wownero 0.1.2

// Rust Wownero Library
// Written in 2021-2022 by
//   Monero Rust Contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//

//! Amounts, denominations, and errors types and arithmetic.
//!
//! This implementation is based on
//! [`rust-bitcoin`](https://github.com/rust-bitcoin/rust-bitcoin/blob/20f1543f79066886b3ae12fff4f5bb58dd8cc1ab/src/util/amount.rs)
//! `Amount` and `SignedAmount` implementations.
//!

use std::cmp::Ordering;
use std::default;
use std::fmt::{self, Write};
use std::ops;
use std::str::FromStr;

use thiserror::Error;

/// A set of denominations in which amounts can be expressed.
#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
pub enum Denomination {
    /// WOW
    Wownero,
    /// Very wow
    Verywow,
    /// Much wow
    Muchwow,
    /// Such wow
    Suchwow,
    /// Dust
    Dust,
}

impl Denomination {
    /// The number of decimal places more than a Dust.
    fn precision(self) -> i32 {
        match self {
            Denomination::Wownero => -11,
            Denomination::Verywow => -8,
            Denomination::Muchwow => -5,
            Denomination::Suchwow => -2,
            Denomination::Dust => 0,
        }
    }
}

impl fmt::Display for Denomination {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(match *self {
            Denomination::Wownero => "WOW",
            Denomination::Verywow => "Verywow",
            Denomination::Muchwow => "Muchwow",
            Denomination::Suchwow => "Suchwow",
            Denomination::Dust => "Dust",
        })
    }
}

impl FromStr for Denomination {
    type Err = ParsingError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "WOW" => Ok(Denomination::Wownero),
            "Verywow" => Ok(Denomination::Verywow),
            "Muchwow" => Ok(Denomination::Muchwow),
            "Suchwow" => Ok(Denomination::Suchwow),
            "Dust" => Ok(Denomination::Dust),
            d => Err(ParsingError::UnknownDenomination(d.to_owned())),
        }
    }
}

/// An error during amount parsing.
#[derive(Error, Debug, Clone, PartialEq, Eq)]
pub enum ParsingError {
    /// Amount is negative.
    #[error("Amount is negative")]
    Negative,
    /// Amount is too big to fit inside the type.
    #[error("Amount is too big to fit inside the type")]
    TooBig,
    /// Amount has higher precision than supported by the type.
    #[error("Amount has higher precision than supported by the type")]
    TooPrecise,
    /// Invalid number format.
    #[error("Invalid number format")]
    InvalidFormat,
    /// Input string was too large.
    #[error("Input string was too large")]
    InputTooLarge,
    /// Invalid character in input.
    #[error("Invalid character in input: {0}")]
    InvalidCharacter(char),
    /// The denomination was unknown.
    #[error("The denomination was unknown: {0}")]
    UnknownDenomination(String),
}

fn is_too_precise(s: &str, precision: usize) -> bool {
    s.contains('.') || precision >= s.len() || s.chars().rev().take(precision).any(|d| d != '0')
}

/// Parse decimal string in the given denomination into a dust value and a bool indicator for a
/// negative amount.
fn parse_signed_to_dust(mut s: &str, denom: Denomination) -> Result<(bool, u64), ParsingError> {
    if s.is_empty() {
        return Err(ParsingError::InvalidFormat);
    }
    if s.len() > 50 {
        return Err(ParsingError::InputTooLarge);
    }

    let is_negative = s.starts_with('-');
    if is_negative {
        if s.len() == 1 {
            return Err(ParsingError::InvalidFormat);
        }
        s = &s[1..];
    }

    let max_decimals = {
        // The difference in precision between native (Dust) and desired denomination.
        let precision_diff = -denom.precision();
        if precision_diff < 0 {
            // If precision diff is negative, this means we are parsing
            // into a less precise amount. That is not allowed unless
            // there are no decimals and the last digits are zeroes as
            // many as the difference in precision.
            let last_n = precision_diff.unsigned_abs() as usize;
            if is_too_precise(s, last_n) {
                return Err(ParsingError::TooPrecise);
            }
            s = &s[0..s.len() - last_n];
            0
        } else {
            precision_diff
        }
    };

    let mut decimals = None;
    let mut value: u64 = 0; // as Dust
    for c in s.chars() {
        match c {
            '0'..='9' => {
                // Do `value = 10 * value + digit`, catching overflows.
                match 10_u64.checked_mul(value) {
                    None => return Err(ParsingError::TooBig),
                    Some(val) => match val.checked_add((c as u8 - b'0') as u64) {
                        None => return Err(ParsingError::TooBig),
                        Some(val) => value = val,
                    },
                }
                // Increment the decimal digit counter if past decimal.
                decimals = match decimals {
                    None => None,
                    Some(d) if d < max_decimals => Some(d + 1),
                    _ => return Err(ParsingError::TooPrecise),
                };
            }
            '.' => match decimals {
                None => decimals = Some(0),
                // Double decimal dot.
                _ => return Err(ParsingError::InvalidFormat),
            },
            c => return Err(ParsingError::InvalidCharacter(c)),
        }
    }

    // Decimally shift left by `max_decimals - decimals`.
    let scale_factor = max_decimals - decimals.unwrap_or(0);
    for _ in 0..scale_factor {
        value = match 10_u64.checked_mul(value) {
            Some(v) => v,
            None => return Err(ParsingError::TooBig),
        };
    }

    Ok((is_negative, value))
}

/// Format the given Dust amount in the given denomination without including the denomination.
fn fmt_dust_in(
    dust: u64,
    negative: bool,
    f: &mut dyn fmt::Write,
    denom: Denomination,
) -> fmt::Result {
    if negative {
        f.write_str("-")?;
    }

    let precision = denom.precision();
    match precision.cmp(&0) {
        Ordering::Greater => {
            // add zeroes in the end
            let width = precision as usize;
            write!(f, "{}{:0width$}", dust, 0, width = width)?;
        }
        Ordering::Less => {
            // need to inject a comma in the number
            let nb_decimals = precision.unsigned_abs() as usize;
            let real = format!("{:0width$}", dust, width = nb_decimals);
            if real.len() == nb_decimals {
                write!(f, "0.{}", &real[real.len() - nb_decimals..])?;
            } else {
                write!(
                    f,
                    "{}.{}",
                    &real[0..(real.len() - nb_decimals)],
                    &real[real.len() - nb_decimals..]
                )?;
            }
        }
        Ordering::Equal => write!(f, "{}", dust)?,
    }
    Ok(())
}

/// Represent an unsigned quantity of Wownero, internally as Dust.
///
/// The [`Amount`] type can be used to express Wownero amounts that supports arithmetic and
/// conversion to various denominations.
///
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Amount(u64);

impl Amount {
    /// The zero amount.
    pub const ZERO: Amount = Amount(0);
    /// Exactly one Dust.
    pub const ONE_DUST: Amount = Amount(1);
    /// Exactly one Wownero.
    pub const ONE_WOW: Amount = Amount(100_000_000_000);

