bitcoin-bitcoin-core/src/rpc/util.cpp

// Copyright (c) 2017-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#if defined(HAVE_CONFIG_H)
#include <config/bitcoin-config.h>
#endif

#include <clientversion.h>
#include <core_io.h>
#include <common/args.h>
#include <consensus/amount.h>
#include <script/interpreter.h>
#include <key_io.h>
#include <outputtype.h>
#include <rpc/util.h>
#include <script/descriptor.h>
#include <script/signingprovider.h>
#include <script/solver.h>
#include <tinyformat.h>
#include <util/check.h>
#include <util/result.h>
#include <util/strencodings.h>
#include <util/string.h>
#include <util/translation.h>

#include <string_view>
#include <tuple>

const std::string UNIX_EPOCH_TIME = "UNIX epoch time";
const std::string EXAMPLE_ADDRESS[2] = {"bc1q09vm5lfy0j5reeulh4x5752q25uqqvz34hufdl", "bc1q02ad21edsxd23d32dfgqqsz4vv4nmtfzuklhy3"};

std::string GetAllOutputTypes()
{
    std::vector<std::string> ret;
    using U = std::underlying_type<TxoutType>::type;
    for (U i = (U)TxoutType::NONSTANDARD; i <= (U)TxoutType::WITNESS_UNKNOWN; ++i) {
        ret.emplace_back(GetTxnOutputType(static_cast<TxoutType>(i)));
    }
    return Join(ret, ", ");
}

void RPCTypeCheckObj(const UniValue& o,
    const std::map<std::string, UniValueType>& typesExpected,
    bool fAllowNull,
    bool fStrict)
{
    for (const auto& t : typesExpected) {
        const UniValue& v = o.find_value(t.first);
        if (!fAllowNull && v.isNull())
            throw JSONRPCError(RPC_TYPE_ERROR, strprintf("Missing %s", t.first));

        if (!(t.second.typeAny || v.type() == t.second.type || (fAllowNull && v.isNull())))
            throw JSONRPCError(RPC_TYPE_ERROR, strprintf("JSON value of type %s for field %s is not of expected type %s", uvTypeName(v.type()),  t.first, uvTypeName(t.second.type)));
    }

    if (fStrict)
    {
        for (const std::string& k : o.getKeys())
        {
            if (typesExpected.count(k) == 0)
            {
                std::string err = strprintf("Unexpected key %s", k);
                throw JSONRPCError(RPC_TYPE_ERROR, err);
            }
        }
    }
}

CAmount AmountFromValue(const UniValue& value, int decimals)
{
    if (!value.isNum() && !value.isStr())
        throw JSONRPCError(RPC_TYPE_ERROR, "Amount is not a number or string");
    CAmount amount;
    if (!ParseFixedPoint(value.getValStr(), decimals, &amount))
        throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount");
    if (!MoneyRange(amount))
        throw JSONRPCError(RPC_TYPE_ERROR, "Amount out of range");
    return amount;
}

uint256 ParseHashV(const UniValue& v, std::string_view name)
{
    const std::string& strHex(v.get_str());
    if (64 != strHex.length())
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("%s must be of length %d (not %d, for '%s')", name, 64, strHex.length(), strHex));
    if (!IsHex(strHex)) // Note: IsHex("") is false
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("%s must be hexadecimal string (not '%s')", name, strHex));
    return uint256S(strHex);
}
uint256 ParseHashO(const UniValue& o, std::string_view strKey)
{
    return ParseHashV(o.find_value(strKey), strKey);
}
std::vector<unsigned char> ParseHexV(const UniValue& v, std::string_view name)
{
    std::string strHex;
    if (v.isStr())
        strHex = v.get_str();
    if (!IsHex(strHex))
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("%s must be hexadecimal string (not '%s')", name, strHex));
    return ParseHex(strHex);
}
std::vector<unsigned char> ParseHexO(const UniValue& o, std::string_view strKey)
{
    return ParseHexV(o.find_value(strKey), strKey);
}

namespace {

/**
 * Quote an argument for shell.
 *
 * @note This is intended for help, not for security-sensitive purposes.
 */
std::string ShellQuote(const std::string& s)
{
    std::string result;
    result.reserve(s.size() * 2);
    for (const char ch: s) {
        if (ch == '\'') {
            result += "'\''";
        } else {
            result += ch;
        }
    }
    return "'" + result + "'";
}

/**
 * Shell-quotes the argument if it needs quoting, else returns it literally, to save typing.
 *
 * @note This is intended for help, not for security-sensitive purposes.
 */
std::string ShellQuoteIfNeeded(const std::string& s)
{
    for (const char ch: s) {
        if (ch == ' ' || ch == '\'' || ch == '"') {
            return ShellQuote(s);
        }
    }

    return s;
}

}

std::string HelpExampleCli(const std::string& methodname, const std::string& args)
{
    return "> bitcoin-cli " + methodname + " " + args + "\n";
}

std::string HelpExampleCliNamed(const std::string& methodname, const RPCArgList& args)
{
    std::string result = "> bitcoin-cli -named " + methodname;
    for (const auto& argpair: args) {
        const auto& value = argpair.second.isStr()
                ? argpair.second.get_str()
                : argpair.second.write();
        result += " " + argpair.first + "=" + ShellQuoteIfNeeded(value);
    }
    result += "\n";
    return result;
}

std::string HelpExampleRpc(const std::string& methodname, const std::string& args)
{
    return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", "
        "\"method\": \"" + methodname + "\", \"params\": [" + args + "]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
}

std::string HelpExampleRpcNamed(const std::string& methodname, const RPCArgList& args)
{
    UniValue params(UniValue::VOBJ);
    for (const auto& param: args) {
        params.pushKV(param.first, param.second);
    }

    return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", "
           "\"method\": \"" + methodname + "\", \"params\": " + params.write() + "}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
}

