NFTokenUtils.cpp

//------------------------------------------------------------------------------
/*
  This file is part of rippled: https://github.com/ripple/rippled
  Copyright (c) 2021 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/NFTokenUtils.h>
#include <xrpld/ledger/Dir.h>
#include <xrpld/ledger/View.h>
 
#include <xrpl/basics/algorithm.h>
#include <xrpl/protocol/Feature.h>
#include <xrpl/protocol/STArray.h>
#include <xrpl/protocol/TxFlags.h>
#include <xrpl/protocol/nftPageMask.h>
 
#include <functional>
#include <memory>
 
namespace ripple {
 
namespace nft {
 
static std::shared_ptr<SLE const>
locatePage(ReadView const& view, AccountID const& owner, uint256 const& id)
{
    auto const first = keylet::nftpage(keylet::nftpage_min(owner), id);
    auto const last = keylet::nftpage_max(owner);
 
    // This NFT can only be found in the first page with a key that's strictly
    // greater than `first`, so look for that, up until the maximum possible
    // page.
    return view.read(Keylet(
        ltNFTOKEN_PAGE,
        view.succ(first.key, last.key.next()).value_or(last.key)));
}
 
static std::shared_ptr<SLE>
locatePage(ApplyView& view, AccountID const& owner, uint256 const& id)
{
    auto const first = keylet::nftpage(keylet::nftpage_min(owner), id);
    auto const last = keylet::nftpage_max(owner);
 
    // This NFT can only be found in the first page with a key that's strictly
    // greater than `first`, so look for that, up until the maximum possible
    // page.
    return view.peek(Keylet(
        ltNFTOKEN_PAGE,
        view.succ(first.key, last.key.next()).value_or(last.key)));
}
 
static std::shared_ptr<SLE>
getPageForToken(
    ApplyView& view,
    AccountID const& owner,
    uint256 const& id,
    std::function<void(ApplyView&, AccountID const&)> const& createCallback)
{
    auto const base = keylet::nftpage_min(owner);
    auto const first = keylet::nftpage(base, id);
    auto const last = keylet::nftpage_max(owner);
 
    // This NFT can only be found in the first page with a key that's strictly
    // greater than `first`, so look for that, up until the maximum possible
    // page.
    auto cp = view.peek(Keylet(
        ltNFTOKEN_PAGE,
        view.succ(first.key, last.key.next()).value_or(last.key)));
 
    // A suitable page doesn't exist; we'll have to create one.
    if (!cp)
    {
        STArray arr;
        cp = std::make_shared<SLE>(last);
        cp->setFieldArray(sfNFTokens, arr);
        view.insert(cp);
        createCallback(view, owner);
        return cp;
    }
 
    STArray narr = cp->getFieldArray(sfNFTokens);
 
    // The right page still has space: we're good.
    if (narr.size() != dirMaxTokensPerPage)
        return cp;
 
    // We need to split the page in two: the first half of the items in this
    // page will go into the new page; the rest will stay with the existing
    // page.
    //
    // Note we can't always split the page exactly in half.  All equivalent
    // NFTs must be kept on the same page.  So when the page contains
    // equivalent NFTs, the split may be lopsided in order to keep equivalent
    // NFTs on the same page.
    STArray carr;
    {
        // We prefer to keep equivalent NFTs on a page boundary.  That gives
        // any additional equivalent NFTs maximum room for expansion.
        // Round up the boundary until there's a non-equivalent entry.
        uint256 const cmp =
            narr[(dirMaxTokensPerPage / 2) - 1].getFieldH256(sfNFTokenID) &
            nft::pageMask;
 
        // Note that the calls to find_if_not() and (later) find_if()
        // rely on the fact that narr is kept in sorted order.
        auto splitIter = std::find_if_not(
            narr.begin() + (dirMaxTokensPerPage / 2),
            narr.end(),
            [&cmp](STObject const& obj) {
                return (obj.getFieldH256(sfNFTokenID) & nft::pageMask) == cmp;
            });
 
        // If we get all the way from the middle to the end with only
        // equivalent NFTokens then check the front of the page for a
        // place to make the split.
        if (splitIter == narr.end())
            splitIter = std::find_if(
                narr.begin(), narr.end(), [&cmp](STObject const& obj) {
                    return (obj.getFieldH256(sfNFTokenID) & nft::pageMask) ==
                        cmp;
                });
 
        // There should be no circumstance when splitIter == end(), but if it
        // were to happen we should bail out because something is confused.
        if (splitIter == narr.end())
            return nullptr;
 
