use crate::errors::{Error, Result};
use serde::{Deserialize, Serialize};
use std::{
fmt::{self, Debug, Display, Formatter},
str::FromStr,
};
const MONEY_TO_RAW_POWER_OF_10_CONVERSION: u32 = 9;
const MONEY_TO_RAW_CONVERSION: u64 = 1_000_000_000;
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct Money(u64);
impl Money {
pub const fn zero() -> Self {
Self(0)
}
pub const fn from_nano(value: u64) -> Self {
Self(value)
}
pub const fn as_nano(self) -> u64 {
self.0
}
pub fn checked_add(self, rhs: Money) -> Option<Money> {
self.0.checked_add(rhs.0).map(Self::from_nano)
}
pub fn checked_sub(self, rhs: Money) -> Option<Money> {
self.0.checked_sub(rhs.0).map(Self::from_nano)
}
}
impl FromStr for Money {
type Err = Error;
fn from_str(value_str: &str) -> Result<Self> {
let mut itr = value_str.splitn(2, '.');
let converted_units = {
let units = itr
.next()
.and_then(|s| s.parse::<u64>().ok())
.ok_or_else(|| Error::FailedToParse("Can't parse Money units".to_string()))?;
units
.checked_mul(MONEY_TO_RAW_CONVERSION)
.ok_or_else(|| Error::ExcessiveValue)?
};
let remainder = {
let remainder_str = itr.next().unwrap_or_default().trim_end_matches('0');
if remainder_str.is_empty() {
0
} else {
let parsed_remainder = remainder_str
.parse::<u64>()
.map_err(|_| Error::FailedToParse("Can't parse Money remainder".to_string()))?;
let remainder_conversion = MONEY_TO_RAW_POWER_OF_10_CONVERSION
.checked_sub(remainder_str.len() as u32)
.ok_or_else(|| Error::LossOfPrecision)?;
parsed_remainder * 10_u64.pow(remainder_conversion)
}
};
Ok(Self::from_nano(converted_units + remainder))
}
}
impl Debug for Money {
fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
Display::fmt(self, formatter)
}
}
impl Display for Money {
fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
let unit = self.0 / MONEY_TO_RAW_CONVERSION;
let remainder = self.0 % MONEY_TO_RAW_CONVERSION;
write!(formatter, "{}.{}", unit, format!("{:09}", remainder))
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::u64;
use unwrap::unwrap;
#[test]
fn from_str() {
assert_eq!(Money(0), unwrap!(Money::from_str("0")));
assert_eq!(Money(0), unwrap!(Money::from_str("0.")));
assert_eq!(Money(0), unwrap!(Money::from_str("0.0")));
assert_eq!(Money(1), unwrap!(Money::from_str("0.000000001")));
assert_eq!(Money(1_000_000_000), unwrap!(Money::from_str("1")));
assert_eq!(Money(1_000_000_000), unwrap!(Money::from_str("1.")));
assert_eq!(Money(1_000_000_000), unwrap!(Money::from_str("1.0")));
assert_eq!(
Money(1_000_000_001),
unwrap!(Money::from_str("1.000000001"))
);
assert_eq!(Money(1_100_000_000), unwrap!(Money::from_str("1.1")));
assert_eq!(
Money(1_100_000_001),
unwrap!(Money::from_str("1.100000001"))
);
assert_eq!(
Money(4_294_967_295_000_000_000),
unwrap!(Money::from_str("4294967295"))
);
assert_eq!(
Money(4_294_967_295_999_999_999),
unwrap!(Money::from_str("4294967295.999999999")),
);
assert_eq!(
Money(4_294_967_295_999_999_999),
unwrap!(Money::from_str("4294967295.9999999990000")),
);
assert_eq!(
Err(Error::FailedToParse("Can't parse Money units".to_string())),
Money::from_str("a")
);
assert_eq!(
Err(Error::FailedToParse(
"Can't parse Money remainder".to_string()
)),
Money::from_str("0.a")
);
assert_eq!(
Err(Error::FailedToParse(
"Can't parse Money remainder".to_string()
)),
Money::from_str("0.0.0")
);
assert_eq!(Err(Error::LossOfPrecision), Money::from_str("0.0000000009"));
assert_eq!(Err(Error::ExcessiveValue), Money::from_str("18446744074"));
}
#[test]
fn display() {
assert_eq!("0.000000000", format!("{}", Money(0)));
assert_eq!("0.000000001", format!("{}", Money(1)));
assert_eq!("0.000000010", format!("{}", Money(10)));
assert_eq!("1.000000000", format!("{}", Money(1_000_000_000)));
assert_eq!("1.000000001", format!("{}", Money(1_000_000_001)));
assert_eq!(
"4294967295.000000000",
format!("{}", Money(4_294_967_295_000_000_000))
);
}
#[test]
fn checked_add_sub() {
assert_eq!(Some(Money(3)), Money(1).checked_add(Money(2)));
assert_eq!(None, Money(u64::MAX).checked_add(Money(1)));
assert_eq!(None, Money(u64::MAX).checked_add(Money(u64::MAX)));
assert_eq!(Some(Money(0)), Money(u64::MAX).checked_sub(Money(u64::MAX)));
assert_eq!(None, Money(0).checked_sub(Money(u64::MAX)));
assert_eq!(None, Money(10).checked_sub(Money(11)));
}
}