STParsedJSON.cpp

#include <xrpl/protocol/STParsedJSON.h>
 
#include <xrpl/basics/StringUtilities.h>
#include <xrpl/basics/base_uint.h>
#include <xrpl/basics/contract.h>
#include <xrpl/basics/safe_cast.h>
#include <xrpl/beast/core/LexicalCast.h>
#include <xrpl/beast/utility/Zero.h>
#include <xrpl/json/json_forwards.h>
#include <xrpl/json/json_value.h>
#include <xrpl/protocol/AccountID.h>
#include <xrpl/protocol/ErrorCodes.h>
#include <xrpl/protocol/LedgerFormats.h>
#include <xrpl/protocol/MPTIssue.h>
#include <xrpl/protocol/PathAsset.h>
#include <xrpl/protocol/Permissions.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/STAccount.h>
#include <xrpl/protocol/STAmount.h>
#include <xrpl/protocol/STArray.h>
#include <xrpl/protocol/STBitString.h>
#include <xrpl/protocol/STBlob.h>
#include <xrpl/protocol/STCurrency.h>
#include <xrpl/protocol/STInteger.h>
#include <xrpl/protocol/STIssue.h>
#include <xrpl/protocol/STNumber.h>
#include <xrpl/protocol/STPathSet.h>
#include <xrpl/protocol/STVector256.h>
#include <xrpl/protocol/STXChainBridge.h>
#include <xrpl/protocol/TER.h>
#include <xrpl/protocol/TxFormats.h>
#include <xrpl/protocol/UintTypes.h>
#include <xrpl/protocol/detail/STVar.h>
#include <xrpl/protocol/jss.h>
 
#include <charconv>
#include <cstdint>
#include <exception>
#include <iostream>
#include <limits>
#include <optional>
#include <sstream>
#include <stdexcept>
#include <string>
#include <system_error>
#include <type_traits>
#include <utility>
 
namespace xrpl {
 
namespace STParsedJSONDetail {
template <typename U, typename S>
constexpr std::enable_if_t<std::is_unsigned_v<U> && std::is_signed_v<S>, U>
toUnsigned(S value)
{
    if (value < 0 || std::numeric_limits<U>::max() < value)
        Throw<std::runtime_error>("Value out of range");
    return static_cast<U>(value);
}
 
template <typename U1, typename U2>
constexpr std::enable_if_t<std::is_unsigned_v<U1> && std::is_unsigned_v<U2>, U1>
toUnsigned(U2 value)
{
    if (std::numeric_limits<U1>::max() < value)
        Throw<std::runtime_error>("Value out of range");
    return static_cast<U1>(value);
}
 
// LCOV_EXCL_START
static inline std::string
makeName(std::string const& object, std::string const& field)
{
    if (field.empty())
        return object;
 
    return object + "." + field;
}
 
static inline json::Value
notAnObject(std::string const& object, std::string const& field)
{
    return RPC::makeError(
        RpcInvalidParams, "Field '" + makeName(object, field) + "' is not a JSON object.");
}
 
static inline json::Value
notAnObject(std::string const& object)
{
    return notAnObject(object, "");
}
 
static inline json::Value
notAnArray(std::string const& object)
{
    return RPC::makeError(RpcInvalidParams, "Field '" + object + "' is not a JSON array.");
}
 
static inline json::Value
unknownField(std::string const& object, std::string const& field)
{
    return RPC::makeError(RpcInvalidParams, "Field '" + makeName(object, field) + "' is unknown.");
}
 
static inline json::Value
outOfRange(std::string const& object, std::string const& field)
{
    return RPC::makeError(
        RpcInvalidParams, "Field '" + makeName(object, field) + "' is out of range.");
}
 
static inline json::Value
badType(std::string const& object, std::string const& field)
{
    return RPC::makeError(
        RpcInvalidParams, "Field '" + makeName(object, field) + "' has bad type.");
}
 
static inline json::Value
invalidData(std::string const& object, std::string const& field)
{
    return RPC::makeError(
        RpcInvalidParams, "Field '" + makeName(object, field) + "' has invalid data.");
}
 
static inline json::Value
invalidData(std::string const& object)
{
    return invalidData(object, "");
}
 
