rippled/include/xrpl/protocol/STObject.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 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.
*/
//==============================================================================

#ifndef RIPPLE_PROTOCOL_STOBJECT_H_INCLUDED
#define RIPPLE_PROTOCOL_STOBJECT_H_INCLUDED

#include <xrpl/basics/CountedObject.h>
#include <xrpl/basics/Slice.h>
#include <xrpl/basics/chrono.h>
#include <xrpl/basics/contract.h>
#include <xrpl/beast/utility/instrumentation.h>
#include <xrpl/protocol/FeeUnits.h>
#include <xrpl/protocol/HashPrefix.h>
#include <xrpl/protocol/SOTemplate.h>
#include <xrpl/protocol/STAmount.h>
#include <xrpl/protocol/STBase.h>
#include <xrpl/protocol/STCurrency.h>
#include <xrpl/protocol/STIssue.h>
#include <xrpl/protocol/STPathSet.h>
#include <xrpl/protocol/STVector256.h>
#include <xrpl/protocol/detail/STVar.h>

#include <boost/iterator/transform_iterator.hpp>

#include <optional>
#include <stdexcept>
#include <type_traits>
#include <utility>

namespace ripple {

class STArray;

inline void
throwFieldNotFound(SField const& field)
{
    Throw<std::runtime_error>("Field not found: " + field.getName());
}

class STObject : public STBase, public CountedObject<STObject>
{
    // Proxy value for a STBase derived class
    template <class T>
    class Proxy;
    template <class T>
    class ValueProxy;
    template <class T>
    class OptionalProxy;

    struct Transform
    {
        explicit Transform() = default;

        using argument_type = detail::STVar;
        using result_type = STBase;

        STBase const&
        operator()(detail::STVar const& e) const;
    };

    using list_type = std::vector<detail::STVar>;

    list_type v_;
    SOTemplate const* mType;

public:
    using iterator = boost::
        transform_iterator<Transform, STObject::list_type::const_iterator>;

    virtual ~STObject() = default;
    STObject(STObject const&) = default;

    template <typename F>
    STObject(SOTemplate const& type, SField const& name, F&& f)
        : STObject(type, name)
    {
        f(*this);
    }

    STObject&
    operator=(STObject const&) = default;
    STObject(STObject&&);
    STObject&
    operator=(STObject&& other);

    STObject(const SOTemplate& type, SField const& name);
    STObject(const SOTemplate& type, SerialIter& sit, SField const& name);
    STObject(SerialIter& sit, SField const& name, int depth = 0);
    STObject(SerialIter&& sit, SField const& name);
    explicit STObject(SField const& name);

    static STObject
    makeInnerObject(SField const& name);

    iterator
    begin() const;

    iterator
    end() const;

    bool
    empty() const;

    void
    reserve(std::size_t n);

    void
    applyTemplate(const SOTemplate& type);

    void
    applyTemplateFromSField(SField const&);

    bool
    isFree() const;

    void
    set(const SOTemplate&);

    bool
    set(SerialIter& u, int depth = 0);

    SerializedTypeID
    getSType() const override;

    bool
    isEquivalent(const STBase& t) const override;

    bool
    isDefault() const override;

    void
    add(Serializer& s) const override;

    std::string
    getFullText() const override;

    std::string
    getText() const override;

    // TODO(tom): options should be an enum.
    Json::Value
    getJson(JsonOptions options) const override;

    void
    addWithoutSigningFields(Serializer& s) const;

    Serializer
    getSerializer() const;

    template <class... Args>
    std::size_t
    emplace_back(Args&&... args);

    int
    getCount() const;

    bool setFlag(std::uint32_t);
    bool clearFlag(std::uint32_t);
    bool isFlag(std::uint32_t) const;

    std::uint32_t
    getFlags() const;

    uint256
    getHash(HashPrefix prefix) const;

    uint256
    getSigningHash(HashPrefix prefix) const;

    const STBase&
    peekAtIndex(int offset) const;

    STBase&
    getIndex(int offset);

    const STBase*
    peekAtPIndex(int offset) const;

    STBase*
    getPIndex(int offset);

    int
    getFieldIndex(SField const& field) const;

    SField const&
    getFieldSType(int index) const;

    const STBase&
    peekAtField(SField const& field) const;