// Converts a hex string to a public key if possible
CPubKey HexToPubKey(const std::string& hex_in)
{
    if (!IsHex(hex_in)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid public key: " + hex_in);
    }
    CPubKey vchPubKey(ParseHex(hex_in));
    if (!vchPubKey.IsFullyValid()) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid public key: " + hex_in);
    }
    return vchPubKey;
}

// Retrieves a public key for an address from the given FillableSigningProvider
CPubKey AddrToPubKey(const FillableSigningProvider& keystore, const std::string& addr_in)
{
    CTxDestination dest = DecodeDestination(addr_in);
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address: " + addr_in);
    }
    CKeyID key = GetKeyForDestination(keystore, dest);
    if (key.IsNull()) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("'%s' does not refer to a key", addr_in));
    }
    CPubKey vchPubKey;
    if (!keystore.GetPubKey(key, vchPubKey)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("no full public key for address %s", addr_in));
    }
    if (!vchPubKey.IsFullyValid()) {
       throw JSONRPCError(RPC_INTERNAL_ERROR, "Wallet contains an invalid public key");
    }
    return vchPubKey;
}

// Creates a multisig address from a given list of public keys, number of signatures required, and the address type
CTxDestination AddAndGetMultisigDestination(const int required, const std::vector<CPubKey>& pubkeys, OutputType type, FillableSigningProvider& keystore, CScript& script_out)
{
    // Gather public keys
    if (required < 1) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "a multisignature address must require at least one key to redeem");
    }
    if ((int)pubkeys.size() < required) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("not enough keys supplied (got %u keys, but need at least %d to redeem)", pubkeys.size(), required));
    }
    if (pubkeys.size() > MAX_PUBKEYS_PER_MULTISIG) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Number of keys involved in the multisignature address creation > %d\nReduce the number", MAX_PUBKEYS_PER_MULTISIG));
    }

    script_out = GetScriptForMultisig(required, pubkeys);

    // Check if any keys are uncompressed. If so, the type is legacy
    for (const CPubKey& pk : pubkeys) {
        if (!pk.IsCompressed()) {
            type = OutputType::LEGACY;
            break;
        }
    }

    if (type == OutputType::LEGACY && script_out.size() > MAX_SCRIPT_ELEMENT_SIZE) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, (strprintf("redeemScript exceeds size limit: %d > %d", script_out.size(), MAX_SCRIPT_ELEMENT_SIZE)));
    }

    // Make the address
    CTxDestination dest = AddAndGetDestinationForScript(keystore, script_out, type);

    return dest;
}

class DescribeAddressVisitor
{
public:
    explicit DescribeAddressVisitor() = default;

    UniValue operator()(const CNoDestination& dest) const
    {
        return UniValue(UniValue::VOBJ);
    }

    UniValue operator()(const PubKeyDestination& dest) const
    {
        return UniValue(UniValue::VOBJ);
    }

    UniValue operator()(const PKHash& keyID) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("isscript", false);
        obj.pushKV("iswitness", false);
        return obj;
    }

    UniValue operator()(const ScriptHash& scriptID) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("isscript", true);
        obj.pushKV("iswitness", false);
        return obj;
    }

    UniValue operator()(const WitnessV0KeyHash& id) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("isscript", false);
        obj.pushKV("iswitness", true);
        obj.pushKV("witness_version", 0);
        obj.pushKV("witness_program", HexStr(id));
        return obj;
    }

    UniValue operator()(const WitnessV0ScriptHash& id) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("isscript", true);
        obj.pushKV("iswitness", true);
        obj.pushKV("witness_version", 0);
        obj.pushKV("witness_program", HexStr(id));
        return obj;
    }

    UniValue operator()(const WitnessV1Taproot& tap) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("isscript", true);
        obj.pushKV("iswitness", true);
        obj.pushKV("witness_version", 1);
        obj.pushKV("witness_program", HexStr(tap));
        return obj;
    }

    UniValue operator()(const WitnessUnknown& id) const
    {
        UniValue obj(UniValue::VOBJ);
        obj.pushKV("iswitness", true);
        obj.pushKV("witness_version", id.GetWitnessVersion());
        obj.pushKV("witness_program", HexStr(id.GetWitnessProgram()));
        return obj;
    }
};

UniValue DescribeAddress(const CTxDestination& dest)
{
    return std::visit(DescribeAddressVisitor(), dest);
}

/**
 * Returns a sighash value corresponding to the passed in argument.
 *
 * @pre The sighash argument should be string or null.
*/
int ParseSighashString(const UniValue& sighash)
{
    if (sighash.isNull()) {
        return SIGHASH_DEFAULT;
    }
    const auto result{SighashFromStr(sighash.get_str())};
    if (!result) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, util::ErrorString(result).original);
    }
    return result.value();
}

unsigned int ParseConfirmTarget(const UniValue& value, unsigned int max_target)
{
    const int target{value.getInt<int>()};
    const unsigned int unsigned_target{static_cast<unsigned int>(target)};
    if (target < 1 || unsigned_target > max_target) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid conf_target, must be between %u and %u", 1, max_target));
    }
    return unsigned_target;
}

RPCErrorCode RPCErrorFromTransactionError(TransactionError terr)
{
    switch (terr) {
        case TransactionError::MEMPOOL_REJECTED:
            return RPC_TRANSACTION_REJECTED;
        case TransactionError::ALREADY_IN_CHAIN:
            return RPC_TRANSACTION_ALREADY_IN_CHAIN;
        case TransactionError::P2P_DISABLED:
            return RPC_CLIENT_P2P_DISABLED;
        case TransactionError::INVALID_PSBT:
        case TransactionError::PSBT_MISMATCH:
            return RPC_INVALID_PARAMETER;
        case TransactionError::SIGHASH_MISMATCH:
            return RPC_DESERIALIZATION_ERROR;
        default: break;
    }
    return RPC_TRANSACTION_ERROR;
}

