use core::cmp::min;
#[cfg(feature = "async")]
use core::task::Waker;

use crate::iface::Context;
use crate::phy::ChecksumCapabilities;
use crate::socket::PollAt;
#[cfg(feature = "async")]
use crate::socket::WakerRegistration;
use crate::storage::{PacketBuffer, PacketMetadata};
use crate::{Error, Result};

use crate::wire::{IpProtocol, IpRepr, IpVersion};
#[cfg(feature = "proto-ipv4")]
use crate::wire::{Ipv4Packet, Ipv4Repr};
#[cfg(feature = "proto-ipv6")]
use crate::wire::{Ipv6Packet, Ipv6Repr};

/// A UDP packet metadata.
pub type RawPacketMetadata = PacketMetadata<()>;

/// A UDP packet ring buffer.
pub type RawSocketBuffer<'a> = PacketBuffer<'a, ()>;

/// A raw IP socket.
///
/// A raw socket is bound to a specific IP protocol, and owns
/// transmit and receive packet buffers.
#[derive(Debug)]
pub struct RawSocket<'a> {
    ip_version: IpVersion,
    ip_protocol: IpProtocol,
    rx_buffer: RawSocketBuffer<'a>,
    tx_buffer: RawSocketBuffer<'a>,
    #[cfg(feature = "async")]
    rx_waker: WakerRegistration,
    #[cfg(feature = "async")]
    tx_waker: WakerRegistration,
}

impl<'a> RawSocket<'a> {
    /// Create a raw IP socket bound to the given IP version and datagram protocol,
    /// with the given buffers.
    pub fn new(
        ip_version: IpVersion,
        ip_protocol: IpProtocol,
        rx_buffer: RawSocketBuffer<'a>,
        tx_buffer: RawSocketBuffer<'a>,
    ) -> RawSocket<'a> {
        RawSocket {
            ip_version,
            ip_protocol,
            rx_buffer,
            tx_buffer,
            #[cfg(feature = "async")]
            rx_waker: WakerRegistration::new(),
            #[cfg(feature = "async")]
            tx_waker: WakerRegistration::new(),
        }
    }

    /// Register a waker for receive operations.
    ///
    /// The waker is woken on state changes that might affect the return value
    /// of `recv` method calls, such as receiving data, or the socket closing.
    ///
    /// Notes:
    ///
    /// - Only one waker can be registered at a time. If another waker was previously registered,
    ///   it is overwritten and will no longer be woken.
    /// - The Waker is woken only once. Once woken, you must register it again to receive more wakes.
    /// - "Spurious wakes" are allowed: a wake doesn't guarantee the result of `recv` has
    ///   necessarily changed.
    #[cfg(feature = "async")]
    pub fn register_recv_waker(&mut self, waker: &Waker) {
        self.rx_waker.register(waker)
    }

    /// Register a waker for send operations.
    ///
    /// The waker is woken on state changes that might affect the return value
    /// of `send` method calls, such as space becoming available in the transmit
    /// buffer, or the socket closing.
    ///
    /// Notes:
    ///
    /// - Only one waker can be registered at a time. If another waker was previously registered,
    ///   it is overwritten and will no longer be woken.
    /// - The Waker is woken only once. Once woken, you must register it again to receive more wakes.
    /// - "Spurious wakes" are allowed: a wake doesn't guarantee the result of `send` has
    ///   necessarily changed.
    #[cfg(feature = "async")]
    pub fn register_send_waker(&mut self, waker: &Waker) {
        self.tx_waker.register(waker)
    }

    /// Return the IP version the socket is bound to.
    #[inline]
    pub fn ip_version(&self) -> IpVersion {
        self.ip_version
    }

    /// Return the IP protocol the socket is bound to.
    #[inline]
    pub fn ip_protocol(&self) -> IpProtocol {
        self.ip_protocol
    }

    /// Check whether the transmit buffer is full.
    #[inline]
    pub fn can_send(&self) -> bool {
        !self.tx_buffer.is_full()
    }

    /// Check whether the receive buffer is not empty.
    #[inline]
    pub fn can_recv(&self) -> bool {
        !self.rx_buffer.is_empty()
    }

    /// Return the maximum number packets the socket can receive.
    #[inline]
    pub fn packet_recv_capacity(&self) -> usize {
        self.rx_buffer.packet_capacity()
    }

    /// Return the maximum number packets the socket can transmit.
    #[inline]
    pub fn packet_send_capacity(&self) -> usize {
        self.tx_buffer.packet_capacity()
    }

