use crate::{Edit, Patch};use parking_lot::Mutex;use std::{    mem,    sync::{Arc, Weak},}; #[derive(Default)]pub struct Topic(Mutex<Vec<Weak<Mutex<Patch<usize>>>>>); pub struct Subscription(Arc<Mutex<Patch<usize>>>); impl Topic {    pub fn subscribe(&mut self) -> Subscription {        let subscription = Subscription(Default::default());        self.0.get_mut().push(Arc::downgrade(&subscription.0));        subscription    }     pub fn publish(&self, edits: impl Clone + IntoIterator<Item = Edit<usize>>) {        publish(&mut self.0.lock(), edits);    }     pub fn publish_mut(&mut self, edits: impl Clone + IntoIterator<Item = Edit<usize>>) {        publish(self.0.get_mut(), edits);    }} impl Subscription {    pub fn consume(&self) -> Patch<usize> {        mem::take(&mut *self.0.lock())    }} fn publish(    subscriptions: &mut Vec<Weak<Mutex<Patch<usize>>>>,    edits: impl Clone + IntoIterator<Item = Edit<usize>>,) {    subscriptions.retain(|subscription| {        if let Some(subscription) = subscription.upgrade() {            let mut patch = subscription.lock();            *patch = patch.compose(edits.clone());            true        } else {            false        }    });}