UniValue JSONRPCTransactionError(TransactionError terr, const std::string& err_string)
{
    if (err_string.length() > 0) {
        return JSONRPCError(RPCErrorFromTransactionError(terr), err_string);
    } else {
        return JSONRPCError(RPCErrorFromTransactionError(terr), TransactionErrorString(terr).original);
    }
}

/**
 * A pair of strings that can be aligned (through padding) with other Sections
 * later on
 */
struct Section {
    Section(const std::string& left, const std::string& right)
        : m_left{left}, m_right{right} {}
    std::string m_left;
    const std::string m_right;
};

/**
 * Keeps track of RPCArgs by transforming them into sections for the purpose
 * of serializing everything to a single string
 */
struct Sections {
    std::vector<Section> m_sections;
    size_t m_max_pad{0};

    void PushSection(const Section& s)
    {
        m_max_pad = std::max(m_max_pad, s.m_left.size());
        m_sections.push_back(s);
    }

    /**
     * Recursive helper to translate an RPCArg into sections
     */
    void Push(const RPCArg& arg, const size_t current_indent = 5, const OuterType outer_type = OuterType::NONE)
    {
        const auto indent = std::string(current_indent, ' ');
        const auto indent_next = std::string(current_indent + 2, ' ');
        const bool push_name{outer_type == OuterType::OBJ}; // Dictionary keys must have a name
        const bool is_top_level_arg{outer_type == OuterType::NONE}; // True on the first recursion

        switch (arg.m_type) {
        case RPCArg::Type::STR_HEX:
        case RPCArg::Type::STR:
        case RPCArg::Type::NUM:
        case RPCArg::Type::AMOUNT:
        case RPCArg::Type::RANGE:
        case RPCArg::Type::BOOL:
        case RPCArg::Type::OBJ_NAMED_PARAMS: {
            if (is_top_level_arg) return; // Nothing more to do for non-recursive types on first recursion
            auto left = indent;
            if (arg.m_opts.type_str.size() != 0 && push_name) {
                left += "\"" + arg.GetName() + "\": " + arg.m_opts.type_str.at(0);
            } else {
                left += push_name ? arg.ToStringObj(/*oneline=*/false) : arg.ToString(/*oneline=*/false);
            }
            left += ",";
            PushSection({left, arg.ToDescriptionString(/*is_named_arg=*/push_name)});
            break;
        }
        case RPCArg::Type::OBJ:
        case RPCArg::Type::OBJ_USER_KEYS: {
            const auto right = is_top_level_arg ? "" : arg.ToDescriptionString(/*is_named_arg=*/push_name);
            PushSection({indent + (push_name ? "\"" + arg.GetName() + "\": " : "") + "{", right});
            for (const auto& arg_inner : arg.m_inner) {
                Push(arg_inner, current_indent + 2, OuterType::OBJ);
            }
            if (arg.m_type != RPCArg::Type::OBJ) {
                PushSection({indent_next + "...", ""});
            }
            PushSection({indent + "}" + (is_top_level_arg ? "" : ","), ""});
            break;
        }
        case RPCArg::Type::ARR: {
            auto left = indent;
            left += push_name ? "\"" + arg.GetName() + "\": " : "";
            left += "[";
            const auto right = is_top_level_arg ? "" : arg.ToDescriptionString(/*is_named_arg=*/push_name);
            PushSection({left, right});
            for (const auto& arg_inner : arg.m_inner) {
                Push(arg_inner, current_indent + 2, OuterType::ARR);
            }
            PushSection({indent_next + "...", ""});
            PushSection({indent + "]" + (is_top_level_arg ? "" : ","), ""});
            break;
        }
        } // no default case, so the compiler can warn about missing cases
    }

    /**
     * Concatenate all sections with proper padding
     */
    std::string ToString() const
    {
        std::string ret;
        const size_t pad = m_max_pad + 4;
        for (const auto& s : m_sections) {
            // The left part of a section is assumed to be a single line, usually it is the name of the JSON struct or a
            // brace like {, }, [, or ]
            CHECK_NONFATAL(s.m_left.find('\n') == std::string::npos);
            if (s.m_right.empty()) {
                ret += s.m_left;
                ret += "\n";
                continue;
            }

            std::string left = s.m_left;
            left.resize(pad, ' ');
            ret += left;

            // Properly pad after newlines
            std::string right;
            size_t begin = 0;
            size_t new_line_pos = s.m_right.find_first_of('\n');
            while (true) {
                right += s.m_right.substr(begin, new_line_pos - begin);
                if (new_line_pos == std::string::npos) {
                    break; //No new line
                }
                right += "\n" + std::string(pad, ' ');
                begin = s.m_right.find_first_not_of(' ', new_line_pos + 1);
                if (begin == std::string::npos) {
                    break; // Empty line
                }
                new_line_pos = s.m_right.find_first_of('\n', begin + 1);
            }
            ret += right;
            ret += "\n";
        }
        return ret;
    }
};

RPCHelpMan::RPCHelpMan(std::string name, std::string description, std::vector<RPCArg> args, RPCResults results, RPCExamples examples)
    : RPCHelpMan{std::move(name), std::move(description), std::move(args), std::move(results), std::move(examples), nullptr} {}

