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use std::collections::VecDeque;
use std::mem::MaybeUninit;
use futures::future::BoxFuture;
use futures::FutureExt;
use crate::map_layer::MapLayer;
use crate::recursive::{Collapse, Expand, ExpandAsync};
use crate::recursive_tree::{RecursiveTree, RecursiveTreeRef};
#[derive(Debug, Clone, Copy)]
pub struct ArenaIndex(usize);
impl ArenaIndex {
fn head() -> Self {
ArenaIndex(0)
}
}
impl<A, Underlying, Wrapped> Expand<A, Wrapped> for RecursiveTree<Underlying, ArenaIndex>
where
Wrapped: MapLayer<ArenaIndex, Unwrapped = A, To = Underlying>,
{
fn expand_layers<F: Fn(A) -> Wrapped>(a: A, expand_layer: F) -> Self {
let mut frontier = VecDeque::from([a]);
let mut elems = vec![];
while let Some(seed) = frontier.pop_front() {
let layer = expand_layer(seed);
let layer = layer.map_layer(|aa| {
frontier.push_back(aa);
ArenaIndex(elems.len() + frontier.len())
});
elems.push(layer);
}
Self {
elems,
_underlying: std::marker::PhantomData,
}
}
}
impl<A, U: Send, O: MapLayer<ArenaIndex, Unwrapped = A, To = U>> ExpandAsync<A, O>
for RecursiveTree<U, ArenaIndex>
{
fn expand_layers_async<
'a,
E: Send + 'a,
F: Fn(A) -> BoxFuture<'a, Result<O, E>> + Send + Sync + 'a,
>(
seed: A,
generate_layer: F,
) -> BoxFuture<'a, Result<Self, E>>
where
Self: Sized,
U: Send,
A: Send + 'a,
{
async move {
let mut frontier = VecDeque::from([seed]);
let mut elems = vec![];
while let Some(seed) = frontier.pop_front() {
let layer = generate_layer(seed).await?;
let layer = layer.map_layer(|aa| {
frontier.push_back(aa);
ArenaIndex(elems.len() + frontier.len())
});
elems.push(layer);
}
Ok(Self {
elems,
_underlying: std::marker::PhantomData,
})
}
.boxed()
}
}
impl<A, Wrapped, Underlying> Collapse<A, Wrapped> for RecursiveTree<Underlying, ArenaIndex>
where
Underlying: MapLayer<A, To = Wrapped, Unwrapped = ArenaIndex>,
{
fn collapse_layers<F: FnMut(Wrapped) -> A>(self, mut collapse_layer: F) -> A {
let mut results = std::iter::repeat_with(|| MaybeUninit::<A>::uninit())
.take(self.elems.len())
.collect::<Vec<_>>();
for (idx, node) in self.elems.into_iter().enumerate().rev() {
let alg_res = {
let node = node.map_layer(|ArenaIndex(x)| unsafe {
let maybe_uninit =
std::mem::replace(results.get_unchecked_mut(x), MaybeUninit::uninit());
maybe_uninit.assume_init()
});
collapse_layer(node)
};
results[idx].write(alg_res);
}
unsafe {
let maybe_uninit = std::mem::replace(
results.get_unchecked_mut(ArenaIndex::head().0),
MaybeUninit::uninit(),
);
maybe_uninit.assume_init()
}
}
}
impl<'a, A, O: 'a, U> Collapse<A, O> for RecursiveTreeRef<'a, U, ArenaIndex>
where
&'a U: MapLayer<A, To = O, Unwrapped = ArenaIndex>,
{
fn collapse_layers<F: FnMut(O) -> A>(self, mut collapse_layer: F) -> A {
let mut results = std::iter::repeat_with(|| MaybeUninit::<A>::uninit())
.take(self.elems.len())
.collect::<Vec<_>>();
for (idx, node) in self.elems.iter().enumerate().rev() {
let alg_res = {
let node = node.map_layer(|ArenaIndex(x)| unsafe {
let maybe_uninit =
std::mem::replace(results.get_unchecked_mut(x), MaybeUninit::uninit());
maybe_uninit.assume_init()
});
collapse_layer(node)
};
results[idx].write(alg_res);
}
unsafe {
let maybe_uninit = std::mem::replace(
results.get_unchecked_mut(ArenaIndex::head().0),
MaybeUninit::uninit(),
);
maybe_uninit.assume_init()
}
}
}