        // If splitIter == begin(), then the entire page is filled with
        // equivalent tokens.  This requires special handling.
        if (splitIter == narr.begin())
        {
            // Prior to fixNFTokenDirV1 we simply stopped.
            if (!view.rules().enabled(fixNFTokenDirV1))
                return nullptr;
            else
            {
                auto const relation{(id & nft::pageMask) <=> cmp};
                if (relation == 0)
                {
                    // If the passed in id belongs exactly on this (full) page
                    // this account simply cannot store the NFT.
                    return nullptr;
                }
 
                if (relation > 0)
                {
                    // We need to leave the entire contents of this page in
                    // narr so carr stays empty.  The new NFT will be
                    // inserted in carr.  This keeps the NFTs that must be
                    // together all on their own page.
                    splitIter = narr.end();
                }
 
                // If neither of those conditions apply then put all of
                // narr into carr and produce an empty narr where the new NFT
                // will be inserted.  Leave the split at narr.begin().
            }
        }
 
        // Split narr at splitIter.
        STArray newCarr(
            std::make_move_iterator(splitIter),
            std::make_move_iterator(narr.end()));
        narr.erase(splitIter, narr.end());
        std::swap(carr, newCarr);
    }
 
    // Determine the ID for the page index.  This decision is conditional on
    // fixNFTokenDirV1 being enabled.  But the condition for the decision
    // is not possible unless fixNFTokenDirV1 is enabled.
    //
    // Note that we use uint256::next() because there's a subtlety in the way
    // NFT pages are structured.  The low 96-bits of NFT ID must be strictly
    // less than the low 96-bits of the enclosing page's index.  In order to
    // accommodate that requirement we use an index one higher than the
    // largest NFT in the page.
    uint256 const tokenIDForNewPage = narr.size() == dirMaxTokensPerPage
        ? narr[dirMaxTokensPerPage - 1].getFieldH256(sfNFTokenID).next()
        : carr[0].getFieldH256(sfNFTokenID);
 
    auto np = std::make_shared<SLE>(keylet::nftpage(base, tokenIDForNewPage));
    XRPL_ASSERT(
        np->key() > base.key,
        "ripple::nft::getPageForToken : valid NFT page index");
    np->setFieldArray(sfNFTokens, narr);
    np->setFieldH256(sfNextPageMin, cp->key());
 
    if (auto ppm = (*cp)[~sfPreviousPageMin])
    {
        np->setFieldH256(sfPreviousPageMin, *ppm);
 
        if (auto p3 = view.peek(Keylet(ltNFTOKEN_PAGE, *ppm)))
        {
            p3->setFieldH256(sfNextPageMin, np->key());
            view.update(p3);
        }
    }
 
    view.insert(np);
 
    cp->setFieldArray(sfNFTokens, carr);
    cp->setFieldH256(sfPreviousPageMin, np->key());
    view.update(cp);
 
    createCallback(view, owner);
 
    // fixNFTokenDirV1 corrects a bug in the initial implementation that
    // would put an NFT in the wrong page.  The problem was caused by an
    // off-by-one subtlety that the NFT can only be stored in the first page
    // with a key that's strictly greater than `first`
    if (!view.rules().enabled(fixNFTokenDirV1))
        return (first.key <= np->key()) ? np : cp;
 
    return (first.key < np->key()) ? np : cp;
}
 
bool
compareTokens(uint256 const& a, uint256 const& b)
{
    // The sort of NFTokens needs to be fully deterministic, but the sort
    // is weird because we sort on the low 96-bits first. But if the low
    // 96-bits are identical we still need a fully deterministic sort.
    // So we sort on the low 96-bits first. If those are equal we sort on
    // the whole thing.
    if (auto const lowBitsCmp{(a & nft::pageMask) <=> (b & nft::pageMask)};
        lowBitsCmp != 0)
        return lowBitsCmp < 0;
 
    return a < b;
}
 
TER
changeTokenURI(
    ApplyView& view,
    AccountID const& owner,
    uint256 const& nftokenID,
    std::optional<ripple::Slice> const& uri)
{
    std::shared_ptr<SLE> const page = locatePage(view, owner, nftokenID);
 
    // If the page couldn't be found, the given NFT isn't owned by this account
    if (!page)
        return tecINTERNAL;  // LCOV_EXCL_LINE
 
    // Locate the NFT in the page
    STArray& arr = page->peekFieldArray(sfNFTokens);
 
    auto const nftIter =
        std::find_if(arr.begin(), arr.end(), [&nftokenID](STObject const& obj) {
            return (obj[sfNFTokenID] == nftokenID);
        });
 
    if (nftIter == arr.end())
        return tecINTERNAL;  // LCOV_EXCL_LINE
 
    if (uri)
        nftIter->setFieldVL(sfURI, *uri);
    else if (nftIter->isFieldPresent(sfURI))
        nftIter->makeFieldAbsent(sfURI);
 
    view.update(page);
    return tesSUCCESS;
}
 
TER
insertToken(ApplyView& view, AccountID owner, STObject&& nft)
{
    XRPL_ASSERT(
        nft.isFieldPresent(sfNFTokenID),
        "ripple::nft::insertToken : has NFT token");
 
