use std::sync::OnceLock;
use icu_decimal::DecimalFormatter;
use icu_decimal::input::Decimal;
use icu_decimal::options::DecimalFormatterOptions;
use icu_locale_core::Locale;
fn make_local_formatter() -> Option<DecimalFormatter> {
let loc: Locale = sys_locale::get_locale()?.parse().ok()?;
DecimalFormatter::try_new(loc.into(), DecimalFormatterOptions::default()).ok()
}
fn make_en_us_formatter() -> DecimalFormatter {
#![allow(clippy::expect_used)]
let loc: Locale = "en-US".parse().expect("en-US wasn't a valid locale");
DecimalFormatter::try_new(loc.into(), DecimalFormatterOptions::default())
.expect("en-US wasn't a valid locale")
}
fn formatter() -> &'static DecimalFormatter {
static FORMATTER: OnceLock<DecimalFormatter> = OnceLock::new();
FORMATTER.get_or_init(|| make_local_formatter().unwrap_or_else(make_en_us_formatter))
}
pub fn format_with_separators(n: i64) -> String {
formatter().format(&Decimal::from(n)).to_string()
}
fn format_si_suffix_with_formatter(n: i64, formatter: &DecimalFormatter) -> String {
let n = n.max(0);
if n < 1000 {
return formatter.format(&Decimal::from(n)).to_string();
}
let format_scaled = |n: i64, scale: i64, frac_digits: u32| -> String {
let value = n as f64 / scale as f64;
let scaled: i64 = (value * 10f64.powi(frac_digits as i32)).round() as i64;
let mut dec = Decimal::from(scaled);
dec.multiply_pow10(-(frac_digits as i16));
formatter.format(&dec).to_string()
};
const UNITS: [(i64, &str); 3] = [(1_000, "K"), (1_000_000, "M"), (1_000_000_000, "G")];
let f = n as f64;
for &(scale, suffix) in &UNITS {
if (100.0 * f / scale as f64).round() < 1000.0 {
return format!("{}{}", format_scaled(n, scale, 2), suffix);
} else if (10.0 * f / scale as f64).round() < 1000.0 {
return format!("{}{}", format_scaled(n, scale, 1), suffix);
} else if (f / scale as f64).round() < 1000.0 {
return format!("{}{}", format_scaled(n, scale, 0), suffix);
}
}
format!(
"{}G",
format_with_separators(((n as f64) / 1e9).round() as i64)
)
}
pub fn format_si_suffix(n: i64) -> String {
format_si_suffix_with_formatter(n, formatter())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn kmg() {
let formatter = make_en_us_formatter();
let fmt = |n: i64| format_si_suffix_with_formatter(n, &formatter);
assert_eq!(fmt(0), "0");
assert_eq!(fmt(999), "999");
assert_eq!(fmt(1_000), "1.00K");
assert_eq!(fmt(1_200), "1.20K");
assert_eq!(fmt(10_000), "10.0K");
assert_eq!(fmt(100_000), "100K");
assert_eq!(fmt(999_500), "1.00M");
assert_eq!(fmt(1_000_000), "1.00M");
assert_eq!(fmt(1_234_000), "1.23M");
assert_eq!(fmt(12_345_678), "12.3M");
assert_eq!(fmt(999_950_000), "1.00G");
assert_eq!(fmt(1_000_000_000), "1.00G");
assert_eq!(fmt(1_234_000_000), "1.23G");
assert_eq!(fmt(1_234_000_000_000), "1,234G");
}
}