    /// Create an [`Amount`] with Dust precision and the given number of Dust.
    pub fn from_dust(dust: u64) -> Amount {
        Amount(dust)
    }

    /// Get the number of Dusts in this [`Amount`].
    pub fn as_dust(self) -> u64 {
        self.0
    }

    /// The maximum value of an [`Amount`].
    pub fn max_value() -> Amount {
        Amount(u64::max_value())
    }

    /// The minimum value of an [`Amount`].
    pub fn min_value() -> Amount {
        Amount(u64::min_value())
    }

    /// Convert from a value expressing Wowneros to an [`Amount`].
    pub fn from_wow(wow: f64) -> Result<Amount, ParsingError> {
        Amount::from_float_in(wow, Denomination::Wownero)
    }

    /// Parse a decimal string as a value in the given denomination.
    ///
    /// Note: This only parses the value string. If you want to parse a value with denomination,
    /// use [`FromStr`].
    pub fn from_str_in(s: &str, denom: Denomination) -> Result<Amount, ParsingError> {
        let (negative, dust) = parse_signed_to_dust(s, denom)?;
        if negative {
            return Err(ParsingError::Negative);
        }
        if dust > i64::max_value() as u64 {
            return Err(ParsingError::TooBig);
        }
        Ok(Amount::from_dust(dust))
    }

    /// Parses amounts with denomination suffix like they are produced with
    /// `to_string_with_denomination` or with [`fmt::Display`]. If you want to parse only the
    /// amount without the denomination, use `from_str_in`.
    pub fn from_str_with_denomination(s: &str) -> Result<Amount, ParsingError> {
        let mut split = s.splitn(3, ' ');
        let amt_str = split.next().unwrap();
        let denom_str = split.next().ok_or(ParsingError::InvalidFormat)?;
        if split.next().is_some() {
            return Err(ParsingError::InvalidFormat);
        }

        Amount::from_str_in(amt_str, denom_str.parse()?)
    }

    /// Express this [`Amount`] as a floating-point value in the given denomination.
    ///
    /// Please be aware of the risk of using floating-point numbers.
    pub fn to_float_in(self, denom: Denomination) -> f64 {
        f64::from_str(&self.to_string_in(denom)).unwrap()
    }

    /// Express this [`Amount`] as a floating-point value in Wownero.
    ///
    /// Equivalent to `to_float_in(Denomination::Wownero)`.
    ///
    /// Please be aware of the risk of using floating-point numbers.
    pub fn as_wow(self) -> f64 {
        self.to_float_in(Denomination::Wownero)
    }

    /// Convert this [`Amount`] in floating-point notation with a given denomination. Can return
    /// error if the amount is too big, too precise or negative.
    ///
    /// Please be aware of the risk of using floating-point numbers.
    pub fn from_float_in(value: f64, denom: Denomination) -> Result<Amount, ParsingError> {
        if value < 0.0 {
            return Err(ParsingError::Negative);
        }
        // This is inefficient, but the safest way to deal with this. The parsing logic is safe.
        // Any performance-critical application should not be dealing with floats.
        Amount::from_str_in(&value.to_string(), denom)
    }

    /// Format the value of this [`Amount`] in the given denomination.
    ///
    /// Does not include the denomination.
    pub fn fmt_value_in(self, f: &mut dyn fmt::Write, denom: Denomination) -> fmt::Result {
        fmt_dust_in(self.as_dust(), false, f, denom)
    }

    /// Get a string number of this [`Amount`] in the given denomination.
    ///
    /// Does not include the denomination.
    pub fn to_string_in(self, denom: Denomination) -> String {
        let mut buf = String::new();
        self.fmt_value_in(&mut buf, denom).unwrap();
        buf
    }

    /// Get a formatted string of this [`Amount`] in the given denomination, suffixed with the
    /// abbreviation for the denomination.
    pub fn to_string_with_denomination(self, denom: Denomination) -> String {
        let mut buf = String::new();
        self.fmt_value_in(&mut buf, denom).unwrap();
        write!(buf, " {}", denom).unwrap();
        buf
    }

    // Some arithmetic that doesn't fit in `std::ops` traits.

    /// Checked addition.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_add(self, rhs: Amount) -> Option<Amount> {
        self.0.checked_add(rhs.0).map(Amount)
    }

    /// Checked subtraction.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_sub(self, rhs: Amount) -> Option<Amount> {
        self.0.checked_sub(rhs.0).map(Amount)
    }

    /// Checked multiplication.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_mul(self, rhs: u64) -> Option<Amount> {
        self.0.checked_mul(rhs).map(Amount)
    }

    /// Checked integer division.
    /// Be aware that integer division loses the remainder if no exact division
    /// can be made.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_div(self, rhs: u64) -> Option<Amount> {
        self.0.checked_div(rhs).map(Amount)
    }

    /// Checked remainder.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_rem(self, rhs: u64) -> Option<Amount> {
        self.0.checked_rem(rhs).map(Amount)
    }

    /// Convert to a signed amount.
    pub fn to_signed(self) -> Result<SignedAmount, ParsingError> {
        if self.as_dust() > SignedAmount::max_value().as_dust() as u64 {
            Err(ParsingError::TooBig)
        } else {
            Ok(SignedAmount::from_dust(self.as_dust() as i64))
        }
    }
}

impl default::Default for Amount {
    fn default() -> Self {
        Amount::ZERO
    }
}

impl fmt::Debug for Amount {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Amount({:.12} WOW)", self.as_wow())
    }
}

// No one should depend on a binding contract for Display for this type.
// Just using Wownero denominated string.
impl fmt::Display for Amount {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.fmt_value_in(f, Denomination::Wownero)?;
        write!(f, " {}", Denomination::Wownero)
    }
}

impl ops::Add for Amount {
    type Output = Amount;

    fn add(self, rhs: Amount) -> Self::Output {
        self.checked_add(rhs).expect("Amount addition error")
    }
}

impl ops::AddAssign for Amount {
    fn add_assign(&mut self, other: Amount) {
        *self = *self + other
    }
}

impl ops::Sub for Amount {
    type Output = Amount;

    fn sub(self, rhs: Amount) -> Self::Output {
        self.checked_sub(rhs).expect("Amount subtraction error")
    }
}

impl ops::SubAssign for Amount {
    fn sub_assign(&mut self, other: Amount) {
        *self = *self - other
    }
}

impl ops::Rem<u64> for Amount {
    type Output = Amount;

    fn rem(self, modulus: u64) -> Self {
        self.checked_rem(modulus).expect("Amount remainder error")
    }
}

impl ops::RemAssign<u64> for Amount {
    fn rem_assign(&mut self, modulus: u64) {
        *self = *self % modulus
    }
}

impl ops::Mul<u64> for Amount {
    type Output = Amount;

    fn mul(self, rhs: u64) -> Self::Output {
        self.checked_mul(rhs).expect("Amount multiplication error")
    }
}

impl ops::MulAssign<u64> for Amount {
    fn mul_assign(&mut self, rhs: u64) {
        *self = *self * rhs
    }
}

impl ops::Div<u64> for Amount {
    type Output = Amount;

    fn div(self, rhs: u64) -> Self::Output {
        self.checked_div(rhs).expect("Amount division error")
    }
}

impl ops::DivAssign<u64> for Amount {
    fn div_assign(&mut self, rhs: u64) {
        *self = *self / rhs
    }
}

impl FromStr for Amount {
    type Err = ParsingError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Amount::from_str_with_denomination(s)
    }
}

