// SPDX-License-Identifier: MIT

use std::{convert::TryFrom, mem::size_of, os::fd::RawFd};

use anyhow::Context;
use byteorder::{ByteOrder, NativeEndian};
use netlink_packet_utils::{
    nla::{DefaultNla, Nla, NlaBuffer, NlasIterator},
    parsers::{parse_i32, parse_u32},
    DecodeError, Parseable,
};

use crate::constants::*;

#[non_exhaustive]
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum Xdp {
    Fd(RawFd),
    Attached(XdpAttached),
    Flags(u32),
    ProgId(u32),
    DrvProgId(u32),
    SkbProgId(u32),
    HwProgId(u32),
    ExpectedFd(u32),
    Other(DefaultNla),
}

impl Nla for Xdp {
    #[rustfmt::skip]
    fn value_len(&self) -> usize {
        use self::Xdp::*;
        match self {
            Fd(_) => size_of::<RawFd>(),
            Attached(_) => size_of::<u8>(),
            Flags(_) => size_of::<u32>(),
            ProgId(_) => size_of::<u32>(),
            DrvProgId(_) => size_of::<u32>(),
            SkbProgId(_) => size_of::<u32>(),
            HwProgId(_) => size_of::<u32>(),
            ExpectedFd(_) => size_of::<u32>(),
            Other(nla) => nla.value_len()
        }
    }

    #[rustfmt::skip]
    fn emit_value(&self, buffer: &mut [u8]) {
        use self::Xdp::*;
        match self {
            Fd(ref value) => NativeEndian::write_i32(buffer, *value),
            Attached(ref value) => buffer[0] = value.as_u8(),
            Flags(ref value) => NativeEndian::write_u32(buffer, *value),
            ProgId(ref value) => NativeEndian::write_u32(buffer, *value),
            DrvProgId(ref value) => NativeEndian::write_u32(buffer, *value),
            SkbProgId(ref value) => NativeEndian::write_u32(buffer, *value),
            HwProgId(ref value) => NativeEndian::write_u32(buffer, *value),
            ExpectedFd(ref value) => NativeEndian::write_u32(buffer, *value),
            Other(ref nla) => nla.emit_value(buffer)
        }
    }

    fn kind(&self) -> u16 {
        use self::Xdp::*;
        match self {
            Fd(_) => IFLA_XDP_FD as u16,
            Attached(_) => IFLA_XDP_ATTACHED as u16,
            Flags(_) => IFLA_XDP_FLAGS as u16,
            ProgId(_) => IFLA_XDP_PROG_ID as u16,
            DrvProgId(_) => IFLA_XDP_DRV_PROG_ID as u16,
            SkbProgId(_) => IFLA_XDP_SKB_PROG_ID as u16,
            HwProgId(_) => IFLA_XDP_HW_PROG_ID as u16,
            ExpectedFd(_) => IFLA_XDP_EXPECTED_FD as u16,
            Other(nla) => nla.kind(),
        }
    }
}

pub(crate) struct VecXdp(pub(crate) Vec<Xdp>);

// These NLAs are nested, meaning they are NLAs that contain NLAs. These NLAs
// can contain more nested NLAs nla->type     // IFLA_XDP
// nla->len
// nla->data[]   // <- You are here == Vec<Xdp>
//  nla->data[0].type   <- nla.kind()
//  nla->data[0].len
impl<'a, T: AsRef<[u8]> + ?Sized> Parseable<NlaBuffer<&'a T>> for VecXdp {
    fn parse(buf: &NlaBuffer<&'a T>) -> Result<Self, DecodeError> {
        let mut res = Vec::new();
        let nlas = NlasIterator::new(buf.into_inner());
        for nla in nlas {
            let nla = nla?;
            match nla.kind() as u32 {
                IFLA_XDP_FD => res.push(Xdp::Fd(
                    parse_i32(nla.value())
                        .context("invalid IFLA_XDP_FD value")?,
                )),
                IFLA_XDP_ATTACHED => res.push(Xdp::Attached(
                    XdpAttached::try_from(nla.value()[0])
                        .context("invalid IFLA_XDP_ATTACHED value")?,
                )),
                IFLA_XDP_FLAGS => res.push(Xdp::Flags(
                    parse_u32(nla.value())
                        .context("invalid IFLA_XDP_FLAGS value")?,
                )),
                IFLA_XDP_PROG_ID => res.push(Xdp::ProgId(
                    parse_u32(nla.value())
                        .context("invalid IFLA_XDP_PROG_ID value")?,
                )),
                IFLA_XDP_DRV_PROG_ID => res.push(Xdp::DrvProgId(
                    parse_u32(nla.value())
                        .context("invalid IFLA_XDP_PROG_ID value")?,
                )),
                IFLA_XDP_SKB_PROG_ID => res.push(Xdp::SkbProgId(
                    parse_u32(nla.value())
                        .context("invalid IFLA_XDP_PROG_ID value")?,
                )),
                IFLA_XDP_HW_PROG_ID => res.push(Xdp::HwProgId(
                    parse_u32(nla.value())
                        .context("invalid IFLA_XDP_PROG_ID value")?,
                )),
                IFLA_XDP_EXPECTED_FD => res.push(Xdp::ExpectedFd(
                    parse_u32(nla.value())
                        .context("invalid IFLA_XDP_PROG_ID value")?,
                )),
                _ => res
                    .push(Xdp::Other(DefaultNla::parse(&nla).context(
                        format!("unknown NLA type {}", nla.kind()),
                    )?)),
            }
        }
        Ok(VecXdp(res))
    }
}

