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use rand::Rng;
use std::fmt;
use std::fmt::Formatter;
pub struct DieRoll {
sides: u32,
face: u32,
}
impl DieRoll {
fn new(sides: u32, face: u32) -> Self {
DieRoll { sides, face }
}
}
pub struct RollResult {
rolls: Vec<DieRoll>,
}
impl RollResult {
pub fn new() -> Self {
RollResult { rolls: Vec::new() }
}
fn add_roll(&mut self, roll: DieRoll) {
self.rolls.push(roll)
}
pub fn total(&self) -> u32 {
self.rolls.iter().map(|die_roll| die_roll.face).sum()
}
pub fn increase_sides_below_max(&mut self, max_value: u32, increase_by: u32) {
for roll in &mut self.rolls {
if roll.face < max_value {
roll.face += increase_by;
}
}
}
}
impl fmt::Display for RollResult {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
write!(
f,
"{} ({})",
self.total(),
self.rolls
.iter()
.map(|dr| dr.face.to_string())
.collect::<Vec<String>>()
.join(", ")
)
}
}
/// Roll a single die with the specified number of sides.
pub fn roll_die(sides: u32) -> u32 {
let mut rng = rand::thread_rng();
rng.gen_range(1..=sides)
}
/// Parse and roll dice from a dice formula (e.g. "4d6+2" or "d12*3").
pub fn roll_formula(formula: &str) -> Option<RollResult> {
let delimiters = ['d', '+', '-', '*', '/']; // Only d implemented right now.
let parts: Vec<&str> = formula.split(|c| delimiters.contains(&c)).collect();
if parts.len() < 2 {
return None;
}
let num_dice = if parts[0].is_empty() {
1
} else {
match parts[0].parse::<u32>() {
Ok(num) => num,
Err(_) => return None,
}
};
let sides = match parts[1].parse::<u32>() {
Ok(num) => num,
Err(_) => return None,
};
let mut roll_result = RollResult::new();
for _ in 0..num_dice {
let face = roll_die(sides);
roll_result.add_roll(DieRoll::new(sides, face));
}
Some(roll_result)
}
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