//! AS path verification with ASPAs, end to end: a server that gets ASPAs
//! from a cache, a peer that announces routes, and the ASPAs changing
//! under both.

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

use bgp_integration_tests::default_policy;
use bgp_integration_tests::test_cache::TestCache;
use bgp_integration_tests::test_peer::TestPeer;
use bgp_integration_tests::test_server::TestServer;
use bgp_packet::message::{
    AsPathAttribute, Message, NextHopPathAttribute, OriginPathAttribute, PathAttribute,
    UpdateMessage,
};
use bgp_primitives::ip_prefix::IpPrefix;
use bgp_rpki::{CacheState, RpkiConfig};
use bgp_server::config::PeerConfig;
use bgp_server::family::FamilySet;
use bgp_server::policy::{ImportPolicy, PeerRole};
use eyre::Result;
use serde_json::Value;
use tokio::net::TcpListener;

const LOCAL_ASN: u32 = 1299;
const PEER_ASN: u32 = 3333;
const TIMEOUT: Duration = Duration::from_secs(5);

fn prefix(s: &str) -> IpPrefix {
    IpPrefix::try_from(s).unwrap()
}

/// What a test holds on to: the server, and the listener its dialling
/// goes to.
struct Setup {
    server: TestServer,
    _listener: TcpListener,
}

/// A server that validates against `cache`, with one configured peer at
/// the address the test connects from, which is `role` to it. Returns once
/// the server has the cache's data.
async fn server_with(
    cache: &TestCache,
    role: Option<PeerRole>,
    import: ImportPolicy,
) -> Result<Setup> {
    let listener = TcpListener::bind((Ipv4Addr::LOCALHOST, 0)).await?;
    let endpoint = listener.local_addr()?;
    let cache = cache.address();
    let server = TestServer::start_with(LOCAL_ASN, |c| {
        c.accept_unconfigured_peers = false;
        c.rpki = Some(RpkiConfig {
            caches: vec![cache],
            retry: Some(Duration::from_millis(100)),
            ..RpkiConfig::default()
        });
        c.peers = vec![PeerConfig {
            name: "r1".into(),
            endpoint: endpoint.into(),
            remote_asn: PEER_ASN,
            hold_time_secs: 90,
            local_address: None,
            families: FamilySet::supported(),
            add_path: None,
            import,
            role,
            require_role: false,
        }];
    })
    .await?;
    let rpki = server.rpki.clone().expect("validation is configured");
    tokio::time::timeout(TIMEOUT, async {
        while rpki.status().state != CacheState::Synchronised {
            tokio::time::sleep(Duration::from_millis(5)).await;
        }
    })
    .await?;
    Ok(Setup {
        server,
        _listener: listener,
    })
}

async fn established(server: &TestServer) -> Result<TestPeer> {
    let mut peer = TestPeer::connect(server.addr).await?;
    peer.handshake(PEER_ASN, Ipv4Addr::new(10, 0, 0, 2), 90)
        .await?;
    tokio::time::timeout(TIMEOUT, async {
        while server.registry.list().is_empty() {
            tokio::time::sleep(Duration::from_millis(5)).await;
        }
    })
    .await?;
    Ok(peer)
}

/// Announces `prefixes` with the AS path `path`.
async fn announce(peer: &mut TestPeer, prefixes: &[&str], path: &[u32]) -> Result<()> {
    peer.send(&Message::Update(UpdateMessage {
        withdrawn_routes: vec![],
        path_attributes: vec![
            PathAttribute::Origin(OriginPathAttribute::IGP),
            AsPathAttribute::from_asns(path.to_vec()),
            PathAttribute::NextHop(NextHopPathAttribute(Ipv4Addr::new(192, 0, 2, 1))),
        ],
        announced_routes: prefixes.iter().map(|p| prefix(p).into()).collect(),
    }))
    .await
}

/// Waits until the table holds exactly `expected` and the peer has `held`
/// routes held aside.
async fn table_becomes(server: &TestServer, expected: &[&str], held: u64) -> Result<()> {
    let expected: BTreeSet<String> = expected.iter().map(|p| p.to_string()).collect();
    let table = || -> BTreeSet<String> {
        server
            .received_routes()
            .iter()
            .map(|route| route.prefix.to_string())
            .collect()
    };
    let held_now = || {
        server
            .registry
            .list()
            .first()
            .map_or(0, |session| session.counters.held())
    };
    tokio::time::timeout(TIMEOUT, async {
        while table() != expected || held_now() != held {
            tokio::time::sleep(Duration::from_millis(5)).await;
        }
    })
    .await
    .map_err(|_| {
        eyre::eyre!(
            "the table has {:?} with {} held; expected {expected:?} with {held} held",
            table(),
            held_now()
        )
    })
}

/// AS 15169 buys from 3356 and says so; 3356 and the peer, 3333, have no
/// providers.
fn aspas() -> Vec<(u32, Vec<u32>)> {
    vec![(15169, vec![3356]), (3356, vec![0]), (PEER_ASN, vec![0])]
}

/// A peer that hands us a route it got from one of its own peers is
/// leaking it. The route is refused; routes whose paths are attested, or
/// that nothing is known about, are taken.
#[tokio::test]
async fn test_a_leaked_route_is_refused_and_the_rest_are_taken() -> Result<()> {
    let cache = TestCache::start_with(vec![], aspas()).await;
    let Setup { server, .. } = server_with(&cache, Some(PeerRole::Peer), default_policy()).await?;
    let (base, _http) = server.serve_http().await?;
    let mut peer = established(&server).await?;