#[non_exhaustive]
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum XdpAttached {
    /// XDP_ATTACHED_NONE
    None,
    /// XDP_ATTACHED_DRV
    Driver,
    /// XDP_ATTACHED_SKB
    SocketBuffer,
    /// XDP_ATTACHED_HW
    Hardware,
    /// XDP_ATTACHED_MULTI
    Multiple,
    /// This crate is unaware of the attachment type the kernel is reporting
    Other(u8),
}

impl TryFrom<u8> for XdpAttached {
    type Error = DecodeError;

    fn try_from(value: u8) -> Result<Self, Self::Error> {
        match value {
            XDP_ATTACHED_NONE => Ok(XdpAttached::None),
            XDP_ATTACHED_DRV => Ok(XdpAttached::Driver),
            XDP_ATTACHED_SKB => Ok(XdpAttached::SocketBuffer),
            XDP_ATTACHED_HW => Ok(XdpAttached::Hardware),
            XDP_ATTACHED_MULTI => Ok(XdpAttached::Multiple),
            _ => Ok(XdpAttached::Other(value)),
        }
    }
}

impl XdpAttached {
    fn as_u8(&self) -> u8 {
        match self {
            XdpAttached::None => XDP_ATTACHED_NONE,
            XdpAttached::Driver => XDP_ATTACHED_DRV,
            XdpAttached::SocketBuffer => XDP_ATTACHED_SKB,
            XdpAttached::Hardware => XDP_ATTACHED_HW,
            XdpAttached::Multiple => XDP_ATTACHED_MULTI,
            XdpAttached::Other(other) => *other,
        }
    }
}

#[cfg(test)]
mod tests {
    use netlink_packet_utils::Emitable;

    use super::*;

    #[rustfmt::skip]
    static ATTACHED: [u8; 48] = [
        0x05, 0x00, // length = 5
        0x02, 0x00, // type = 2 = IFLA_XDP_ATTACHED
        0x00, 0x00, // none = XDP_ATTACHED_NONE
        0x00, 0x00, // padding
        0x05, 0x00, // length = 5
        0x02, 0x00, // type = 2 = IFLA_XDP_ATTACHED
        0x01, 0x00, // driver = XDP_ATTACHED_DRV
        0x00, 0x00, // padding
        0x05, 0x00, // length = 5
        0x02, 0x00, // type = 2 = IFLA_XDP_ATTACHED
        0x02, 0x00, // skb = XDP_ATTACHED_SKB
        0x00, 0x00, // padding
        0x05, 0x00, // length = 5
        0x02, 0x00, // type = 2 = IFLA_XDP_ATTACHED
        0x03, 0x00, // hw = XDP_ATTACHED_HW
        0x00, 0x00, // padding
        0x05, 0x00, // length = 5
        0x02, 0x00, // type = 2 = IFLA_XDP_ATTACHED
        0x04, 0x00, // multi = XDP_ATTACHED_MULTI
        0x00, 0x00, // padding
        0x05, 0x00, // length = 5
        0x02, 0x00, // type = 2 = IFLA_XDP_ATTACHED
        0xfc, 0x00, // other = random number = 252
        0x00, 0x00, // padding
    ];

    #[test]
    fn parse_xdp_attached() {
        let nla = NlaBuffer::new_checked(&ATTACHED[..]).unwrap();
        let parsed = VecXdp::parse(&nla).unwrap().0;
        let expected = vec![
            Xdp::Attached(XdpAttached::None),
            Xdp::Attached(XdpAttached::Driver),
            Xdp::Attached(XdpAttached::SocketBuffer),
            Xdp::Attached(XdpAttached::Hardware),
            Xdp::Attached(XdpAttached::Multiple),
            Xdp::Attached(XdpAttached::Other(252)),
        ];
        assert_eq!(expected, parsed);
    }

    #[test]
    fn emit_xdp_attached() {
        // None
        let nlas = vec![Xdp::Attached(XdpAttached::None)];
        assert_eq!(nlas.as_slice().buffer_len(), 8);

        let mut vec = vec![0xff; 8];
        nlas.as_slice().emit(&mut vec);
        assert_eq!(&vec[..], &ATTACHED[..8]);