    /// Return the maximum number of bytes inside the recv buffer.
    #[inline]
    pub fn payload_recv_capacity(&self) -> usize {
        self.rx_buffer.payload_capacity()
    }

    /// Return the maximum number of bytes inside the transmit buffer.
    #[inline]
    pub fn payload_send_capacity(&self) -> usize {
        self.tx_buffer.payload_capacity()
    }

    /// Enqueue a packet to send, and return a pointer to its payload.
    ///
    /// This function returns `Err(Error::Exhausted)` if the transmit buffer is full,
    /// and `Err(Error::Truncated)` if there is not enough transmit buffer capacity
    /// to ever send this packet.
    ///
    /// If the buffer is filled in a way that does not match the socket's
    /// IP version or protocol, the packet will be silently dropped.
    ///
    /// **Note:** The IP header is parsed and reserialized, and may not match
    /// the header actually transmitted bit for bit.
    pub fn send(&mut self, size: usize) -> Result<&mut [u8]> {
        let packet_buf = self.tx_buffer.enqueue(size, ())?;

        net_trace!(
            "raw:{}:{}: buffer to send {} octets",
            self.ip_version,
            self.ip_protocol,
            packet_buf.len()
        );
        Ok(packet_buf)
    }

    /// Enqueue a packet to send, and fill it from a slice.
    ///
    /// See also [send](#method.send).
    pub fn send_slice(&mut self, data: &[u8]) -> Result<()> {
        self.send(data.len())?.copy_from_slice(data);
        Ok(())
    }

    /// Dequeue a packet, and return a pointer to the payload.
    ///
    /// This function returns `Err(Error::Exhausted)` if the receive buffer is empty.
    ///
    /// **Note:** The IP header is parsed and reserialized, and may not match
    /// the header actually received bit for bit.
    pub fn recv(&mut self) -> Result<&[u8]> {
        let ((), packet_buf) = self.rx_buffer.dequeue()?;

        net_trace!(
            "raw:{}:{}: receive {} buffered octets",
            self.ip_version,
            self.ip_protocol,
            packet_buf.len()
        );
        Ok(packet_buf)
    }

    /// Dequeue a packet, and copy the payload into the given slice.
    ///
    /// See also [recv](#method.recv).
    pub fn recv_slice(&mut self, data: &mut [u8]) -> Result<usize> {
        let buffer = self.recv()?;
        let length = min(data.len(), buffer.len());
        data[..length].copy_from_slice(&buffer[..length]);
        Ok(length)
    }

    pub(crate) fn accepts(&self, ip_repr: &IpRepr) -> bool {
        if ip_repr.version() != self.ip_version {
            return false;
        }
        if ip_repr.protocol() != self.ip_protocol {
            return false;
        }

        true
    }

    pub(crate) fn process(
        &mut self,
        cx: &mut Context,
        ip_repr: &IpRepr,
        payload: &[u8],
    ) -> Result<()> {
        debug_assert!(self.accepts(ip_repr));

        let header_len = ip_repr.buffer_len();
        let total_len = header_len + payload.len();
        let packet_buf = self.rx_buffer.enqueue(total_len, ())?;
        ip_repr.emit(&mut packet_buf[..header_len], &cx.checksum_caps());
        packet_buf[header_len..].copy_from_slice(payload);

        net_trace!(
            "raw:{}:{}: receiving {} octets",
            self.ip_version,
            self.ip_protocol,
            packet_buf.len()
        );

        #[cfg(feature = "async")]
        self.rx_waker.wake();

        Ok(())
    }

    pub(crate) fn dispatch<F>(&mut self, cx: &mut Context, emit: F) -> Result<()>
    where
        F: FnOnce(&mut Context, (IpRepr, &[u8])) -> Result<()>,
    {
        fn prepare<'a>(
            protocol: IpProtocol,
            buffer: &'a mut [u8],
            _checksum_caps: &ChecksumCapabilities,
        ) -> Result<(IpRepr, &'a [u8])> {
            match IpVersion::of_packet(buffer)? {
                #[cfg(feature = "proto-ipv4")]
                IpVersion::Ipv4 => {
                    let mut packet = Ipv4Packet::new_checked(buffer)?;
                    if packet.protocol() != protocol {
                        return Err(Error::Unaddressable);
                    }
                    if _checksum_caps.ipv4.tx() {
                        packet.fill_checksum();
                    } else {
                        // make sure we get a consistently zeroed checksum,
                        // since implementations might rely on it
                        packet.set_checksum(0);
                    }

