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//! The daily challenge: one beach a day, the same one for everybody.
//!
//! No server and no handshake - determinism means the seed *is* the
//! agreement, and the seed is the date.
use bevy::prelude::*;
/// The daily challenge: everyone in the world gets the same generated
/// arena for a given (UTC) day, thanks to determinism. `active` while the
/// current versus round is the daily.
#[derive(Resource, Default)]
pub struct Daily {
pub active: bool,
/// The day the round on the sand was seeded for, set when its board is
/// built. The trophies count the round under this day rather than
/// asking the clock again when it ends: a round begun at a minute to
/// midnight was played on yesterday's beach, and counting it under
/// today's put yesterday's score on a beach nobody had played yet.
pub day: u32,
}
impl Daily {
/// Days since the epoch, UTC: the worldwide shared seed basis.
pub fn today() -> u32 {
(crate::app::clock::now_secs() / 86_400) as u32
}
/// The arena seed for a given day number; pure so it can be tested.
pub fn seed_for(day: u32) -> u64 {
0xDA11_0000 ^ u64::from(day)
}
}
#[cfg(test)]
mod tests {
use super::Daily;
#[test]
fn daily_seed_is_stable_within_a_day_and_fresh_across_days() {
assert_eq!(Daily::seed_for(20_662), Daily::seed_for(20_662));
assert_ne!(Daily::seed_for(20_662), Daily::seed_for(20_663));
}
}