use futures::channel::mpsc::{unbounded, UnboundedSender};
use futures::Stream;
use netlink_packet_core::NetlinkMessage;
use std::fmt::Debug;

use crate::errors::{Error, ErrorKind};
use crate::Request;
use netlink_sys::SocketAddr;

/// A handle to pass requests to a [`Connection`](struct.Connection.html).
#[derive(Clone, Debug)]
pub struct ConnectionHandle<T>
where
    T: Debug + Clone + Eq + PartialEq,
{
    requests_tx: UnboundedSender<Request<T>>,
}

impl<T> ConnectionHandle<T>
where
    T: Debug + Clone + Eq + PartialEq,
{
    pub(crate) fn new(requests_tx: UnboundedSender<Request<T>>) -> Self {
        ConnectionHandle { requests_tx }
    }

    /// Send a new request and get the response as a stream of messages. Note that some messages
    /// are not part of the response stream:
    ///
    /// - **acknowledgements**: when an acknowledgement is received, the stream is closed
    /// - **end of dump messages**: similarly, upon receiving an "end of dump" message, the stream is
    /// closed
    pub fn request(
        &mut self,
        message: NetlinkMessage<T>,
        destination: SocketAddr,
    ) -> Result<impl Stream<Item = NetlinkMessage<T>>, Error<T>> {
        let (tx, rx) = unbounded::<NetlinkMessage<T>>();
        let request = Request::from((message, destination, tx));
        debug!("handle: forwarding new request to connection");
        UnboundedSender::unbounded_send(&self.requests_tx, request).map_err(|e| {
            // the channel is unbounded, so it can't be full. If this
            // failed, it means the Connection shut down.
            if e.is_full() {
                panic!("internal error: unbounded channel full?!");
            } else if e.is_disconnected() {
                Error::from(ErrorKind::ConnectionClosed)
            } else {
                panic!("unknown error: {:?}", e);
            }
        })?;
        Ok(rx)
    }

    pub fn notify(
        &mut self,
        message: NetlinkMessage<T>,
        destination: SocketAddr,
    ) -> Result<(), Error<T>> {
        let (tx, _rx) = unbounded::<NetlinkMessage<T>>();
        let request = Request::from((message, destination, tx));
        debug!("handle: forwarding new request to connection");
        UnboundedSender::unbounded_send(&self.requests_tx, request)
            .map_err(|_| ErrorKind::ConnectionClosed.into())
    }
}