RPCHelpMan::RPCHelpMan(std::string name, std::string description, std::vector<RPCArg> args, RPCResults results, RPCExamples examples, RPCMethodImpl fun)
    : m_name{std::move(name)},
      m_fun{std::move(fun)},
      m_description{std::move(description)},
      m_args{std::move(args)},
      m_results{std::move(results)},
      m_examples{std::move(examples)}
{
    // Map of parameter names and types just used to check whether the names are
    // unique. Parameter names always need to be unique, with the exception that
    // there can be pairs of POSITIONAL and NAMED parameters with the same name.
    enum ParamType { POSITIONAL = 1, NAMED = 2, NAMED_ONLY = 4 };
    std::map<std::string, int> param_names;

    for (const auto& arg : m_args) {
        std::vector<std::string> names = SplitString(arg.m_names, '|');
        // Should have unique named arguments
        for (const std::string& name : names) {
            auto& param_type = param_names[name];
            CHECK_NONFATAL(!(param_type & POSITIONAL));
            CHECK_NONFATAL(!(param_type & NAMED_ONLY));
            param_type |= POSITIONAL;
        }
        if (arg.m_type == RPCArg::Type::OBJ_NAMED_PARAMS) {
            for (const auto& inner : arg.m_inner) {
                std::vector<std::string> inner_names = SplitString(inner.m_names, '|');
                for (const std::string& inner_name : inner_names) {
                    auto& param_type = param_names[inner_name];
                    CHECK_NONFATAL(!(param_type & POSITIONAL) || inner.m_opts.also_positional);
                    CHECK_NONFATAL(!(param_type & NAMED));
                    CHECK_NONFATAL(!(param_type & NAMED_ONLY));
                    param_type |= inner.m_opts.also_positional ? NAMED : NAMED_ONLY;
                }
            }
        }
        // Default value type should match argument type only when defined
        if (arg.m_fallback.index() == 2) {
            const RPCArg::Type type = arg.m_type;
            switch (std::get<RPCArg::Default>(arg.m_fallback).getType()) {
            case UniValue::VOBJ:
                CHECK_NONFATAL(type == RPCArg::Type::OBJ);
                break;
            case UniValue::VARR:
                CHECK_NONFATAL(type == RPCArg::Type::ARR);
                break;
            case UniValue::VSTR:
                CHECK_NONFATAL(type == RPCArg::Type::STR || type == RPCArg::Type::STR_HEX || type == RPCArg::Type::AMOUNT);
                break;
            case UniValue::VNUM:
                CHECK_NONFATAL(type == RPCArg::Type::NUM || type == RPCArg::Type::AMOUNT || type == RPCArg::Type::RANGE);
                break;
            case UniValue::VBOOL:
                CHECK_NONFATAL(type == RPCArg::Type::BOOL);
                break;
            case UniValue::VNULL:
                // Null values are accepted in all arguments
                break;
            default:
                NONFATAL_UNREACHABLE();
                break;
            }
        }
    }
}

std::string RPCResults::ToDescriptionString() const
{
    std::string result;
    for (const auto& r : m_results) {
        if (r.m_type == RPCResult::Type::ANY) continue; // for testing only
        if (r.m_cond.empty()) {
            result += "\nResult:\n";
        } else {
            result += "\nResult (" + r.m_cond + "):\n";
        }
        Sections sections;
        r.ToSections(sections);
        result += sections.ToString();
    }
    return result;
}

std::string RPCExamples::ToDescriptionString() const
{
    return m_examples.empty() ? m_examples : "\nExamples:\n" + m_examples;
}

UniValue RPCHelpMan::HandleRequest(const JSONRPCRequest& request) const
{
    if (request.mode == JSONRPCRequest::GET_ARGS) {
        return GetArgMap();
    }
    /*
     * Check if the given request is valid according to this command or if
     * the user is asking for help information, and throw help when appropriate.
     */
    if (request.mode == JSONRPCRequest::GET_HELP || !IsValidNumArgs(request.params.size())) {
        throw std::runtime_error(ToString());
    }
    UniValue arg_mismatch{UniValue::VOBJ};
    for (size_t i{0}; i < m_args.size(); ++i) {
        const auto& arg{m_args.at(i)};
        UniValue match{arg.MatchesType(request.params[i])};
        if (!match.isTrue()) {
            arg_mismatch.pushKV(strprintf("Position %s (%s)", i + 1, arg.m_names), std::move(match));
        }
    }
    if (!arg_mismatch.empty()) {
        throw JSONRPCError(RPC_TYPE_ERROR, strprintf("Wrong type passed:\n%s", arg_mismatch.write(4)));
    }
    CHECK_NONFATAL(m_req == nullptr);
    m_req = &request;
    UniValue ret = m_fun(*this, request);
    m_req = nullptr;
    if (gArgs.GetBoolArg("-rpcdoccheck", DEFAULT_RPC_DOC_CHECK)) {
        UniValue mismatch{UniValue::VARR};
        for (const auto& res : m_results.m_results) {
            UniValue match{res.MatchesType(ret)};
            if (match.isTrue()) {
                mismatch.setNull();
                break;
            }
            mismatch.push_back(match);
        }
        if (!mismatch.isNull()) {
            std::string explain{
                mismatch.empty() ? "no possible results defined" :
                mismatch.size() == 1 ? mismatch[0].write(4) :
                mismatch.write(4)};
            throw std::runtime_error{
                strprintf("Internal bug detected: RPC call \"%s\" returned incorrect type:\n%s\n%s %s\nPlease report this issue here: %s\n",
                          m_name, explain,
                          PACKAGE_NAME, FormatFullVersion(),
                          PACKAGE_BUGREPORT)};
        }
    }
    return ret;
}

using CheckFn = void(const RPCArg&);
static const UniValue* DetailMaybeArg(CheckFn* check, const std::vector<RPCArg>& params, const JSONRPCRequest* req, size_t i)
{
    CHECK_NONFATAL(i < params.size());
    const UniValue& arg{CHECK_NONFATAL(req)->params[i]};
    const RPCArg& param{params.at(i)};
    if (check) check(param);

    if (!arg.isNull()) return &arg;
    if (!std::holds_alternative<RPCArg::Default>(param.m_fallback)) return nullptr;
    return &std::get<RPCArg::Default>(param.m_fallback);
}

static void CheckRequiredOrDefault(const RPCArg& param)
{
    // Must use `Arg<Type>(i)` to get the argument or its default value.
    const bool required{
        std::holds_alternative<RPCArg::Optional>(param.m_fallback) && RPCArg::Optional::NO == std::get<RPCArg::Optional>(param.m_fallback),
    };
    CHECK_NONFATAL(required || std::holds_alternative<RPCArg::Default>(param.m_fallback));
}

