use std::fmt;
use std::io::{self, Read, Write};
use std::mem;
use std::net::{self, SocketAddr, Shutdown};

use futures::stream::Stream;
use futures::sync::oneshot;
use futures::{self, Future, failed, Poll, Async};
use mio;

use io::{Io, IoFuture};
use reactor::{Handle, PollEvented};

/// An I/O object representing a TCP socket listening for incoming connections.
///
/// This object can be converted into a stream of incoming connections for
/// various forms of processing.
pub struct TcpListener {
    io: PollEvented<mio::tcp::TcpListener>,
    pending_accept: Option<oneshot::Receiver<io::Result<(TcpStream, SocketAddr)>>>,
}

/// Stream returned by the `TcpListener::incoming` function representing the
/// stream of sockets received from a listener.
pub struct Incoming {
    inner: TcpListener,
}

impl TcpListener {
    /// Create a new TCP listener associated with this event loop.
    ///
    /// The TCP listener will bind to the provided `addr` address, if available.
    /// If the result is `Ok`, the socket has successfully bound.
    pub fn bind(addr: &SocketAddr, handle: &Handle) -> io::Result<TcpListener> {
        let l = try!(mio::tcp::TcpListener::bind(addr));
        TcpListener::new(l, handle)
    }

    /// Attempt to accept a connection and create a new connected `TcpStream` if
    /// successful.
    ///
    /// This function will attempt an accept operation, but will not block
    /// waiting for it to complete. If the operation would block then a "would
    /// block" error is returned. Additionally, if this method would block, it
    /// registers the current task to receive a notification when it would
    /// otherwise not block.
    ///
    /// Note that typically for simple usage it's easier to treat incoming
    /// connections as a `Stream` of `TcpStream`s with the `incoming` method
    /// below.
    ///
    /// # Panics
    ///
    /// This function will panic if it is called outside the context of a
    /// future's task. It's recommended to only call this from the
    /// implementation of a `Future::poll`, if necessary.
    pub fn accept(&mut self) -> io::Result<(TcpStream, SocketAddr)> {
        loop {
            if let Some(mut pending) = self.pending_accept.take() {
                match pending.poll().expect("shouldn't be canceled") {
                    Async::NotReady => {
                        self.pending_accept = Some(pending);
                        return Err(mio::would_block())
                    },
                    Async::Ready(r) => return r,
                }
            }

            if let Async::NotReady = self.io.poll_read() {
                return Err(io::Error::new(io::ErrorKind::WouldBlock, "not ready"))
            }

            match self.io.get_ref().accept() {
                Err(e) => {
                    if e.kind() == io::ErrorKind::WouldBlock {
                        self.io.need_read();
                    }
                    return Err(e)
                },
                Ok((sock, addr)) => {
                    let (tx, rx) = oneshot::channel();
                    let remote = self.io.remote().clone();
                    remote.spawn(move |handle| {
                        let res = PollEvented::new(sock, handle)
                            .map(move |io| {
                                (TcpStream { io: io }, addr)
                            });
                        tx.complete(res);
                        Ok(())
                    });
                    self.pending_accept = Some(rx);
                    // continue to polling the `rx` at the beginning of the loop
                }
            }
        }
    }

    /// Create a new TCP listener from the standard library's TCP listener.
    ///
    /// This method can be used when the `Handle::tcp_listen` method isn't
    /// sufficient because perhaps some more configuration is needed in terms of
    /// before the calls to `bind` and `listen`.
    ///
    /// This API is typically paired with the `net2` crate and the `TcpBuilder`
    /// type to build up and customize a listener before it's shipped off to the
    /// backing event loop. This allows configuration of options like
    /// `SO_REUSEPORT`, binding to multiple addresses, etc.
    ///
    /// The `addr` argument here is one of the addresses that `listener` is
    /// bound to and the listener will only be guaranteed to accept connections
    /// of the same address type currently.
    ///
    /// Finally, the `handle` argument is the event loop that this listener will
    /// be bound to.
    ///
    /// The platform specific behavior of this function looks like:
    ///
    /// * On Unix, the socket is placed into nonblocking mode and connections
    ///   can be accepted as normal
    ///
    /// * On Windows, the address is stored internally and all future accepts
    ///   will only be for the same IP version as `addr` specified. That is, if
    ///   `addr` is an IPv4 address then all sockets accepted will be IPv4 as
    ///   well (same for IPv6).
    pub fn from_listener(listener: net::TcpListener,
                         addr: &SocketAddr,
                         handle: &Handle) -> io::Result<TcpListener> {
        let l = try!(mio::tcp::TcpListener::from_listener(listener, addr));
        TcpListener::new(l, handle)
    }

    fn new(listener: mio::tcp::TcpListener, handle: &Handle)
           -> io::Result<TcpListener> {
        let io = try!(PollEvented::new(listener, handle));
        Ok(TcpListener { io: io, pending_accept: None })
    }