/// Represent an signed quantity of Wownero, internally as signed Wownero.
///
/// The [`SignedAmount`] type can be used to express Wownero amounts that supports arithmetic and
/// conversion to various denominations.
///
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct SignedAmount(i64);

impl SignedAmount {
    /// The zero amount.
    pub const ZERO: SignedAmount = SignedAmount(0);
    /// Exactly one Dust.
    pub const ONE_DUST: SignedAmount = SignedAmount(1);
    /// Exactly one Wownero.
    pub const ONE_WOW: SignedAmount = SignedAmount(100_000_000_000);

    /// Create an [`SignedAmount`] with Dust precision and the given number of Dusts.
    pub fn from_dust(dust: i64) -> SignedAmount {
        SignedAmount(dust)
    }

    /// Get the number of Dusts in this [`SignedAmount`].
    pub fn as_dust(self) -> i64 {
        self.0
    }

    /// The maximum value of an [`SignedAmount`].
    pub fn max_value() -> SignedAmount {
        SignedAmount(i64::max_value())
    }

    /// The minimum value of an [`SignedAmount`].
    pub fn min_value() -> SignedAmount {
        SignedAmount(i64::min_value())
    }

    /// Convert from a value expressing Wowneros to an [`SignedAmount`].
    pub fn from_wow(wow: f64) -> Result<SignedAmount, ParsingError> {
        SignedAmount::from_float_in(wow, Denomination::Wownero)
    }

    /// Parse a decimal string as a value in the given denomination.
    ///
    /// Note: This only parses the value string.  If you want to parse a value with denomination,
    /// use [`FromStr`].
    pub fn from_str_in(s: &str, denom: Denomination) -> Result<SignedAmount, ParsingError> {
        let (negative, dust) = parse_signed_to_dust(s, denom)?;
        if dust > i64::max_value() as u64 {
            return Err(ParsingError::TooBig);
        }
        Ok(match negative {
            true => SignedAmount(-(dust as i64)),
            false => SignedAmount(dust as i64),
        })
    }

    /// Parses amounts with denomination suffix like they are produced with
    /// `to_string_with_denomination` or with [`fmt::Display`].
    ///
    /// If you want to parse only the amount without the denomination, use `from_str_in`.
    pub fn from_str_with_denomination(s: &str) -> Result<SignedAmount, ParsingError> {
        let mut split = s.splitn(3, ' ');
        let amt_str = split.next().unwrap();
        let denom_str = split.next().ok_or(ParsingError::InvalidFormat)?;
        if split.next().is_some() {
            return Err(ParsingError::InvalidFormat);
        }

        SignedAmount::from_str_in(amt_str, denom_str.parse()?)
    }

    /// Express this [`SignedAmount`] as a floating-point value in the given denomination.
    ///
    /// Please be aware of the risk of using floating-point numbers.
    pub fn to_float_in(self, denom: Denomination) -> f64 {
        f64::from_str(&self.to_string_in(denom)).unwrap()
    }

    /// Express this [`SignedAmount`] as a floating-point value in Wownero.
    ///
    /// Equivalent to `to_float_in(Denomination::Wownero)`.
    ///
    /// Please be aware of the risk of using floating-point numbers.
    pub fn as_wow(self) -> f64 {
        self.to_float_in(Denomination::Wownero)
    }

    /// Convert this [`SignedAmount`] in floating-point notation with a given denomination.
    /// Can return error if the amount is too big, too precise or negative.
    ///
    /// Please be aware of the risk of using floating-point numbers.
    pub fn from_float_in(value: f64, denom: Denomination) -> Result<SignedAmount, ParsingError> {
        // This is inefficient, but the safest way to deal with this. The parsing logic is safe.
        // Any performance-critical application should not be dealing with floats.
        SignedAmount::from_str_in(&value.to_string(), denom)
    }

    /// Format the value of this [`SignedAmount`] in the given denomination.
    ///
    /// Does not include the denomination.
    pub fn fmt_value_in(self, f: &mut dyn fmt::Write, denom: Denomination) -> fmt::Result {
        let dusts = self
            .as_dust()
            .checked_abs()
            .map(|a: i64| a as u64)
            .unwrap_or_else(|| {
                // We could also hard code this into `9223372036854775808`
                u64::max_value() - self.as_dust() as u64 + 1
            });
        fmt_dust_in(dusts, self.is_negative(), f, denom)
    }

    /// Get a string number of this [`SignedAmount`] in the given denomination.
    ///
    /// Does not include the denomination.
    pub fn to_string_in(self, denom: Denomination) -> String {
        let mut buf = String::new();
        self.fmt_value_in(&mut buf, denom).unwrap();
        buf
    }

    /// Get a formatted string of this [`SignedAmount`] in the given denomination, suffixed with
    /// the abbreviation for the denomination.
    pub fn to_string_with_denomination(self, denom: Denomination) -> String {
        let mut buf = String::new();
        self.fmt_value_in(&mut buf, denom).unwrap();
        write!(buf, " {}", denom).unwrap();
        buf
    }

    // Some arithmetic that doesn't fit in `std::ops` traits.

    /// Get the absolute value of this [`SignedAmount`].
    pub fn abs(self) -> SignedAmount {
        SignedAmount(self.0.abs())
    }

    /// Returns a number representing sign of this [`SignedAmount`].
    ///
    /// - `0` if the amount is zero
    /// - `1` if the amount is positive
    /// - `-1` if the amount is negative
    pub fn signum(self) -> i64 {
        self.0.signum()
    }

    /// Returns `true` if this [`SignedAmount`] is positive and `false` if this [`SignedAmount`] is
    /// zero or negative.
    pub fn is_positive(self) -> bool {
        self.0.is_positive()
    }

    /// Returns `true` if this [`SignedAmount`] is negative and `false` if this [`SignedAmount`] is
    /// zero or positive.
    pub fn is_negative(self) -> bool {
        self.0.is_negative()
    }

    /// Get the absolute value of this [`SignedAmount`].  Returns [`None`] if overflow occurred.
    /// (`self == min_value()`)
    pub fn checked_abs(self) -> Option<SignedAmount> {
        self.0.checked_abs().map(SignedAmount)
    }

    /// Checked addition.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_add(self, rhs: SignedAmount) -> Option<SignedAmount> {
        self.0.checked_add(rhs.0).map(SignedAmount)
    }

