, carol);

            env(pay(gw, alice, USD(1000)));
            env(pay(gw, bob, EUR(1000)));

            Keylet const bobUsdOffer = keylet::offer(bob, env.seq(bob));
            env(offer(bob, USD(1), drops(2)), txflags(tfPassive));
            env(offer(bob, drops(1), EUR(1000)), txflags(tfPassive));

            bool const reducedOffersV2 = features[fixReducedOffersV2];

            // With reducedOffersV2, it is not allowed to accept less than
            // USD(0.5) of bob's USD offer.  If we provide 1 drop for less
            // than USD(0.5), then the remaining fractional offer would
            // block the order book.
            TER const expectedTER = reducedOffersV2 ? TER(tecPATH_DRY) : TER(tesSUCCESS);
            env(pay(alice, carol, EUR(1)),
                path(~XRP, ~EUR),
                sendmax(USD(0.4)),
                txflags(tfNoRippleDirect | tfPartialPayment),
                ter(expectedTER));

            if (!reducedOffersV2)
            {
                env.require(balance(carol, EUR(1)));
                env.require(balance(bob, USD(0.4)));
                env.require(balance(bob, EUR(999)));

                // Show that bob's USD offer is now a blocker.
                std::shared_ptr<SLE const> const usdOffer = env.le(bobUsdOffer);
                if (BEAST_EXPECT(usdOffer))
                {
                    std::uint64_t const bookRate = [&usdOffer]() {
                        // Extract the least significant 64 bits from the
                        // book page.  That's where the quality is stored.
                        std::string bookDirStr = to_string(usdOffer->at(sfBookDirectory));
                        bookDirStr.erase(0, 48);
                        return std::stoull(bookDirStr, nullptr, 16);
                    }();
                    std::uint64_t const actualRate =
                        getRate(usdOffer->at(sfTakerGets), usdOffer->at(sfTakerPays));

                    // We expect the actual rate of the offer to be worse
                    // (larger) than the rate of the book page holding the
                    // offer.  This is a defect which is corrected by
                    // fixReducedOffersV2.
                    BEAST_EXPECT(actualRate > bookRate);
                }
            }
        }
    }

    void
    testTransferRate(FeatureBitset features)
    {
        testcase("Transfer Rate");

        using namespace jtx;

        auto const gw = Account("gateway");
        auto const USD = gw["USD"];
        auto const BTC = gw["BTC"];
        auto const EUR = gw["EUR"];
        Account const alice("alice");
        Account const bob("bob");
        Account const carol("carol");

        // Offer where the owner is also the issuer, sender pays fee
        Env env(*this, features);

        env.fund(XRP(10000), alice, bob, gw);
        env.close();
        env(rate(gw, 1.25));
        env.trust(USD(1000), alice, bob);
        env(offer(gw, XRP(125), USD(125)));
        env(pay(alice, bob, USD(100)), sendmax(XRP(200)));
        env.require(balance(alice, xrpMinusFee(env, 10000 - 125)), balance(bob, USD(100)));
    }

    void
    testFalseDry(FeatureBitset features)
    {
        testcase("falseDryChanges");

        using namespace jtx;

        auto const gw = Account("gateway");
        auto const USD = gw["USD"];
        auto const EUR = gw["EUR"];
        Account const alice("alice");
        Account const bob("bob");
        Account const carol("carol");

        Env env(*this, features);

        env.fund(XRP(10000), alice, carol, gw);
        env.fund(reserve(env, 5), bob);
        env.close();
        env.trust(USD(1000), alice, bob, carol);
        env.trust(EUR(1000), alice, bob, carol);

        env(pay(gw, alice, EUR(50)));
        env(pay(gw, bob, USD(50)));

