1//! Household names for the harness: a new one for every empty hub, never repeating across runs (the
2//! hosts keep state between runs).
3
4use std::cell::Cell;
5use std::time::{SystemTime, UNIX_EPOCH};
6
7pub struct Households {
8    run: String,
9    n: Cell<u64>,
10}
11
12impl Households {
13    pub fn new(label: &str) -> Self {
14        let ms = SystemTime::now().duration_since(UNIX_EPOCH).map_or(0, |d| d.as_millis());
15        Self { run: format!("{label}-{ms:x}"), n: Cell::new(0) }
16    }
17
18    /// A household nobody has used.
19    pub fn next(&self) -> String {
20        self.n.set(self.n.get() + 1);
21        format!("{}-{}", self.run, self.n.get())
22    }
23}
24
25#[cfg(test)]
26mod tests {
27    use super::*;
28
29    #[test]
30    fn a_name_is_a_household_id_and_never_repeats() {
31        let h = Households::new("celld");
32        let (a, b) = (h.next(), h.next());
33        assert_ne!(a, b);
34        for id in [&a, &b] {
35            assert!(id.len() <= 63 && id.bytes().all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == b'-'), "{id}");
36            assert!(!id.starts_with('-') && !id.ends_with('-'));
37        }
38    }
39}