    STBase&
    getField(SField const& field);

    const STBase*
    peekAtPField(SField const& field) const;

    STBase*
    getPField(SField const& field, bool createOkay = false);

    // these throw if the field type doesn't match, or return default values
    // if the field is optional but not present
    unsigned char
    getFieldU8(SField const& field) const;
    std::uint16_t
    getFieldU16(SField const& field) const;
    std::uint32_t
    getFieldU32(SField const& field) const;
    std::uint64_t
    getFieldU64(SField const& field) const;
    uint128
    getFieldH128(SField const& field) const;

    uint160
    getFieldH160(SField const& field) const;
    uint192
    getFieldH192(SField const& field) const;
    uint256
    getFieldH256(SField const& field) const;
    AccountID
    getAccountID(SField const& field) const;

    Blob
    getFieldVL(SField const& field) const;
    STAmount const&
    getFieldAmount(SField const& field) const;
    STPathSet const&
    getFieldPathSet(SField const& field) const;
    const STVector256&
    getFieldV256(SField const& field) const;
    const STArray&
    getFieldArray(SField const& field) const;
    const STCurrency&
    getFieldCurrency(SField const& field) const;
    STNumber const&
    getFieldNumber(SField const& field) const;

    /** Get the value of a field.
        @param A TypedField built from an SField value representing the desired
            object field. In typical use, the TypedField will be implicitly
            constructed.
        @return The value of the specified field.
        @throws STObject::FieldErr if the field is not present.
    */
    template <class T>
    typename T::value_type
    operator[](TypedField<T> const& f) const;

    /** Get the value of a field as a std::optional

        @param An OptionaledField built from an SField value representing the
           desired object field. In typical use, the OptionaledField will be
           constructed by using the ~ operator on an SField.
        @return std::nullopt if the field is not present, else the value of
           the specified field.
    */
    template <class T>
    std::optional<std::decay_t<typename T::value_type>>
    operator[](OptionaledField<T> const& of) const;

    /** Get a modifiable field value.
        @param A TypedField built from an SField value representing the desired
            object field. In typical use, the TypedField will be implicitly
            constructed.
        @return A modifiable reference to the value of the specified field.
        @throws STObject::FieldErr if the field is not present.
    */
    template <class T>
    ValueProxy<T>
    operator[](TypedField<T> const& f);

    /** Return a modifiable field value as std::optional

        @param An OptionaledField built from an SField value representing the
            desired object field. In typical use, the OptionaledField will be
            constructed by using the ~ operator on an SField.
        @return Transparent proxy object to an `optional` holding a modifiable
            reference to the value of the specified field. Returns
            std::nullopt if the field is not present.
    */
    template <class T>
    OptionalProxy<T>
    operator[](OptionaledField<T> const& of);

    /** Get the value of a field.
        @param A TypedField built from an SField value representing the desired
            object field. In typical use, the TypedField will be implicitly
            constructed.
        @return The value of the specified field.
        @throws STObject::FieldErr if the field is not present.
    */
    template <class T>
    typename T::value_type
    at(TypedField<T> const& f) const;

    /** Get the value of a field as std::optional

        @param An OptionaledField built from an SField value representing the
           desired object field. In typical use, the OptionaledField will be
           constructed by using the ~ operator on an SField.
        @return std::nullopt if the field is not present, else the value of
           the specified field.
    */
    template <class T>
    std::optional<std::decay_t<typename T::value_type>>
    at(OptionaledField<T> const& of) const;

    /** Get a modifiable field value.
        @param A TypedField built from an SField value representing the desired
            object field. In typical use, the TypedField will be implicitly
            constructed.
        @return A modifiable reference to the value of the specified field.
        @throws STObject::FieldErr if the field is not present.
    */
    template <class T>
    ValueProxy<T>
    at(TypedField<T> const& f);

    /** Return a modifiable field value as std::optional

        @param An OptionaledField built from an SField value representing the
            desired object field. In typical use, the OptionaledField will be
            constructed by using the ~ operator on an SField.
        @return Transparent proxy object to an `optional` holding a modifiable
            reference to the value of the specified field. Returns
            std::nullopt if the field is not present.
    */
    template <class T>
    OptionalProxy<T>
    at(OptionaledField<T> const& of);