    /// Checked subtraction.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_sub(self, rhs: SignedAmount) -> Option<SignedAmount> {
        self.0.checked_sub(rhs.0).map(SignedAmount)
    }

    /// Checked multiplication.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_mul(self, rhs: i64) -> Option<SignedAmount> {
        self.0.checked_mul(rhs).map(SignedAmount)
    }

    /// Checked integer division.
    /// Be aware that integer division loses the remainder if no exact division
    /// can be made.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_div(self, rhs: i64) -> Option<SignedAmount> {
        self.0.checked_div(rhs).map(SignedAmount)
    }

    /// Checked remainder.
    /// Returns [`None`] if overflow occurred.
    pub fn checked_rem(self, rhs: i64) -> Option<SignedAmount> {
        self.0.checked_rem(rhs).map(SignedAmount)
    }

    /// Subtraction that doesn't allow negative [`SignedAmount`]s.
    /// Returns [`None`] if either `self`, `rhs` or the result is strictly negative.
    pub fn positive_sub(self, rhs: SignedAmount) -> Option<SignedAmount> {
        if self.is_negative() || rhs.is_negative() || rhs > self {
            None
        } else {
            self.checked_sub(rhs)
        }
    }

    /// Convert to an unsigned amount.
    pub fn to_unsigned(self) -> Result<Amount, ParsingError> {
        if self.is_negative() {
            Err(ParsingError::Negative)
        } else {
            Ok(Amount::from_dust(self.as_dust() as u64))
        }
    }
}

impl default::Default for SignedAmount {
    fn default() -> Self {
        SignedAmount::ZERO
    }
}

impl fmt::Debug for SignedAmount {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "SignedAmount({:.12} WOW)", self.as_wow())
    }
}

// No one should depend on a binding contract for Display for this type.
// Just using Wownero denominated string.
impl fmt::Display for SignedAmount {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.fmt_value_in(f, Denomination::Wownero)?;
        write!(f, " {}", Denomination::Wownero)
    }
}

impl ops::Add for SignedAmount {
    type Output = SignedAmount;

    fn add(self, rhs: SignedAmount) -> Self::Output {
        self.checked_add(rhs).expect("SignedAmount addition error")
    }
}

impl ops::AddAssign for SignedAmount {
    fn add_assign(&mut self, other: SignedAmount) {
        *self = *self + other
    }
}

impl ops::Sub for SignedAmount {
    type Output = SignedAmount;

    fn sub(self, rhs: SignedAmount) -> Self::Output {
        self.checked_sub(rhs)
            .expect("SignedAmount subtraction error")
    }
}

impl ops::SubAssign for SignedAmount {
    fn sub_assign(&mut self, other: SignedAmount) {
        *self = *self - other
    }
}

impl ops::Rem<i64> for SignedAmount {
    type Output = SignedAmount;

    fn rem(self, modulus: i64) -> Self {
        self.checked_rem(modulus)
            .expect("SignedAmount remainder error")
    }
}

impl ops::RemAssign<i64> for SignedAmount {
    fn rem_assign(&mut self, modulus: i64) {
        *self = *self % modulus
    }
}

impl ops::Mul<i64> for SignedAmount {
    type Output = SignedAmount;

    fn mul(self, rhs: i64) -> Self::Output {
        self.checked_mul(rhs)
            .expect("SignedAmount multiplication error")
    }
}

impl ops::MulAssign<i64> for SignedAmount {
    fn mul_assign(&mut self, rhs: i64) {
        *self = *self * rhs
    }
}

impl ops::Div<i64> for SignedAmount {
    type Output = SignedAmount;

    fn div(self, rhs: i64) -> Self::Output {
        self.checked_div(rhs).expect("SignedAmount division error")
    }
}

impl ops::DivAssign<i64> for SignedAmount {
    fn div_assign(&mut self, rhs: i64) {
        *self = *self / rhs
    }
}

impl FromStr for SignedAmount {
    type Err = ParsingError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        SignedAmount::from_str_with_denomination(s)
    }
}

#[cfg(feature = "serde")]
#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
pub mod serde {
    //! This module adds serde serialization and deserialization support for Amounts.
    //! Since there is not a default way to serialize and deserialize Amounts, multiple
    //! ways are supported and it's up to the user to decide which serialiation to use.
    //! The provided modules can be used as follows:
    //!
    //! ```rust,ignore
    //! use serde::{Serialize, Deserialize};
    //! use wownero::Amount;
    //!
    //! #[derive(Serialize, Deserialize)]
    //! pub struct HasAmount {
    //!     #[serde(with = "wownero::util::amount::serde::as_wow")]
    //!     pub amount: Amount,
    //! }
    //! ```
    //!
    //! Notabene that due to the limits of floating point precission, ::as_wow
    //! serializes amounts as strings.

    use super::{Amount, Denomination, SignedAmount};
    use sealed::sealed;
    use serde_crate::{Deserialize, Deserializer, Serialize, Serializer};

    #[sealed]
    /// This trait is used only to avoid code duplication and naming collisions of the different
    /// serde serialization crates.
    pub trait SerdeAmount: Copy + Sized {
        /// Serialize with [`Serializer`] the amount as dustnero.
        fn ser_dust<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error>;
        /// Deserialize with [`Deserializer`] an amount in dustnero.
        fn des_dust<'d, D: Deserializer<'d>>(d: D) -> Result<Self, D::Error>;
        /// Serialize with [`Serializer`] the amount as Wownero.
        fn ser_wow<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error>;
        /// Deserialize with [`Deserializer`] an amount in Wownero.
        fn des_wow<'d, D: Deserializer<'d>>(d: D) -> Result<Self, D::Error>;
    }

    #[sealed]
    /// This trait is only for internal Amount type serialization/deserialization.
    pub trait SerdeAmountForOpt: Copy + Sized + SerdeAmount {
        /// Return the type prefix (`i` or `u`) used to sign or not the amount.
        fn type_prefix() -> &'static str;
        /// Serialize with [`Serializer`] an optional amount as dustnero.
        fn ser_dust_opt<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error>;
        /// Serialize with [`Serializer`] an optional amount as Wownero.
        fn ser_wow_opt<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error>;
    }

    #[sealed]
    impl SerdeAmount for Amount {
        fn ser_dust<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            u64::serialize(&self.as_dust(), s)
        }
        fn des_dust<'d, D: Deserializer<'d>>(d: D) -> Result<Self, D::Error> {
            Ok(Amount::from_dust(u64::deserialize(d)?))
        }
        fn ser_wow<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            String::serialize(&self.to_string_in(Denomination::Wownero), s)
        }
        fn des_wow<'d, D: Deserializer<'d>>(d: D) -> Result<Self, D::Error> {
            use serde_crate::de::Error;
            Amount::from_str_in(&String::deserialize(d)?, Denomination::Wownero)
                .map_err(D::Error::custom)
        }
    }

