Function shuffle_flags

src/display.rs:225–247

Print the top title row: version (left) + country flags (right). Returns a shuffled copy of `flags` using xorshift64 seeded from time + PID. Avoids pulling in `rand` for what is purely a cosmetic per-render shuffle.

(flags: &[String])

///
/// Avoids pulling in `rand` for what is purely a cosmetic per-render shuffle.
fn shuffle_flags(flags: &[String]) -> Vec<String> {
    use std::time::{SystemTime, UNIX_EPOCH};
    let mut out = flags.to_vec();
    if out.len() < 2 {
        return out;
    }
    let mut state: u64 = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map_or(0xdead_beef_cafe_babe, |d| d.as_nanos() as u64)
        .wrapping_add(u64::from(std::process::id()));
    if state == 0 {
        state = 0xdead_beef_cafe_babe;
    }
    for i in (1..out.len()).rev() {
        // xorshift64
        state ^= state << 13;
        state ^= state >> 7;
        state ^= state << 17;
        let j = (state % (i as u64 + 1)) as usize;
        out.swap(i, j);
    }
    out
}

fn print_version_flags_row(country_flags: &[String], inner_width: usize) {
    let version = env!("CARGO_PKG_VERSION");