    /** Set a field.
        if the field already exists, it is replaced.
    */
    void
    set(std::unique_ptr<STBase> v);

    void
    set(STBase&& v);

    void
    setFieldU8(SField const& field, unsigned char);
    void
    setFieldU16(SField const& field, std::uint16_t);
    void
    setFieldU32(SField const& field, std::uint32_t);
    void
    setFieldU64(SField const& field, std::uint64_t);
    void
    setFieldH128(SField const& field, uint128 const&);
    void
    setFieldH256(SField const& field, uint256 const&);
    void
    setFieldVL(SField const& field, Blob const&);
    void
    setFieldVL(SField const& field, Slice const&);

    void
    setAccountID(SField const& field, AccountID const&);

    void
    setFieldAmount(SField const& field, STAmount const&);
    void
    setFieldIssue(SField const& field, STIssue const&);
    void
    setFieldCurrency(SField const& field, STCurrency const&);
    void
    setFieldNumber(SField const& field, STNumber const&);
    void
    setFieldPathSet(SField const& field, STPathSet const&);
    void
    setFieldV256(SField const& field, STVector256 const& v);
    void
    setFieldArray(SField const& field, STArray const& v);

    template <class Tag>
    void
    setFieldH160(SField const& field, base_uint<160, Tag> const& v);

    STObject&
    peekFieldObject(SField const& field);
    STArray&
    peekFieldArray(SField const& field);

    bool
    isFieldPresent(SField const& field) const;
    STBase*
    makeFieldPresent(SField const& field);
    void
    makeFieldAbsent(SField const& field);
    bool
    delField(SField const& field);
    void
    delField(int index);

    bool
    hasMatchingEntry(const STBase&);

    bool
    operator==(const STObject& o) const;
    bool
    operator!=(const STObject& o) const;

    class FieldErr;

private:
    enum WhichFields : bool {
        // These values are carefully chosen to do the right thing if passed
        // to SField::shouldInclude (bool)
        omitSigningFields = false,
        withAllFields = true
    };

    void
    add(Serializer& s, WhichFields whichFields) const;

    // Sort the entries in an STObject into the order that they will be
    // serialized.  Note: they are not sorted into pointer value order, they
    // are sorted by SField::fieldCode.
    static std::vector<STBase const*>
    getSortedFields(STObject const& objToSort, WhichFields whichFields);

    // Implementation for getting (most) fields that return by value.
    //
    // The remove_cv and remove_reference are necessitated by the STBitString
    // types.  Their value() returns by const ref.  We return those types
    // by value.
    template <
        typename T,
        typename V = typename std::remove_cv<typename std::remove_reference<
            decltype(std::declval<T>().value())>::type>::type>
    V
    getFieldByValue(SField const& field) const;

    // Implementations for getting (most) fields that return by const reference.
    //
    // If an absent optional field is deserialized we don't have anything
    // obvious to return.  So we insist on having the call provide an
    // 'empty' value we return in that circumstance.
    template <typename T, typename V>
    V const&
    getFieldByConstRef(SField const& field, V const& empty) const;

    // Implementation for setting most fields with a setValue() method.
    template <typename T, typename V>
    void
    setFieldUsingSetValue(SField const& field, V value);

    // Implementation for setting fields using assignment
    template <typename T>
    void
    setFieldUsingAssignment(SField const& field, T const& value);

    // Implementation for peeking STObjects and STArrays
    template <typename T>
    T&
    peekField(SField const& field);

    STBase*
    copy(std::size_t n, void* buf) const override;
    STBase*
    move(std::size_t n, void* buf) override;

    friend class detail::STVar;
};

//------------------------------------------------------------------------------

template <class T>
class STObject::Proxy
{
protected:
    using value_type = typename T::value_type;

    STObject* st_;
    SOEStyle style_;
    TypedField<T> const* f_;

    Proxy(Proxy const&) = default;

    Proxy(STObject* st, TypedField<T> const* f);

    value_type
    value() const;

    T const*
    find() const;

    template <class U>
    void
    assign(U&& u);
};