                    let packet = Ipv4Packet::new_checked(&*packet.into_inner())?;
                    let ipv4_repr = Ipv4Repr::parse(&packet, _checksum_caps)?;
                    Ok((IpRepr::Ipv4(ipv4_repr), packet.payload()))
                }
                #[cfg(feature = "proto-ipv6")]
                IpVersion::Ipv6 => {
                    let packet = Ipv6Packet::new_checked(buffer)?;
                    if packet.next_header() != protocol {
                        return Err(Error::Unaddressable);
                    }
                    let packet = Ipv6Packet::new_unchecked(&*packet.into_inner());
                    let ipv6_repr = Ipv6Repr::parse(&packet)?;
                    Ok((IpRepr::Ipv6(ipv6_repr), packet.payload()))
                }
                IpVersion::Unspecified => unreachable!(),
            }
        }

        let ip_protocol = self.ip_protocol;
        let ip_version = self.ip_version;
        self.tx_buffer.dequeue_with(|&mut (), packet_buf| {
            match prepare(ip_protocol, packet_buf, &cx.checksum_caps()) {
                Ok((ip_repr, raw_packet)) => {
                    net_trace!(
                        "raw:{}:{}: sending {} octets",
                        ip_version,
                        ip_protocol,
                        ip_repr.buffer_len() + raw_packet.len()
                    );
                    emit(cx, (ip_repr, raw_packet))
                }
                Err(error) => {
                    net_debug!(
                        "raw:{}:{}: dropping outgoing packet ({})",
                        ip_version,
                        ip_protocol,
                        error
                    );
                    // Return Ok(()) so the packet is dequeued.
                    Ok(())
                }
            }
        })?;

        #[cfg(feature = "async")]
        self.tx_waker.wake();

        Ok(())
    }

    pub(crate) fn poll_at(&self, _cx: &mut Context) -> PollAt {
        if self.tx_buffer.is_empty() {
            PollAt::Ingress
        } else {
            PollAt::Now
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::wire::IpRepr;
    #[cfg(feature = "proto-ipv4")]
    use crate::wire::{Ipv4Address, Ipv4Repr};
    #[cfg(feature = "proto-ipv6")]
    use crate::wire::{Ipv6Address, Ipv6Repr};

    fn buffer(packets: usize) -> RawSocketBuffer<'static> {
        RawSocketBuffer::new(
            vec![RawPacketMetadata::EMPTY; packets],
            vec![0; 48 * packets],
        )
    }

    #[cfg(feature = "proto-ipv4")]
    mod ipv4_locals {
        use super::*;

        pub fn socket(
            rx_buffer: RawSocketBuffer<'static>,
            tx_buffer: RawSocketBuffer<'static>,
        ) -> RawSocket<'static> {
            RawSocket::new(
                IpVersion::Ipv4,
                IpProtocol::Unknown(IP_PROTO),
                rx_buffer,
                tx_buffer,
            )
        }

        pub const IP_PROTO: u8 = 63;
        pub const HEADER_REPR: IpRepr = IpRepr::Ipv4(Ipv4Repr {
            src_addr: Ipv4Address([10, 0, 0, 1]),
            dst_addr: Ipv4Address([10, 0, 0, 2]),
            protocol: IpProtocol::Unknown(IP_PROTO),
            payload_len: 4,
            hop_limit: 64,
        });
        pub const PACKET_BYTES: [u8; 24] = [
            0x45, 0x00, 0x00, 0x18, 0x00, 0x00, 0x40, 0x00, 0x40, 0x3f, 0x00, 0x00, 0x0a, 0x00,
            0x00, 0x01, 0x0a, 0x00, 0x00, 0x02, 0xaa, 0x00, 0x00, 0xff,
        ];
        pub const PACKET_PAYLOAD: [u8; 4] = [0xaa, 0x00, 0x00, 0xff];
    }

    #[cfg(feature = "proto-ipv6")]
    mod ipv6_locals {
        use super::*;

        pub fn socket(
            rx_buffer: RawSocketBuffer<'static>,
            tx_buffer: RawSocketBuffer<'static>,
        ) -> RawSocket<'static> {
            RawSocket::new(
                IpVersion::Ipv6,
                IpProtocol::Unknown(IP_PROTO),
                rx_buffer,
                tx_buffer,
            )
        }

        pub const IP_PROTO: u8 = 63;
        pub const HEADER_REPR: IpRepr = IpRepr::Ipv6(Ipv6Repr {
            src_addr: Ipv6Address([
                0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x01,
            ]),
            dst_addr: Ipv6Address([
                0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x02,
            ]),
            next_header: IpProtocol::Unknown(IP_PROTO),
            payload_len: 4,
            hop_limit: 64,
        });

