purefetch 0.2.0

A fast, fastfetch-style system information tool written entirely in Rust with zero dependencies
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//! Memory: used / total (percent), e.g. "37.69 GiB / 62.61 GiB (60%)".
//! Linux: used = MemTotal - MemAvailable, matching `free` and htop. On ZFS the
//! ARC counts as used because MemAvailable does not treat it as reclaimable —
//! which is honest: that RAM is genuinely occupied by the cache until the
//! kernel reclaims it under pressure.
//! macOS: mach vm statistics, matching vm_stat and Activity Monitor.
use crate::detect::{Row, Rows};
use crate::util::{human_iec, percent};

#[cfg(target_os = "linux")]
pub fn detect() -> Rows {
    let Ok(info) = std::fs::read_to_string("/proc/meminfo") else {
        return Vec::new();
    };
    let mut total = 0u64;
    let mut available = 0u64;
    for line in info.lines() {
        if let Some(v) = line.strip_prefix("MemTotal:") {
            total = parse_kb(v);
        } else if let Some(v) = line.strip_prefix("MemAvailable:") {
            available = parse_kb(v);
        }
    }
    if total == 0 {
        return Vec::new();
    }

    let used = total.saturating_sub(available);
    vec![row(used, total)]
}

#[cfg(target_os = "macos")]
pub fn detect() -> Rows {
    let Some((used, total)) = crate::sys::memory_used_total() else {
        return Vec::new();
    };
    vec![row(used, total)]
}

fn row(used: u64, total: u64) -> Row {
    Row::val(format!(
        "{} / {} ({}%)",
        human_iec(used),
        human_iec(total),
        percent(used, total)
    ))
}

#[cfg(any(target_os = "linux", test))]
fn parse_kb(s: &str) -> u64 {
    s.split_whitespace()
        .next()
        .and_then(|n| n.parse::<u64>().ok())
        .map(|kb| kb * 1024)
        .unwrap_or(0)
}

#[cfg(test)]
mod tests {
    use super::parse_kb;

    #[test]
    fn parse_kb_to_bytes() {
        assert_eq!(parse_kb("  62518234 kB"), 62_518_234 * 1024);
        assert_eq!(parse_kb("0 kB"), 0);
        assert_eq!(parse_kb("garbage"), 0);
        assert_eq!(parse_kb(""), 0);
    }
}