static inline json::Value
arrayExpected(std::string const& object, std::string const& field)
{
    return RPC::makeError(
        RpcInvalidParams, "Field '" + makeName(object, field) + "' must be a JSON array.");
}
 
static inline json::Value
arrayTooBig(std::string const& object, std::string const& field)
{
    return RPC::makeError(
        RpcInvalidParams,
        "Field '" + makeName(object, field) + "' exceeds allowed JSON array size of " +
            std::to_string(kMaxParsedJsonArraySize) + " elements per field.");
}
 
static inline json::Value
stringExpected(std::string const& object, std::string const& field)
{
    return RPC::makeError(
        RpcInvalidParams, "Field '" + makeName(object, field) + "' must be a string.");
}
 
static inline json::Value
tooDeep(std::string const& object)
{
    return RPC::makeError(RpcInvalidParams, "Field '" + object + "' exceeds nesting depth limit.");
}
 
static inline json::Value
singletonExpected(std::string const& object, unsigned int index)
{
    return RPC::makeError(
        RpcInvalidParams,
        "Field '" + object + "[" + std::to_string(index) +
            "]' must be an object with a single key/object value.");
}
 
static inline json::Value
templateMismatch(SField const& sField)
{
    return RPC::makeError(
        RpcInvalidParams,
        "Object '" + sField.getName() + "' contents did not meet requirements for that type.");
}
 
static inline json::Value
nonObjectInArray(std::string const& item, json::UInt index)
{
    return RPC::makeError(
        RpcInvalidParams,
        "Item '" + item + "' at index " + std::to_string(index) +
            " is not an object.  Arrays may only contain objects.");
}
// LCOV_EXCL_STOP
 
template <class STResult, class Integer>
static std::optional<detail::STVar>
parseUnsigned(
    SField const& field,
    std::string const& jsonName,
    std::string const& fieldName,
    SField const* name,
    json::Value const& value,
    json::Value& error)
{
    std::optional<detail::STVar> ret;
 
    try
    {
        if (value.isString())
        {
            ret = detail::makeStvar<STResult>(
                field,
                safeCast<typename STResult::value_type>(
                    beast::lexicalCastThrow<Integer>(value.asString())));
        }
        else if (value.isInt())
        {
            ret = detail::makeStvar<STResult>(
                field, toUnsigned<typename STResult::value_type>(value.asInt()));
        }
        else if (value.isUInt())
        {
            ret = detail::makeStvar<STResult>(
                field, toUnsigned<typename STResult::value_type>(value.asUInt()));
        }
        else
        {
            error = badType(jsonName, fieldName);
            return ret;
        }
    }
    catch (std::exception const&)
    {
        error = invalidData(jsonName, fieldName);
        return ret;
    }
 
    return ret;
}
 
template <class STResult, class Integer = std::uint16_t>
static std::optional<detail::STVar>
parseUInt16(
    SField const& field,
    std::string const& jsonName,
    std::string const& fieldName,
    SField const* name,
    json::Value const& value,
    json::Value& error)
{
    std::optional<detail::STVar> ret;
 
    try
    {
        if (value.isString())
        {
            std::string const strValue = value.asString();
 
            if (!strValue.empty() && ((strValue[0] < '0') || (strValue[0] > '9')))
            {
                if (field == sfTransactionType)
                {
                    ret = detail::makeStvar<STResult>(
                        field,
                        safeCast<typename STResult::value_type>(static_cast<Integer>(
                            TxFormats::getInstance().findTypeByName(strValue))));
 
                    if (*name == sfGeneric)
                        name = &sfTransaction;
                }
                else if (field == sfLedgerEntryType)
                {
                    ret = detail::makeStvar<STResult>(
                        field,
                        safeCast<typename STResult::value_type>(static_cast<Integer>(
                            LedgerFormats::getInstance().findTypeByName(strValue))));
 
                    if (*name == sfGeneric)
                        name = &sfLedgerEntry;
                }
                else
                {
                    error = invalidData(jsonName, fieldName);
                    return ret;
                }
            }
        }
        if (!ret)
        {
            return parseUnsigned<STResult, Integer>(field, jsonName, fieldName, name, value, error);
        }
    }
    catch (std::exception const&)
    {
        error = invalidData(jsonName, fieldName);
        return ret;
    }
 