#define TMPL_INST(check_param, ret_type, return_code)       \
    template <>                                             \
    ret_type RPCHelpMan::ArgValue<ret_type>(size_t i) const \
    {                                                       \
        const UniValue* maybe_arg{                          \
            DetailMaybeArg(check_param, m_args, m_req, i),  \
        };                                                  \
        return return_code                                  \
    }                                                       \
    void force_semicolon(ret_type)

// Optional arg (without default). Can also be called on required args, if needed.
TMPL_INST(nullptr, std::optional<double>, maybe_arg ? std::optional{maybe_arg->get_real()} : std::nullopt;);
TMPL_INST(nullptr, std::optional<bool>, maybe_arg ? std::optional{maybe_arg->get_bool()} : std::nullopt;);
TMPL_INST(nullptr, const std::string*, maybe_arg ? &maybe_arg->get_str() : nullptr;);

// Required arg or optional arg with default value.
TMPL_INST(CheckRequiredOrDefault, bool, CHECK_NONFATAL(maybe_arg)->get_bool(););
TMPL_INST(CheckRequiredOrDefault, int, CHECK_NONFATAL(maybe_arg)->getInt<int>(););
TMPL_INST(CheckRequiredOrDefault, uint64_t, CHECK_NONFATAL(maybe_arg)->getInt<uint64_t>(););
TMPL_INST(CheckRequiredOrDefault, const std::string&, CHECK_NONFATAL(maybe_arg)->get_str(););

bool RPCHelpMan::IsValidNumArgs(size_t num_args) const
{
    size_t num_required_args = 0;
    for (size_t n = m_args.size(); n > 0; --n) {
        if (!m_args.at(n - 1).IsOptional()) {
            num_required_args = n;
            break;
        }
    }
    return num_required_args <= num_args && num_args <= m_args.size();
}

std::vector<std::pair<std::string, bool>> RPCHelpMan::GetArgNames() const
{
    std::vector<std::pair<std::string, bool>> ret;
    ret.reserve(m_args.size());
    for (const auto& arg : m_args) {
        if (arg.m_type == RPCArg::Type::OBJ_NAMED_PARAMS) {
            for (const auto& inner : arg.m_inner) {
                ret.emplace_back(inner.m_names, /*named_only=*/true);
            }
        }
        ret.emplace_back(arg.m_names, /*named_only=*/false);
    }
    return ret;
}

std::string RPCHelpMan::ToString() const
{
    std::string ret;

    // Oneline summary
    ret += m_name;
    bool was_optional{false};
    for (const auto& arg : m_args) {
        if (arg.m_opts.hidden) break; // Any arg that follows is also hidden
        const bool optional = arg.IsOptional();
        ret += " ";
        if (optional) {
            if (!was_optional) ret += "( ";
            was_optional = true;
        } else {
            if (was_optional) ret += ") ";
            was_optional = false;
        }
        ret += arg.ToString(/*oneline=*/true);
    }
    if (was_optional) ret += " )";

    // Description
    ret += "\n\n" + TrimString(m_description) + "\n";

    // Arguments
    Sections sections;
    Sections named_only_sections;
    for (size_t i{0}; i < m_args.size(); ++i) {
        const auto& arg = m_args.at(i);
        if (arg.m_opts.hidden) break; // Any arg that follows is also hidden

        // Push named argument name and description
        sections.m_sections.emplace_back(::ToString(i + 1) + ". " + arg.GetFirstName(), arg.ToDescriptionString(/*is_named_arg=*/true));
        sections.m_max_pad = std::max(sections.m_max_pad, sections.m_sections.back().m_left.size());

        // Recursively push nested args
        sections.Push(arg);

        // Push named-only argument sections
        if (arg.m_type == RPCArg::Type::OBJ_NAMED_PARAMS) {
            for (const auto& arg_inner : arg.m_inner) {
                named_only_sections.PushSection({arg_inner.GetFirstName(), arg_inner.ToDescriptionString(/*is_named_arg=*/true)});
                named_only_sections.Push(arg_inner);
            }
        }
    }

    if (!sections.m_sections.empty()) ret += "\nArguments:\n";
    ret += sections.ToString();
    if (!named_only_sections.m_sections.empty()) ret += "\nNamed Arguments:\n";
    ret += named_only_sections.ToString();

    // Result
    ret += m_results.ToDescriptionString();

    // Examples
    ret += m_examples.ToDescriptionString();

    return ret;
}

UniValue RPCHelpMan::GetArgMap() const
{
    UniValue arr{UniValue::VARR};

    auto push_back_arg_info = [&arr](const std::string& rpc_name, int pos, const std::string& arg_name, const RPCArg::Type& type) {
        UniValue map{UniValue::VARR};
        map.push_back(rpc_name);
        map.push_back(pos);
        map.push_back(arg_name);
        map.push_back(type == RPCArg::Type::STR ||
                      type == RPCArg::Type::STR_HEX);
        arr.push_back(map);
    };

    for (int i{0}; i < int(m_args.size()); ++i) {
        const auto& arg = m_args.at(i);
        std::vector<std::string> arg_names = SplitString(arg.m_names, '|');
        for (const auto& arg_name : arg_names) {
            push_back_arg_info(m_name, i, arg_name, arg.m_type);
            if (arg.m_type == RPCArg::Type::OBJ_NAMED_PARAMS) {
                for (const auto& inner : arg.m_inner) {
                    std::vector<std::string> inner_names = SplitString(inner.m_names, '|');
                    for (const std::string& inner_name : inner_names) {
                        push_back_arg_info(m_name, i, inner_name, inner.m_type);
                    }
                }
            }
        }
    }
    return arr;
}