    /// Test whether this socket is ready to be read or not.
    pub fn poll_read(&self) -> Async<()> {
        self.io.poll_read()
    }

    /// Returns the local address that this listener is bound to.
    ///
    /// This can be useful, for example, when binding to port 0 to figure out
    /// which port was actually bound.
    pub fn local_addr(&self) -> io::Result<SocketAddr> {
        self.io.get_ref().local_addr()
    }

    /// Consumes this listener, returning a stream of the sockets this listener
    /// accepts.
    ///
    /// This method returns an implementation of the `Stream` trait which
    /// resolves to the sockets the are accepted on this listener.
    pub fn incoming(self) -> Incoming {
        Incoming { inner: self }
    }

    /// Sets the value for the `IP_TTL` option on this socket.
    ///
    /// This value sets the time-to-live field that is used in every packet sent
    /// from this socket.
    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
        self.io.get_ref().set_ttl(ttl)
    }

    /// Gets the value of the `IP_TTL` option for this socket.
    ///
    /// For more information about this option, see [`set_ttl`][link].
    ///
    /// [link]: #method.set_ttl
    pub fn ttl(&self) -> io::Result<u32> {
        self.io.get_ref().ttl()
    }

    /// Sets the value for the `IPV6_V6ONLY` option on this socket.
    ///
    /// If this is set to `true` then the socket is restricted to sending and
    /// receiving IPv6 packets only. In this case two IPv4 and IPv6 applications
    /// can bind the same port at the same time.
    ///
    /// If this is set to `false` then the socket can be used to send and
    /// receive packets from an IPv4-mapped IPv6 address.
    pub fn set_only_v6(&self, only_v6: bool) -> io::Result<()> {
        self.io.get_ref().set_only_v6(only_v6)
    }

    /// Gets the value of the `IPV6_V6ONLY` option for this socket.
    ///
    /// For more information about this option, see [`set_only_v6`][link].
    ///
    /// [link]: #method.set_only_v6
    pub fn only_v6(&self) -> io::Result<bool> {
        self.io.get_ref().only_v6()
    }
}

impl fmt::Debug for TcpListener {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.io.get_ref().fmt(f)
    }
}

impl Stream for Incoming {
    type Item = (TcpStream, SocketAddr);
    type Error = io::Error;

    fn poll(&mut self) -> Poll<Option<Self::Item>, io::Error> {
        Ok(Async::Ready(Some(try_nb!(self.inner.accept()))))
    }
}

/// An I/O object representing a TCP stream connected to a remote endpoint.
///
/// A TCP stream can either be created by connecting to an endpoint or by
/// accepting a connection from a listener. Inside the stream is access to the
/// raw underlying I/O object as well as streams for the read/write
/// notifications on the stream itself.
pub struct TcpStream {
    io: PollEvented<mio::tcp::TcpStream>,
}

/// Future returned by `TcpStream::connect` which will resolve to a `TcpStream`
/// when the stream is connected.
pub struct TcpStreamNew {
    inner: IoFuture<TcpStream>,
}

enum TcpStreamConnect {
    Waiting(TcpStream),
    Empty,
}

impl TcpStream {
    /// Create a new TCP stream connected to the specified address.
    ///
    /// This function will create a new TCP socket and attempt to connect it to
    /// the `addr` provided. The returned future will be resolved once the
    /// stream has successfully connected. If an error happens during the
    /// connection or during the socket creation, that error will be returned to
    /// the future instead.
    pub fn connect(addr: &SocketAddr, handle: &Handle) -> TcpStreamNew {
        let future = match mio::tcp::TcpStream::connect(addr) {
            Ok(tcp) => TcpStream::new(tcp, handle),
            Err(e) => failed(e).boxed(),
        };
        TcpStreamNew { inner: future }
    }

    fn new(connected_stream: mio::tcp::TcpStream, handle: &Handle)
           -> IoFuture<TcpStream> {
        let tcp = PollEvented::new(connected_stream, handle);
        futures::done(tcp).and_then(|io| {
            TcpStreamConnect::Waiting(TcpStream { io: io })
        }).boxed()
    }