    return ret;
}
 
template <class STResult, class Integer = std::uint32_t>
static std::optional<detail::STVar>
parseUInt32(
    SField const& field,
    std::string const& jsonName,
    std::string const& fieldName,
    SField const* name,
    json::Value const& value,
    json::Value& error)
{
    std::optional<detail::STVar> ret;
 
    try
    {
        if (value.isString())
        {
            if (field == sfPermissionValue)
            {
                std::string const strValue = value.asString();
                auto const granularPermission =
                    Permission::getInstance().getGranularValue(strValue);
                if (granularPermission)
                {
                    ret = detail::makeStvar<STResult>(field, *granularPermission);
                }
                else
                {
                    auto const& txType = TxFormats::getInstance().findTypeByName(strValue);
                    ret = detail::makeStvar<STResult>(
                        field, Permission::getInstance().txToPermissionType(txType));
                }
            }
            else
            {
                ret = detail::makeStvar<STResult>(
                    field,
                    safeCast<typename STResult::value_type>(
                        beast::lexicalCastThrow<Integer>(value.asString())));
            }
        }
        if (!ret)
        {
            return parseUnsigned<STResult, Integer>(field, jsonName, fieldName, name, value, error);
        }
    }
    catch (std::exception const&)
    {
        error = invalidData(jsonName, fieldName);
        return ret;
    }
 
    return ret;
}
 
// This function is used by parseObject to parse any JSON type that doesn't
// recurse.  Everything represented here is a leaf-type.
static std::optional<detail::STVar>
parseLeaf(
    std::string const& jsonName,
    std::string const& fieldName,
    SField const* name,
    json::Value const& value,
    json::Value& error)
{
    std::optional<detail::STVar> ret;
 
    auto const& field = SField::getField(fieldName);
 
    // checked in parseObject
    if (field == sfInvalid)
    {
        // LCOV_EXCL_START
        error = unknownField(jsonName, fieldName);
        return ret;
        // LCOV_EXCL_STOP
    }
 
    switch (field.fieldType)
    {
        case STI_UINT8:
            try
            {
                constexpr auto kMinValue = std::numeric_limits<std::uint8_t>::min();
                constexpr auto kMaxValue = std::numeric_limits<std::uint8_t>::max();
                if (value.isString())
                {
                    std::string const strValue = value.asString();
 
                    if (!strValue.empty() && ((strValue[0] < '0') || (strValue[0] > '9')))
                    {
                        if (field == sfTransactionResult)
                        {
                            auto ter = transCode(strValue);
 
                            if (!ter || TERtoInt(*ter) < kMinValue || TERtoInt(*ter) > kMaxValue)
                            {
                                error = outOfRange(jsonName, fieldName);
                                return ret;
                            }
 
                            ret = detail::makeStvar<STUInt8>(
                                field, static_cast<std::uint8_t>(TERtoInt(*ter)));
                        }
                        else
                        {
                            error = badType(jsonName, fieldName);
                            return ret;
                        }
                    }
                    else
                    {
                        ret = detail::makeStvar<STUInt8>(
                            field, beast::lexicalCastThrow<std::uint8_t>(strValue));
                    }
                }
                else if (value.isInt())
                {
                    if (value.asInt() < kMinValue || value.asInt() > kMaxValue)
                    {
                        error = outOfRange(jsonName, fieldName);
                        return ret;
                    }
 
                    ret =
                        detail::makeStvar<STUInt8>(field, static_cast<std::uint8_t>(value.asInt()));
                }
                else if (value.isUInt())
                {
                    if (value.asUInt() > kMaxValue)
                    {
                        error = outOfRange(jsonName, fieldName);
                        return ret;
                    }
 
                    ret = detail::makeStvar<STUInt8>(
                        field, static_cast<std::uint8_t>(value.asUInt()));
                }
                else
                {
                    error = badType(jsonName, fieldName);
                    return ret;
                }
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
            break;
 
        case STI_UINT16:
            ret = parseUInt16<STUInt16>(field, jsonName, fieldName, name, value, error);
            if (!ret)
                return ret;
 
            break;
 
        case STI_UINT32:
            ret = parseUInt32<STUInt32>(field, jsonName, fieldName, name, value, error);
            if (!ret)
                return ret;
 
            break;
 
        case STI_UINT64:
            try
            {
                if (value.isString())
                {
                    auto const str = value.asString();
 
                    std::uint64_t val = 0;
 
                    bool const useBase10 = field.shouldMeta(SField::kSmdBaseTen);
 