static std::optional<UniValue::VType> ExpectedType(RPCArg::Type type)
{
    using Type = RPCArg::Type;
    switch (type) {
    case Type::STR_HEX:
    case Type::STR: {
        return UniValue::VSTR;
    }
    case Type::NUM: {
        return UniValue::VNUM;
    }
    case Type::AMOUNT: {
        // VNUM or VSTR, checked inside AmountFromValue()
        return std::nullopt;
    }
    case Type::RANGE: {
        // VNUM or VARR, checked inside ParseRange()
        return std::nullopt;
    }
    case Type::BOOL: {
        return UniValue::VBOOL;
    }
    case Type::OBJ:
    case Type::OBJ_NAMED_PARAMS:
    case Type::OBJ_USER_KEYS: {
        return UniValue::VOBJ;
    }
    case Type::ARR: {
        return UniValue::VARR;
    }
    } // no default case, so the compiler can warn about missing cases
    NONFATAL_UNREACHABLE();
}

UniValue RPCArg::MatchesType(const UniValue& request) const
{
    if (m_opts.skip_type_check) return true;
    if (IsOptional() && request.isNull()) return true;
    const auto exp_type{ExpectedType(m_type)};
    if (!exp_type) return true; // nothing to check

    if (*exp_type != request.getType()) {
        return strprintf("JSON value of type %s is not of expected type %s", uvTypeName(request.getType()), uvTypeName(*exp_type));
    }
    return true;
}

std::string RPCArg::GetFirstName() const
{
    return m_names.substr(0, m_names.find('|'));
}

std::string RPCArg::GetName() const
{
    CHECK_NONFATAL(std::string::npos == m_names.find('|'));
    return m_names;
}

bool RPCArg::IsOptional() const
{
    if (m_fallback.index() != 0) {
        return true;
    } else {
        return RPCArg::Optional::NO != std::get<RPCArg::Optional>(m_fallback);
    }
}

std::string RPCArg::ToDescriptionString(bool is_named_arg) const
{
    std::string ret;
    ret += "(";
    if (m_opts.type_str.size() != 0) {
        ret += m_opts.type_str.at(1);
    } else {
        switch (m_type) {
        case Type::STR_HEX:
        case Type::STR: {
            ret += "string";
            break;
        }
        case Type::NUM: {
            ret += "numeric";
            break;
        }
        case Type::AMOUNT: {
            ret += "numeric or string";
            break;
        }
        case Type::RANGE: {
            ret += "numeric or array";
            break;
        }
        case Type::BOOL: {
            ret += "boolean";
            break;
        }
        case Type::OBJ:
        case Type::OBJ_NAMED_PARAMS:
        case Type::OBJ_USER_KEYS: {
            ret += "json object";
            break;
        }
        case Type::ARR: {
            ret += "json array";
            break;
        }
        } // no default case, so the compiler can warn about missing cases
    }
    if (m_fallback.index() == 1) {
        ret += ", optional, default=" + std::get<RPCArg::DefaultHint>(m_fallback);
    } else if (m_fallback.index() == 2) {
        ret += ", optional, default=" + std::get<RPCArg::Default>(m_fallback).write();
    } else {
        switch (std::get<RPCArg::Optional>(m_fallback)) {
        case RPCArg::Optional::OMITTED: {
            if (is_named_arg) ret += ", optional"; // Default value is "null" in dicts. Otherwise,
            // nothing to do. Element is treated as if not present and has no default value
            break;
        }
        case RPCArg::Optional::NO: {
            ret += ", required";
            break;
        }
        } // no default case, so the compiler can warn about missing cases
    }
    ret += ")";
    if (m_type == Type::OBJ_NAMED_PARAMS) ret += " Options object that can be used to pass named arguments, listed below.";
    ret += m_description.empty() ? "" : " " + m_description;
    return ret;
}

void RPCResult::ToSections(Sections& sections, const OuterType outer_type, const int current_indent) const
{
    // Indentation
    const std::string indent(current_indent, ' ');
    const std::string indent_next(current_indent + 2, ' ');

    // Elements in a JSON structure (dictionary or array) are separated by a comma
    const std::string maybe_separator{outer_type != OuterType::NONE ? "," : ""};

    // The key name if recursed into a dictionary
    const std::string maybe_key{
        outer_type == OuterType::OBJ ?
            "\"" + this->m_key_name + "\" : " :
            ""};

    // Format description with type
    const auto Description = [&](const std::string& type) {
        return "(" + type + (this->m_optional ? ", optional" : "") + ")" +
               (this->m_description.empty() ? "" : " " + this->m_description);
    };