        // Bob has _just_ slightly less than 50 xrp available
        // If his owner count changes, he will have more liquidity.
        // This is one error case to test (when Flow is used).
        // Computing the incoming xrp to the XRP/USD offer will require two
        // recursive calls to the EUR/XRP offer. The second call will return
        // tecPATH_DRY, but the entire path should not be marked as dry. This
        // is the second error case to test (when flowV1 is used).
        env(offer(bob, EUR(50), XRP(50)));
        env(offer(bob, XRP(50), USD(50)));

        env(pay(alice, carol, USD(1000000)),
            path(~XRP, ~USD),
            sendmax(EUR(500)),
            txflags(tfNoRippleDirect | tfPartialPayment));

        auto const carolUSD = env.balance(carol, USD).value();
        BEAST_EXPECT(carolUSD > USD(0) && carolUSD < USD(50));
    }

    void
    testLimitQuality()
    {
        // Single path with two offers and limit quality. The quality limit is
        // such that the first offer should be taken but the second should not.
        // The total amount delivered should be the sum of the two offers and
        // sendMax should be more than the first offer.
        testcase("limitQuality");
        using namespace jtx;

        auto const gw = Account("gateway");
        auto const USD = gw["USD"];
        Account const alice("alice");
        Account const bob("bob");
        Account const carol("carol");

        {
            Env env(*this);

            env.fund(XRP(10000), alice, bob, carol, gw);
            env.close();

            env.trust(USD(100), alice, bob, carol);
            env(pay(gw, bob, USD(100)));
            env(offer(bob, XRP(50), USD(50)));
            env(offer(bob, XRP(100), USD(50)));

            env(pay(alice, carol, USD(100)),
                path(~USD),
                sendmax(XRP(100)),
                txflags(tfNoRippleDirect | tfPartialPayment | tfLimitQuality));

            env.require(balance(carol, USD(50)));
        }
    }

    // Helper function that returns the reserve on an account based on
    // the passed in number of owners.
    static XRPAmount
    reserve(jtx::Env& env, std::uint32_t count)
    {
        return env.current()->fees().accountReserve(count);
    }

    // Helper function that returns the Offers on an account.
    static std::vector<std::shared_ptr<SLE const>>
    offersOnAccount(jtx::Env& env, jtx::Account account)
    {
        std::vector<std::shared_ptr<SLE const>> result;
        forEachItem(*env.current(), account, [&result](std::shared_ptr<SLE const> const& sle) {
            if (sle->getType() == ltOFFER)
                result.push_back(sle);
        });
        return result;
    }

    void
    testSelfPayment1(FeatureBitset features)
    {
        testcase("Self-payment 1");

        // In this test case the new flow code mis-computes the amount
        // of money to move.  Fortunately the new code's re-execute
        // check catches the problem and throws out the transaction.
        //
        // The old payment code handles the payment correctly.
        using namespace jtx;

        auto const gw1 = Account("gw1");
        auto const gw2 = Account("gw2");
        auto const alice = Account("alice");
        auto const USD = gw1["USD"];
        auto const EUR = gw2["EUR"];

        Env env(*this, features);

        env.fund(XRP(1000000), gw1, gw2);
        env.close();

        // The fee that's charged for transactions.
        auto const f = env.current()->fees().base;

        env.fund(reserve(env, 3) + f * 4, alice);
        env.close();

        env(trust(alice, USD(2000)));
        env(trust(alice, EUR(2000)));
        env.close();

        env(pay(gw1, alice, USD(1)));
        env(pay(gw2, alice, EUR(1000)));
        env.close();

        env(offer(alice, USD(500), EUR(600)));
        env.close();

        env.require(owners(alice, 3));
        env.require(balance(alice, USD(1)));
        env.require(balance(alice, EUR(1000)));

        auto aliceOffers = offersOnAccount(env, alice);
        BEAST_EXPECT(aliceOffers.size() == 1);
        for (auto const& offerPtr : aliceOffers)
        {
            auto const offer = *offerPtr;
            BEAST_EXPECT(offer[sfLedgerEntryType] == ltOFFER);
            BEAST_EXPECT(offer[sfTakerGets] == EUR(600));
            BEAST_EXPECT(offer[sfTakerPays] == USD(500));
        }

        env(pay(alice, alice, EUR(600)), sendmax(USD(500)), txflags(tfPartialPayment));
        env.close();

        env.require(owners(alice, 3));
        env.require(balance(alice, USD(1)));
        env.require(balance(alice, EUR(1000)));
        aliceOffers = offersOnAccount(env, alice);
        BEAST_EXPECT(aliceOffers.size() == 1);
        for (auto const& offerPtr : aliceOffers)
        {
            auto const offer = *offerPtr;
            BEAST_EXPECT(offer[sfLedgerEntryType] == ltOFFER);
            BEAST_EXPECT(offer[sfTakerGets] == EUR(598.8));
            BEAST_EXPECT(offer[sfTakerPays] == USD(499));
        }
    }

    void
    testSelfPayment2(FeatureBitset features)
    {
        testcase("Self-payment 2");

