build.rs

//  Project:   macbash
//  File:      build.rs
//  Purpose:   Emit build timestamp and git SHA as env vars for --version output
//  Language:  Rust
//
//  License:   Apache-2.0
//  Copyright: (c) 2025-2026 HYPERI PTY LIMITED

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

fn main() {
    let sha = Command::new("git")
        .args(["rev-parse", "HEAD"])
        .output()
        .ok()
        .filter(|o| o.status.success())
        .map(|o| String::from_utf8_lossy(&o.stdout).trim().to_string())
        .unwrap_or_else(|| "unknown".into());
    println!("cargo:rustc-env=VERGEN_GIT_SHA={sha}");

    let secs = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0);
    println!(
        "cargo:rustc-env=VERGEN_BUILD_TIMESTAMP={}",
        rfc3339_utc(secs)
    );

    println!("cargo:rerun-if-changed=.git/HEAD");
    println!("cargo:rerun-if-changed=.git/refs");
}

fn rfc3339_utc(secs: u64) -> String {
    let days = (secs / 86_400) as i64;
    let tod = secs % 86_400;
    let hour = (tod / 3600) as u32;
    let minute = ((tod % 3600) / 60) as u32;
    let second = (tod % 60) as u32;
    let (year, month, day) = civil_from_days(days);
    format!("{year:04}-{month:02}-{day:02}T{hour:02}:{minute:02}:{second:02}Z")
}

// Howard Hinnant's days-from-epoch -> (year, month, day) algorithm.
fn civil_from_days(z: i64) -> (i32, 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;
    let m = if mp < 10 { mp + 3 } else { mp - 9 };
    let y = if m <= 2 { y + 1 } else { y };
    (y as i32, m as u32, d as u32)
}