    #[sealed]
    impl SerdeAmountForOpt for Amount {
        fn type_prefix() -> &'static str {
            "u"
        }
        fn ser_dust_opt<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            s.serialize_some(&self.as_dust())
        }
        fn ser_wow_opt<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            s.serialize_some(&self.to_string_in(Denomination::Wownero))
        }
    }

    #[sealed]
    impl SerdeAmount for SignedAmount {
        fn ser_dust<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            i64::serialize(&self.as_dust(), s)
        }
        fn des_dust<'d, D: Deserializer<'d>>(d: D) -> Result<Self, D::Error> {
            Ok(SignedAmount::from_dust(i64::deserialize(d)?))
        }
        fn ser_wow<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            String::serialize(&self.to_string_in(Denomination::Wownero), s)
        }
        fn des_wow<'d, D: Deserializer<'d>>(d: D) -> Result<Self, D::Error> {
            use serde_crate::de::Error;
            SignedAmount::from_str_in(&String::deserialize(d)?, Denomination::Wownero)
                .map_err(D::Error::custom)
        }
    }

    #[sealed]
    impl SerdeAmountForOpt for SignedAmount {
        fn type_prefix() -> &'static str {
            "i"
        }
        fn ser_dust_opt<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            s.serialize_some(&self.as_dust())
        }
        fn ser_wow_opt<S: Serializer>(self, s: S) -> Result<S::Ok, S::Error> {
            s.serialize_some(&self.to_string_in(Denomination::Wownero))
        }
    }

    pub mod as_dust {
        // methods are implementation of a standardized serde-specific signature
        #![allow(missing_docs)]

        //! Serialize and deserialize [`Amount`] as real numbers denominated in dustnero.
        //! Use with `#[serde(with = "amount::serde::as_dust")]`.
        //!
        //! [`Amount`]: crate::util::amount::Amount

        use super::SerdeAmount;
        use serde_crate::{Deserializer, Serializer};

        pub fn serialize<A: SerdeAmount, S: Serializer>(a: &A, s: S) -> Result<S::Ok, S::Error> {
            a.ser_dust(s)
        }
        pub fn deserialize<'d, A: SerdeAmount, D: Deserializer<'d>>(d: D) -> Result<A, D::Error> {
            A::des_dust(d)
        }

        pub mod opt {
            //! Serialize and deserialize [Option] as JSON numbers denominated in dustnero.
            //! Use with `#[serde(default, with = "amount::serde::as_dust::opt")]`.

            use super::super::SerdeAmountForOpt;
            use core::fmt;
            use core::marker::PhantomData;
            use serde_crate::{de, Deserializer, Serializer};

            pub fn serialize<A: SerdeAmountForOpt, S: Serializer>(
                a: &Option<A>,
                s: S,
            ) -> Result<S::Ok, S::Error> {
                match *a {
                    Some(a) => a.ser_dust_opt(s),
                    None => s.serialize_none(),
                }
            }

            pub fn deserialize<'d, A: SerdeAmountForOpt, D: Deserializer<'d>>(
                d: D,
            ) -> Result<Option<A>, D::Error> {
                struct VisitOptAmt<X>(PhantomData<X>);

                impl<'de, X: SerdeAmountForOpt> de::Visitor<'de> for VisitOptAmt<X> {
                    type Value = Option<X>;

                    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                        write!(formatter, "An Option<{}64>", X::type_prefix())
                    }

                    fn visit_none<E>(self) -> Result<Self::Value, E>
                    where
                        E: de::Error,
                    {
                        Ok(None)
                    }
                    fn visit_some<D>(self, d: D) -> Result<Self::Value, D::Error>
                    where
                        D: Deserializer<'de>,
                    {
                        Ok(Some(X::des_dust(d)?))
                    }
                }
                d.deserialize_option(VisitOptAmt::<A>(PhantomData))
            }
        }
    }

    pub mod as_wow {
        // methods are implementation of a standardized serde-specific signature
        #![allow(missing_docs)]

        //! Serialize and deserialize [`Amount`] as JSON strings denominated in wow.
        //! Use with `#[serde(with = "amount::serde::as_wow")]`.
        //!
        //! [`Amount`]: crate::util::amount::Amount

        use super::SerdeAmount;
        use serde_crate::{Deserializer, Serializer};

        pub fn serialize<A: SerdeAmount, S: Serializer>(a: &A, s: S) -> Result<S::Ok, S::Error> {
            a.ser_wow(s)
        }

        pub fn deserialize<'d, A: SerdeAmount, D: Deserializer<'d>>(d: D) -> Result<A, D::Error> {
            A::des_wow(d)
        }

        pub mod opt {
            //! Serialize and deserialize [Option] as JSON numbers denominated in wow.
            //! Use with `#[serde(default, with = "amount::serde::as_wow::opt")]`.

            use super::super::SerdeAmountForOpt;
            use core::fmt;
            use core::marker::PhantomData;
            use serde_crate::{de, Deserializer, Serializer};

            pub fn serialize<A: SerdeAmountForOpt, S: Serializer>(
                a: &Option<A>,
                s: S,
            ) -> Result<S::Ok, S::Error> {
                match *a {
                    Some(a) => a.ser_wow_opt(s),
                    None => s.serialize_none(),
                }
            }

            pub fn deserialize<'d, A: SerdeAmountForOpt, D: Deserializer<'d>>(
                d: D,
            ) -> Result<Option<A>, D::Error> {
                struct VisitOptAmt<X>(PhantomData<X>);

                impl<'de, X: SerdeAmountForOpt> de::Visitor<'de> for VisitOptAmt<X> {
                    type Value = Option<X>;

                    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                        write!(formatter, "An Option<String>")
                    }

                    fn visit_none<E>(self) -> Result<Self::Value, E>
                    where
                        E: de::Error,
                    {
                        Ok(None)
                    }
                    fn visit_some<D>(self, d: D) -> Result<Self::Value, D::Error>
                    where
                        D: Deserializer<'de>,
                    {
                        Ok(Some(X::des_wow(d)?))
                    }
                }
                d.deserialize_option(VisitOptAmt::<A>(PhantomData))
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::panic;
    use std::str::FromStr;

    #[cfg(feature = "serde")]
    use serde_test;

    #[test]
    fn add_sub_mul_div() {
        let dust = Amount::from_dust;
        let sdust = SignedAmount::from_dust;

        assert_eq!(dust(15) + dust(15), dust(30));
        assert_eq!(dust(15) - dust(15), dust(0));
        assert_eq!(dust(14) * 3, dust(42));
        assert_eq!(dust(14) / 2, dust(7));
        assert_eq!(dust(14) % 3, dust(2));
        assert_eq!(sdust(15) - sdust(20), sdust(-5));
        assert_eq!(sdust(-14) * 3, sdust(-42));
        assert_eq!(sdust(-14) / 2, sdust(-7));
        assert_eq!(sdust(-14) % 3, sdust(-2));

        let mut b = sdust(-5);
        b += sdust(13);
        assert_eq!(b, sdust(8));
        b -= sdust(3);
        assert_eq!(b, sdust(5));
        b *= 6;
        assert_eq!(b, sdust(30));
        b /= 3;
        assert_eq!(b, sdust(10));
        b %= 3;
        assert_eq!(b, sdust(1));