// Constraint += and -= ValueProxy operators
// to value types that support arithmetic operations
template <typename U>
concept IsArithmetic = std::is_arithmetic_v<U> || std::is_same_v<U, STAmount>;

template <class T>
class STObject::ValueProxy : private Proxy<T>
{
private:
    using value_type = typename T::value_type;

public:
    ValueProxy(ValueProxy const&) = default;
    ValueProxy&
    operator=(ValueProxy const&) = delete;

    template <class U>
    std::enable_if_t<std::is_assignable_v<T, U>, ValueProxy&>
    operator=(U&& u);

    // Convenience operators for value types supporting
    // arithmetic operations
    template <IsArithmetic U>
    ValueProxy&
    operator+=(U const& u);

    template <IsArithmetic U>
    ValueProxy&
    operator-=(U const& u);

    operator value_type() const;

private:
    friend class STObject;

    ValueProxy(STObject* st, TypedField<T> const* f);
};

template <class T>
class STObject::OptionalProxy : private Proxy<T>
{
private:
    using value_type = typename T::value_type;

    using optional_type = std::optional<typename std::decay<value_type>::type>;

public:
    OptionalProxy(OptionalProxy const&) = default;
    OptionalProxy&
    operator=(OptionalProxy const&) = delete;

    /** Returns `true` if the field is set.

        Fields with soeDEFAULT and set to the
        default value will return `true`
    */
    explicit
    operator bool() const noexcept;

    /** Return the contained value

        Throws:

            STObject::FieldErr if !engaged()
    */
    value_type
    operator*() const;

    operator optional_type() const;

    /** Explicit conversion to std::optional */
    optional_type
    operator~() const;

    friend bool
    operator==(OptionalProxy const& lhs, std::nullopt_t) noexcept
    {
        return !lhs.engaged();
    }

    friend bool
    operator==(std::nullopt_t, OptionalProxy const& rhs) noexcept
    {
        return rhs == std::nullopt;
    }

    friend bool
    operator==(OptionalProxy const& lhs, optional_type const& rhs) noexcept
    {
        if (!lhs.engaged())
            return !rhs;
        if (!rhs)
            return false;
        return *lhs == *rhs;
    }

    friend bool
    operator==(optional_type const& lhs, OptionalProxy const& rhs) noexcept
    {
        return rhs == lhs;
    }

    friend bool
    operator==(OptionalProxy const& lhs, OptionalProxy const& rhs) noexcept
    {
        if (lhs.engaged() != rhs.engaged())
            return false;
        return !lhs.engaged() || *lhs == *rhs;
    }

    friend bool
    operator!=(OptionalProxy const& lhs, std::nullopt_t) noexcept
    {
        return !(lhs == std::nullopt);
    }

    friend bool
    operator!=(std::nullopt_t, OptionalProxy const& rhs) noexcept
    {
        return !(rhs == std::nullopt);
    }

    friend bool
    operator!=(OptionalProxy const& lhs, optional_type const& rhs) noexcept
    {
        return !(lhs == rhs);
    }

    friend bool
    operator!=(optional_type const& lhs, OptionalProxy const& rhs) noexcept
    {
        return !(lhs == rhs);
    }

    friend bool
    operator!=(OptionalProxy const& lhs, OptionalProxy const& rhs) noexcept
    {
        return !(lhs == rhs);
    }

    // Emulate std::optional::value_or
    value_type
    value_or(value_type val) const;

    OptionalProxy&
    operator=(std::nullopt_t const&);
    OptionalProxy&
    operator=(optional_type&& v);
    OptionalProxy&
    operator=(optional_type const& v);

    template <class U>
    std::enable_if_t<std::is_assignable_v<T, U>, OptionalProxy&>
    operator=(U&& u);

private:
    friend class STObject;

