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use std::{
fmt::{self, Display, Formatter},
ops::Mul,
};
pub trait Volume {
/// Returns the volume in SI units (cubic metres).
fn si(self) -> CubicMetre;
fn set(&mut self, val: f64);
fn unit(&self) -> Unit;
fn convert(self, unit: Unit) -> Box<dyn Volume>;
}
pub enum Unit {
CubicMetre,
Litre,
}
impl Display for Unit {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
write!(
f,
"{}",
match self {
Self::CubicMetre => "m³",
Self::Litre => "L",
}
)
}
}
#[derive(Debug, Default, PartialEq)]
pub struct CubicMetre(f64);
impl Volume for CubicMetre {
fn si(self) -> CubicMetre {
self
}
fn set(&mut self, val: f64) {
self.0 = val;
}
fn unit(&self) -> Unit {
Unit::CubicMetre
}
fn convert(self, unit: Unit) -> Box<dyn Volume> {
match unit {
Unit::CubicMetre => Box::new(self),
Unit::Litre => Box::new(Litre::from(self)),
}
}
}
impl From<Litre> for CubicMetre {
fn from(value: Litre) -> Self {
value.si()
}
}
#[derive(Debug, PartialEq)]
struct Litre(f64);
impl Volume for Litre {
fn si(self) -> CubicMetre {
CubicMetre(self.0 * 10_f64.powf(-3.))
}
fn set(&mut self, val: f64) {
self.0 = val
}
fn unit(&self) -> Unit {
Unit::Litre
}
fn convert(self, unit: Unit) -> Box<dyn Volume> {
match unit {
Unit::CubicMetre => Box::new(CubicMetre::from(self)),
Unit::Litre => Box::new(self),
}
}
}
impl From<i32> for Litre {
fn from(value: i32) -> Self {
Self(value as f64)
}
}
impl From<CubicMetre> for Litre {
fn from(value: CubicMetre) -> Self {
Self(value.0 * 10_f64.powf(3.))
}
}
impl Mul<f64> for Litre {
type Output = Self;
fn mul(self, rhs: f64) -> Self::Output {
Self(self.0 * rhs)
}
}
#[cfg(test)]
mod tests {
use crate::volume::{CubicMetre, Litre, Volume};
#[test]
fn litre_to_cubic_metre() {
assert_eq!(Litre(1000.).si(), CubicMetre(1.))
}
#[test]
fn cubic_metre_to_litre() {
assert_eq!(Litre::from(CubicMetre(1.)), Litre(1000.))
}
}
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