        // panic on overflow
        let result = panic::catch_unwind(|| Amount::max_value() + Amount::from_dust(1));
        assert!(result.is_err());
        let result = panic::catch_unwind(|| Amount::from_dust(8446744073709551615) * 3);
        assert!(result.is_err());
    }

    #[test]
    fn checked_arithmetic() {
        let dust = Amount::from_dust;
        let sdust = SignedAmount::from_dust;

        assert_eq!(dust(42).checked_add(dust(1)), Some(dust(43)));
        assert_eq!(SignedAmount::max_value().checked_add(sdust(1)), None);
        assert_eq!(SignedAmount::min_value().checked_sub(sdust(1)), None);
        assert_eq!(Amount::max_value().checked_add(dust(1)), None);
        assert_eq!(Amount::min_value().checked_sub(dust(1)), None);

        assert_eq!(dust(5).checked_sub(dust(3)), Some(dust(2)));
        assert_eq!(dust(5).checked_sub(dust(6)), None);
        assert_eq!(sdust(5).checked_sub(sdust(6)), Some(sdust(-1)));
        assert_eq!(dust(5).checked_rem(2), Some(dust(1)));

        assert_eq!(dust(5).checked_div(2), Some(dust(2))); // integer division
        assert_eq!(sdust(-6).checked_div(2), Some(sdust(-3)));

        assert_eq!(sdust(-5).positive_sub(sdust(3)), None);
        assert_eq!(sdust(5).positive_sub(sdust(-3)), None);
        assert_eq!(sdust(3).positive_sub(sdust(5)), None);
        assert_eq!(sdust(3).positive_sub(sdust(3)), Some(sdust(0)));
        assert_eq!(sdust(5).positive_sub(sdust(3)), Some(sdust(2)));
    }

    #[test]
    #[allow(clippy::float_cmp)]
    fn floating_point() {
        use super::Denomination as D;
        let f = Amount::from_float_in;
        let sf = SignedAmount::from_float_in;
        let dust = Amount::from_dust;
        let sdust = SignedAmount::from_dust;

        assert_eq!(f(112.2, D::Wownero), Ok(dust(11220000000000)));
        assert_eq!(sf(-112.2, D::Verywow), Ok(sdust(-11220000000)));
        assert_eq!(f(112.2, D::Muchwow), Ok(dust(11220000)));
        assert_eq!(f(0.001234, D::Wownero), Ok(dust(123400000)));
        assert_eq!(sf(-0.0012345, D::Wownero), Ok(sdust(-123450000)));

        assert_eq!(f(-1000.0, D::Dust), Err(ParsingError::Negative));
        assert_eq!(f(112.2, D::Dust), Err(ParsingError::TooPrecise));
        assert_eq!(sf(-0.1, D::Dust), Err(ParsingError::TooPrecise));
        assert_eq!(
            f(42.000_000_000_000_1, D::Wownero),
            Err(ParsingError::TooPrecise)
        );
        assert_eq!(sf(-184467440738.0, D::Wownero), Err(ParsingError::TooBig));
        assert_eq!(
            f(18446744073709551617.0, D::Dust),
            Err(ParsingError::TooBig)
        );
        assert_eq!(
            f(
                SignedAmount::max_value().to_float_in(D::Dust) + 1.0,
                D::Dust
            ),
            Err(ParsingError::TooBig)
        );
        assert_eq!(
            f(Amount::max_value().to_float_in(D::Dust) + 1.0, D::Dust),
            Err(ParsingError::TooBig)
        );

        let wow = move |f| SignedAmount::from_wow(f).unwrap();
        assert_eq!(wow(2.5).to_float_in(D::Wownero), 2.5);
        assert_eq!(wow(-2.5).to_float_in(D::Verywow), -2500.0);
        assert_eq!(wow(-2.5).to_float_in(D::Muchwow), -2500000.0);
        assert_eq!(wow(-2.5).to_float_in(D::Suchwow), -2500000000.0);
        assert_eq!(wow(2.5).to_float_in(D::Dust), 250000000000.0);

        let wow = move |f| Amount::from_wow(f).unwrap();
        assert_eq!(&wow(0.0012).to_float_in(D::Wownero).to_string(), "0.0012")
    }

    #[test]
    fn parsing() {
        use super::ParsingError as E;
        let wow = Denomination::Wownero;
        let dust = Denomination::Dust;
        let p = Amount::from_str_in;
        let sp = SignedAmount::from_str_in;

        assert_eq!(p("x", wow), Err(E::InvalidCharacter('x')));
        assert_eq!(p("-", wow), Err(E::InvalidFormat));
        assert_eq!(sp("-", wow), Err(E::InvalidFormat));
        assert_eq!(p("-1.0x", wow), Err(E::InvalidCharacter('x')));
        assert_eq!(p("0.0 ", wow), Err(ParsingError::InvalidCharacter(' ')));
        assert_eq!(p("0.000.000", wow), Err(E::InvalidFormat));
        let more_than_max = format!("1{}", Amount::max_value());
        assert_eq!(p(&more_than_max, wow), Err(E::TooBig));
        assert_eq!(p("0.0000000000042", wow), Err(E::TooPrecise));

        assert_eq!(p("1", wow), Ok(Amount::from_dust(100_000_000_000)));
        assert_eq!(sp("-.5", wow), Ok(SignedAmount::from_dust(-50_000_000_000)));
        assert_eq!(p("1.1", wow), Ok(Amount::from_dust(110_000_000_000)));
        assert_eq!(p("100", dust), Ok(Amount::from_dust(100)));
        assert_eq!(p("55", dust), Ok(Amount::from_dust(55)));
        assert_eq!(
            p("5500000000000000000", dust),
            Ok(Amount::from_dust(5_500_000_000_000_000_000))
        );
        // Should this even pass?
        assert_eq!(
            p("5500000000000000000.", dust),
            Ok(Amount::from_dust(5_500_000_000_000_000_000))
        );
        assert_eq!(
            p("12345671.2345678912", wow),
            Ok(Amount::from_dust(1_234_567_123_456_789_120))
        );

        // make sure Dust > i64::max_value() is checked.
        let amount = Amount::from_dust(i64::max_value() as u64);
        assert_eq!(
            Amount::from_str_in(&amount.to_string_in(dust), dust),
            Ok(amount)
        );
        assert_eq!(
            Amount::from_str_in(&(amount + Amount(1)).to_string_in(dust), dust),
            Err(E::TooBig)
        );

        // exactly 50 chars.
        assert_eq!(
            p(
                "100000000000000.0000000000000000000000000000000000",
                Denomination::Wownero
            ),
            Err(E::TooBig)
        );
        // more than 50 chars.
        assert_eq!(
            p(
                "100000000000000.00000000000000000000000000000000000",
                Denomination::Wownero
            ),
            Err(E::InputTooLarge)
        );
    }