    OptionalProxy(STObject* st, TypedField<T> const* f);

    bool
    engaged() const noexcept;

    void
    disengage();

    optional_type
    optional_value() const;
};

class STObject::FieldErr : public std::runtime_error
{
    using std::runtime_error::runtime_error;
};

template <class T>
STObject::Proxy<T>::Proxy(STObject* st, TypedField<T> const* f) : st_(st), f_(f)
{
    if (st_->mType)
    {
        // STObject has associated template
        if (!st_->peekAtPField(*f_))
            Throw<STObject::FieldErr>(
                "Template field error '" + this->f_->getName() + "'");
        style_ = st_->mType->style(*f_);
    }
    else
    {
        style_ = soeINVALID;
    }
}

template <class T>
auto
STObject::Proxy<T>::value() const -> value_type
{
    auto const t = find();
    if (t)
        return t->value();
    if (style_ == soeINVALID)
    {
        Throw<STObject::FieldErr>("Value requested from invalid STObject.");
    }
    if (style_ != soeDEFAULT)
    {
        Throw<STObject::FieldErr>(
            "Missing field '" + this->f_->getName() + "'");
    }
    return value_type{};
}

template <class T>
inline T const*
STObject::Proxy<T>::find() const
{
    return dynamic_cast<T const*>(st_->peekAtPField(*f_));
}

template <class T>
template <class U>
void
STObject::Proxy<T>::assign(U&& u)
{
    if (style_ == soeDEFAULT && u == value_type{})
    {
        st_->makeFieldAbsent(*f_);
        return;
    }
    T* t;
    if (style_ == soeINVALID)
        t = dynamic_cast<T*>(st_->getPField(*f_, true));
    else
        t = dynamic_cast<T*>(st_->makeFieldPresent(*f_));
    XRPL_ASSERT(t, "ripple::STObject::Proxy::assign : type cast succeeded");
    *t = std::forward<U>(u);
}

//------------------------------------------------------------------------------

template <class T>
template <class U>
std::enable_if_t<std::is_assignable_v<T, U>, STObject::ValueProxy<T>&>
STObject::ValueProxy<T>::operator=(U&& u)
{
    this->assign(std::forward<U>(u));
    return *this;
}

template <typename T>
template <IsArithmetic U>
STObject::ValueProxy<T>&
STObject::ValueProxy<T>::operator+=(U const& u)
{
    this->assign(this->value() + u);
    return *this;
}

template <class T>
template <IsArithmetic U>
STObject::ValueProxy<T>&
STObject::ValueProxy<T>::operator-=(U const& u)
{
    this->assign(this->value() - u);
    return *this;
}

template <class T>
STObject::ValueProxy<T>::operator value_type() const
{
    return this->value();
}

template <class T>
STObject::ValueProxy<T>::ValueProxy(STObject* st, TypedField<T> const* f)
    : Proxy<T>(st, f)
{
}

//------------------------------------------------------------------------------

template <class T>
STObject::OptionalProxy<T>::operator bool() const noexcept
{
    return engaged();
}

template <class T>
auto
STObject::OptionalProxy<T>::operator*() const -> value_type
{
    return this->value();
}

template <class T>
STObject::OptionalProxy<T>::operator typename STObject::OptionalProxy<
    T>::optional_type() const
{
    return optional_value();
}

template <class T>
typename STObject::OptionalProxy<T>::optional_type
STObject::OptionalProxy<T>::operator~() const
{
    return optional_value();
}

template <class T>
auto
STObject::OptionalProxy<T>::operator=(std::nullopt_t const&) -> OptionalProxy&
{
    disengage();
    return *this;
}

template <class T>
auto
STObject::OptionalProxy<T>::operator=(optional_type&& v) -> OptionalProxy&
{
    if (v)
        this->assign(std::move(*v));
    else
        disengage();
    return *this;
}

template <class T>
auto
STObject::OptionalProxy<T>::operator=(optional_type const& v) -> OptionalProxy&
{
    if (v)
        this->assign(*v);
    else
        disengage();
    return *this;
}

template <class T>
template <class U>
std::enable_if_t<std::is_assignable_v<T, U>, STObject::OptionalProxy<T>&>
STObject::OptionalProxy<T>::operator=(U&& u)
{
    this->assign(std::forward<U>(u));
    return *this;
}

template <class T>
STObject::OptionalProxy<T>::OptionalProxy(STObject* st, TypedField<T> const* f)
    : Proxy<T>(st, f)
{
}

template <class T>
bool
STObject::OptionalProxy<T>::engaged() const noexcept
{
    return this->style_ == soeDEFAULT || this->find() != nullptr;
}

template <class T>
void
STObject::OptionalProxy<T>::disengage()
{
    if (this->style_ == soeREQUIRED || this->style_ == soeDEFAULT)
        Throw<STObject::FieldErr>(
            "Template field error '" + this->f_->getName() + "'");
    if (this->style_ == soeINVALID)
        this->st_->delField(*this->f_);
    else
        this->st_->makeFieldAbsent(*this->f_);
}

template <class T>
auto
STObject::OptionalProxy<T>::optional_value() const -> optional_type
{
    if (!engaged())
        return std::nullopt;
    return this->value();
}

template <class T>
typename STObject::OptionalProxy<T>::value_type
STObject::OptionalProxy<T>::value_or(value_type val) const
{
    return engaged() ? this->value() : val;
}