    // First, we need to locate the page the NFT belongs to, creating it
    // if necessary. This operation may fail if it is impossible to insert
    // the NFT.
    std::shared_ptr<SLE> page = getPageForToken(
        view,
        owner,
        nft[sfNFTokenID],
        [](ApplyView& view, AccountID const& owner) {
            adjustOwnerCount(
                view,
                view.peek(keylet::account(owner)),
                1,
                beast::Journal{beast::Journal::getNullSink()});
        });
 
    if (!page)
        return tecNO_SUITABLE_NFTOKEN_PAGE;
 
    {
        auto arr = page->getFieldArray(sfNFTokens);
        arr.push_back(std::move(nft));
 
        arr.sort([](STObject const& o1, STObject const& o2) {
            return compareTokens(
                o1.getFieldH256(sfNFTokenID), o2.getFieldH256(sfNFTokenID));
        });
 
        page->setFieldArray(sfNFTokens, arr);
    }
 
    view.update(page);
 
    return tesSUCCESS;
}
 
static bool
mergePages(
    ApplyView& view,
    std::shared_ptr<SLE> const& p1,
    std::shared_ptr<SLE> const& p2)
{
    if (p1->key() >= p2->key())
        Throw<std::runtime_error>("mergePages: pages passed in out of order!");
 
    if ((*p1)[~sfNextPageMin] != p2->key())
        Throw<std::runtime_error>("mergePages: next link broken!");
 
    if ((*p2)[~sfPreviousPageMin] != p1->key())
        Throw<std::runtime_error>("mergePages: previous link broken!");
 
    auto const p1arr = p1->getFieldArray(sfNFTokens);
    auto const p2arr = p2->getFieldArray(sfNFTokens);
 
    // Now check whether to merge the two pages; it only makes sense to do
    // this it would mean that one of them can be deleted as a result of
    // the merge.
 
    if (p1arr.size() + p2arr.size() > dirMaxTokensPerPage)
        return false;
 
    STArray x(p1arr.size() + p2arr.size());
 
    std::merge(
        p1arr.begin(),
        p1arr.end(),
        p2arr.begin(),
        p2arr.end(),
        std::back_inserter(x),
        [](STObject const& a, STObject const& b) {
            return compareTokens(
                a.getFieldH256(sfNFTokenID), b.getFieldH256(sfNFTokenID));
        });
 
    p2->setFieldArray(sfNFTokens, x);
 
    // So, at this point we need to unlink "p1" (since we just emptied it) but
    // we need to first relink the directory: if p1 has a previous page (p0),
    // load it, point it to p2 and point p2 to it.
 
    p2->makeFieldAbsent(sfPreviousPageMin);
 
    if (auto const ppm = (*p1)[~sfPreviousPageMin])
    {
        auto p0 = view.peek(Keylet(ltNFTOKEN_PAGE, *ppm));
 
        if (!p0)
            Throw<std::runtime_error>("mergePages: p0 can't be located!");
 
        p0->setFieldH256(sfNextPageMin, p2->key());
        view.update(p0);
 
        p2->setFieldH256(sfPreviousPageMin, *ppm);
    }
 
    view.update(p2);
    view.erase(p1);
 
    return true;
}
 
TER
removeToken(ApplyView& view, AccountID const& owner, uint256 const& nftokenID)
{
    std::shared_ptr<SLE> page = locatePage(view, owner, nftokenID);
 
    // If the page couldn't be found, the given NFT isn't owned by this account
    if (!page)
        return tecNO_ENTRY;
 
    return removeToken(view, owner, nftokenID, std::move(page));
}
 
TER
removeToken(
    ApplyView& view,
    AccountID const& owner,
    uint256 const& nftokenID,
    std::shared_ptr<SLE>&& curr)
{
    // We found a page, but the given NFT may not be in it.
    auto arr = curr->getFieldArray(sfNFTokens);
 
    {
        auto x = std::find_if(
            arr.begin(), arr.end(), [&nftokenID](STObject const& obj) {
                return (obj[sfNFTokenID] == nftokenID);
            });
 
        if (x == arr.end())
            return tecNO_ENTRY;
 
        arr.erase(x);
    }
 
    // Page management:
    auto const loadPage = [&view](
                              std::shared_ptr<SLE> const& page1,
                              SF_UINT256 const& field) {
        std::shared_ptr<SLE> page2;
 
        if (auto const id = (*page1)[~field])
        {
            page2 = view.peek(Keylet(ltNFTOKEN_PAGE, *id));
 
            if (!page2)
                Throw<std::runtime_error>(
                    "page " + to_string(page1->key()) + " has a broken " +
                    field.getName() + " field pointing to " + to_string(*id));
        }
 