    #[test]
    fn to_string() {
        use super::Denomination as D;

        assert_eq!(Amount::ONE_WOW.to_string_in(D::Wownero), "1.00000000000");
        assert_eq!(Amount::ONE_WOW.to_string_in(D::Dust), "100000000000");
        assert_eq!(Amount::ONE_DUST.to_string_in(D::Wownero), "0.00000000001");
        assert_eq!(
            SignedAmount::from_dust(-42).to_string_in(D::Wownero),
            "-0.00000000042"
        );

        assert_eq!(
            Amount::ONE_WOW.to_string_with_denomination(D::Wownero),
            "1.00000000000 WOW"
        );
        assert_eq!(
            SignedAmount::ONE_WOW.to_string_with_denomination(D::Dust),
            "100000000000 Dust"
        );
        assert_eq!(
            Amount::ONE_DUST.to_string_with_denomination(D::Wownero),
            "0.00000000001 WOW"
        );
        assert_eq!(
            SignedAmount::from_dust(-42).to_string_with_denomination(D::Wownero),
            "-0.00000000042 WOW"
        );
    }

    #[test]
    fn test_unsigned_signed_conversion() {
        use super::ParsingError as E;
        let p = Amount::from_dust;
        let sp = SignedAmount::from_dust;

        assert_eq!(Amount::max_value().to_signed(), Err(E::TooBig));
        assert_eq!(
            p(i64::max_value() as u64).to_signed(),
            Ok(sp(i64::max_value()))
        );
        assert_eq!(p(0).to_signed(), Ok(sp(0)));
        assert_eq!(p(1).to_signed(), Ok(sp(1)));
        assert_eq!(p(1).to_signed(), Ok(sp(1)));
        assert_eq!(p(i64::max_value() as u64 + 1).to_signed(), Err(E::TooBig));

        assert_eq!(sp(-1).to_unsigned(), Err(E::Negative));
        assert_eq!(
            sp(i64::max_value()).to_unsigned(),
            Ok(p(i64::max_value() as u64))
        );

        assert_eq!(sp(0).to_unsigned().unwrap().to_signed(), Ok(sp(0)));
        assert_eq!(sp(1).to_unsigned().unwrap().to_signed(), Ok(sp(1)));
        assert_eq!(
            sp(i64::max_value()).to_unsigned().unwrap().to_signed(),
            Ok(sp(i64::max_value()))
        );
    }

    #[test]
    fn from_str() {
        use super::ParsingError as E;
        let p = Amount::from_str;
        let sp = SignedAmount::from_str;

        assert_eq!(p("x WOW"), Err(E::InvalidCharacter('x')));
        assert_eq!(p("5 WOW WOW"), Err(E::InvalidFormat));
        assert_eq!(p("5 5 WOW"), Err(E::InvalidFormat));

        assert_eq!(p("5 BCH"), Err(E::UnknownDenomination("BCH".to_owned())));

        assert_eq!(p("-1 WOW"), Err(E::Negative));
        assert_eq!(p("-0.0 WOW"), Err(E::Negative));
        assert_eq!(p("0.1234567891234 WOW"), Err(E::TooPrecise));
        assert_eq!(sp("-0.1 Dust"), Err(E::TooPrecise));
        assert_eq!(p("0.1234567 Muchwow"), Err(E::TooPrecise));
        assert_eq!(sp("-1.0001 Suchwow"), Err(E::TooPrecise));
        assert_eq!(sp("-200000000000 WOW"), Err(E::TooBig));
        assert_eq!(p("18446744073709551616 Dust"), Err(E::TooBig));

        assert_eq!(p(".5 Suchwow"), Ok(Amount::from_dust(50)));
        assert_eq!(sp("-.5 Suchwow"), Ok(SignedAmount::from_dust(-50)));
        assert_eq!(p("0.00000253583 WOW"), Ok(Amount::from_dust(253583)));
        assert_eq!(sp("-5 Dust"), Ok(SignedAmount::from_dust(-5)));
        assert_eq!(
            p("0.10000000000 WOW"),
            Ok(Amount::from_dust(10_000_000_000))
        );
        assert_eq!(sp("-10 Suchwow"), Ok(SignedAmount::from_dust(-1_000)));
        assert_eq!(sp("-10 Muchwow"), Ok(SignedAmount::from_dust(-1_000_000)));
        assert_eq!(
            sp("-10 Verywow"),
            Ok(SignedAmount::from_dust(-1_000_000_000))
        );
    }

    #[test]
    fn to_from_string_in() {
        use super::Denomination as D;
        let ua_str = Amount::from_str_in;
        let ua_sat = Amount::from_dust;
        let sa_str = SignedAmount::from_str_in;
        let sa_sat = SignedAmount::from_dust;

        assert_eq!("0.50", Amount::from_dust(50).to_string_in(D::Suchwow));
        assert_eq!(
            "-0.50",
            SignedAmount::from_dust(-50).to_string_in(D::Suchwow)
        );
        assert_eq!(
            "0.02535830000",
            Amount::from_dust(2535830000).to_string_in(D::Wownero)
        );
        assert_eq!("-5", SignedAmount::from_dust(-5).to_string_in(D::Dust));
        assert_eq!(
            "0.10000000000",
            Amount::from_dust(10_000_000_000).to_string_in(D::Wownero)
        );
        assert_eq!(
            "-10.00",
            SignedAmount::from_dust(-1_000).to_string_in(D::Suchwow)
        );

        assert_eq!(
            ua_str(&ua_sat(0).to_string_in(D::Dust), D::Dust),
            Ok(ua_sat(0))
        );
        assert_eq!(
            ua_str(&ua_sat(500).to_string_in(D::Wownero), D::Wownero),
            Ok(ua_sat(500))
        );
        assert_eq!(
            ua_str(&ua_sat(21_000_000).to_string_in(D::Suchwow), D::Suchwow),
            Ok(ua_sat(21_000_000))
        );
        assert_eq!(
            ua_str(&ua_sat(1).to_string_in(D::Muchwow), D::Muchwow),
            Ok(ua_sat(1))
        );
        assert_eq!(
            ua_str(
                &ua_sat(1_000_000_000_000).to_string_in(D::Verywow),
                D::Verywow
            ),
            Ok(ua_sat(1_000_000_000_000))
        );
        assert_eq!(
            ua_str(
                &ua_sat(u64::max_value()).to_string_in(D::Verywow),
                D::Verywow
            ),
            Err(ParsingError::TooBig)
        );

        assert_eq!(
            sa_str(&sa_sat(-1).to_string_in(D::Muchwow), D::Muchwow),
            Ok(sa_sat(-1))
        );

        assert_eq!(
            sa_str(&sa_sat(i64::max_value()).to_string_in(D::Dust), D::Muchwow),
            Err(ParsingError::TooBig)
        );
        // Test an overflow bug in `abs()`
        assert_eq!(
            sa_str(&sa_sat(i64::min_value()).to_string_in(D::Dust), D::Muchwow),
            Err(ParsingError::TooBig)
        );
    }