//------------------------------------------------------------------------------

inline STBase const&
STObject::Transform::operator()(detail::STVar const& e) const
{
    return e.get();
}

//------------------------------------------------------------------------------

inline STObject::STObject(SerialIter&& sit, SField const& name)
    : STObject(sit, name)
{
}

inline STObject::iterator
STObject::begin() const
{
    return iterator(v_.begin());
}

inline STObject::iterator
STObject::end() const
{
    return iterator(v_.end());
}

inline bool
STObject::empty() const
{
    return v_.empty();
}

inline void
STObject::reserve(std::size_t n)
{
    v_.reserve(n);
}

inline bool
STObject::isFree() const
{
    return mType == nullptr;
}

inline void
STObject::addWithoutSigningFields(Serializer& s) const
{
    add(s, omitSigningFields);
}

// VFALCO NOTE does this return an expensive copy of an object with a
//             dynamic buffer?
// VFALCO TODO Remove this function and fix the few callers.
inline Serializer
STObject::getSerializer() const
{
    Serializer s;
    add(s, withAllFields);
    return s;
}

template <class... Args>
inline std::size_t
STObject::emplace_back(Args&&... args)
{
    v_.emplace_back(std::forward<Args>(args)...);
    return v_.size() - 1;
}

inline int
STObject::getCount() const
{
    return v_.size();
}

inline const STBase&
STObject::peekAtIndex(int offset) const
{
    return v_[offset].get();
}

inline STBase&
STObject::getIndex(int offset)
{
    return v_[offset].get();
}

inline const STBase*
STObject::peekAtPIndex(int offset) const
{
    return &v_[offset].get();
}

inline STBase*
STObject::getPIndex(int offset)
{
    return &v_[offset].get();
}

template <class T>
typename T::value_type
STObject::operator[](TypedField<T> const& f) const
{
    return at(f);
}

template <class T>
std::optional<std::decay_t<typename T::value_type>>
STObject::operator[](OptionaledField<T> const& of) const
{
    return at(of);
}

template <class T>
inline auto
STObject::operator[](TypedField<T> const& f) -> ValueProxy<T>
{
    return at(f);
}

template <class T>
inline auto
STObject::operator[](OptionaledField<T> const& of) -> OptionalProxy<T>
{
    return at(of);
}

template <class T>
typename T::value_type
STObject::at(TypedField<T> const& f) const
{
    auto const b = peekAtPField(f);
    if (!b)
        // This is a free object (no constraints)
        // with no template
        Throw<STObject::FieldErr>("Missing field: " + f.getName());

    if (auto const u = dynamic_cast<T const*>(b))
        return u->value();

    XRPL_ASSERT(
        mType,
        "ripple::STObject::at(TypedField auto) : field template non-null");
    XRPL_ASSERT(
        b->getSType() == STI_NOTPRESENT,
        "ripple::STObject::at(TypedField auto) : type not present");

    if (mType->style(f) == soeOPTIONAL)
        Throw<STObject::FieldErr>("Missing optional field: " + f.getName());

    XRPL_ASSERT(
        mType->style(f) == soeDEFAULT,
        "ripple::STObject::at(TypedField auto) : template style is default");

