NFTOffersHelpers.h

#pragma once
 
#include <xrpld/rpc/Context.h>
#include <xrpld/rpc/detail/RPCHelpers.h>
#include <xrpld/rpc/detail/RPCLedgerHelpers.h>
#include <xrpld/rpc/detail/Tuning.h>
 
#include <xrpl/basics/base_uint.h>
#include <xrpl/core/ServiceRegistry.h>
#include <xrpl/json/json_value.h>
#include <xrpl/ledger/ReadView.h>
#include <xrpl/ledger/helpers/DirectoryHelpers.h>
#include <xrpl/protocol/AccountID.h>
#include <xrpl/protocol/ErrorCodes.h>
#include <xrpl/protocol/Indexes.h>
#include <xrpl/protocol/Keylet.h>
#include <xrpl/protocol/LedgerFormats.h>
#include <xrpl/protocol/RPCErr.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/jss.h>
#include <xrpl/resource/Fees.h>
 
#include <cstdint>
#include <memory>
#include <vector>
 
namespace xrpl {
 
inline void
appendNftOfferJson(Application const& app, SLE::ConstRef offer, json::Value& offers)
{
    json::Value& obj(offers.append(json::ValueType::Object));
 
    obj[jss::nft_offer_index] = to_string(offer->key());
    obj[jss::flags] = (*offer)[sfFlags];
    obj[jss::owner] = toBase58(offer->getAccountID(sfOwner));
 
    if (offer->isFieldPresent(sfDestination))
        obj[jss::destination] = toBase58(offer->getAccountID(sfDestination));
 
    if (offer->isFieldPresent(sfExpiration))
        obj[jss::expiration] = offer->getFieldU32(sfExpiration);
 
    offer->getFieldAmount(sfAmount).setJson(obj[jss::amount]);
}
 
// {
//   nft_id: <token hash>
//   ledger_hash : <ledger>
//   ledger_index : <ledger_index>
//   limit: integer                 // optional
//   marker: opaque                 // optional, resume previous query
// }
inline json::Value
enumerateNFTOffers(rpc::JsonContext& context, UInt256 const& nftId, Keylet const& directory)
{
    unsigned int limit = 0;
    if (auto err = readLimitField(limit, rpc::tuning::kNftOffers, context))
        return *err;
 
    std::shared_ptr<ReadView const> ledger;
 
    if (auto result = rpc::lookupLedger(ledger, context); !ledger)
        return result;
 
    if (!ledger->exists(directory))
        return rpcError(RpcObjectNotFound);
 
    json::Value result;
    result[jss::nft_id] = to_string(nftId);
 
    json::Value& jsonOffers(result[jss::offers] = json::ValueType::Array);
 
    std::vector<SLE::const_pointer> offers;
    unsigned int reserve(limit);
    UInt256 startAfter;
    std::uint64_t startHint = 0;
 
    if (context.params.isMember(jss::marker))
    {
        // We have a start point. Use limit - 1 from the result and use the
        // very last one for the resume.
        json::Value const& marker(context.params[jss::marker]);
 
        if (!marker.isString())
            return rpc::expectedFieldError(jss::marker, "string");
 
        if (!startAfter.parseHex(marker.asString()))
            return rpcError(RpcInvalidParams);
 
        auto const sle = ledger->read(keylet::nftokenOffer(startAfter));
 
        if (!sle || nftId != sle->getFieldH256(sfNFTokenID))
            return rpcError(RpcInvalidParams);
 
        // Reject a marker that references an offer on the opposite side
        // (buy vs. sell) of the directory being enumerated.  Without this
        // check the marker's node hint points into the other directory, so
        // forEachItemAfter never finds `startAfter` and instead scans every
        // page of `directory` before returning invalidParams -- turning an
        // O(1) rejection into an O(directory size) walk.
        auto const offerDir =
            sle->isFlag(lsfSellNFToken) ? keylet::nftSells(nftId) : keylet::nftBuys(nftId);
        if (directory.key != offerDir.key)
            return rpcError(RpcInvalidParams);
 
        startHint = sle->getFieldU64(sfNFTokenOfferNode);
        appendNftOfferJson(context.app, sle, jsonOffers);
        offers.reserve(reserve);
    }
    else
    {
        // We have no start point, limit should be one higher than requested.
        offers.reserve(++reserve);
    }
 
    if (!forEachItemAfter(
            *ledger, directory, startAfter, startHint, reserve, [&offers](SLE::ConstRef offer) {
                if (offer->getType() == ltNFTOKEN_OFFER)
                {
                    offers.emplace_back(offer);
                    return true;
                }
 
                return false;
            }))
    {
        return rpcError(RpcInvalidParams);
    }
 
    if (offers.size() == reserve)
    {
        result[jss::limit] = limit;
        result[jss::marker] = to_string(offers.back()->key());
        offers.pop_back();
    }
 
    for (auto const& offer : offers)
        appendNftOfferJson(context.app, offer, jsonOffers);
 
    context.loadType = resource::kFeeMediumBurdenRpc;
    return result;
}
 
}  // namespace xrpl