intl 0.3.1

Pure-Rust, no_std internationalization primitives (a pure-Rust ICU analog). The `unicode` module provides General_Category, character predicates, scripts, East Asian Width, numeric values, case mapping/folding, UAX #15 normalization (NFC/NFD/NFKC/NFKD), and UTS #10 collation — property tables compiled into const-fn match lookups, with feature-selectable codepoint ranges.
Documentation 
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//! Locale-aware relative time formatting (CLDR / UTS #35): "in 3 days",
//! "2 hours ago", "yesterday". Requires the `alloc` feature.
//!
//! The count-specific wording is chosen with the CLDR plural rules
//! ([`crate::plural`]) and the number is rendered with [`crate::number`].
//!
//! ```
//! use intl::relative::{format_relative, RelativeUnit};
//! assert_eq!(format_relative("en", -1, RelativeUnit::Day), "yesterday");
//! assert_eq!(format_relative("en", 3, RelativeUnit::Day), "in 3 days");
//! assert_eq!(format_relative("en", -2, RelativeUnit::Hour), "2 hours ago");
//! ```

use crate::number::format_decimal;
use crate::plural::{plural_category, PluralCategory, PluralOperands};
use alloc::string::String;

pub use crate::cldr::{RelUnit, RelativeSpec};

/// A relative time unit.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum RelativeUnit {
    /// Years.
    Year,
    /// Months.
    Month,
    /// Weeks.
    Week,
    /// Days.
    Day,
    /// Hours.
    Hour,
    /// Minutes.
    Minute,
    /// Seconds.
    Second,
}

fn spec(lang: &str) -> RelativeSpec {
    use crate::cldr::relative_spec;
    let norm: String = lang
        .chars()
        .map(|c| {
            if c == '_' {
                '-'
            } else {
                c.to_ascii_lowercase()
            }
        })
        .collect();
    let mut end = norm.len();
    loop {
        if let Some(s) = relative_spec(&norm[..end]) {
            return s;
        }
        match norm[..end].rfind('-') {
            Some(i) => end = i,
            None => return relative_spec("en").expect("root relative spec present"),
        }
    }
}

/// Format `value` of `unit` relative to now: negative is past ("2 days ago"),
/// positive is future ("in 2 days"), with the literal forms used for −1/0/+1
/// when the locale defines them ("yesterday"/"today"/"tomorrow").
#[must_use]
pub fn format_relative(lang: &str, value: i64, unit: RelativeUnit) -> String {
    let ru = spec(lang).units[unit as usize];

    if value == -1 {
        if let Some(s) = ru.prev {
            return String::from(s);
        }
    } else if value == 0 {
        if let Some(s) = ru.cur {
            return String::from(s);
        }
    } else if value == 1 {
        if let Some(s) = ru.next {
            return String::from(s);
        }
    }

    let table = if value < 0 { &ru.past } else { &ru.future };
    let magnitude = value.unsigned_abs();
    let cat = plural_category(lang, &PluralOperands::from_int(magnitude as i64));
    let pattern = table[cat as usize]
        .or(table[PluralCategory::Other as usize])
        .unwrap_or("{0}");
    let number = format_decimal(lang, magnitude as f64);
    pattern.replace("{0}", &number)
}