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// SPDX-License-Identifier: MIT

use anyhow::Context;
use netlink_packet_utils::{
    nla::{DefaultNla, Nla, NlaBuffer},
    parsers::parse_u8,
    traits::Parseable,
    DecodeError,
};

use crate::constants::*;

/// Netlink attributes for `RTA_ENCAP` with `RTA_ENCAP_TYPE` set to
/// `LWTUNNEL_ENCAP_MPLS`.
#[non_exhaustive]
pub enum MplsIpTunnel {
    Destination(Vec<u8>),
    Ttl(u8),
    Other(DefaultNla),
}

impl Nla for MplsIpTunnel {
    fn value_len(&self) -> usize {
        use self::MplsIpTunnel::*;
        match self {
            Destination(bytes) => bytes.len(),
            Ttl(_) => 1,
            Other(attr) => attr.value_len(),
        }
    }

    fn kind(&self) -> u16 {
        use self::MplsIpTunnel::*;
        match self {
            Destination(_) => MPLS_IPTUNNEL_DST,
            Ttl(_) => MPLS_IPTUNNEL_TTL,
            Other(attr) => attr.kind(),
        }
    }

    fn emit_value(&self, buffer: &mut [u8]) {
        use self::MplsIpTunnel::*;
        match self {
            Destination(bytes) => buffer.copy_from_slice(bytes.as_slice()),
            Ttl(ttl) => buffer[0] = *ttl,
            Other(attr) => attr.emit_value(buffer),
        }
    }
}

impl<'a, T: AsRef<[u8]> + ?Sized> Parseable<NlaBuffer<&'a T>> for MplsIpTunnel {
    fn parse(buf: &NlaBuffer<&'a T>) -> Result<Self, DecodeError> {
        use self::MplsIpTunnel::*;
        let payload = buf.value();
        Ok(match buf.kind() {
            MPLS_IPTUNNEL_DST => Destination(payload.to_vec()),
            MPLS_IPTUNNEL_TTL => {
                Ttl(parse_u8(payload)
                    .context("invalid MPLS_IPTUNNEL_TTL value")?)
            }
            _ => Other(
                DefaultNla::parse(buf)
                    .context("invalid NLA value (unknown type) value")?,
            ),
        })
    }
}