use std::time::{SystemTime, UNIX_EPOCH};

/// Civil date from days since Unix epoch (Howard Hinnant's algorithm) —
/// avoids pulling chrono into build-dependencies for one date string.
fn civil_from_days(z: i64) -> (i64, u32, u32) {
    let z = z + 719_468;
    let era = if z >= 0 { z } else { z - 146_096 } / 146_097;
    let doe = (z - era * 146_097) as u64;
    let yoe = (doe - doe / 1460 + doe / 36_524 - doe / 146_096) / 365;
    let y = yoe as i64 + era * 400;
    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
    let mp = (5 * doy + 2) / 153;
    let d = (doy - (153 * mp + 2) / 5 + 1) as u32;
    let m = (if mp < 10 { mp + 3 } else { mp - 9 }) as u32;
    (if m <= 2 { y + 1 } else { y }, m, d)
}

fn main() {
    let secs = SystemTime::now().duration_since(UNIX_EPOCH).map(|d| d.as_secs() as i64).unwrap_or(0);
    let (y, m, d) = civil_from_days(secs / 86_400);
    println!("cargo:rustc-env=VULP_BUILD_DATE={y:04}-{m:02}-{d:02}");
}