        return page2;
    };
 
    auto const prev = loadPage(curr, sfPreviousPageMin);
    auto const next = loadPage(curr, sfNextPageMin);
 
    if (!arr.empty())
    {
        // The current page isn't empty. Update it and then try to consolidate
        // pages. Note that this consolidation attempt may actually merge three
        // pages into one!
        curr->setFieldArray(sfNFTokens, arr);
        view.update(curr);
 
        int cnt = 0;
 
        if (prev && mergePages(view, prev, curr))
            cnt--;
 
        if (next && mergePages(view, curr, next))
            cnt--;
 
        if (cnt != 0)
            adjustOwnerCount(
                view,
                view.peek(keylet::account(owner)),
                cnt,
                beast::Journal{beast::Journal::getNullSink()});
 
        return tesSUCCESS;
    }
 
    if (prev)
    {
        // With fixNFTokenPageLinks...
        // The page is empty and there is a prev.  If the last page of the
        // directory is empty then we need to:
        //  1. Move the contents of the previous page into the last page.
        //  2. Fix up the link from prev's previous page.
        //  3. Fix up the owner count.
        //  4. Erase the previous page.
        if (view.rules().enabled(fixNFTokenPageLinks) &&
            ((curr->key() & nft::pageMask) == pageMask))
        {
            // Copy all relevant information from prev to curr.
            curr->peekFieldArray(sfNFTokens) = prev->peekFieldArray(sfNFTokens);
 
            if (auto const prevLink = prev->at(~sfPreviousPageMin))
            {
                curr->at(sfPreviousPageMin) = *prevLink;
 
                // Also fix up the NextPageMin link in the new Previous.
                auto const newPrev = loadPage(curr, sfPreviousPageMin);
                newPrev->at(sfNextPageMin) = curr->key();
                view.update(newPrev);
            }
            else
            {
                curr->makeFieldAbsent(sfPreviousPageMin);
            }
 
            adjustOwnerCount(
                view,
                view.peek(keylet::account(owner)),
                -1,
                beast::Journal{beast::Journal::getNullSink()});
 
            view.update(curr);
            view.erase(prev);
            return tesSUCCESS;
        }
 
        // The page is empty and not the last page, so we can just unlink it
        // and then remove it.
        if (next)
            prev->setFieldH256(sfNextPageMin, next->key());
        else
            prev->makeFieldAbsent(sfNextPageMin);
 
        view.update(prev);
    }
 
    if (next)
    {
        // Make our next page point to our previous page:
        if (prev)
            next->setFieldH256(sfPreviousPageMin, prev->key());
        else
            next->makeFieldAbsent(sfPreviousPageMin);
 
        view.update(next);
    }
 
    view.erase(curr);
 
    int cnt = 1;
 
    // Since we're here, try to consolidate the previous and current pages
    // of the page we removed (if any) into one.  mergePages() _should_
    // always return false.  Since tokens are burned one at a time, there
    // should never be a page containing one token sitting between two pages
    // that have few enough tokens that they can be merged.
    //
    // But, in case that analysis is wrong, it's good to leave this code here
    // just in case.
    if (prev && next &&
        mergePages(
            view,
            view.peek(Keylet(ltNFTOKEN_PAGE, prev->key())),
            view.peek(Keylet(ltNFTOKEN_PAGE, next->key()))))
        cnt++;
 
    adjustOwnerCount(
        view,
        view.peek(keylet::account(owner)),
        -1 * cnt,
        beast::Journal{beast::Journal::getNullSink()});
 
    return tesSUCCESS;
}
 
std::optional<STObject>
findToken(
    ReadView const& view,
    AccountID const& owner,
    uint256 const& nftokenID)
{
    std::shared_ptr<SLE const> page = locatePage(view, owner, nftokenID);
 
    // If the page couldn't be found, the given NFT isn't owned by this account
    if (!page)
        return std::nullopt;
 
    // We found a candidate page, but the given NFT may not be in it.
    for (auto const& t : page->getFieldArray(sfNFTokens))
    {
        if (t[sfNFTokenID] == nftokenID)
            return t;
    }
 
    return std::nullopt;
}
 
std::optional<TokenAndPage>
findTokenAndPage(
    ApplyView& view,
    AccountID const& owner,
    uint256 const& nftokenID)
{
    std::shared_ptr<SLE> page = locatePage(view, owner, nftokenID);
 
    // If the page couldn't be found, the given NFT isn't owned by this account
    if (!page)
        return std::nullopt;
 