    switch (m_type) {
    case Type::ELISION: {
        // If the inner result is empty, use three dots for elision
        sections.PushSection({indent + "..." + maybe_separator, m_description});
        return;
    }
    case Type::ANY: {
        NONFATAL_UNREACHABLE(); // Only for testing
    }
    case Type::NONE: {
        sections.PushSection({indent + "null" + maybe_separator, Description("json null")});
        return;
    }
    case Type::STR: {
        sections.PushSection({indent + maybe_key + "\"str\"" + maybe_separator, Description("string")});
        return;
    }
    case Type::STR_AMOUNT: {
        sections.PushSection({indent + maybe_key + "n" + maybe_separator, Description("numeric")});
        return;
    }
    case Type::STR_HEX: {
        sections.PushSection({indent + maybe_key + "\"hex\"" + maybe_separator, Description("string")});
        return;
    }
    case Type::NUM: {
        sections.PushSection({indent + maybe_key + "n" + maybe_separator, Description("numeric")});
        return;
    }
    case Type::NUM_TIME: {
        sections.PushSection({indent + maybe_key + "xxx" + maybe_separator, Description("numeric")});
        return;
    }
    case Type::BOOL: {
        sections.PushSection({indent + maybe_key + "true|false" + maybe_separator, Description("boolean")});
        return;
    }
    case Type::ARR_FIXED:
    case Type::ARR: {
        sections.PushSection({indent + maybe_key + "[", Description("json array")});
        for (const auto& i : m_inner) {
            i.ToSections(sections, OuterType::ARR, current_indent + 2);
        }
        CHECK_NONFATAL(!m_inner.empty());
        if (m_type == Type::ARR && m_inner.back().m_type != Type::ELISION) {
            sections.PushSection({indent_next + "...", ""});
        } else {
            // Remove final comma, which would be invalid JSON
            sections.m_sections.back().m_left.pop_back();
        }
        sections.PushSection({indent + "]" + maybe_separator, ""});
        return;
    }
    case Type::OBJ_DYN:
    case Type::OBJ: {
        if (m_inner.empty()) {
            sections.PushSection({indent + maybe_key + "{}", Description("empty JSON object")});
            return;
        }
        sections.PushSection({indent + maybe_key + "{", Description("json object")});
        for (const auto& i : m_inner) {
            i.ToSections(sections, OuterType::OBJ, current_indent + 2);
        }
        if (m_type == Type::OBJ_DYN && m_inner.back().m_type != Type::ELISION) {
            // If the dictionary keys are dynamic, use three dots for continuation
            sections.PushSection({indent_next + "...", ""});
        } else {
            // Remove final comma, which would be invalid JSON
            sections.m_sections.back().m_left.pop_back();
        }
        sections.PushSection({indent + "}" + maybe_separator, ""});
        return;
    }
    } // no default case, so the compiler can warn about missing cases
    NONFATAL_UNREACHABLE();
}

static std::optional<UniValue::VType> ExpectedType(RPCResult::Type type)
{
    using Type = RPCResult::Type;
    switch (type) {
    case Type::ELISION:
    case Type::ANY: {
        return std::nullopt;
    }
    case Type::NONE: {
        return UniValue::VNULL;
    }
    case Type::STR:
    case Type::STR_HEX: {
        return UniValue::VSTR;
    }
    case Type::NUM:
    case Type::STR_AMOUNT:
    case Type::NUM_TIME: {
        return UniValue::VNUM;
    }
    case Type::BOOL: {
        return UniValue::VBOOL;
    }
    case Type::ARR_FIXED:
    case Type::ARR: {
        return UniValue::VARR;
    }
    case Type::OBJ_DYN:
    case Type::OBJ: {
        return UniValue::VOBJ;
    }
    } // no default case, so the compiler can warn about missing cases
    NONFATAL_UNREACHABLE();
}

UniValue RPCResult::MatchesType(const UniValue& result) const
{
    if (m_skip_type_check) {
        return true;
    }

    const auto exp_type = ExpectedType(m_type);
    if (!exp_type) return true; // can be any type, so nothing to check

    if (*exp_type != result.getType()) {
        return strprintf("returned type is %s, but declared as %s in doc", uvTypeName(result.getType()), uvTypeName(*exp_type));
    }

    if (UniValue::VARR == result.getType()) {
        UniValue errors(UniValue::VOBJ);
        for (size_t i{0}; i < result.get_array().size(); ++i) {
            // If there are more results than documented, reuse the last doc_inner.
            const RPCResult& doc_inner{m_inner.at(std::min(m_inner.size() - 1, i))};
            UniValue match{doc_inner.MatchesType(result.get_array()[i])};
            if (!match.isTrue()) errors.pushKV(strprintf("%d", i), match);
        }
        if (errors.empty()) return true; // empty result array is valid
        return errors;
    }

    if (UniValue::VOBJ == result.getType()) {
        if (!m_inner.empty() && m_inner.at(0).m_type == Type::ELISION) return true;
        UniValue errors(UniValue::VOBJ);
        if (m_type == Type::OBJ_DYN) {
            const RPCResult& doc_inner{m_inner.at(0)}; // Assume all types are the same, randomly pick the first
            for (size_t i{0}; i < result.get_obj().size(); ++i) {
                UniValue match{doc_inner.MatchesType(result.get_obj()[i])};
                if (!match.isTrue()) errors.pushKV(result.getKeys()[i], match);
            }
            if (errors.empty()) return true; // empty result obj is valid
            return errors;
        }
        std::set<std::string> doc_keys;
        for (const auto& doc_entry : m_inner) {
            doc_keys.insert(doc_entry.m_key_name);
        }
        std::map<std::string, UniValue> result_obj;
        result.getObjMap(result_obj);
        for (const auto& result_entry : result_obj) {
            if (doc_keys.find(result_entry.first) == doc_keys.end()) {
                errors.pushKV(result_entry.first, "key returned that was not in doc");
            }
        }

        for (const auto& doc_entry : m_inner) {
            const auto result_it{result_obj.find(doc_entry.m_key_name)};
            if (result_it == result_obj.end()) {
                if (!doc_entry.m_optional) {
                    errors.pushKV(doc_entry.m_key_name, "key missing, despite not being optional in doc");
                }
                continue;
            }
            UniValue match{doc_entry.MatchesType(result_it->second)};
            if (!match.isTrue()) errors.pushKV(doc_entry.m_key_name, match);
        }
        if (errors.empty()) return true;
        return errors;
    }

    return true;
}

void RPCResult::CheckInnerDoc() const
{
    if (m_type == Type::OBJ) {
        // May or may not be empty
        return;
    }
    // Everything else must either be empty or not
    const bool inner_needed{m_type == Type::ARR || m_type == Type::ARR_FIXED || m_type == Type::OBJ_DYN};
    CHECK_NONFATAL(inner_needed != m_inner.empty());
}

