use std::io;
use std::mem;
use std::net::{self, SocketAddr, Ipv4Addr, Ipv6Addr};
use std::fmt;

use futures::{Async, Future, Poll};
use mio;

use reactor::{Handle, PollEvented};

/// An I/O object representing a UDP socket.
pub struct UdpSocket {
    io: PollEvented<mio::udp::UdpSocket>,
}

mod frame;
pub use self::frame::{UdpFramed, UdpCodec};

impl UdpSocket {
    /// Create a new UDP socket bound to the specified address.
    ///
    /// This function will create a new UDP socket and attempt to bind it to the
    /// `addr` provided. If the result is `Ok`, the socket has successfully bound.
    pub fn bind(addr: &SocketAddr, handle: &Handle) -> io::Result<UdpSocket> {
        let udp = try!(mio::udp::UdpSocket::bind(addr));
        UdpSocket::new(udp, handle)
    }

    fn new(socket: mio::udp::UdpSocket, handle: &Handle) -> io::Result<UdpSocket> {
        let io = try!(PollEvented::new(socket, handle));
        Ok(UdpSocket { io: io })
    }

    /// Creates a new `UdpSocket` from the previously bound socket provided.
    ///
    /// The socket given will be registered with the event loop that `handle` is
    /// associated with. This function requires that `socket` has previously
    /// been bound to an address to work correctly.
    ///
    /// This can be used in conjunction with net2's `UdpBuilder` interface to
    /// configure a socket before it's handed off, such as setting options like
    /// `reuse_address` or binding to multiple addresses.
    pub fn from_socket(socket: net::UdpSocket,
                       handle: &Handle) -> io::Result<UdpSocket> {
        let udp = try!(mio::udp::UdpSocket::from_socket(socket));
        UdpSocket::new(udp, handle)
    }

    /// Provides a `Stream` and `Sink` interface for reading and writing to this
    /// `UdpSocket` object, using the provided `UdpCodec` to read and write the
    /// raw data.
    ///
    /// Raw UDP sockets work with datagrams, but higher-level code usually
    /// wants to batch these into meaningful chunks, called "frames". This
    /// method layers framing on top of this socket by using the `UdpCodec`
    /// trait to handle encoding and decoding of messages frames. Note that
    /// the incoming and outgoing frame types may be distinct.
    ///
    /// This function returns a *single* object that is both `Stream` and
    /// `Sink`; grouping this into a single object is often useful for layering
    /// things which require both read and write access to the underlying
    /// object.
    ///
    /// If you want to work more directly with the streams and sink, consider
    /// calling `split` on the `UdpFramed` returned by this method, which will
    /// break them into separate objects, allowing them to interact more
    /// easily.
    pub fn framed<C: UdpCodec>(self, codec: C) -> UdpFramed<C> {
        frame::new(self, codec)
    }

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

    /// 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()
    }

    /// Sends data on the socket to the given address. On success, returns the
    /// number of bytes written.
    ///
    /// Address type can be any implementor of `ToSocketAddrs` trait. See its
    /// documentation for concrete examples.
    pub fn send_to(&self, buf: &[u8], target: &SocketAddr) -> io::Result<usize> {
        if let Async::NotReady = self.io.poll_write() {
            return Err(mio::would_block())
        }
        match self.io.get_ref().send_to(buf, target) {
            Ok(Some(n)) => Ok(n),
            Ok(None) => {
                self.io.need_write();
                Err(mio::would_block())
            }
            Err(e) => Err(e),
        }
    }

    /// Creates a future that will write the entire contents of the buffer
    /// `buf` provided as a datagram to this socket.
    ///
    /// The returned future will return after data has been written to the
    /// outbound socket.  The future will resolve to the stream as well as the
    /// buffer (for reuse if needed).
    ///
    /// Any error which happens during writing will cause both the stream and
    /// the buffer to get destroyed. Note that failure to write the entire
    /// buffer is considered an error for the purposes of sending a datagram.
    ///
    /// The `buf` parameter here only requires the `AsRef<[u8]>` trait, which
    /// should be broadly applicable to accepting data which can be converted
    /// to a slice.  The `Window` struct is also available in this crate to
    /// provide a different window into a slice if necessary.
    pub fn send_dgram<T>(self, buf: T, addr: SocketAddr) -> SendDgram<T>
        where T: AsRef<[u8]>,
    {
        SendDgram {
            state: SendState::Writing {
                sock: self,
                addr: addr,
                buf: buf,
            },
        }
    }