    // We found a candidate page, but the given NFT may not be in it.
    for (auto const& t : page->getFieldArray(sfNFTokens))
    {
        if (t[sfNFTokenID] == nftokenID)
            // This std::optional constructor is explicit, so it is spelled out.
            return std::optional<TokenAndPage>(
                std::in_place, t, std::move(page));
    }
    return std::nullopt;
}
 
std::size_t
removeTokenOffersWithLimit(
    ApplyView& view,
    Keylet const& directory,
    std::size_t maxDeletableOffers)
{
    if (maxDeletableOffers == 0)
        return 0;
 
    std::optional<std::uint64_t> pageIndex{0};
    std::size_t deletedOffersCount = 0;
 
    do
    {
        auto const page = view.peek(keylet::page(directory, *pageIndex));
        if (!page)
            break;
 
        // We get the index of the next page in case the current
        // page is deleted after all of its entries have been removed
        pageIndex = (*page)[~sfIndexNext];
 
        auto offerIndexes = page->getFieldV256(sfIndexes);
 
        // We reverse-iterate the offer directory page to delete all entries.
        // Deleting an entry in a NFTokenOffer directory page won't cause
        // entries from other pages to move to the current, so, it is safe to
        // delete entries one by one in the page. It is required to iterate
        // backwards to handle iterator invalidation for vector, as we are
        // deleting during iteration.
        for (int i = offerIndexes.size() - 1; i >= 0; --i)
        {
            if (auto const offer = view.peek(keylet::nftoffer(offerIndexes[i])))
            {
                if (deleteTokenOffer(view, offer))
                    ++deletedOffersCount;
                else
                    Throw<std::runtime_error>(
                        "Offer " + to_string(offerIndexes[i]) +
                        " cannot be deleted!");
            }
 
            if (maxDeletableOffers == deletedOffersCount)
                break;
        }
    } while (pageIndex.value_or(0) && maxDeletableOffers != deletedOffersCount);
 
    return deletedOffersCount;
}
 
TER
notTooManyOffers(ReadView const& view, uint256 const& nftokenID)
{
    std::size_t totalOffers = 0;
 
    {
        Dir buys(view, keylet::nft_buys(nftokenID));
        for (auto iter = buys.begin(); iter != buys.end(); iter.next_page())
        {
            totalOffers += iter.page_size();
            if (totalOffers > maxDeletableTokenOfferEntries)
                return tefTOO_BIG;
        }
    }
 
    {
        Dir sells(view, keylet::nft_sells(nftokenID));
        for (auto iter = sells.begin(); iter != sells.end(); iter.next_page())
        {
            totalOffers += iter.page_size();
            if (totalOffers > maxDeletableTokenOfferEntries)
                return tefTOO_BIG;
        }
    }
    return tesSUCCESS;
}
 
bool
deleteTokenOffer(ApplyView& view, std::shared_ptr<SLE> const& offer)
{
    if (offer->getType() != ltNFTOKEN_OFFER)
        return false;
 
    auto const owner = (*offer)[sfOwner];
 
    if (!view.dirRemove(
            keylet::ownerDir(owner),
            (*offer)[sfOwnerNode],
            offer->key(),
            false))
        return false;
 
    auto const nftokenID = (*offer)[sfNFTokenID];
 
    if (!view.dirRemove(
            ((*offer)[sfFlags] & tfSellNFToken) ? keylet::nft_sells(nftokenID)
                                                : keylet::nft_buys(nftokenID),
            (*offer)[sfNFTokenOfferNode],
            offer->key(),
            false))
        return false;
 
    adjustOwnerCount(
        view,
        view.peek(keylet::account(owner)),
        -1,
        beast::Journal{beast::Journal::getNullSink()});
 
    view.erase(offer);
    return true;
}
 
bool
repairNFTokenDirectoryLinks(ApplyView& view, AccountID const& owner)
{
    bool didRepair = false;
 
    auto const last = keylet::nftpage_max(owner);
 
    std::shared_ptr<SLE> page = view.peek(Keylet(
        ltNFTOKEN_PAGE,
        view.succ(keylet::nftpage_min(owner).key, last.key.next())
            .value_or(last.key)));
 
    if (!page)
        return didRepair;
 
    if (page->key() == last.key)
    {
        // There's only one page in this entire directory.  There should be
        // no links on that page.
        bool const nextPresent = page->isFieldPresent(sfNextPageMin);
        bool const prevPresent = page->isFieldPresent(sfPreviousPageMin);
        if (nextPresent || prevPresent)
        {
            didRepair = true;
            if (prevPresent)
                page->makeFieldAbsent(sfPreviousPageMin);
            if (nextPresent)
                page->makeFieldAbsent(sfNextPageMin);
            view.update(page);
        }
        return didRepair;
    }
 