                    // if the field is amount, serialize as base 10
                    auto [p, ec] = std::from_chars(
                        str.data(), str.data() + str.size(), val, useBase10 ? 10 : 16);
 
                    if (ec != std::errc() || (p != str.data() + str.size()))
                        Throw<std::invalid_argument>("invalid data");
 
                    ret = detail::makeStvar<STUInt64>(field, val);
                }
                else if (value.isInt())
                {
                    ret = detail::makeStvar<STUInt64>(
                        field, toUnsigned<std::uint64_t>(value.asInt()));
                }
                else if (value.isUInt())
                {
                    ret =
                        detail::makeStvar<STUInt64>(field, safeCast<std::uint64_t>(value.asUInt()));
                }
                else
                {
                    error = badType(jsonName, fieldName);
                    return ret;
                }
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
 
            break;
 
        case STI_UINT128: {
            if (!value.isString())
            {
                error = badType(jsonName, fieldName);
                return ret;
            }
 
            uint128 num;
 
            if (auto const s = value.asString(); !num.parseHex(s))
            {
                if (!s.empty())
                {
                    error = invalidData(jsonName, fieldName);
                    return ret;
                }
 
                num.zero();
            }
 
            ret = detail::makeStvar<STUInt128>(field, num);
            break;
        }
 
        case STI_UINT160: {
            if (!value.isString())
            {
                error = badType(jsonName, fieldName);
                return ret;
            }
 
            uint160 num;
 
            if (auto const s = value.asString(); !num.parseHex(s))
            {
                if (!s.empty())
                {
                    error = invalidData(jsonName, fieldName);
                    return ret;
                }
 
                num.zero();
            }
 
            ret = detail::makeStvar<STUInt160>(field, num);
            break;
        }
 
        case STI_UINT192: {
            if (!value.isString())
            {
                error = badType(jsonName, fieldName);
                return ret;
            }
 
            uint192 num;
 
            if (auto const s = value.asString(); !num.parseHex(s))
            {
                if (!s.empty())
                {
                    error = invalidData(jsonName, fieldName);
                    return ret;
                }
 
                num.zero();
            }
 
            ret = detail::makeStvar<STUInt192>(field, num);
            break;
        }
 
        case STI_UINT256: {
            if (!value.isString())
            {
                error = badType(jsonName, fieldName);
                return ret;
            }
 
            uint256 num;
 
            if (auto const s = value.asString(); !num.parseHex(s))
            {
                if (!s.empty())
                {
                    error = invalidData(jsonName, fieldName);
                    return ret;
                }
 
                num.zero();
            }
 
            ret = detail::makeStvar<STUInt256>(field, num);
            break;
        }
 
        case STI_INT32:
            try
            {
                if (value.isString())
                {
                    ret = detail::makeStvar<STInt32>(
                        field, beast::lexicalCastThrow<std::int32_t>(value.asString()));
                }
                else if (value.isInt())
                {
                    // future-proofing - a static assert failure if the JSON
                    // library ever supports larger ints
                    // In such case, we will need additional bounds checks here
                    static_assert(std::is_same_v<decltype(value.asInt()), std::int32_t>);
                    ret = detail::makeStvar<STInt32>(field, value.asInt());
                }
                else if (value.isUInt())
                {
                    auto const uintValue = value.asUInt();
                    if (uintValue >
                        static_cast<std::uint32_t>(std::numeric_limits<std::int32_t>::max()))
                    {
                        error = outOfRange(jsonName, fieldName);
                        return ret;
                    }
                    ret = detail::makeStvar<STInt32>(field, static_cast<std::int32_t>(uintValue));
                }
                else
                {
                    error = badType(jsonName, fieldName);
                    return ret;
                }
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
 
            break;
 
        case STI_VL:
            if (!value.isString())
            {
                error = badType(jsonName, fieldName);
                return ret;
            }
 