    /// Creates a new `TcpStream` from the pending socket inside the given
    /// `std::net::TcpStream`, connecting it to the address specified.
    ///
    /// This constructor allows configuring the socket before it's actually
    /// connected, and this function will transfer ownership to the returned
    /// `TcpStream` if successful. An unconnected `TcpStream` can be created
    /// with the `net2::TcpBuilder` type (and also configured via that route).
    ///
    /// The platform specific behavior of this function looks like:
    ///
    /// * On Unix, the socket is placed into nonblocking mode and then a
    ///   `connect` call is issued.
    ///
    /// * On Windows, the address is stored internally and the connect operation
    ///   is issued when the returned `TcpStream` is registered with an event
    ///   loop. Note that on Windows you must `bind` a socket before it can be
    ///   connected, so if a custom `TcpBuilder` is used it should be bound
    ///   (perhaps to `INADDR_ANY`) before this method is called.
    pub fn connect_stream(stream: net::TcpStream,
                          addr: &SocketAddr,
                          handle: &Handle) -> IoFuture<TcpStream> {
        match mio::tcp::TcpStream::connect_stream(stream, addr) {
            Ok(tcp) => TcpStream::new(tcp, handle),
            Err(e) => failed(e).boxed(),
        }
    }

    /// Test whether this socket is ready to be read or not.
    ///
    /// If the socket is *not* readable then the current task is scheduled to
    /// get a notification when the socket does become readable. That is, this
    /// is only suitable for calling in a `Future::poll` method and will
    /// automatically handle ensuring a retry once the socket is readable again.
    pub fn poll_read(&self) -> Async<()> {
        self.io.poll_read()
    }

    /// Test whether this socket is ready to be written to or not.
    ///
    /// If the socket is *not* writable then the current task is scheduled to
    /// get a notification when the socket does become writable. That is, this
    /// is only suitable for calling in a `Future::poll` method and will
    /// automatically handle ensuring a retry once the socket is writable again.
    pub fn poll_write(&self) -> Async<()> {
        self.io.poll_write()
    }

    /// Returns the local address that this stream is bound to.
    pub fn local_addr(&self) -> io::Result<SocketAddr> {
        self.io.get_ref().local_addr()
    }

    /// Returns the remote address that this stream is connected to.
    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
        self.io.get_ref().peer_addr()
    }

    /// Shuts down the read, write, or both halves of this connection.
    ///
    /// This function will cause all pending and future I/O on the specified
    /// portions to return immediately with an appropriate value (see the
    /// documentation of `Shutdown`).
    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
        self.io.get_ref().shutdown(how)
    }

    /// Sets the value of the `TCP_NODELAY` option on this socket.
    ///
    /// If set, this option disables the Nagle algorithm. This means that
    /// segments are always sent as soon as possible, even if there is only a
    /// small amount of data. When not set, data is buffered until there is a
    /// sufficient amount to send out, thereby avoiding the frequent sending of
    /// small packets.
    pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
        self.io.get_ref().set_nodelay(nodelay)
    }

    /// Gets the value of the `TCP_NODELAY` option on this socket.
    ///
    /// For more information about this option, see [`set_nodelay`][link].
    ///
    /// [link]: #method.set_nodelay
    pub fn nodelay(&self) -> io::Result<bool> {
        self.io.get_ref().nodelay()
    }

    /// Sets whether keepalive messages are enabled to be sent on this socket.
    ///
    /// On Unix, this option will set the `SO_KEEPALIVE` as well as the
    /// `TCP_KEEPALIVE` or `TCP_KEEPIDLE` option (depending on your platform).
    /// On Windows, this will set the `SIO_KEEPALIVE_VALS` option.
    ///
    /// If `None` is specified then keepalive messages are disabled, otherwise
    /// the number of milliseconds specified will be the time to remain idle
    /// before sending a TCP keepalive probe.
    ///
    /// Some platforms specify this value in seconds, so sub-second millisecond
    /// specifications may be omitted.
    pub fn set_keepalive_ms(&self, keepalive: Option<u32>) -> io::Result<()> {
        self.io.get_ref().set_keepalive_ms(keepalive)
    }

