use crate::common::*;
#[derive(Debug)]
pub struct TryFlatMap<I, F, J> {
pub(super) iter: Option<I>,
pub(super) sub_iter: Option<J>,
pub(super) f: F,
}
impl<I, F, J, T, U, V, E> Iterator for TryFlatMap<I, F, J>
where
I: Iterator<Item = Result<T, E>>,
J: Iterator<Item = Result<V, E>>,
F: FnMut(T) -> Result<U, E>,
U: IntoIterator<Item = Result<V, E>, IntoIter = J>,
{
type Item = Result<V, E>;
fn next(&mut self) -> Option<Self::Item> {
let mut iter = match self.iter.take() {
Some(iter) => iter,
None => return None,
};
let mut sub_iter = match self.sub_iter.take() {
Some(sub_iter) => sub_iter,
None => {
let item = match iter.next() {
Some(Ok(item)) => item,
Some(Err(err)) => {
return Some(Err(err));
}
None => {
return None;
}
};
let into_iter = match (self.f)(item) {
Ok(into_iter) => into_iter,
Err(err) => return Some(Err(err)),
};
into_iter.into_iter()
}
};
loop {
match sub_iter.next() {
Some(Ok(item)) => {
self.iter = Some(iter);
self.sub_iter = Some(sub_iter);
return Some(Ok(item));
}
Some(Err(err)) => {
return Some(Err(err));
}
None => {
let item = match iter.next() {
Some(Ok(item)) => item,
Some(Err(err)) => {
return Some(Err(err));
}
None => {
return None;
}
};
let into_iter = match (self.f)(item) {
Ok(into_iter) => into_iter,
Err(err) => return Some(Err(err)),
};
sub_iter = into_iter.into_iter();
}
}
}
}
}