            try
            {
                if (auto vBlob = strUnHex(value.asString()))
                {
                    ret = detail::makeStvar<STBlob>(field, vBlob->data(), vBlob->size());
                }
                else
                {
                    Throw<std::invalid_argument>("invalid data");
                }
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
 
            break;
 
        case STI_AMOUNT:
            try
            {
                ret = detail::makeStvar<STAmount>(amountFromJson(field, value));
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
 
            break;
 
        case STI_NUMBER:
            try
            {
                ret = detail::makeStvar<STNumber>(numberFromJson(field, value));
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
 
            break;
 
        case STI_VECTOR256:
            if (not value.isArrayOrNull())
            {
                error = arrayExpected(jsonName, fieldName);
                return ret;
            }
 
            if (not value.isNull() and value.size() > kMaxParsedJsonArraySize)
            {
                error = arrayTooBig(jsonName, fieldName);
                return ret;
            }
 
            try
            {
                STVector256 tail(field);
                for (json::UInt i = 0; value.isValidIndex(i); ++i)
                {
                    uint256 s;
                    if (!s.parseHex(value[i].asString()))
                        Throw<std::invalid_argument>("invalid data");
                    tail.pushBack(s);
                }
                ret = detail::makeStvar<STVector256>(std::move(tail));
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
 
            break;
 
        case STI_PATHSET:
            if (not value.isArrayOrNull())
            {
                error = arrayExpected(jsonName, fieldName);
                return ret;
            }
 
            if (not value.isNull() and value.size() > kMaxParsedJsonArraySize)
            {
                error = arrayTooBig(jsonName, fieldName);
                return ret;
            }
 
            try
            {
                STPathSet tail(field);
 
                for (json::UInt i = 0; value.isValidIndex(i); ++i)
                {
                    STPath p;
 
                    if (not value[i].isArrayOrNull())
                    {
                        std::stringstream ss;
                        ss << fieldName << "[" << i << "]";
                        error = arrayExpected(jsonName, ss.str());
                        return ret;
                    }
 
                    if (not value[i].isNull() and value[i].size() > kMaxParsedJsonArraySize)
                    {
                        std::stringstream ss;
                        ss << fieldName << "[" << i << "]";
                        error = arrayTooBig(jsonName, ss.str());
                        return ret;
                    }
 
                    for (json::UInt j = 0; value[i].isValidIndex(j); ++j)
                    {
                        std::stringstream ss;
                        ss << fieldName << "[" << i << "][" << j << "]";
                        std::string const elementName(jsonName + "." + ss.str());
 
                        // each element in this path has some combination of
                        // account, asset, or issuer
 
                        json::Value pathEl = value[i][j];
 
                        if (!pathEl.isObject())
                        {
                            error = notAnObject(elementName);
                            return ret;
                        }
 
                        if (pathEl.isMember(jss::currency) && pathEl.isMember(jss::mpt_issuance_id))
                        {
                            error = RPC::makeError(RpcInvalidParams, "Invalid Asset.");
                            return ret;
                        }
 
                        bool const isMPT = pathEl.isMember(jss::mpt_issuance_id);
                        auto const assetName = isMPT ? jss::mpt_issuance_id : jss::currency;
                        json::Value const& account = pathEl[jss::account];
                        json::Value const& asset = pathEl[assetName];
                        json::Value const& issuer = pathEl[jss::issuer];
                        bool hasAsset = false;
                        AccountID uAccount, uIssuer;
                        PathAsset uAsset;
 
                        if (!account && !asset && !issuer)
                        {
                            error = invalidData(elementName);
                            return ret;
                        }
 
                        if (account)
                        {
                            // human account id
                            if (!account.isString())
                            {
                                error = stringExpected(elementName, jss::account.cStr());
                                return ret;
                            }
 
                            // If we have what looks like a 160-bit hex value,
                            // we set it, otherwise, we assume it's an AccountID
                            if (!uAccount.parseHex(account.asString()))
                            {
                                auto const a = parseBase58<AccountID>(account.asString());
                                if (!a)
                                {
                                    error = invalidData(elementName, jss::account.cStr());
                                    return ret;
                                }
                                uAccount = *a;
                            }
                        }
 
                        if (asset)
                        {
                            // human asset
                            if (!asset.isString())
                            {
                                error = stringExpected(elementName, assetName.cStr());
                                return ret;
                            }
 