        // Driver
        let nlas = vec![Xdp::Attached(XdpAttached::Driver)];
        assert_eq!(nlas.as_slice().buffer_len(), 8);

        let mut vec = vec![0xff; 8];
        nlas.as_slice().emit(&mut vec);
        assert_eq!(&vec[..], &ATTACHED[8..16]);

        // SocketBuffer/skb
        let nlas = vec![Xdp::Attached(XdpAttached::SocketBuffer)];
        assert_eq!(nlas.as_slice().buffer_len(), 8);

        let mut vec = vec![0xff; 8];
        nlas.as_slice().emit(&mut vec);
        assert_eq!(&vec[..], &ATTACHED[16..24]);

        // Hardware
        let nlas = vec![Xdp::Attached(XdpAttached::Hardware)];
        assert_eq!(nlas.as_slice().buffer_len(), 8);

        let mut vec = vec![0xff; 8];
        nlas.as_slice().emit(&mut vec);
        assert_eq!(&vec[..], &ATTACHED[24..32]);

        // Multiple
        let nlas = vec![Xdp::Attached(XdpAttached::Multiple)];
        assert_eq!(nlas.as_slice().buffer_len(), 8);

        let mut vec = vec![0xff; 8];
        nlas.as_slice().emit(&mut vec);
        assert_eq!(&vec[..], &ATTACHED[32..40]);

        // Multiple
        let nlas = vec![Xdp::Attached(XdpAttached::Other(252))];
        assert_eq!(nlas.as_slice().buffer_len(), 8);

        let mut vec = vec![0xff; 8];
        nlas.as_slice().emit(&mut vec);
        assert_eq!(&vec[..], &ATTACHED[40..48]);
    }

    #[rustfmt::skip]
    static XDP: [u8; 72] = [
        0x08, 0x00, // length = 8
        0x01, 0x00, // type = 1 = IFLA_XDP_FD
        0xA0, 0x74, 0x00, 0x00, // 29856
        0x08, 0x00, // length = 8
        0x03, 0x00, // type = 3 = IFLA_XDP_FLAGS
        0x00, 0x00, 0x00, 0x00, // empty
        0x08, 0x00, // length = 8
        0x04, 0x00, // type = 4 = IFLA_XDP_PROG_ID
        0x67, 0x00, 0x00, 0x00, // 103
        0x08, 0x00, // length = 8
        0x05, 0x00, // type = 5 = IFLA_XDP_DRV_PROG_ID
        0x65, 0x00, 0x00, 0x00, // 101
        0x08, 0x00, // length = 8
        0x06, 0x00, // type = 6 = IFLA_XDP_DRV_SKB_ID
        0x65, 0x00, 0x00, 0x00, // 101
        0x08, 0x00, // length = 8
        0x07, 0x00, // type = 7 = IFLA_XDP_DRV_HW_ID
        0x65, 0x00, 0x00, 0x00, // 101
        0x08, 0x00, // length = 8
        0x08, 0x00, // type = 8 = IFLA_XDP_DRV_EXPECTED_FD
        0xA1, 0x74, 0x00, 0x00, // 29857
        0x08, 0x00, // length = 8
        0xfc, 0x00, // type = 252 = random number/unknown type
        0xA1, 0x74, 0x00, 0x00, // 29857
        0x06, 0x00, // length = 6
        0xfb, 0x00, // type = 251 = random number/unknown type
        0xaa, 0xab, // 29857
        0x00, 0x00, // padding
    ];

    #[test]
    fn parse_xdp() {
        let nla = NlaBuffer::new_checked(&XDP[..]).unwrap();
        let parsed = VecXdp::parse(&nla).unwrap().0;
        let expected = vec![
            Xdp::Fd(29856),
            Xdp::Flags(0),
            Xdp::ProgId(103),
            Xdp::DrvProgId(101),
            Xdp::SkbProgId(101),
            Xdp::HwProgId(101),
            Xdp::ExpectedFd(29857),
            Xdp::Other(
                DefaultNla::parse(&NlaBuffer::new(&XDP[56..64])).unwrap(),
            ),
            Xdp::Other(DefaultNla::parse(&NlaBuffer::new(&XDP[64..])).unwrap()),
        ];
        assert_eq!(expected, parsed);
    }

    #[test]
    fn emit_xdp() {
        let nlas = vec![
            Xdp::Fd(29856),
            Xdp::Flags(0),
            Xdp::ProgId(103),
            Xdp::DrvProgId(101),
            Xdp::SkbProgId(101),
            Xdp::HwProgId(101),
            Xdp::ExpectedFd(29857),
            Xdp::Other(
                DefaultNla::parse(&NlaBuffer::new(&XDP[56..64])).unwrap(),
            ),
            Xdp::Other(DefaultNla::parse(&NlaBuffer::new(&XDP[64..])).unwrap()),
        ];
        assert_eq!(nlas.as_slice().buffer_len(), XDP.len());

        let mut vec = vec![0xff; XDP.len()];
        nlas.as_slice().emit(&mut vec);
        assert_eq!(&vec[..], &XDP[..]);
    }
}