    #[test]
    fn to_string_with_denomination_from_str_roundtrip() {
        use super::Denomination as D;
        let amt = Amount::from_dust(42);
        let denom = Amount::to_string_with_denomination;
        assert_eq!(Amount::from_str(&denom(amt, D::Wownero)), Ok(amt));
        assert_eq!(Amount::from_str(&denom(amt, D::Verywow)), Ok(amt));
        assert_eq!(Amount::from_str(&denom(amt, D::Muchwow)), Ok(amt));
        assert_eq!(Amount::from_str(&denom(amt, D::Suchwow)), Ok(amt));
        assert_eq!(Amount::from_str(&denom(amt, D::Dust)), Ok(amt));

        assert_eq!(
            Amount::from_str("42 Dust WOW"),
            Err(ParsingError::InvalidFormat)
        );
        assert_eq!(
            SignedAmount::from_str("-42 Dust WOW"),
            Err(ParsingError::InvalidFormat)
        );
    }

    #[cfg(feature = "serde")]
    #[test]
    fn serde_as_dust() {
        use serde_crate::{Deserialize, Serialize};

        #[derive(Serialize, Deserialize, PartialEq, Debug)]
        #[cfg_attr(feature = "serde", serde(crate = "serde_crate"))]
        struct T {
            #[serde(with = "super::serde::as_dust")]
            pub amt: Amount,
            #[serde(with = "super::serde::as_dust")]
            pub samt: SignedAmount,
        }
        serde_test::assert_tokens(
            &T {
                amt: Amount::from_dust(123456789),
                samt: SignedAmount::from_dust(-123456789),
            },
            &[
                serde_test::Token::Struct { name: "T", len: 2 },
                serde_test::Token::Str("amt"),
                serde_test::Token::U64(123456789),
                serde_test::Token::Str("samt"),
                serde_test::Token::I64(-123456789),
                serde_test::Token::StructEnd,
            ],
        );
    }

    #[cfg(feature = "serde")]
    #[test]
    fn serde_as_dust_opt() {
        use serde_crate::{Deserialize, Serialize};
        use serde_json;

        #[derive(Serialize, Deserialize, PartialEq, Debug, Eq)]
        #[cfg_attr(feature = "serde", serde(crate = "serde_crate"))]
        struct T {
            #[serde(default, with = "super::serde::as_dust::opt")]
            pub amt: Option<Amount>,
            #[serde(default, with = "super::serde::as_dust::opt")]
            pub samt: Option<SignedAmount>,
        }

        let with = T {
            amt: Some(Amount::from_dust(2_500_000_000_000)),
            samt: Some(SignedAmount::from_dust(-2_500_000_000_000)),
        };
        let without = T {
            amt: None,
            samt: None,
        };

        // Test Roundtripping
        for s in [&with, &without].iter() {
            let v = serde_json::to_string(s).unwrap();
            let w: T = serde_json::from_str(&v).unwrap();
            assert_eq!(w, **s);
        }

        let t: T =
            serde_json::from_str("{\"amt\": 2500000000000, \"samt\": -2500000000000}").unwrap();
        assert_eq!(t, with);

        let t: T = serde_json::from_str("{}").unwrap();
        assert_eq!(t, without);

        let value_with: serde_json::Value =
            serde_json::from_str("{\"amt\": 2500000000000, \"samt\": -2500000000000}").unwrap();
        assert_eq!(with, serde_json::from_value(value_with).unwrap());

        let value_without: serde_json::Value = serde_json::from_str("{}").unwrap();
        assert_eq!(without, serde_json::from_value(value_without).unwrap());
    }

    #[cfg(feature = "serde")]
    #[test]
    fn serde_as_wow() {
        use serde_crate::{Deserialize, Serialize};
        use serde_json;

        #[derive(Serialize, Deserialize, PartialEq, Debug)]
        #[cfg_attr(feature = "serde", serde(crate = "serde_crate"))]
        struct T {
            #[serde(with = "super::serde::as_wow")]
            pub amt: Amount,
            #[serde(with = "super::serde::as_wow")]
            pub samt: SignedAmount,
        }

        let orig = T {
            amt: Amount::from_dust(900_000_000_000_000_001),
            samt: SignedAmount::from_dust(-900_000_000_000_000_001),
        };

        let json = "{\"amt\": \"9000000.00000000001\", \
                   \"samt\": \"-9000000.00000000001\"}";
        let t: T = serde_json::from_str(json).unwrap();
        assert_eq!(t, orig);

        let value: serde_json::Value = serde_json::from_str(json).unwrap();
        assert_eq!(t, serde_json::from_value(value).unwrap());

        // errors
        let t: Result<T, serde_json::Error> =
            serde_json::from_str("{\"amt\": \"1000000.0000000000001\", \"samt\": \"1\"}");
        assert!(t
            .unwrap_err()
            .to_string()
            .contains(&ParsingError::TooPrecise.to_string()));
        let t: Result<T, serde_json::Error> =
            serde_json::from_str("{\"amt\": \"-1\", \"samt\": \"1\"}");
        assert!(t
            .unwrap_err()
            .to_string()
            .contains(&ParsingError::Negative.to_string()));
    }

    #[cfg(feature = "serde")]
    #[test]
    fn serde_as_wow_opt() {
        use serde_crate::{Deserialize, Serialize};
        use serde_json;

        #[derive(Serialize, Deserialize, PartialEq, Debug, Eq)]
        #[cfg_attr(feature = "serde", serde(crate = "serde_crate"))]
        struct T {
            #[serde(default, with = "super::serde::as_wow::opt")]
            pub amt: Option<Amount>,
            #[serde(default, with = "super::serde::as_wow::opt")]
            pub samt: Option<SignedAmount>,
        }

        let with = T {
            amt: Some(Amount::from_dust(250_000_000_000)),
            samt: Some(SignedAmount::from_dust(-250_000_000_000)),
        };
        let without = T {
            amt: None,
            samt: None,
        };

        // Test Roundtripping
        for s in [&with, &without].iter() {
            let v = serde_json::to_string(s).unwrap();
            let w: T = serde_json::from_str(&v).unwrap();
            assert_eq!(w, **s);
        }

        let t: T = serde_json::from_str("{\"amt\": \"2.5\", \"samt\": \"-2.5\"}").unwrap();
        assert_eq!(t, with);

        let t: T = serde_json::from_str("{}").unwrap();
        assert_eq!(t, without);

        let value_with: serde_json::Value =
            serde_json::from_str("{\"amt\": \"2.5\", \"samt\": \"-2.5\"}").unwrap();
        assert_eq!(with, serde_json::from_value(value_with).unwrap());

        let value_without: serde_json::Value = serde_json::from_str("{}").unwrap();
        assert_eq!(without, serde_json::from_value(value_without).unwrap());
    }
}