                            hasAsset = true;
 
                            if (isMPT)
                            {
                                MPTID u;
                                if (!u.parseHex(asset.asString()))
                                {
                                    error = invalidData(elementName, assetName.cStr());
                                    return ret;
                                }
                                if (getMPTIssuer(u) == beast::kZero)
                                {
                                    error = invalidData(elementName, jss::account.cStr());
                                    return ret;
                                }
                                uAsset = u;
                            }
                            else
                            {
                                Currency currency;
                                if (!currency.parseHex(asset.asString()))
                                {
                                    if (!toCurrency(currency, asset.asString()))
                                    {
                                        error = invalidData(elementName, assetName.cStr());
                                        return ret;
                                    }
                                }
                                uAsset = currency;
                            }
                        }
 
                        if (issuer)
                        {
                            // human account id
                            if (!issuer.isString())
                            {
                                error = stringExpected(elementName, jss::issuer.cStr());
                                return ret;
                            }
 
                            if (!uIssuer.parseHex(issuer.asString()))
                            {
                                auto const a = parseBase58<AccountID>(issuer.asString());
                                if (!a)
                                {
                                    error = invalidData(elementName, jss::issuer.cStr());
                                    return ret;
                                }
                                uIssuer = *a;
                            }
 
                            if (isMPT && uIssuer != getMPTIssuer(uAsset.get<MPTID>()))
                            {
                                error = invalidData(elementName, jss::issuer.cStr());
                                return ret;
                            }
                        }
 
                        p.emplaceBack(uAccount, uAsset, uIssuer, hasAsset);
                    }
 
                    tail.pushBack(p);
                }
                ret = detail::makeStvar<STPathSet>(std::move(tail));
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
 
            break;
 
        case STI_ACCOUNT: {
            if (!value.isString())
            {
                error = badType(jsonName, fieldName);
                return ret;
            }
 
            std::string const strValue = value.asString();
 
            try
            {
                if (AccountID account; account.parseHex(strValue))
                    return detail::makeStvar<STAccount>(field, account);
 
                if (auto result = parseBase58<AccountID>(strValue))
                    return detail::makeStvar<STAccount>(field, *result);
 
                error = invalidData(jsonName, fieldName);
                return ret;
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
        }
        break;
 
        case STI_ISSUE:
            try
            {
                ret = detail::makeStvar<STIssue>(issueFromJson(field, value));
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
            break;
 
        case STI_XCHAIN_BRIDGE:
            try
            {
                ret = detail::makeStvar<STXChainBridge>(STXChainBridge(field, value));
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
            break;
 
        case STI_CURRENCY:
            try
            {
                ret = detail::makeStvar<STCurrency>(currencyFromJson(field, value));
            }
            catch (std::exception const&)
            {
                error = invalidData(jsonName, fieldName);
                return ret;
            }
            break;
 
        default:
            error = badType(jsonName, fieldName);
            return ret;
    }
 
    return ret;
}
 
// Forward declaration since parseObject() and parseArray() call each other.
static std::optional<detail::STVar>
parseArray(
    std::string const& jsonName,
    json::Value const& json,
    SField const& inName,
    int depth,
    json::Value& error);
 
static std::optional<STObject>
parseObject(
    std::string const& jsonName,
    json::Value const& json,
    SField const& inName,
    int depth,
    json::Value& error)
{
    if (not json.isObjectOrNull())
    {
        error = notAnObject(jsonName);
        return std::nullopt;
    }
 
    if (depth > kMaxParsedJsonDepth)
    {
        error = tooDeep(jsonName);
        return std::nullopt;
    }
 
    try
    {
        STObject data(inName);
 
        for (auto const& fieldName : json.getMemberNames())
        {
            json::Value const& value = json[fieldName];
            auto const& field = SField::getField(fieldName);
 
            if (field == sfInvalid)
            {
                error = unknownField(jsonName, fieldName);
                return std::nullopt;
            }
 
            switch (field.fieldType)
            {
                // Object-style containers (which recurse).
                case STI_OBJECT:
                case STI_TRANSACTION:
                case STI_LEDGERENTRY:
                case STI_VALIDATION:
                    if (!value.isObject())
                    {
                        error = notAnObject(jsonName, fieldName);
                        return std::nullopt;
                    }
 
                    try
                    {
                        auto ret =
                            parseObject(jsonName + "." + fieldName, value, field, depth + 1, error);
                        if (!ret)
                            return std::nullopt;
                        data.emplaceBack(std::move(*ret));
                    }
                    catch (std::exception const&)
                    {
                        error = invalidData(jsonName, fieldName);
                        return std::nullopt;
                    }
 
                    break;
 