    // First page is not the same as last page.  The first page should not
    // contain a previous link.
    if (page->isFieldPresent(sfPreviousPageMin))
    {
        didRepair = true;
        page->makeFieldAbsent(sfPreviousPageMin);
        view.update(page);
    }
 
    std::shared_ptr<SLE> nextPage;
    while (
        (nextPage = view.peek(Keylet(
             ltNFTOKEN_PAGE,
             view.succ(page->key().next(), last.key.next())
                 .value_or(last.key)))))
    {
        if (!page->isFieldPresent(sfNextPageMin) ||
            page->getFieldH256(sfNextPageMin) != nextPage->key())
        {
            didRepair = true;
            page->setFieldH256(sfNextPageMin, nextPage->key());
            view.update(page);
        }
 
        if (!nextPage->isFieldPresent(sfPreviousPageMin) ||
            nextPage->getFieldH256(sfPreviousPageMin) != page->key())
        {
            didRepair = true;
            nextPage->setFieldH256(sfPreviousPageMin, page->key());
            view.update(nextPage);
        }
 
        if (nextPage->key() == last.key)
            // We need special handling for the last page.
            break;
 
        page = nextPage;
    }
 
    // When we arrive here, nextPage should have the same index as last.
    // If not, then that's something we need to fix.
    if (!nextPage)
    {
        // It turns out that page is the last page for this owner, but
        // that last page does not have the expected final index.  We need
        // to move the contents of the current last page into a page with the
        // correct index.
        //
        // The owner count does not need to change because, even though
        // we're adding a page, we'll also remove the page that used to be
        // last.
        didRepair = true;
        nextPage = std::make_shared<SLE>(last);
 
        // Copy all relevant information from prev to curr.
        nextPage->peekFieldArray(sfNFTokens) = page->peekFieldArray(sfNFTokens);
 
        if (auto const prevLink = page->at(~sfPreviousPageMin))
        {
            nextPage->at(sfPreviousPageMin) = *prevLink;
 
            // Also fix up the NextPageMin link in the new Previous.
            auto const newPrev = view.peek(Keylet(ltNFTOKEN_PAGE, *prevLink));
            if (!newPrev)
                Throw<std::runtime_error>(
                    "NFTokenPage directory for " + to_string(owner) +
                    " cannot be repaired.  Unexpected link problem.");
            newPrev->at(sfNextPageMin) = nextPage->key();
            view.update(newPrev);
        }
        view.erase(page);
        view.insert(nextPage);
        return didRepair;
    }
 
    XRPL_ASSERT(
        nextPage,
        "ripple::nft::repairNFTokenDirectoryLinks : next page is available");
    if (nextPage->isFieldPresent(sfNextPageMin))
    {
        didRepair = true;
        nextPage->makeFieldAbsent(sfNextPageMin);
        view.update(nextPage);
    }
    return didRepair;
}
 
NotTEC
tokenOfferCreatePreflight(
    AccountID const& acctID,
    STAmount const& amount,
    std::optional<AccountID> const& dest,
    std::optional<std::uint32_t> const& expiration,
    std::uint16_t nftFlags,
    Rules const& rules,
    std::optional<AccountID> const& owner,
    std::uint32_t txFlags)
{
    if (amount.negative() && rules.enabled(fixNFTokenNegOffer))
        // An offer for a negative amount makes no sense.
        return temBAD_AMOUNT;
 
    if (!isXRP(amount))
    {
        if (nftFlags & nft::flagOnlyXRP)
            return temBAD_AMOUNT;
 
        if (!amount)
            return temBAD_AMOUNT;
    }
 
    // If this is an offer to buy, you must offer something; if it's an
    // offer to sell, you can ask for nothing.
    bool const isSellOffer = txFlags & tfSellNFToken;
    if (!isSellOffer && !amount)
        return temBAD_AMOUNT;
 
    if (expiration.has_value() && expiration.value() == 0)
        return temBAD_EXPIRATION;
 
    // The 'Owner' field must be present when offering to buy, but can't
    // be present when selling (it's implicit):
    if (owner.has_value() == isSellOffer)
        return temMALFORMED;
 
    if (owner && owner == acctID)
        return temMALFORMED;
 
    if (dest)
    {
        // Some folks think it makes sense for a buy offer to specify a
        // specific broker using the Destination field.  This change doesn't
        // deserve it's own amendment, so we're piggy-backing on
        // fixNFTokenNegOffer.
        //
        // Prior to fixNFTokenNegOffer any use of the Destination field on
        // a buy offer was malformed.
        if (!isSellOffer && !rules.enabled(fixNFTokenNegOffer))
            return temMALFORMED;
 
        // The destination can't be the account executing the transaction.
        if (dest == acctID)
            return temMALFORMED;
    }
    return tesSUCCESS;
}
 
TER
tokenOfferCreatePreclaim(
    ReadView const& view,
    AccountID const& acctID,
    AccountID const& nftIssuer,
    STAmount const& amount,
    std::optional<AccountID> const& dest,
    std::uint16_t nftFlags,
    std::uint16_t xferFee,
    beast::Journal j,
    std::optional<AccountID> const& owner,
    std::uint32_t txFlags)
{
    if (!(nftFlags & nft::flagCreateTrustLines) && !amount.native() && xferFee)
    {
        if (!view.exists(keylet::account(nftIssuer)))
            return tecNO_ISSUER;
 