    // Used to help handle the case where value_type is a const reference,
    // otherwise we would return the address of a temporary.
    static std::decay_t<typename T::value_type> const dv{};
    return dv;
}

template <class T>
std::optional<std::decay_t<typename T::value_type>>
STObject::at(OptionaledField<T> const& of) const
{
    auto const b = peekAtPField(*of.f);
    if (!b)
        return std::nullopt;
    auto const u = dynamic_cast<T const*>(b);
    if (!u)
    {
        XRPL_ASSERT(
            mType,
            "ripple::STObject::at(OptionaledField auto) : field template "
            "non-null");
        XRPL_ASSERT(
            b->getSType() == STI_NOTPRESENT,
            "ripple::STObject::at(OptionaledField auto) : type not present");
        if (mType->style(*of.f) == soeOPTIONAL)
            return std::nullopt;
        XRPL_ASSERT(
            mType->style(*of.f) == soeDEFAULT,
            "ripple::STObject::at(OptionaledField auto) : template style is "
            "default");
        return typename T::value_type{};
    }
    return u->value();
}

template <class T>
inline auto
STObject::at(TypedField<T> const& f) -> ValueProxy<T>
{
    return ValueProxy<T>(this, &f);
}

template <class T>
inline auto
STObject::at(OptionaledField<T> const& of) -> OptionalProxy<T>
{
    return OptionalProxy<T>(this, of.f);
}

template <class Tag>
void
STObject::setFieldH160(SField const& field, base_uint<160, Tag> const& v)
{
    STBase* rf = getPField(field, true);

    if (!rf)
        throwFieldNotFound(field);

    if (rf->getSType() == STI_NOTPRESENT)
        rf = makeFieldPresent(field);

    using Bits = STBitString<160>;
    if (auto cf = dynamic_cast<Bits*>(rf))
        cf->setValue(v);
    else
        Throw<std::runtime_error>("Wrong field type");
}

inline bool
STObject::operator!=(const STObject& o) const
{
    return !(*this == o);
}

template <typename T, typename V>
V
STObject::getFieldByValue(SField const& field) const
{
    const STBase* rf = peekAtPField(field);

    if (!rf)
        throwFieldNotFound(field);

    SerializedTypeID id = rf->getSType();

    if (id == STI_NOTPRESENT)
        return V();  // optional field not present

    const T* cf = dynamic_cast<const T*>(rf);

    if (!cf)
        Throw<std::runtime_error>("Wrong field type");

    return cf->value();
}

// Implementations for getting (most) fields that return by const reference.
//
// If an absent optional field is deserialized we don't have anything
// obvious to return.  So we insist on having the call provide an
// 'empty' value we return in that circumstance.
template <typename T, typename V>
V const&
STObject::getFieldByConstRef(SField const& field, V const& empty) const
{
    const STBase* rf = peekAtPField(field);

    if (!rf)
        throwFieldNotFound(field);

    SerializedTypeID id = rf->getSType();

    if (id == STI_NOTPRESENT)
        return empty;  // optional field not present

    const T* cf = dynamic_cast<const T*>(rf);

    if (!cf)
        Throw<std::runtime_error>("Wrong field type");

    return *cf;
}

// Implementation for setting most fields with a setValue() method.
template <typename T, typename V>
void
STObject::setFieldUsingSetValue(SField const& field, V value)
{
    static_assert(!std::is_lvalue_reference<V>::value, "");

    STBase* rf = getPField(field, true);

    if (!rf)
        throwFieldNotFound(field);

    if (rf->getSType() == STI_NOTPRESENT)
        rf = makeFieldPresent(field);

    T* cf = dynamic_cast<T*>(rf);

    if (!cf)
        Throw<std::runtime_error>("Wrong field type");

    cf->setValue(std::move(value));
}

// Implementation for setting fields using assignment
template <typename T>
void
STObject::setFieldUsingAssignment(SField const& field, T const& value)
{
    STBase* rf = getPField(field, true);

    if (!rf)
        throwFieldNotFound(field);

    if (rf->getSType() == STI_NOTPRESENT)
        rf = makeFieldPresent(field);

    T* cf = dynamic_cast<T*>(rf);

    if (!cf)
        Throw<std::runtime_error>("Wrong field type");

    (*cf) = value;
}

// Implementation for peeking STObjects and STArrays
template <typename T>
T&
STObject::peekField(SField const& field)
{
    STBase* rf = getPField(field, true);

    if (!rf)
        throwFieldNotFound(field);

    if (rf->getSType() == STI_NOTPRESENT)
        rf = makeFieldPresent(field);

    T* cf = dynamic_cast<T*>(rf);

    if (!cf)
        Throw<std::runtime_error>("Wrong field type");

    return *cf;
}

}  // namespace ripple

#endif