std::string RPCArg::ToStringObj(const bool oneline) const
{
    std::string res;
    res += "\"";
    res += GetFirstName();
    if (oneline) {
        res += "\":";
    } else {
        res += "\": ";
    }
    switch (m_type) {
    case Type::STR:
        return res + "\"str\"";
    case Type::STR_HEX:
        return res + "\"hex\"";
    case Type::NUM:
        return res + "n";
    case Type::RANGE:
        return res + "n or [n,n]";
    case Type::AMOUNT:
        return res + "amount";
    case Type::BOOL:
        return res + "bool";
    case Type::ARR:
        res += "[";
        for (const auto& i : m_inner) {
            res += i.ToString(oneline) + ",";
        }
        return res + "...]";
    case Type::OBJ:
    case Type::OBJ_NAMED_PARAMS:
    case Type::OBJ_USER_KEYS:
        // Currently unused, so avoid writing dead code
        NONFATAL_UNREACHABLE();
    } // no default case, so the compiler can warn about missing cases
    NONFATAL_UNREACHABLE();
}

std::string RPCArg::ToString(const bool oneline) const
{
    if (oneline && !m_opts.oneline_description.empty()) {
        if (m_opts.oneline_description[0] == '\"' && m_type != Type::STR_HEX && m_type != Type::STR && gArgs.GetBoolArg("-rpcdoccheck", DEFAULT_RPC_DOC_CHECK)) {
            throw std::runtime_error{
                STR_INTERNAL_BUG(strprintf("non-string RPC arg \"%s\" quotes oneline_description:\n%s",
                    m_names, m_opts.oneline_description)
                )};
        }
        return m_opts.oneline_description;
    }

    switch (m_type) {
    case Type::STR_HEX:
    case Type::STR: {
        return "\"" + GetFirstName() + "\"";
    }
    case Type::NUM:
    case Type::RANGE:
    case Type::AMOUNT:
    case Type::BOOL: {
        return GetFirstName();
    }
    case Type::OBJ:
    case Type::OBJ_NAMED_PARAMS:
    case Type::OBJ_USER_KEYS: {
        const std::string res = Join(m_inner, ",", [&](const RPCArg& i) { return i.ToStringObj(oneline); });
        if (m_type == Type::OBJ) {
            return "{" + res + "}";
        } else {
            return "{" + res + ",...}";
        }
    }
    case Type::ARR: {
        std::string res;
        for (const auto& i : m_inner) {
            res += i.ToString(oneline) + ",";
        }
        return "[" + res + "...]";
    }
    } // no default case, so the compiler can warn about missing cases
    NONFATAL_UNREACHABLE();
}

static std::pair<int64_t, int64_t> ParseRange(const UniValue& value)
{
    if (value.isNum()) {
        return {0, value.getInt<int64_t>()};
    }
    if (value.isArray() && value.size() == 2 && value[0].isNum() && value[1].isNum()) {
        int64_t low = value[0].getInt<int64_t>();
        int64_t high = value[1].getInt<int64_t>();
        if (low > high) throw JSONRPCError(RPC_INVALID_PARAMETER, "Range specified as [begin,end] must not have begin after end");
        return {low, high};
    }
    throw JSONRPCError(RPC_INVALID_PARAMETER, "Range must be specified as end or as [begin,end]");
}

std::pair<int64_t, int64_t> ParseDescriptorRange(const UniValue& value)
{
    int64_t low, high;
    std::tie(low, high) = ParseRange(value);
    if (low < 0) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Range should be greater or equal than 0");
    }
    if ((high >> 31) != 0) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "End of range is too high");
    }
    if (high >= low + 1000000) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Range is too large");
    }
    return {low, high};
}

std::vector<CScript> EvalDescriptorStringOrObject(const UniValue& scanobject, FlatSigningProvider& provider, const bool expand_priv)
{
    std::string desc_str;
    std::pair<int64_t, int64_t> range = {0, 1000};
    if (scanobject.isStr()) {
        desc_str = scanobject.get_str();
    } else if (scanobject.isObject()) {
        const UniValue& desc_uni{scanobject.find_value("desc")};
        if (desc_uni.isNull()) throw JSONRPCError(RPC_INVALID_PARAMETER, "Descriptor needs to be provided in scan object");
        desc_str = desc_uni.get_str();
        const UniValue& range_uni{scanobject.find_value("range")};
        if (!range_uni.isNull()) {
            range = ParseDescriptorRange(range_uni);
        }
    } else {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Scan object needs to be either a string or an object");
    }

    std::string error;
    auto desc = Parse(desc_str, provider, error);
    if (!desc) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, error);
    }
    if (!desc->IsRange()) {
        range.first = 0;
        range.second = 0;
    }
    std::vector<CScript> ret;
    for (int i = range.first; i <= range.second; ++i) {
        std::vector<CScript> scripts;
        if (!desc->Expand(i, provider, scripts, provider)) {
            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Cannot derive script without private keys: '%s'", desc_str));
        }
        if (expand_priv) {
            desc->ExpandPrivate(/*pos=*/i, provider, /*out=*/provider);
        }
        std::move(scripts.begin(), scripts.end(), std::back_inserter(ret));
    }
    return ret;
}

/** Convert a vector of bilingual strings to a UniValue::VARR containing their original untranslated values. */
[[nodiscard]] static UniValue BilingualStringsToUniValue(const std::vector<bilingual_str>& bilingual_strings)
{
    CHECK_NONFATAL(!bilingual_strings.empty());
    UniValue result{UniValue::VARR};
    for (const auto& s : bilingual_strings) {
        result.push_back(s.original);
    }
    return result;
}

void PushWarnings(const UniValue& warnings, UniValue& obj)
{
    if (warnings.empty()) return;
    obj.pushKV("warnings", warnings);
}

void PushWarnings(const std::vector<bilingual_str>& warnings, UniValue& obj)
{
    if (warnings.empty()) return;
    obj.pushKV("warnings", BilingualStringsToUniValue(warnings));
}