    /// Receives data from the socket. On success, returns the number of bytes
    /// read and the address from whence the data came.
    pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
        if let Async::NotReady = self.io.poll_read() {
            return Err(mio::would_block())
        }
        match self.io.get_ref().recv_from(buf) {
            Ok(Some(n)) => Ok(n),
            Ok(None) => {
                self.io.need_read();
                Err(mio::would_block())
            }
            Err(e) => Err(e),
        }
    }

    /// Creates a future that receive a datagram to be written to the buffer
    /// provided.
    ///
    /// The returned future will return after a datagram has been received on
    /// this socket. The future will resolve to the socket, the buffer, the
    /// amount of data read, and the address the data was received from.
    ///
    /// An error during reading will cause the socket and buffer to get
    /// destroyed and the socket will be returned.
    ///
    /// The `buf` parameter here only requires the `AsMut<[u8]>` trait, which
    /// should be broadly applicable to accepting data which can be converted
    /// to a slice.  The `Window` struct is also available in this crate to
    /// provide a different window into a slice if necessary.
    pub fn recv_dgram<T>(self, buf: T) -> RecvDgram<T>
        where T: AsMut<[u8]>,
    {
        RecvDgram {
            state: RecvState::Reading {
                sock: self,
                buf: buf,
            },
        }
    }

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

    /// Sets the value of the `SO_BROADCAST` option for this socket.
    ///
    /// When enabled, this socket is allowed to send packets to a broadcast
    /// address.
    pub fn set_broadcast(&self, on: bool) -> io::Result<()> {
        self.io.get_ref().set_broadcast(on)
    }

    /// Gets the value of the `IP_MULTICAST_LOOP` option for this socket.
    ///
    /// For more information about this option, see
    /// [`set_multicast_loop_v4`][link].
    ///
    /// [link]: #method.set_multicast_loop_v4
    pub fn multicast_loop_v4(&self) -> io::Result<bool> {
        self.io.get_ref().multicast_loop_v4()
    }

    /// Sets the value of the `IP_MULTICAST_LOOP` option for this socket.
    ///
    /// If enabled, multicast packets will be looped back to the local socket.
    /// Note that this may not have any affect on IPv6 sockets.
    pub fn set_multicast_loop_v4(&self, on: bool) -> io::Result<()> {
        self.io.get_ref().set_multicast_loop_v4(on)
    }

    /// Gets the value of the `IP_MULTICAST_TTL` option for this socket.
    ///
    /// For more information about this option, see
    /// [`set_multicast_ttl_v4`][link].
    ///
    /// [link]: #method.set_multicast_ttl_v4
    pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
        self.io.get_ref().multicast_ttl_v4()
    }

    /// Sets the value of the `IP_MULTICAST_TTL` option for this socket.
    ///
    /// Indicates the time-to-live value of outgoing multicast packets for
    /// this socket. The default value is 1 which means that multicast packets
    /// don't leave the local network unless explicitly requested.
    ///
    /// Note that this may not have any affect on IPv6 sockets.
    pub fn set_multicast_ttl_v4(&self, ttl: u32) -> io::Result<()> {
        self.io.get_ref().set_multicast_ttl_v4(ttl)
    }

    /// Gets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
    ///
    /// For more information about this option, see
    /// [`set_multicast_loop_v6`][link].
    ///
    /// [link]: #method.set_multicast_loop_v6
    pub fn multicast_loop_v6(&self) -> io::Result<bool> {
        self.io.get_ref().multicast_loop_v6()
    }

    /// Sets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
    ///
    /// Controls whether this socket sees the multicast packets it sends itself.
    /// Note that this may not have any affect on IPv4 sockets.
    pub fn set_multicast_loop_v6(&self, on: bool) -> io::Result<()> {
        self.io.get_ref().set_multicast_loop_v6(on)
    }

    /// 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 `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)
    }

    /// Executes an operation of the `IP_ADD_MEMBERSHIP` type.
    ///
    /// This function specifies a new multicast group for this socket to join.
    /// The address must be a valid multicast address, and `interface` is the
    /// address of the local interface with which the system should join the
    /// multicast group. If it's equal to `INADDR_ANY` then an appropriate
    /// interface is chosen by the system.
    pub fn join_multicast_v4(&self,
                             multiaddr: &Ipv4Addr,
                             interface: &Ipv4Addr) -> io::Result<()> {
        self.io.get_ref().join_multicast_v4(multiaddr, interface)
    }

