#[cfg(feature = "use_std")]
use std::error::Error;
use std::fmt::{Debug, Display, Formatter, Result as FmtResult};
use std::iter::ExactSizeIterator;
use either::Either;
use crate::size_hint;
#[derive(Clone)]
pub struct ExactlyOneError<I>
where
I: Iterator,
{
first_two: Option<Either<[I::Item; 2], I::Item>>,
inner: I,
}
impl<I> ExactlyOneError<I>
where
I: Iterator,
{
pub(crate) fn new(first_two: Option<Either<[I::Item; 2], I::Item>>, inner: I) -> Self {
Self { first_two, inner }
}
fn additional_len(&self) -> usize {
match self.first_two {
Some(Either::Left(_)) => 2,
Some(Either::Right(_)) => 1,
None => 0,
}
}
}
impl<I> Iterator for ExactlyOneError<I>
where
I: Iterator,
{
type Item = I::Item;
fn next(&mut self) -> Option<Self::Item> {
match self.first_two.take() {
Some(Either::Left([first, second])) => {
self.first_two = Some(Either::Right(second));
Some(first)
}
Some(Either::Right(second)) => Some(second),
None => self.inner.next(),
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
size_hint::add_scalar(self.inner.size_hint(), self.additional_len())
}
fn fold<B, F>(self, mut init: B, mut f: F) -> B
where
F: FnMut(B, Self::Item) -> B,
{
match self.first_two {
Some(Either::Left([first, second])) => {
init = f(init, first);
init = f(init, second);
}
Some(Either::Right(second)) => init = f(init, second),
None => {}
}
self.inner.fold(init, f)
}
}
impl<I> ExactSizeIterator for ExactlyOneError<I> where I: ExactSizeIterator {}
impl<I> Display for ExactlyOneError<I>
where
I: Iterator,
{
fn fmt(&self, f: &mut Formatter) -> FmtResult {
let additional = self.additional_len();
if additional > 0 {
write!(f, "got at least 2 elements when exactly one was expected")
} else {
write!(f, "got zero elements when exactly one was expected")
}
}
}
impl<I> Debug for ExactlyOneError<I>
where
I: Iterator + Debug,
I::Item: Debug,
{
fn fmt(&self, f: &mut Formatter) -> FmtResult {
let mut dbg = f.debug_struct("ExactlyOneError");
match &self.first_two {
Some(Either::Left([first, second])) => {
dbg.field("first", first).field("second", second);
}
Some(Either::Right(second)) => {
dbg.field("second", second);
}
None => {}
}
dbg.field("inner", &self.inner).finish()
}
}
#[cfg(feature = "use_std")]
impl<I> Error for ExactlyOneError<I>
where
I: Iterator + Debug,
I::Item: Debug,
{
}