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|
use crate::entities::Describe;
pub fn list_to_sentence(lst: &[String]) -> String {
let mut buf = String::with_capacity(
lst.iter()
.map(|e| e.len() + 2usize /* ", " */)
.sum::<usize>()
+ if lst.len() >= 3 {
3usize /* "and" */
} else {
0usize
},
);
match lst.len() {
0 => {}
1 => buf.push_str(&lst[0]),
2 => {
buf.push_str(&lst[0]);
buf.push_str(" and ");
buf.push_str(&lst[1]);
}
_ => {
for desc in &lst[..lst.len() - 1] {
buf.push_str(desc);
buf.push_str(", ");
}
buf.push_str("and ");
buf.push_str(&lst[lst.len() - 1]);
}
}
buf
}
pub fn describe_list<A: Describe>(lst: &[A]) -> String {
list_to_sentence(
&lst.iter().map(|e| e.description()).collect::<Vec<String>>(),
)
}
#[cfg(test)]
mod tests {
use super::*;
use proptest::prelude::*;
use proptest_derive::Arbitrary;
#[derive(Debug, Arbitrary)]
struct Description(String);
impl Describe for Description {
fn description(&self) -> String {
self.0.clone()
}
}
proptest! {
#[test]
fn test_describe_list_includes_all_descriptions(
descriptions: Vec<Description>
) {
let res = describe_list(&descriptions);
for Description(desc) in descriptions {
assert!(res.contains(&desc));
}
}
}
#[test]
fn test_describe_list() {
assert_eq!(
describe_list(&[Description("one".to_string())]),
"one".to_string()
);
assert_eq!(
describe_list(&[
Description("one".to_string()),
Description("two".to_string())
]),
"one and two".to_string()
);
assert_eq!(
describe_list(&[
Description("one".to_string()),
Description("two".to_string()),
Description("three".to_string())
]),
"one, two, and three".to_string()
);
}
}
|
