XRPAmount.h

#pragma once
 
#include <xrpl/basics/Number.h>
#include <xrpl/basics/contract.h>
#include <xrpl/beast/utility/Zero.h>
#include <xrpl/json/json_forwards.h>
#include <xrpl/json/json_value.h>
#include <xrpl/protocol/Units.h>
 
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/operators.hpp>
 
#include <cstdint>
#include <istream>
#include <limits>
#include <optional>
#include <ostream>
#include <stdexcept>
#include <string>
#include <type_traits>
 
namespace xrpl {
 
class XRPAmount : private boost::totally_ordered<XRPAmount>,
                  private boost::additive<XRPAmount>,
                  private boost::equality_comparable<XRPAmount, std::int64_t>,
                  private boost::additive<XRPAmount, std::int64_t>
{
public:
    using unit_type = unit::dropTag;
    using value_type = std::int64_t;
 
private:
    value_type drops_;
 
public:
    XRPAmount() = default;
    constexpr XRPAmount(XRPAmount const& other) = default;
    constexpr XRPAmount&
    operator=(XRPAmount const& other) = default;
 
    // Round to nearest, even on tie.
    explicit XRPAmount(Number const& x) : XRPAmount(static_cast<value_type>(x))
    {
    }
 
    constexpr XRPAmount(beast::Zero) : drops_(0)
    {
    }
 
    constexpr XRPAmount&
    operator=(beast::Zero)
    {
        drops_ = 0;
        return *this;
    }
 
    constexpr explicit XRPAmount(value_type drops) : drops_(drops)
    {
    }
 
    XRPAmount&
    operator=(value_type drops)
    {
        drops_ = drops;
        return *this;
    }
 
    constexpr XRPAmount
    operator*(value_type const& rhs) const
    {
        return XRPAmount{drops_ * rhs};
    }
 
    friend constexpr XRPAmount
    operator*(value_type lhs, XRPAmount const& rhs)
    {
        // multiplication is commutative
        return rhs * lhs;
    }
 
    XRPAmount&
    operator+=(XRPAmount const& other)
    {
        drops_ += other.drops();
        return *this;
    }
 
    XRPAmount&
    operator-=(XRPAmount const& other)
    {
        drops_ -= other.drops();
        return *this;
    }
 
    XRPAmount&
    operator+=(value_type const& rhs)
    {
        drops_ += rhs;
        return *this;
    }
 
    XRPAmount&
    operator-=(value_type const& rhs)
    {
        drops_ -= rhs;
        return *this;
    }
 
    XRPAmount&
    operator*=(value_type const& rhs)
    {
        drops_ *= rhs;
        return *this;
    }
 
    XRPAmount
    operator-() const
    {
        return XRPAmount{-drops_};
    }
 
    bool
    operator==(XRPAmount const& other) const
    {
        return drops_ == other.drops_;
    }
 
    bool
    operator==(value_type other) const
    {
        return drops_ == other;
    }
 
    bool
    operator<(XRPAmount const& other) const
    {
        return drops_ < other.drops_;
    }

    explicit constexpr
    operator bool() const noexcept
    {
        return drops_ != 0;
    }
 
    operator Number() const noexcept
    {
        return drops();
    }

    [[nodiscard]] constexpr int
    signum() const noexcept
    {
        if (drops_ < 0)
            return -1;
        return (drops_ != 0) ? 1 : 0;
    }

    [[nodiscard]] constexpr value_type
    drops() const
    {
        return drops_;
    }
 
    [[nodiscard]] constexpr double
    decimalXRP() const;
 
    template <class Dest>
    [[nodiscard]] std::optional<Dest>
    dropsAs() const
    {
        if ((drops_ > std::numeric_limits<Dest>::max()) ||
            (!std::numeric_limits<Dest>::is_signed && drops_ < 0) ||
            (std::numeric_limits<Dest>::is_signed && drops_ < std::numeric_limits<Dest>::lowest()))
        {
            return std::nullopt;
        }
        return static_cast<Dest>(drops_);
    }
 
    template <class Dest>
    Dest
    dropsAs(Dest defaultValue) const
    {
        return dropsAs<Dest>().value_or(defaultValue);
    }
 
    template <class Dest>
    [[nodiscard]] Dest
    dropsAs(XRPAmount defaultValue) const
    {
        return dropsAs<Dest>().value_or(defaultValue.drops());
    }
 
    /* Clips a 64-bit value to a 32-bit JSON number. It is only used
     * in contexts that don't expect the value to ever approach
     * the 32-bit limits (i.e. fees and reserves).
     */
    [[nodiscard]] json::Value
    jsonClipped() const
    {
        static_assert(
            std::is_signed_v<value_type> && std::is_integral_v<value_type>,
            "Expected XRPAmount to be a signed integral type");
 
        constexpr auto kMin = std::numeric_limits<json::Int>::min();
        constexpr auto kMax = std::numeric_limits<json::Int>::max();
 
        if (drops_ < kMin)
            return kMin;
        if (drops_ > kMax)
            return kMax;
        return static_cast<json::Int>(drops_);
    }

    [[nodiscard]] constexpr value_type
    value() const
    {
        return drops_;
    }
 
    friend std::istream&
    operator>>(std::istream& s, XRPAmount& val)
    {
        s >> val.drops_;
        return s;
    }
 
    static XRPAmount
    minPositiveAmount()
    {
        return XRPAmount{1};
    }
};

constexpr XRPAmount kDropsPerXrp{1'000'000};
 
constexpr double
XRPAmount::decimalXRP() const
{
    return static_cast<double>(drops_) / kDropsPerXrp.drops();
}
 
// Output XRPAmount as just the drops value.
template <class Char, class Traits>
std::basic_ostream<Char, Traits>&
operator<<(std::basic_ostream<Char, Traits>& os, XRPAmount const& q)
{
    return os << q.drops();
}
 
inline std::string
to_string(XRPAmount const& amount)
{
    return std::to_string(amount.drops());
}
 
inline XRPAmount
mulRatio(XRPAmount const& amt, std::uint32_t num, std::uint32_t den, bool roundUp)
{
    using namespace boost::multiprecision;
 
    if (den == 0u)
        Throw<std::runtime_error>("division by zero");
 
    int128_t const amt128(amt.drops());
    auto const neg = amt.drops() < 0;
    auto const m = amt128 * num;
    auto r = m / den;
    if (m % den)
    {
        if (!neg && roundUp)
            r += 1;
        if (neg && !roundUp)
            r -= 1;
    }
    if (r > std::numeric_limits<XRPAmount::value_type>::max())
        Throw<std::overflow_error>("XRP mulRatio overflow");
    return XRPAmount(r.convert_to<XRPAmount::value_type>());
}
 
}  // namespace xrpl