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//! Signals used by this library.
//!
//! See the documentation for `SignalSender` and `SignalReceiver`.

use crate::{ForgettableSignalSender, SignalReceiver, SignalSender};
use core::future::Future;
use core::pin::Pin;
use core::task::{Context, Poll};
use futures::channel::oneshot;
use std::collections::HashMap;
use std::sync::{Arc, Mutex};

/// Remote cancel receiver.
pub struct RemoteCancelReceiver {
    pub(crate) receiver: oneshot::Receiver<()>,
    pub(crate) sender_id: Pin<Box<u8>>,
    pub(crate) senders: Arc<Mutex<HashMap<usize, oneshot::Sender<()>>>>,
}

impl Future for RemoteCancelReceiver {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        Pin::new(&mut self.receiver).poll(cx).map(|_| ())
    }
}

impl Drop for RemoteCancelReceiver {
    fn drop(&mut self) {
        let mut senders = self.senders.lock().unwrap();
        senders.remove(&((&*self.sender_id) as *const u8 as usize));
        senders.shrink_to_fit();
    }
}

impl SignalReceiver for RemoteCancelReceiver {}

/// Remote done sender.
pub struct RemoteDoneSender {
    pub(crate) _sender: oneshot::Sender<()>,
    pub(crate) receiver_id: Pin<Box<u8>>,
    pub(crate) receivers: Arc<Mutex<HashMap<usize, oneshot::Receiver<()>>>>,
}

impl Drop for RemoteDoneSender {
    fn drop(&mut self) {
        let mut receivers = self.receivers.lock().unwrap();
        receivers.remove(&((&*self.receiver_id) as *const u8 as usize));
        receivers.shrink_to_fit();
    }
}

impl SignalSender for RemoteDoneSender {}

/// Remote cancel sender for parent to send cancel signal.
pub struct RemoteCancelSenderWithSignal {
    pub(crate) sender: oneshot::Sender<ForgetMessage>,
}

impl SignalSender for RemoteCancelSenderWithSignal {}

impl ForgettableSignalSender for RemoteCancelSenderWithSignal {
    fn forget(self) {
        let _ = self.sender.send(ForgetMessage::new());
    }
}

/// Remote cancel receiver, which also receives cancel signal from parent.
pub struct RemoteCancelReceiverWithSignal {
    pub(crate) receiver_root: oneshot::Receiver<()>,
    pub(crate) receiver_leaf: Option<oneshot::Receiver<ForgetMessage>>,
    pub(crate) sender_id: Pin<Box<u8>>,
    pub(crate) senders: Arc<Mutex<HashMap<usize, oneshot::Sender<()>>>>,
}

impl Future for RemoteCancelReceiverWithSignal {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        match Pin::new(&mut self.receiver_root).poll(cx) {
            Poll::Pending => {
                match &mut self.receiver_leaf {
                    Some(receiver_leaf) => {
                        // Not forgotten
                        match Pin::new(receiver_leaf).poll(cx) {
                            Poll::Pending => Poll::Pending,
                            Poll::Ready(Err(_)) => Poll::Ready(()),
                            Poll::Ready(Ok(ForgetMessage {})) => {
                                // Forget the receiver
                                self.receiver_leaf = None;
                                Poll::Pending
                            }
                        }
                    }
                    None => {
                        // Already forgotten
                        Poll::Pending
                    }
                }
            }
            Poll::Ready(_) => Poll::Ready(()),
        }
    }
}

impl Drop for RemoteCancelReceiverWithSignal {
    fn drop(&mut self) {
        let mut senders = self.senders.lock().unwrap();
        senders.remove(&((&*self.sender_id) as *const u8 as usize));
        senders.shrink_to_fit();
    }
}

impl SignalReceiver for RemoteCancelReceiverWithSignal {}

/// Remote done sender, which also sends done signal to parent.
pub struct RemoteDoneSenderWithSignal {
    pub(crate) _sender_root: oneshot::Sender<()>,
    pub(crate) _sender_leaf: oneshot::Sender<()>,
    pub(crate) receiver_id: Pin<Box<u8>>,
    pub(crate) receivers: Arc<Mutex<HashMap<usize, oneshot::Receiver<()>>>>,
}

impl Drop for RemoteDoneSenderWithSignal {
    fn drop(&mut self) {
        let mut receivers = self.receivers.lock().unwrap();
        receivers.remove(&((&*self.receiver_id) as *const u8 as usize));
        receivers.shrink_to_fit();
    }
}

impl SignalSender for RemoteDoneSenderWithSignal {}

/// Remote done receiver for parent to receive done signal.
pub struct RemoteDoneReceiverWithSignal {
    pub(crate) receiver: oneshot::Receiver<()>,
}

impl Future for RemoteDoneReceiverWithSignal {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        Pin::new(&mut self.receiver).poll(cx).map(|_| ())
    }
}

impl SignalReceiver for RemoteDoneReceiverWithSignal {}

/// Message to indicate that the receiver should forget the channel from which the message is
/// received.
pub(crate) struct ForgetMessage {}

impl ForgetMessage {
    pub fn new() -> Self {
        Self {}
    }
}