        // In this case the difference between the old payment code and
        // the new is the values left behind in the offer.  Not saying either
        // ios ring, they are just different.
        using namespace jtx;

        auto const gw1 = Account("gw1");
        auto const gw2 = Account("gw2");
        auto const alice = Account("alice");
        auto const USD = gw1["USD"];
        auto const EUR = gw2["EUR"];

        Env env(*this, features);

        env.fund(XRP(1000000), gw1, gw2);
        env.close();

        // The fee that's charged for transactions.
        auto const f = env.current()->fees().base;

        env.fund(reserve(env, 3) + f * 4, alice);
        env.close();

        env(trust(alice, USD(506)));
        env(trust(alice, EUR(606)));
        env.close();

        env(pay(gw1, alice, USD(500)));
        env(pay(gw2, alice, EUR(600)));
        env.close();

        env(offer(alice, USD(500), EUR(600)));
        env.close();

        env.require(owners(alice, 3));
        env.require(balance(alice, USD(500)));
        env.require(balance(alice, EUR(600)));

        auto aliceOffers = offersOnAccount(env, alice);
        BEAST_EXPECT(aliceOffers.size() == 1);
        for (auto const& offerPtr : aliceOffers)
        {
            auto const offer = *offerPtr;
            BEAST_EXPECT(offer[sfLedgerEntryType] == ltOFFER);
            BEAST_EXPECT(offer[sfTakerGets] == EUR(600));
            BEAST_EXPECT(offer[sfTakerPays] == USD(500));
        }

        env(pay(alice, alice, EUR(60)), sendmax(USD(50)), txflags(tfPartialPayment));
        env.close();

        env.require(owners(alice, 3));
        env.require(balance(alice, USD(500)));
        env.require(balance(alice, EUR(600)));
        aliceOffers = offersOnAccount(env, alice);
        BEAST_EXPECT(aliceOffers.size() == 1);
        for (auto const& offerPtr : aliceOffers)
        {
            auto const offer = *offerPtr;
            BEAST_EXPECT(offer[sfLedgerEntryType] == ltOFFER);
            BEAST_EXPECT(offer[sfTakerGets] == EUR(594));
            BEAST_EXPECT(offer[sfTakerPays] == USD(495));
        }
    }
    void
    testSelfFundedXRPEndpoint(bool consumeOffer, FeatureBitset features)
    {
        // Test that the deferred credit table is not bypassed for
        // XRPEndpointSteps. If the account in the first step is sending XRP and
        // that account also owns an offer that receives XRP, it should not be
        // possible for that step to use the XRP received in the offer as part
        // of the payment.
        testcase("Self funded XRPEndpoint");

        using namespace jtx;

        Env env(*this, features);

        auto const alice = Account("alice");
        auto const gw = Account("gw");
        auto const USD = gw["USD"];

        env.fund(XRP(10000), alice, gw);
        env.close();
        env(trust(alice, USD(20)));
        env(pay(gw, alice, USD(10)));
        env(offer(alice, XRP(50000), USD(10)));

        // Consuming the offer changes the owner count, which could also cause
        // liquidity to decrease in the forward pass
        auto const toSend = consumeOffer ? USD(10) : USD(9);
        env(pay(alice, alice, toSend),
            path(~USD),
            sendmax(XRP(20000)),
            txflags(tfPartialPayment | tfNoRippleDirect));
    }

    void
    testUnfundedOffer(FeatureBitset features)
    {
        testcase("Unfunded Offer");

        using namespace jtx;
        {
            // Test reverse
            Env env(*this, features);

            auto const alice = Account("alice");
            auto const bob = Account("bob");
            auto const gw = Account("gw");
            auto const USD = gw["USD"];

            env.fund(XRP(100000), alice, bob, gw);
            env.close();
            env(trust(bob, USD(20)));

