use crate::errors::{Error, Result};
use serde::{Deserialize, Serialize};
use std::{
fmt::{self, Debug, Display, Formatter},
str::FromStr,
};
const TOKEN_TO_RAW_POWER_OF_10_CONVERSION: u32 = 9;
const TOKEN_TO_RAW_CONVERSION: u64 = 1_000_000_000;
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct Token(u64);
impl Token {
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: Token) -> Option<Token> {
self.0.checked_add(rhs.0).map(Self::from_nano)
}
pub fn checked_sub(self, rhs: Token) -> Option<Token> {
self.0.checked_sub(rhs.0).map(Self::from_nano)
}
}
impl FromStr for Token {
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 token units".to_string()))?;
units
.checked_mul(TOKEN_TO_RAW_CONVERSION)
.ok_or(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 token remainder".to_string()))?;
let remainder_conversion = TOKEN_TO_RAW_POWER_OF_10_CONVERSION
.checked_sub(remainder_str.len() as u32)
.ok_or(Error::LossOfPrecision)?;
parsed_remainder * 10_u64.pow(remainder_conversion)
}
};
Ok(Self::from_nano(converted_units + remainder))
}
}
impl Debug for Token {
fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
Display::fmt(self, formatter)
}
}
impl Display for Token {
fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
let unit = self.0 / TOKEN_TO_RAW_CONVERSION;
let remainder = self.0 % TOKEN_TO_RAW_CONVERSION;
write!(formatter, "{}.{}", unit, format!("{:09}", remainder))
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::u64;
#[test]
fn from_str() -> Result<()> {
assert_eq!(Token(0), Token::from_str("0")?);
assert_eq!(Token(0), Token::from_str("0.")?);
assert_eq!(Token(0), Token::from_str("0.0")?);
assert_eq!(Token(1), Token::from_str("0.000000001")?);
assert_eq!(Token(1_000_000_000), Token::from_str("1")?);
assert_eq!(Token(1_000_000_000), Token::from_str("1.")?);
assert_eq!(Token(1_000_000_000), Token::from_str("1.0")?);
assert_eq!(Token(1_000_000_001), Token::from_str("1.000000001")?);
assert_eq!(Token(1_100_000_000), Token::from_str("1.1")?);
assert_eq!(Token(1_100_000_001), Token::from_str("1.100000001")?);
assert_eq!(
Token(4_294_967_295_000_000_000),
Token::from_str("4294967295")?
);
assert_eq!(
Token(4_294_967_295_999_999_999),
Token::from_str("4294967295.999999999")?,
);
assert_eq!(
Token(4_294_967_295_999_999_999),
Token::from_str("4294967295.9999999990000")?,
);
assert_eq!(
Err(Error::FailedToParse("Can't parse token units".to_string())),
Token::from_str("a")
);
assert_eq!(
Err(Error::FailedToParse(
"Can't parse token remainder".to_string()
)),
Token::from_str("0.a")
);
assert_eq!(
Err(Error::FailedToParse(
"Can't parse token remainder".to_string()
)),
Token::from_str("0.0.0")
);
assert_eq!(Err(Error::LossOfPrecision), Token::from_str("0.0000000009"));
assert_eq!(Err(Error::ExcessiveValue), Token::from_str("18446744074"));
Ok(())
}
#[test]
fn display() {
assert_eq!("0.000000000", format!("{}", Token(0)));
assert_eq!("0.000000001", format!("{}", Token(1)));
assert_eq!("0.000000010", format!("{}", Token(10)));
assert_eq!("1.000000000", format!("{}", Token(1_000_000_000)));
assert_eq!("1.000000001", format!("{}", Token(1_000_000_001)));
assert_eq!(
"4294967295.000000000",
format!("{}", Token(4_294_967_295_000_000_000))
);
}
#[test]
fn checked_add_sub() {
assert_eq!(Some(Token(3)), Token(1).checked_add(Token(2)));
assert_eq!(None, Token(u64::MAX).checked_add(Token(1)));
assert_eq!(None, Token(u64::MAX).checked_add(Token(u64::MAX)));
assert_eq!(Some(Token(0)), Token(u64::MAX).checked_sub(Token(u64::MAX)));
assert_eq!(None, Token(0).checked_sub(Token(u64::MAX)));
assert_eq!(None, Token(10).checked_sub(Token(11)));
}
}