        // If the IOU issuer and the NFToken issuer are the same, then that
        // issuer does not need a trust line to accept their fee.
        if (view.rules().enabled(featureNFTokenMintOffer))
        {
            if (nftIssuer != amount.getIssuer() &&
                !view.read(keylet::line(nftIssuer, amount.issue())))
                return tecNO_LINE;
        }
        else if (!view.exists(keylet::line(nftIssuer, amount.issue())))
        {
            return tecNO_LINE;
        }
 
        if (isFrozen(view, nftIssuer, amount.getCurrency(), amount.getIssuer()))
            return tecFROZEN;
    }
 
    if (nftIssuer != acctID && !(nftFlags & nft::flagTransferable))
    {
        auto const root = view.read(keylet::account(nftIssuer));
        XRPL_ASSERT(
            root, "ripple::nft::tokenOfferCreatePreclaim : non-null account");
 
        if (auto minter = (*root)[~sfNFTokenMinter]; minter != acctID)
            return tefNFTOKEN_IS_NOT_TRANSFERABLE;
    }
 
    if (isFrozen(view, acctID, amount.getCurrency(), amount.getIssuer()))
        return tecFROZEN;
 
    // If this is an offer to buy the token, the account must have the
    // needed funds at hand; but note that funds aren't reserved and the
    // offer may later become unfunded.
    if ((txFlags & tfSellNFToken) == 0)
    {
        // After this amendment, we allow an IOU issuer to make a buy offer
        // using their own currency.
        if (view.rules().enabled(fixNonFungibleTokensV1_2))
        {
            if (accountFunds(
                    view, acctID, amount, FreezeHandling::fhZERO_IF_FROZEN, j)
                    .signum() <= 0)
                return tecUNFUNDED_OFFER;
        }
        else if (
            accountHolds(
                view,
                acctID,
                amount.getCurrency(),
                amount.getIssuer(),
                FreezeHandling::fhZERO_IF_FROZEN,
                j)
                .signum() <= 0)
            return tecUNFUNDED_OFFER;
    }
 
    if (dest)
    {
        // If a destination is specified, the destination must already be in
        // the ledger.
        auto const sleDst = view.read(keylet::account(*dest));
 
        if (!sleDst)
            return tecNO_DST;
 
        // check if the destination has disallowed incoming offers
        if (view.rules().enabled(featureDisallowIncoming))
        {
            // flag cannot be set unless amendment is enabled but
            // out of an abundance of caution check anyway
 
            if (sleDst->getFlags() & lsfDisallowIncomingNFTokenOffer)
                return tecNO_PERMISSION;
        }
    }
 
    if (owner)
    {
        // Check if the owner (buy offer) has disallowed incoming offers
        if (view.rules().enabled(featureDisallowIncoming))
        {
            auto const sleOwner = view.read(keylet::account(*owner));
 
            // defensively check
            // it should not be possible to specify owner that doesn't exist
            if (!sleOwner)
                return tecNO_TARGET;
 
            if (sleOwner->getFlags() & lsfDisallowIncomingNFTokenOffer)
                return tecNO_PERMISSION;
        }
    }
 
    if (view.rules().enabled(fixEnforceNFTokenTrustlineV2) && !amount.native())
    {
        // If this is a sell offer, check that the account is allowed to
        // receive IOUs. If this is a buy offer, we have to check that trustline
        // is authorized, even though we previosly checked it's balance via
        // accountHolds. This is due to a possibility of existence of
        // unauthorized trustlines with balance
        auto const res = nft::checkTrustlineAuthorized(
            view, acctID, j, amount.asset().get<Issue>());
        if (res != tesSUCCESS)
            return res;
    }
    return tesSUCCESS;
}
 
TER
tokenOfferCreateApply(
    ApplyView& view,
    AccountID const& acctID,
    STAmount const& amount,
    std::optional<AccountID> const& dest,
    std::optional<std::uint32_t> const& expiration,
    SeqProxy seqProxy,
    uint256 const& nftokenID,
    XRPAmount const& priorBalance,
    beast::Journal j,
    std::uint32_t txFlags)
{
    Keylet const acctKeylet = keylet::account(acctID);
    if (auto const acct = view.read(acctKeylet);
        priorBalance < view.fees().accountReserve((*acct)[sfOwnerCount] + 1))
        return tecINSUFFICIENT_RESERVE;
 
    auto const offerID = keylet::nftoffer(acctID, seqProxy.value());
 