            STAmount tinyAmt1{USD.issue(), 9000000000000000ll, -17, false, STAmount::unchecked{}};
            STAmount tinyAmt3{USD.issue(), 9000000000000003ll, -17, false, STAmount::unchecked{}};

            env(offer(gw, drops(9000000000), tinyAmt3));
            env(pay(alice, bob, tinyAmt1),
                path(~USD),
                sendmax(drops(9000000000)),
                txflags(tfNoRippleDirect));

            BEAST_EXPECT(!isOffer(env, gw, XRP(0), USD(0)));
        }
        {
            // Test forward
            Env env(*this, features);

            auto const alice = Account("alice");
            auto const bob = Account("bob");
            auto const gw = Account("gw");
            auto const USD = gw["USD"];

            env.fund(XRP(100000), alice, bob, gw);
            env.close();
            env(trust(alice, USD(20)));

            STAmount tinyAmt1{USD.issue(), 9000000000000000ll, -17, false, STAmount::unchecked{}};
            STAmount tinyAmt3{USD.issue(), 9000000000000003ll, -17, false, STAmount::unchecked{}};

            env(pay(gw, alice, tinyAmt1));

            env(offer(gw, tinyAmt3, drops(9000000000)));
            env(pay(alice, bob, drops(9000000000)),
                path(~XRP),
                sendmax(USD(1)),
                txflags(tfNoRippleDirect));

            BEAST_EXPECT(!isOffer(env, gw, USD(0), XRP(0)));
        }
    }

    void
    testReExecuteDirectStep(FeatureBitset features)
    {
        testcase("ReExecuteDirectStep");

        using namespace jtx;
        Env env(*this, features);

        auto const alice = Account("alice");
        auto const bob = Account("bob");
        auto const gw = Account("gw");
        auto const USD = gw["USD"];
        auto const usdC = USD.currency;

        env.fund(XRP(10000), alice, bob, gw);
        env.close();
        env(trust(alice, USD(100)));
        env.close();

        BEAST_EXPECT(!getNoRippleFlag(env, gw, alice, usdC));

        env(
            pay(gw,
                alice,
                // 12.55....
                STAmount{USD.issue(), std::uint64_t(1255555555555555ull), -14, false}));

        env(offer(
            gw,
            // 5.0...
            STAmount{USD.issue(), std::uint64_t(5000000000000000ull), -15, false},
            XRP(1000)));

        env(offer(
            gw,
            // .555...
            STAmount{USD.issue(), std::uint64_t(5555555555555555ull), -16, false},
            XRP(10)));

        env(offer(
            gw,
            // 4.44....
            STAmount{USD.issue(), std::uint64_t(4444444444444444ull), -15, false},
            XRP(.1)));

        env(offer(
            alice,
            // 17
            STAmount{USD.issue(), std::uint64_t(1700000000000000ull), -14, false},
            XRP(.001)));

        env(pay(alice, bob, XRP(10000)),
            path(~XRP),
            sendmax(USD(100)),
            txflags(tfPartialPayment | tfNoRippleDirect));
    }

    void
    testRIPD1443()
    {
        testcase("ripd1443");

        using namespace jtx;
        Env env(*this);
        auto const alice = Account("alice");
        auto const bob = Account("bob");
        auto const carol = Account("carol");
        auto const gw = Account("gw");

        env.fund(XRP(100000000), alice, noripple(bob), carol, gw);
        env.close();
        env.trust(gw["USD"](10000), alice, carol);
        env(trust(bob, gw["USD"](10000), tfSetNoRipple));
        env.trust(gw["USD"](10000), bob);
        env.close();

        // set no ripple between bob and the gateway

        env(pay(gw, alice, gw["USD"](1000)));
        env.close();

        env(offer(alice, bob["USD"](1000), XRP(1)));
        env.close();

        env(pay(alice, alice, XRP(1)),
            path(gw, bob, ~XRP),
            sendmax(gw["USD"](1000)),
            txflags(tfNoRippleDirect),
            ter(tecPATH_DRY));
        env.close();

        env.trust(bob["USD"](10000), alice);
        env(pay(bob, alice, bob["USD"](1000)));

        env(offer(alice, XRP(1000), bob["USD"](1000)));
        env.close();

        env(pay(carol, carol, gw["USD"](1000)),
            path(~bob["USD"], gw),
            sendmax(XRP(100000)),
            txflags(tfNoRippleDirect),
            ter(tecPATH_DRY));
        env.close();

        pass();
    }

    void
    testRIPD1449()
    {
        testcase("ripd1449");

        using namespace jtx;
        Env env(*this);