        pub const PACKET_BYTES: [u8; 44] = [
            0x60, 0x00, 0x00, 0x00, 0x00, 0x04, 0x3f, 0x40, 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0xfe, 0x80, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xaa, 0x00,
            0x00, 0xff,
        ];

        pub const PACKET_PAYLOAD: [u8; 4] = [0xaa, 0x00, 0x00, 0xff];
    }

    macro_rules! reusable_ip_specific_tests {
        ($module:ident, $socket:path, $hdr:path, $packet:path, $payload:path) => {
            mod $module {
                use super::*;

                #[test]
                fn test_send_truncated() {
                    let mut socket = $socket(buffer(0), buffer(1));
                    assert_eq!(socket.send_slice(&[0; 56][..]), Err(Error::Truncated));
                }

                #[test]
                fn test_send_dispatch() {
                    let mut socket = $socket(buffer(0), buffer(1));
                    let mut cx = Context::mock();

                    assert!(socket.can_send());
                    assert_eq!(
                        socket.dispatch(&mut cx, |_, _| unreachable!()),
                        Err(Error::Exhausted)
                    );

                    assert_eq!(socket.send_slice(&$packet[..]), Ok(()));
                    assert_eq!(socket.send_slice(b""), Err(Error::Exhausted));
                    assert!(!socket.can_send());

                    assert_eq!(
                        socket.dispatch(&mut cx, |_, (ip_repr, ip_payload)| {
                            assert_eq!(ip_repr, $hdr);
                            assert_eq!(ip_payload, &$payload);
                            Err(Error::Unaddressable)
                        }),
                        Err(Error::Unaddressable)
                    );
                    assert!(!socket.can_send());

                    assert_eq!(
                        socket.dispatch(&mut cx, |_, (ip_repr, ip_payload)| {
                            assert_eq!(ip_repr, $hdr);
                            assert_eq!(ip_payload, &$payload);
                            Ok(())
                        }),
                        Ok(())
                    );
                    assert!(socket.can_send());
                }

                #[test]
                fn test_recv_truncated_slice() {
                    let mut socket = $socket(buffer(1), buffer(0));
                    let mut cx = Context::mock();

                    assert!(socket.accepts(&$hdr));
                    assert_eq!(socket.process(&mut cx, &$hdr, &$payload), Ok(()));

                    let mut slice = [0; 4];
                    assert_eq!(socket.recv_slice(&mut slice[..]), Ok(4));
                    assert_eq!(&slice, &$packet[..slice.len()]);
                }

                #[test]
                fn test_recv_truncated_packet() {
                    let mut socket = $socket(buffer(1), buffer(0));
                    let mut cx = Context::mock();

                    let mut buffer = vec![0; 128];
                    buffer[..$packet.len()].copy_from_slice(&$packet[..]);

                    assert!(socket.accepts(&$hdr));
                    assert_eq!(
                        socket.process(&mut cx, &$hdr, &buffer),
                        Err(Error::Truncated)
                    );
                }
            }
        };
    }

    #[cfg(feature = "proto-ipv4")]
    reusable_ip_specific_tests!(
        ipv4,
        ipv4_locals::socket,
        ipv4_locals::HEADER_REPR,
        ipv4_locals::PACKET_BYTES,
        ipv4_locals::PACKET_PAYLOAD
    );

    #[cfg(feature = "proto-ipv6")]
    reusable_ip_specific_tests!(
        ipv6,
        ipv6_locals::socket,
        ipv6_locals::HEADER_REPR,
        ipv6_locals::PACKET_BYTES,
        ipv6_locals::PACKET_PAYLOAD
    );

    #[test]
    #[cfg(feature = "proto-ipv4")]
    fn test_send_illegal() {
        #[cfg(feature = "proto-ipv4")]
        {
            let mut socket = ipv4_locals::socket(buffer(0), buffer(2));
            let mut cx = Context::mock();

            let mut wrong_version = ipv4_locals::PACKET_BYTES;
            Ipv4Packet::new_unchecked(&mut wrong_version).set_version(6);

            assert_eq!(socket.send_slice(&wrong_version[..]), Ok(()));
            assert_eq!(socket.dispatch(&mut cx, |_, _| unreachable!()), Ok(()));

            let mut wrong_protocol = ipv4_locals::PACKET_BYTES;
            Ipv4Packet::new_unchecked(&mut wrong_protocol).set_protocol(IpProtocol::Tcp);

