// Copyright 2016 Google Inc. All Rights Reserved.
//
// Licensed under the MIT License, <LICENSE or http://opensource.org/licenses/MIT>.
// This file may not be copied, modified, or distributed except according to those terms.

use {REMOTE, Reactor};
use bincode::serde::DeserializeError;
use errors::WireError;
use futures::{self, Async, Future, Stream, future};
use net2;
use protocol::Proto;
use serde::{Deserialize, Serialize};
use std::io;
use std::net::SocketAddr;
use tokio_core::net::TcpListener;
use tokio_core::reactor::{self, Handle};
use tokio_proto::BindServer;
use tokio_service::NewService;

/// Additional options to configure how the server operates.
#[derive(Clone, Default)]
pub struct Options {
    reactor: Option<Reactor>,
}

impl Options {
    /// Listen using the given reactor handle.
    pub fn handle(mut self, handle: reactor::Handle) -> Self {
        self.reactor = Some(Reactor::Handle(handle));
        self
    }

    /// Listen using the given reactor remote.
    pub fn remote(mut self, remote: reactor::Remote) -> Self {
        self.reactor = Some(Reactor::Remote(remote));
        self
    }
}

/// A message from server to client.
#[doc(hidden)]
pub type Response<T, E> = Result<T, WireError<E>>;

#[doc(hidden)]
pub fn listen<S, Req, Resp, E>(new_service: S, addr: SocketAddr, options: Options) -> ListenFuture
    where S: NewService<Request = Result<Req, DeserializeError>,
                        Response = Response<Resp, E>,
                        Error = io::Error> + Send + 'static,
          Req: Deserialize + 'static,
          Resp: Serialize + 'static,
          E: Serialize + 'static
{
    match options.reactor {
        None => {
            let (tx, rx) = futures::oneshot();
            REMOTE.spawn(move |handle| {
                Ok(tx.complete(listen_with(new_service, addr, handle.clone())))
            });
            ListenFuture { inner: future::Either::A(rx) }
        }
        Some(Reactor::Remote(remote)) => {
            let (tx, rx) = futures::oneshot();
            remote.spawn(move |handle| {
                Ok(tx.complete(listen_with(new_service, addr, handle.clone())))
            });
            ListenFuture { inner: future::Either::A(rx) }
        }
        Some(Reactor::Handle(handle)) => {
            ListenFuture {
                inner: future::Either::B(future::ok(listen_with(new_service, addr, handle))),
            }
        }
    }
}

/// Spawns a service that binds to the given address using the given handle.
fn listen_with<S, Req, Resp, E>(new_service: S,
                                addr: SocketAddr,
                                handle: Handle)
                                -> io::Result<SocketAddr>
    where S: NewService<Request = Result<Req, DeserializeError>,
                        Response = Response<Resp, E>,
                        Error = io::Error> + Send + 'static,
          Req: Deserialize + 'static,
          Resp: Serialize + 'static,
          E: Serialize + 'static
{
    let listener = listener(&addr, &handle)?;
    let addr = listener.local_addr()?;

    let handle2 = handle.clone();
    let server = listener.incoming()
        .for_each(move |(socket, _)| {
            Proto::new().bind_server(&handle2, socket, new_service.new_service()?);

            Ok(())
        })
        .map_err(|e| error!("While processing incoming connections: {}", e));
    handle.spawn(server);
    Ok(addr)
}

fn listener(addr: &SocketAddr, handle: &Handle) -> io::Result<TcpListener> {
    const PENDING_CONNECTION_BACKLOG: i32 = 1024;
    #[cfg(unix)]
    use net2::unix::UnixTcpBuilderExt;

    let builder = match *addr {
        SocketAddr::V4(_) => net2::TcpBuilder::new_v4(),
        SocketAddr::V6(_) => net2::TcpBuilder::new_v6(),
    }?;

    builder.reuse_address(true)?;

    #[cfg(unix)]
    builder.reuse_port(true)?;

    builder.bind(addr)?
        .listen(PENDING_CONNECTION_BACKLOG)
        .and_then(|l| TcpListener::from_listener(l, addr, handle))
}

/// A future that resolves to a `ServerHandle`.
#[doc(hidden)]
pub struct ListenFuture {
    inner: future::Either<futures::Oneshot<io::Result<SocketAddr>>,
                          future::FutureResult<io::Result<SocketAddr>, futures::Canceled>>,
}

impl Future for ListenFuture {
    type Item = SocketAddr;
    type Error = io::Error;

    fn poll(&mut self) -> futures::Poll<Self::Item, Self::Error> {
        // Can't panic the oneshot is always completed.
        match self.inner.poll().unwrap() {
            Async::Ready(result) => result.map(Async::Ready),
            Async::NotReady => Ok(Async::NotReady),
        }
    }
}