    /// Returns whether keepalive messages are enabled on this socket, and if so
    /// the amount of milliseconds between them.
    ///
    /// For more information about this option, see [`set_keepalive_ms`][link].
    ///
    /// [link]: #method.set_keepalive_ms
    pub fn keepalive_ms(&self) -> io::Result<Option<u32>> {
        self.io.get_ref().keepalive_ms()
    }

    /// Sets the value for the `IP_TTL` option on this socket.
    ///
    /// This value sets the time-to-live field that is used in every packet sent
    /// from this socket.
    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
        self.io.get_ref().set_ttl(ttl)
    }

    /// Gets the value of the `IP_TTL` option for this socket.
    ///
    /// For more information about this option, see [`set_ttl`][link].
    ///
    /// [link]: #method.set_ttl
    pub fn ttl(&self) -> io::Result<u32> {
        self.io.get_ref().ttl()
    }
}

impl Read for TcpStream {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.io.read(buf)
    }
}

impl Write for TcpStream {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.io.write(buf)
    }
    fn flush(&mut self) -> io::Result<()> {
        self.io.flush()
    }
}

impl Io for TcpStream {
    fn poll_read(&mut self) -> Async<()> {
        <TcpStream>::poll_read(self)
    }

    fn poll_write(&mut self) -> Async<()> {
        <TcpStream>::poll_write(self)
    }
}

impl<'a> Read for &'a TcpStream {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        (&self.io).read(buf)
    }
}

impl<'a> Write for &'a TcpStream {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        (&self.io).write(buf)
    }

    fn flush(&mut self) -> io::Result<()> {
        (&self.io).flush()
    }
}

impl<'a> Io for &'a TcpStream {
    fn poll_read(&mut self) -> Async<()> {
        <TcpStream>::poll_read(self)
    }

    fn poll_write(&mut self) -> Async<()> {
        <TcpStream>::poll_write(self)
    }
}

impl fmt::Debug for TcpStream {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.io.get_ref().fmt(f)
    }
}

impl Future for TcpStreamNew {
    type Item = TcpStream;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<TcpStream, io::Error> {
        self.inner.poll()
    }
}

impl Future for TcpStreamConnect {
    type Item = TcpStream;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<TcpStream, io::Error> {
        {
            let stream = match *self {
                TcpStreamConnect::Waiting(ref s) => s,
                TcpStreamConnect::Empty => panic!("can't poll TCP stream twice"),
            };

            // Once we've connected, wait for the stream to be writable as
            // that's when the actual connection has been initiated. Once we're
            // writable we check for `take_socket_error` to see if the connect
            // actually hit an error or not.
            //
            // If all that succeeded then we ship everything on up.
            if let Async::NotReady = stream.io.poll_write() {
                return Ok(Async::NotReady)
            }
            if let Some(e) = try!(stream.io.get_ref().take_error()) {
                return Err(e)
            }
        }
        match mem::replace(self, TcpStreamConnect::Empty) {
            TcpStreamConnect::Waiting(stream) => Ok(Async::Ready(stream)),
            TcpStreamConnect::Empty => panic!(),
        }
    }
}

#[cfg(unix)]
mod sys {
    use std::os::unix::prelude::*;
    use super::{TcpStream, TcpListener};

    impl AsRawFd for TcpStream {
        fn as_raw_fd(&self) -> RawFd {
            self.io.get_ref().as_raw_fd()
        }
    }

    impl AsRawFd for TcpListener {
        fn as_raw_fd(&self) -> RawFd {
            self.io.get_ref().as_raw_fd()
        }
    }
}

#[cfg(windows)]
mod sys {
    // TODO: let's land these upstream with mio and then we can add them here.
    //
    // use std::os::windows::prelude::*;
    // use super::{TcpStream, TcpListener};
    //
    // impl AsRawHandle for TcpStream {
    //     fn as_raw_handle(&self) -> RawHandle {
    //         self.io.get_ref().as_raw_handle()
    //     }
    // }
    //
    // impl AsRawHandle for TcpListener {
    //     fn as_raw_handle(&self) -> RawHandle {
    //         self.listener.io().as_raw_handle()
    //     }
    // }
}