    // Create the offer:
    {
        // Token offers are always added to the owner's owner directory:
        auto const ownerNode = view.dirInsert(
            keylet::ownerDir(acctID), offerID, describeOwnerDir(acctID));
 
        if (!ownerNode)
            return tecDIR_FULL;
 
        bool const isSellOffer = txFlags & tfSellNFToken;
 
        // Token offers are also added to the token's buy or sell offer
        // directory
        auto const offerNode = view.dirInsert(
            isSellOffer ? keylet::nft_sells(nftokenID)
                        : keylet::nft_buys(nftokenID),
            offerID,
            [&nftokenID, isSellOffer](std::shared_ptr<SLE> const& sle) {
                (*sle)[sfFlags] =
                    isSellOffer ? lsfNFTokenSellOffers : lsfNFTokenBuyOffers;
                (*sle)[sfNFTokenID] = nftokenID;
            });
 
        if (!offerNode)
            return tecDIR_FULL;
 
        std::uint32_t sleFlags = 0;
 
        if (isSellOffer)
            sleFlags |= lsfSellNFToken;
 
        auto offer = std::make_shared<SLE>(offerID);
        (*offer)[sfOwner] = acctID;
        (*offer)[sfNFTokenID] = nftokenID;
        (*offer)[sfAmount] = amount;
        (*offer)[sfFlags] = sleFlags;
        (*offer)[sfOwnerNode] = *ownerNode;
        (*offer)[sfNFTokenOfferNode] = *offerNode;
 
        if (expiration)
            (*offer)[sfExpiration] = *expiration;
 
        if (dest)
            (*offer)[sfDestination] = *dest;
 
        view.insert(offer);
    }
 
    // Update owner count.
    adjustOwnerCount(view, view.peek(acctKeylet), 1, j);
 
    return tesSUCCESS;
}
 
TER
checkTrustlineAuthorized(
    ReadView const& view,
    AccountID const id,
    beast::Journal const j,
    Issue const& issue)
{
    // Only valid for custom currencies
    XRPL_ASSERT(
        !isXRP(issue.currency),
        "ripple::nft::checkTrustlineAuthorized : valid to check.");
 
    if (view.rules().enabled(fixEnforceNFTokenTrustlineV2))
    {
        auto const issuerAccount = view.read(keylet::account(issue.account));
        if (!issuerAccount)
        {
            JLOG(j.debug()) << "ripple::nft::checkTrustlineAuthorized: can't "
                               "receive IOUs from non-existent issuer: "
                            << to_string(issue.account);
 
            return tecNO_ISSUER;
        }
 
        // An account can not create a trustline to itself, so no line can
        // exist to be authorized. Additionally, an issuer can always accept
        // its own issuance.
        if (issue.account == id)
        {
            return tesSUCCESS;
        }
 
        if (issuerAccount->isFlag(lsfRequireAuth))
        {
            auto const trustLine =
                view.read(keylet::line(id, issue.account, issue.currency));
 
            if (!trustLine)
            {
                return tecNO_LINE;
            }
 
            // Entries have a canonical representation, determined by a
            // lexicographical "greater than" comparison employing strict
            // weak ordering. Determine which entry we need to access.
            if (!trustLine->isFlag(
                    id > issue.account ? lsfLowAuth : lsfHighAuth))
            {
                return tecNO_AUTH;
            }
        }
    }
 
    return tesSUCCESS;
}
 
TER
checkTrustlineDeepFrozen(
    ReadView const& view,
    AccountID const id,
    beast::Journal const j,
    Issue const& issue)
{
    // Only valid for custom currencies
    XRPL_ASSERT(
        !isXRP(issue.currency),
        "ripple::nft::checkTrustlineDeepFrozen : valid to check.");
 
    if (view.rules().enabled(featureDeepFreeze))
    {
        auto const issuerAccount = view.read(keylet::account(issue.account));
        if (!issuerAccount)
        {
            JLOG(j.debug()) << "ripple::nft::checkTrustlineDeepFrozen: can't "
                               "receive IOUs from non-existent issuer: "
                            << to_string(issue.account);
 
            return tecNO_ISSUER;
        }
 
        // An account can not create a trustline to itself, so no line can
        // exist to be frozen. Additionally, an issuer can always accept its
        // own issuance.
        if (issue.account == id)
        {
            return tesSUCCESS;
        }
 
        auto const trustLine =
            view.read(keylet::line(id, issue.account, issue.currency));
 
        if (!trustLine)
        {
            return tesSUCCESS;
        }
 
        // There's no difference which side enacted deep freeze, accepting
        // tokens shouldn't be possible.
        bool const deepFrozen =
            (*trustLine)[sfFlags] & (lsfLowDeepFreeze | lsfHighDeepFreeze);
 
        if (deepFrozen)
        {
            return tecFROZEN;
        }
    }
 
    return tesSUCCESS;
}
 
}  // namespace nft
}  // namespace ripple