            assert_eq!(socket.send_slice(&wrong_protocol[..]), Ok(()));
            assert_eq!(socket.dispatch(&mut cx, |_, _| unreachable!()), Ok(()));
        }
        #[cfg(feature = "proto-ipv6")]
        {
            let mut socket = ipv6_locals::socket(buffer(0), buffer(2));
            let mut cx = Context::mock();

            let mut wrong_version = ipv6_locals::PACKET_BYTES;
            Ipv6Packet::new_unchecked(&mut wrong_version[..]).set_version(4);

            assert_eq!(socket.send_slice(&wrong_version[..]), Ok(()));
            assert_eq!(socket.dispatch(&mut cx, |_, _| unreachable!()), Ok(()));

            let mut wrong_protocol = ipv6_locals::PACKET_BYTES;
            Ipv6Packet::new_unchecked(&mut wrong_protocol[..]).set_next_header(IpProtocol::Tcp);

            assert_eq!(socket.send_slice(&wrong_protocol[..]), Ok(()));
            assert_eq!(socket.dispatch(&mut cx, |_, _| unreachable!()), Ok(()));
        }
    }

    #[test]
    fn test_recv_process() {
        #[cfg(feature = "proto-ipv4")]
        {
            let mut socket = ipv4_locals::socket(buffer(1), buffer(0));
            assert!(!socket.can_recv());
            let mut cx = Context::mock();

            let mut cksumd_packet = ipv4_locals::PACKET_BYTES;
            Ipv4Packet::new_unchecked(&mut cksumd_packet).fill_checksum();

            assert_eq!(socket.recv(), Err(Error::Exhausted));
            assert!(socket.accepts(&ipv4_locals::HEADER_REPR));
            assert_eq!(
                socket.process(
                    &mut cx,
                    &ipv4_locals::HEADER_REPR,
                    &ipv4_locals::PACKET_PAYLOAD
                ),
                Ok(())
            );
            assert!(socket.can_recv());

            assert!(socket.accepts(&ipv4_locals::HEADER_REPR));
            assert_eq!(
                socket.process(
                    &mut cx,
                    &ipv4_locals::HEADER_REPR,
                    &ipv4_locals::PACKET_PAYLOAD
                ),
                Err(Error::Exhausted)
            );
            assert_eq!(socket.recv(), Ok(&cksumd_packet[..]));
            assert!(!socket.can_recv());
        }
        #[cfg(feature = "proto-ipv6")]
        {
            let mut socket = ipv6_locals::socket(buffer(1), buffer(0));
            assert!(!socket.can_recv());
            let mut cx = Context::mock();

            assert_eq!(socket.recv(), Err(Error::Exhausted));
            assert!(socket.accepts(&ipv6_locals::HEADER_REPR));
            assert_eq!(
                socket.process(
                    &mut cx,
                    &ipv6_locals::HEADER_REPR,
                    &ipv6_locals::PACKET_PAYLOAD
                ),
                Ok(())
            );
            assert!(socket.can_recv());

            assert!(socket.accepts(&ipv6_locals::HEADER_REPR));
            assert_eq!(
                socket.process(
                    &mut cx,
                    &ipv6_locals::HEADER_REPR,
                    &ipv6_locals::PACKET_PAYLOAD
                ),
                Err(Error::Exhausted)
            );
            assert_eq!(socket.recv(), Ok(&ipv6_locals::PACKET_BYTES[..]));
            assert!(!socket.can_recv());
        }
    }

    #[test]
    fn test_doesnt_accept_wrong_proto() {
        #[cfg(feature = "proto-ipv4")]
        {
            let socket = RawSocket::new(
                IpVersion::Ipv4,
                IpProtocol::Unknown(ipv4_locals::IP_PROTO + 1),
                buffer(1),
                buffer(1),
            );
            assert!(!socket.accepts(&ipv4_locals::HEADER_REPR));
            #[cfg(feature = "proto-ipv6")]
            assert!(!socket.accepts(&ipv6_locals::HEADER_REPR));
        }
        #[cfg(feature = "proto-ipv6")]
        {
            let socket = RawSocket::new(
                IpVersion::Ipv6,
                IpProtocol::Unknown(ipv6_locals::IP_PROTO + 1),
                buffer(1),
                buffer(1),
            );
            assert!(!socket.accepts(&ipv6_locals::HEADER_REPR));
            #[cfg(feature = "proto-ipv4")]
            assert!(!socket.accepts(&ipv4_locals::HEADER_REPR));
        }
    }
}