//! Interoperability with what real routers put on the wire.

use std::net::Ipv4Addr;
use std::time::Duration;

use bgp_integration_tests::test_peer::TestPeer;
use bgp_integration_tests::test_server::TestServer;
use bgp_packet::message::{Message, PathAttribute};
use bgp_packet::open::{Capability, OpenOption};
use bgp_primitives::constants::{AddressFamilyId, SubsequentAfi};
use bgp_primitives::ip_prefix::IpPrefix;
use bgp_rib::{LocalRoute, LocalRouteAttrs};
use eyre::Result;

const TIMEOUT: Duration = Duration::from_secs(5);

/// The OPEN a BIRD 2 router sends for an IPv6-only session from AS210036:
/// one optional parameter carrying MP(IPv6 unicast), route refresh,
/// extended message, graceful restart (aware only), 4-octet AS, enhanced
/// route refresh and long-lived graceful restart (aware only).
#[rustfmt::skip]
const BIRD_OPEN: &[u8] = &[
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0x00, 0x37, 0x01,             // length 55, type OPEN
    0x04,                         // version
    0x5b, 0xa0,                   // AS_TRANS
    0x00, 0xf0,                   // hold time 240
    0x0a, 0xff, 0x00, 0x01,       // router id 10.255.0.1
    0x1a,                         // optional parameters length 26
    0x02, 0x18,                   // capabilities, 24 bytes
    0x01, 0x04, 0x00, 0x02, 0x00, 0x01, // MP: IPv6 unicast
    0x02, 0x00,                   // route refresh
    0x06, 0x00,                   // extended message
    0x40, 0x02, 0x00, 0x00,       // graceful restart, no address families
    0x41, 0x04, 0x00, 0x03, 0x34, 0x74, // 4-octet AS 210036
    0x46, 0x00,                   // enhanced route refresh
    0x47, 0x00,                   // long-lived graceful restart, none
];

/// IPv6 End-of-RIB: an UPDATE whose only attribute is an empty
/// MP_UNREACH_NLRI for IPv6 unicast (RFC 4724 §2).
#[rustfmt::skip]
const IPV6_END_OF_RIB: &[u8] = &[
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0x00, 0x1e, 0x02,             // length 30, type UPDATE
    0x00, 0x00,                   // no withdrawn routes
    0x00, 0x07,                   // 7 bytes of path attributes
    0x90, 0x0f, 0x00, 0x03,       // optional + extended length, MP_UNREACH_NLRI, len 3
    0x00, 0x02, 0x01,             // IPv6 unicast, no prefixes
];

#[tokio::test]
async fn test_server_advertises_ipv4_and_ipv6_unicast() -> Result<()> {
    let server = TestServer::start(65000).await?;
    let mut peer = TestPeer::connect(server.addr).await?;
    let open = peer.recv_open().await?;
    let caps: Vec<&Capability> = open
        .options
        .iter()
        .flat_map(|o| match o {
            OpenOption::Capabilities(c) => c.iter(),
        })
        .collect();
    for afi in [AddressFamilyId::Ipv4, AddressFamilyId::Ipv6] {
        assert!(
            caps.iter().any(|c| matches!(c, Capability::MultiProtocol { afi: a, safi: SubsequentAfi::Unicast } if *a == afi)),
            "missing MP capability for {afi:?}: {caps:?}"
        );
    }
    Ok(())
}

#[tokio::test]
async fn test_bird_open_and_end_of_rib_are_accepted() -> Result<()> {
    let server = TestServer::start(4200000001).await?;
    let mut peer = TestPeer::connect(server.addr).await?;

    peer.send_raw(BIRD_OPEN).await?;
    peer.recv_open().await?;
    match tokio::time::timeout(TIMEOUT, peer.recv()).await?? {
        Message::KeepAlive => {}
        other => eyre::bail!("server did not accept BIRD's OPEN: {other:?}"),
    }
    peer.send(&Message::KeepAlive).await?;

    tokio::time::timeout(TIMEOUT, async {
        while server.registry.list().is_empty() {
            tokio::time::sleep(Duration::from_millis(10)).await;
        }
    })
    .await?;
    let session = server.registry.list().remove(0);
    assert_eq!(session.peer.asn, 210036, "4-octet ASN must come from the capability, not AS_TRANS");
    assert!(session.four_octet_asn);

    // End-of-RIB must neither break the session nor create a route.
    peer.send_raw(IPV6_END_OF_RIB).await?;
    peer.send(&Message::KeepAlive).await?;
    tokio::time::sleep(Duration::from_millis(200)).await;
    assert_eq!(server.registry.list().len(), 1, "session dropped after End-of-RIB");
    assert!(server.adj_rib_in.snapshot().await.is_empty());
    Ok(())
}

/// Over an IPv4 test transport an IPv6 route cannot be sent (no IPv6 next
/// hop), so this only checks the builder the advertiser uses: the UPDATE for
/// a lab /48 carries MP_REACH_NLRI with an IPv6 next hop and no NEXT_HOP.
#[tokio::test]
async fn test_ipv6_lab_prefix_update_shape() -> Result<()> {
    let route = LocalRoute::new(IpPrefix::try_from("2a0d:d741:1::/48")?, "student1", LocalRouteAttrs::default());
    let nh: std::net::Ipv6Addr = "fd00:179::2".parse()?;
    let update = bgp_server::advertise::build_announce(&route, 4200000001, nh.into()).expect("ipv6 over ipv6");
    assert!(update.announced_routes.is_empty());
    assert!(!update.path_attributes.iter().any(|a| matches!(a, PathAttribute::NextHop(_))));
    assert!(update.path_attributes.iter().any(|a| matches!(a, PathAttribute::MpReachNlri(m)
        if m.afi == AddressFamilyId::Ipv6 && m.prefixes[0].to_string() == "2a0d:d741:1::/48")));
    let _ = Ipv4Addr::LOCALHOST;
    Ok(())
}