    /// Executes an operation of the `IPV6_ADD_MEMBERSHIP` type.
    ///
    /// This function specifies a new multicast group for this socket to join.
    /// The address must be a valid multicast address, and `interface` is the
    /// index of the interface to join/leave (or 0 to indicate any interface).
    pub fn join_multicast_v6(&self,
                             multiaddr: &Ipv6Addr,
                             interface: u32) -> io::Result<()> {
        self.io.get_ref().join_multicast_v6(multiaddr, interface)
    }

    /// Executes an operation of the `IP_DROP_MEMBERSHIP` type.
    ///
    /// For more information about this option, see
    /// [`join_multicast_v4`][link].
    ///
    /// [link]: #method.join_multicast_v4
    pub fn leave_multicast_v4(&self,
                              multiaddr: &Ipv4Addr,
                              interface: &Ipv4Addr) -> io::Result<()> {
        self.io.get_ref().leave_multicast_v4(multiaddr, interface)
    }

    /// Executes an operation of the `IPV6_DROP_MEMBERSHIP` type.
    ///
    /// For more information about this option, see
    /// [`join_multicast_v6`][link].
    ///
    /// [link]: #method.join_multicast_v6
    pub fn leave_multicast_v6(&self,
                              multiaddr: &Ipv6Addr,
                              interface: u32) -> io::Result<()> {
        self.io.get_ref().leave_multicast_v6(multiaddr, interface)
    }
}

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

/// A future used to write the entire contents of some data to a UDP socket.
///
/// This is created by the `UdpSocket::send_dgram` method.
pub struct SendDgram<T> {
    state: SendState<T>,
}

enum SendState<T> {
    Writing {
        sock: UdpSocket,
        buf: T,
        addr: SocketAddr,
    },
    Empty,
}

fn incomplete_write(reason: &str) -> io::Error {
    io::Error::new(io::ErrorKind::Other, reason)
}

impl<T> Future for SendDgram<T>
    where T: AsRef<[u8]>,
{
    type Item = (UdpSocket, T);
    type Error = io::Error;

    fn poll(&mut self) -> Poll<(UdpSocket, T), io::Error> {
        match self.state {
            SendState::Writing { ref sock, ref buf, ref addr } => {
                let n = try_nb!(sock.send_to(buf.as_ref(), addr));
                if n != buf.as_ref().len() {
                    return Err(incomplete_write("failed to send entire message \
                                                 in datagram"))
                }
            }
            SendState::Empty => panic!("poll a SendDgram after it's done"),
        }

        match mem::replace(&mut self.state, SendState::Empty) {
            SendState::Writing { sock, buf, addr: _ } => {
                Ok(Async::Ready((sock, buf)))
            }
            SendState::Empty => panic!(),
        }
    }
}

/// A future used to receive a datagram from a UDP socket.
///
/// This is created by the `UdpSocket::recv_dgram` method.
pub struct RecvDgram<T> {
    state: RecvState<T>,
}

enum RecvState<T> {
    Reading {
        sock: UdpSocket,
        buf: T,
    },
    Empty,
}

impl<T> Future for RecvDgram<T>
    where T: AsMut<[u8]>,
{
    type Item = (UdpSocket, T, usize, SocketAddr);
    type Error = io::Error;

    fn poll(&mut self) -> Poll<Self::Item, io::Error> {
        let (n, addr) = match self.state {
            RecvState::Reading { ref sock, ref mut buf } => {
                try_nb!(sock.recv_from(buf.as_mut()))
            }
            RecvState::Empty => panic!("poll a RecvDgram after it's done"),
        };

        match mem::replace(&mut self.state, RecvState::Empty) {
            RecvState::Reading { sock, buf } => {
                Ok(Async::Ready((sock, buf, n, addr)))
            }
            RecvState::Empty => panic!(),
        }
    }
}

#[cfg(unix)]
mod sys {
    use std::os::unix::prelude::*;
    use super::UdpSocket;

    impl AsRawFd for UdpSocket {
        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::UdpSocket;
    //
    // impl AsRawHandle for UdpSocket {
    //     fn as_raw_handle(&self) -> RawHandle {
    //         self.io.get_ref().as_raw_handle()
    //     }
    // }
}