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use crate::{
camel::{Camel, Dice, Race},
fraction::Fraction,
tree::{LeafVisitor, Tree},
};
use std::{collections::HashMap, iter::Iterator, ops::Index};
pub fn project(race: &Race, dice: &Dice) -> Chances {
let mut tree = Tree::singleton(race.clone());
tree.expand(dice);
let mut counter: LeafCounter = Default::default();
tree.visit_leaves(&mut counter);
counter.chances()
}
pub struct Chances {
pub winner: Distribution,
pub runner_up: Distribution,
pub loser: Distribution,
}
pub struct Distribution {
distribution: HashMap<Camel, Fraction>,
default: Fraction,
}
impl Distribution {
pub fn values(&self) -> impl Iterator<Item = (&Camel, &Fraction)> + '_ {
self.distribution.iter()
}
}
impl From<HashMap<Camel, Fraction>> for Distribution {
fn from(distribution: HashMap<Camel, Fraction>) -> Self {
Self {
distribution,
default: Fraction::default(),
}
}
}
impl Index<&Camel> for Distribution {
type Output = Fraction;
fn index(&self, camel: &Camel) -> &Self::Output {
self.distribution.get(camel).unwrap_or(&self.default)
}
}
struct LeafCounter {
total: usize,
winner: HashMap<Camel, usize>,
runner_up: HashMap<Camel, usize>,
loser: HashMap<Camel, usize>,
}
impl LeafCounter {
fn chances(&self) -> Chances {
let winner: HashMap<Camel, Fraction> = self
.winner
.iter()
.map(|(camel, count)| (*camel, Fraction::new(*count as i64, self.total as u64)))
.collect();
let runner_up: HashMap<Camel, Fraction> = self
.runner_up
.iter()
.map(|(camel, count)| (*camel, Fraction::new(*count as i64, self.total as u64)))
.collect();
let loser: HashMap<Camel, Fraction> = self
.loser
.iter()
.map(|(camel, count)| (*camel, Fraction::new(*count as i64, self.total as u64)))
.collect();
Chances {
winner: Distribution::from(winner),
runner_up: Distribution::from(runner_up),
loser: Distribution::from(loser),
}
}
}
impl Default for LeafCounter {
fn default() -> Self {
Self {
total: 0,
winner: HashMap::new(),
runner_up: HashMap::new(),
loser: HashMap::new(),
}
}
}
impl LeafVisitor for LeafCounter {
fn visit(&mut self, race: &Race) {
if let Some(winner) = race.winner() {
*self.winner.entry(winner).or_insert(0) += 1;
};
if let Some(runner_up) = race.runner_up() {
*self.runner_up.entry(runner_up).or_insert(0) += 1;
};
if let Some(loser) = race.loser() {
*self.loser.entry(loser).or_insert(0) += 1;
};
self.total += 1;
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn should_have_a_clear_winner() {
let race = "r,y".parse::<Race>().expect("to parse");
let dice = "r".parse::<Dice>().expect("to parse");
let chances = project(&race, &dice);
assert_eq!(chances.winner[&Camel::Red], Fraction::one());
}
#[test]
fn should_determine_chances() {
let race = "r,,y".parse::<Race>().expect("to parse");
let dice = "r".parse::<Dice>().expect("to parse");
let chances = project(&race, &dice);
assert_eq!(chances.winner[&Camel::Red], Fraction::new(2, 3));
assert_eq!(chances.winner[&Camel::Yellow], Fraction::new(1, 3));
}
}