git.scottworley.com Git - pluta-lesnura/blob - src/lib.rs

   1 use rand::Rng;
   2
   3 pub const NUM_RANKS: u8 = 13;
   4
   5 #[derive(Clone, Copy, Eq, PartialEq)]
   6 pub struct Rank(u8);
   7
   8 #[derive(Clone, Copy)]
   9 pub struct PathLength(Rank);
  10
  11 #[derive(Clone, Copy, Default)]
  12 pub struct PathLengthInfo(u16);
  13 impl PathLengthInfo {
  14     #[must_use]
  15     pub fn is_showing(&self, i: Rank) -> bool {
  16         (self.0 >> i.0) & 1 == 1
  17     }
  18     fn reveal(&mut self, i: Rank) {
  19         self.0 |= 1 << i.0;
  20     }
  21     pub fn reveal_random(&mut self, true_length: PathLength) -> Option<Rank> {
  22         let showing = u8::try_from(self.0.count_ones()).expect("There aren't that many bits");
  23         let not_showing = NUM_RANKS - showing;
  24         if not_showing <= 1 {
  25             return None;
  26         }
  27
  28         let mut show = rand::thread_rng().gen_range(0..not_showing - 1);
  29         for i in 0..NUM_RANKS {
  30             let r = Rank(i);
  31             if !self.is_showing(r) && r != true_length.0 {
  32                 if show == 0 {
  33                     self.reveal(r);
  34                     return Some(r);
  35                 }
  36                 show -= 1;
  37             }
  38         }
  39         unreachable!()
  40     }
  41 }
  42
  43 #[cfg(test)]
  44 mod tests {
  45     use super::*;
  46
  47     #[test]
  48     fn path_length_info_random_reveal() {
  49         let length = PathLength(Rank(7));
  50         let mut pli = PathLengthInfo::default();
  51         for _ in 0..12 {
  52             let old_pli = PathLengthInfo::clone(&pli);
  53             match pli.reveal_random(length) {
  54                 None => panic!("Nothing revealed?"),
  55                 Some(r) => {
  56                     assert!(!old_pli.is_showing(r));
  57                     assert!(pli.is_showing(r));
  58                 }
  59             }
  60             assert_eq!(pli.0.count_ones(), 1 + old_pli.0.count_ones());
  61         }
  62         assert!(pli.reveal_random(length).is_none());
  63     }
  64 }