        // pay alice -> xrp -> USD/bob -> bob -> gw -> alice
        // set no ripple on bob's side of the bob/gw trust line
        // carol has the bob/USD and makes an offer, bob has USD/gw

        auto const alice = Account("alice");
        auto const bob = Account("bob");
        auto const carol = Account("carol");
        auto const gw = Account("gw");
        auto const USD = gw["USD"];

        env.fund(XRP(100000000), alice, bob, carol, gw);
        env.close();
        env.trust(USD(10000), alice, carol);
        env(trust(bob, USD(10000), tfSetNoRipple));
        env.trust(USD(10000), bob);
        env.trust(bob["USD"](10000), carol);
        env.close();

        env(pay(bob, carol, bob["USD"](1000)));
        env(pay(gw, bob, USD(1000)));
        env.close();

        env(offer(carol, XRP(1), bob["USD"](1000)));
        env.close();

        env(pay(alice, alice, USD(1000)),
            path(~bob["USD"], bob, gw),
            sendmax(XRP(1)),
            txflags(tfNoRippleDirect),
            ter(tecPATH_DRY));
        env.close();
    }

    void
    testSelfPayLowQualityOffer(FeatureBitset features)
    {
        // The new payment code used to assert if an offer was made for more
        // XRP than the offering account held.  This unit test reproduces
        // that failing case.
        testcase("Self crossing low quality offer");

        using namespace jtx;

        Env env(*this, features);

        auto const ann = Account("ann");
        auto const gw = Account("gateway");
        auto const CTB = gw["CTB"];

        auto const fee = env.current()->fees().base;
        env.fund(reserve(env, 2) + drops(9999640) + fee, ann);
        env.fund(reserve(env, 2) + fee * 4, gw);
        env.close();

        env(rate(gw, 1.002));
        env(trust(ann, CTB(10)));
        env.close();

        env(pay(gw, ann, CTB(2.856)));
        env.close();

        env(offer(ann, drops(365611702030), CTB(5.713)));
        env.close();

        // This payment caused the assert.
        env(pay(ann, ann, CTB(0.687)), sendmax(drops(20000000000)), txflags(tfPartialPayment));
    }

    void
    testEmptyStrand(FeatureBitset features)
    {
        testcase("Empty Strand");
        using namespace jtx;

        auto const alice = Account("alice");

        Env env(*this, features);

        env.fund(XRP(10000), alice);
        env.close();

        env(pay(alice, alice, alice["USD"](100)), path(~alice["USD"]), ter(temBAD_PATH));
    }

    void
    testXRPPathLoop()
    {
        testcase("Circular XRP");

        using namespace jtx;
        auto const alice = Account("alice");
        auto const bob = Account("bob");
        auto const gw = Account("gw");
        auto const USD = gw["USD"];
        auto const EUR = gw["EUR"];

        {
            // Payment path starting with XRP
            Env env(*this, testable_amendments());
            env.fund(XRP(10000), alice, bob, gw);
            env.close();
            env.trust(USD(1000), alice, bob);
            env.trust(EUR(1000), alice, bob);
            env.close();
            env(pay(gw, alice, USD(100)));
            env(pay(gw, alice, EUR(100)));
            env.close();

            env(offer(alice, XRP(100), USD(100)), txflags(tfPassive));
            env(offer(alice, USD(100), XRP(100)), txflags(tfPassive));
            env(offer(alice, XRP(100), EUR(100)), txflags(tfPassive));
            env.close();