                // Array-style containers (which recurse).
                case STI_ARRAY:
                    try
                    {
                        auto array =
                            parseArray(jsonName + "." + fieldName, value, field, depth + 1, error);
                        if (!array.has_value())
                            return std::nullopt;
                        data.emplaceBack(std::move(*array));
                    }
                    catch (std::exception const&)
                    {
                        error = invalidData(jsonName, fieldName);
                        return std::nullopt;
                    }
 
                    break;
 
                // Everything else (types that don't recurse).
                default: {
                    auto leaf = parseLeaf(jsonName, fieldName, &inName, value, error);
 
                    if (!leaf)
                        return std::nullopt;
 
                    data.emplaceBack(std::move(*leaf));
                }
 
                break;
            }
        }
 
        // Some inner object types have templates.  Attempt to apply that.
        data.applyTemplateFromSField(inName);  // May throw
 
        return data;
    }
    catch (STObject::FieldErr const& e)
    {
        std::cerr << "templateMismatch: " << e.what() << "\n";
        error = templateMismatch(inName);
    }
    catch (std::exception const&)
    {
        error = invalidData(jsonName);
    }
    return std::nullopt;
}
 
static std::optional<detail::STVar>
parseArray(
    std::string const& jsonName,
    json::Value const& json,
    SField const& inName,
    int depth,
    json::Value& error)
{
    if (not json.isArrayOrNull())
    {
        error = notAnArray(jsonName);
        return std::nullopt;
    }
 
    if (depth > kMaxParsedJsonDepth)
    {
        error = tooDeep(jsonName);
        return std::nullopt;
    }
 
    if (not json.isNull() and json.size() > kMaxParsedJsonArraySize)
    {
        error = arrayTooBig(jsonName, "");
        return std::nullopt;
    }
 
    try
    {
        STArray tail(inName);
 
        for (json::UInt i = 0; json.isValidIndex(i); ++i)
        {
            bool const isObjectOrNull(json[i].isObjectOrNull());
            bool const singleKey(isObjectOrNull ? json[i].size() == 1 : true);
 
            if (!isObjectOrNull || !singleKey)
            {
                // null values are !singleKey
                error = singletonExpected(jsonName, i);
                return std::nullopt;
            }
 
            // TODO: There doesn't seem to be a nice way to get just the
            // first/only key in an object without copying all keys into a vector
            std::string const memberName(json[i].getMemberNames()[0]);
            auto const& nameField(SField::getField(memberName));
 
            if (nameField == sfInvalid)
            {
                error = unknownField(jsonName, memberName);
                return std::nullopt;
            }
 
            json::Value const objectFields(json[i][memberName]);
 
            std::stringstream ss;
            ss << jsonName << "." << "[" << i << "]." << memberName;
 
            auto ret = parseObject(ss.str(), objectFields, nameField, depth + 1, error);
            if (!ret)
            {
                std::string const errMsg = error["error_message"].asString();
                error["error_message"] = "Error at '" + ss.str() + "'. " + errMsg;
                return std::nullopt;
            }
 
            if (ret->getFName().fieldType != STI_OBJECT)
            {
                ss << "Field type: " << ret->getFName().fieldType << " ";
                error = nonObjectInArray(ss.str(), i);
                return std::nullopt;
            }
 
            tail.pushBack(std::move(*ret));
        }
 
        return detail::makeStvar<STArray>(std::move(tail));
    }
    catch (std::exception const&)
    {
        error = invalidData(jsonName);
        return std::nullopt;
    }
}
 
}  // namespace STParsedJSONDetail
 
//------------------------------------------------------------------------------
 
STParsedJSONObject::STParsedJSONObject(std::string const& name, json::Value const& json)
{
    using namespace STParsedJSONDetail;
    object = parseObject(name, json, sfGeneric, 0, error);
}
 
}  // namespace xrpl