            TER const expectedTer = TER{temBAD_PATH_LOOP};
            env(pay(alice, bob, EUR(1)),
                path(~USD, ~XRP, ~EUR),
                sendmax(XRP(1)),
                txflags(tfNoRippleDirect),
                ter(expectedTer));

            pass();
        }
        {
            // Payment path ending with XRP
            Env env(*this);
            env.fund(XRP(10000), alice, bob, gw);
            env.close();
            env.trust(USD(1000), alice, bob);
            env.trust(EUR(1000), alice, bob);
            env(pay(gw, alice, USD(100)));
            env(pay(gw, alice, EUR(100)));
            env.close();

            env(offer(alice, XRP(100), USD(100)), txflags(tfPassive));
            env(offer(alice, EUR(100), XRP(100)), txflags(tfPassive));
            env.close();
            // EUR -> //XRP -> //USD ->XRP
            env(pay(alice, bob, XRP(1)),
                path(~XRP, ~USD, ~XRP),
                sendmax(EUR(1)),
                txflags(tfNoRippleDirect),
                ter(temBAD_PATH_LOOP));
        }
        {
            // Payment where loop is formed in the middle of the path, not on an
            // endpoint
            auto const JPY = gw["JPY"];
            Env env(*this);
            env.fund(XRP(10000), alice, bob, gw);
            env.close();
            env.trust(USD(1000), alice, bob);
            env.trust(EUR(1000), alice, bob);
            env.trust(JPY(1000), alice, bob);
            env.close();
            env(pay(gw, alice, USD(100)));
            env(pay(gw, alice, EUR(100)));
            env(pay(gw, alice, JPY(100)));
            env.close();

            env(offer(alice, USD(100), XRP(100)), txflags(tfPassive));
            env(offer(alice, XRP(100), EUR(100)), txflags(tfPassive));
            env(offer(alice, EUR(100), XRP(100)), txflags(tfPassive));
            env(offer(alice, XRP(100), JPY(100)), txflags(tfPassive));
            env.close();

            env(pay(alice, bob, JPY(1)),
                path(~XRP, ~EUR, ~XRP, ~JPY),
                sendmax(USD(1)),
                txflags(tfNoRippleDirect),
                ter(temBAD_PATH_LOOP));
        }
    }

    void
    testTicketPay(FeatureBitset features)
    {
        testcase("Payment with ticket");
        using namespace jtx;

        auto const alice = Account("alice");
        auto const bob = Account("bob");

        Env env(*this, features);

        env.fund(XRP(10000), alice);
        env.close();

        // alice creates a ticket for the payment.
        std::uint32_t const ticketSeq{env.seq(alice) + 1};
        env(ticket::create(alice, 1));

        // Make a payment using the ticket.
        env(pay(alice, bob, XRP(1000)), ticket::use(ticketSeq));
        env.close();
        env.require(balance(bob, XRP(1000)));
        env.require(balance(alice, XRP(9000) - (env.current()->fees().base * 2)));
    }

    void
    testWithFeats(FeatureBitset features)
    {
        using namespace jtx;
        FeatureBitset const reducedOffersV2(fixReducedOffersV2);

        testLineQuality(features);
        testFalseDry(features);
        testBookStep(features - reducedOffersV2);
        testDirectStep(features);
        testBookStep(features);
        testTransferRate(features);
        testSelfPayment1(features);
        testSelfPayment2(features);
        testSelfFundedXRPEndpoint(false, features);
        testSelfFundedXRPEndpoint(true, features);
        testUnfundedOffer(features);
        testReExecuteDirectStep(features);
        testSelfPayLowQualityOffer(features);
        testTicketPay(features);
    }

    void
    run() override
    {
        testLimitQuality();
        testXRPPathLoop();
        testRIPD1443();
        testRIPD1449();

        using namespace jtx;
        auto const sa = testable_amendments();
        testWithFeats(sa - featurePermissionedDEX);
        testWithFeats(sa);
        testEmptyStrand(sa);
    }
};

struct Flow_manual_test : public Flow_test
{
    void
    run() override
    {
        using namespace jtx;
        auto const all = testable_amendments();
        FeatureBitset const permDex{featurePermissionedDEX};

        testWithFeats(all - permDex);
        testWithFeats(all);

        testEmptyStrand(all - permDex);
        testEmptyStrand(all);
    }
};

BEAST_DEFINE_TESTSUITE_PRIO(Flow, app, xrpl, 2);
BEAST_DEFINE_TESTSUITE_MANUAL_PRIO(Flow_manual, app, xrpl, 4);

}  // namespace test
}  // namespace xrpl