    // The peer's own route; one of a customer of its that has no ASPA;
    // and 15169's route by way of 3356, which is not for 3333 to pass on
    // to a peer: 3356 is not its customer.
    announce(&mut peer, &["193.0.0.0/21"], &[PEER_ASN]).await?;
    announce(&mut peer, &["194.0.0.0/24"], &[PEER_ASN, 2121]).await?;
    announce(&mut peer, &["8.8.8.0/24"], &[PEER_ASN, 3356, 15169]).await?;
    table_becomes(&server, &["193.0.0.0/21", "194.0.0.0/24"], 1).await?;

    let client = reqwest::Client::new();
    let get = |path: &str| {
        let request = client.get(format!("{base}{path}"));
        async move { Ok::<Value, eyre::Report>(request.send().await?.error_for_status()?.json().await?) }
    };
    let routes = get("/api/routes/received").await?["routes"].take();
    let validity: Vec<(&str, &str)> = routes
        .as_array()
        .unwrap()
        .iter()
        .map(|r| (r["prefix"].as_str().unwrap(), r["aspa"].as_str().unwrap()))
        .collect();
    assert_eq!(
        validity,
        [("193.0.0.0/21", "valid"), ("194.0.0.0/24", "unknown")]
    );
    let refused = get("/api/routes/rejected").await?;
    assert_eq!(
        refused[0]["by_reason"],
        serde_json::json!({"ASPA invalid": 1})
    );
    let peers = get("/api/peers").await?;
    assert_eq!(peers[0]["role"], "peer");
    assert_eq!(peers[0]["held_routes"], 1);
    let rpki = get("/api/rpki").await?;
    assert_eq!(rpki["aspas"], 3);
    assert_eq!(rpki["protocol_version"], 2);
    Ok(())
}

/// What a path may look like depends on who it comes from. The same route
/// that a peer may not pass on is in order from a provider, which may hand
/// us anything it has. Where it is not said what the peer is, paths are
/// not verified.
#[tokio::test]
async fn test_a_route_that_has_crossed_a_peering_is_taken_from_a_provider_only() -> Result<()> {
    for (role, taken) in [
        (Some(PeerRole::Provider), true),
        (Some(PeerRole::Customer), false),
        (Some(PeerRole::Peer), false),
        (Some(PeerRole::RouteServerClient), false),
        (None, true),
    ] {
        let cache = TestCache::start_with(vec![], aspas()).await;
        let Setup { server, .. } = server_with(&cache, role, default_policy()).await?;
        let mut peer = established(&server).await?;
        announce(&mut peer, &["8.8.8.0/24"], &[PEER_ASN, 3356, 15169]).await?;
        let expected = if taken {
            table_becomes(&server, &["8.8.8.0/24"], 0).await
        } else {
            table_becomes(&server, &[], 1).await
        };
        expected.map_err(|e| eyre::eyre!("from a peer that is {role:?}: {e}"))?;
    }
    Ok(())
}

/// An Internet exchange's route server does not put its AS on the path, so
/// the path need not begin with the route server's AS. A leak is refused
/// across it all the same.
#[tokio::test]
async fn test_paths_from_a_route_server_do_not_begin_with_its_as() -> Result<()> {
    let cache = TestCache::start_with(vec![], aspas()).await;
    let import = ImportPolicy {
        accept_any_first_as: true,
        ..default_policy()
    };
    let Setup { server, .. } = server_with(&cache, Some(PeerRole::RouteServer), import).await?;
    let mut peer = established(&server).await?;

    // 3356's customer route, as 3356 gave it to the route server.
    announce(&mut peer, &["8.8.8.0/24"], &[3356, 15169]).await?;
    // The same route leaked to the route server by another member.
    announce(&mut peer, &["8.8.4.0/24"], &[2121, 3356, 15169]).await?;
    table_becomes(&server, &["8.8.8.0/24"], 1).await
}

/// Validity changes with the ASPAs, and the routes follow: one that was
/// taken goes when its path becomes invalid, and one that was refused is
/// taken when it no longer is. The peer sends nothing more meanwhile.
#[tokio::test]
async fn test_routes_follow_the_aspas() -> Result<()> {
    let cache = TestCache::start_with(vec![], aspas()).await;
    let Setup { server, .. } = server_with(&cache, Some(PeerRole::Peer), default_policy()).await?;
    let mut peer = established(&server).await?;

    announce(&mut peer, &["194.0.0.0/24"], &[PEER_ASN, 2121]).await?;
    announce(&mut peer, &["8.8.8.0/24"], &[PEER_ASN, 3356, 15169]).await?;
    table_becomes(&server, &["194.0.0.0/24"], 1).await?;

    // 2121 says that its only provider is 1101: its route by way of 3333
    // is now invalid, and goes.
    let mut changed = aspas();
    changed.push((2121, vec![1101]));
    cache.set_aspas(changed);
    table_becomes(&server, &[], 2).await?;
    let refused = &server.refusals.peers()[0].1;
    assert_eq!(refused.total(), 2);
    assert_eq!(refused.recent()[0].prefix, prefix("194.0.0.0/24"));
    assert_eq!(&refused.recent()[0].as_path[..], [PEER_ASN, 2121]);

    // 3356 becomes a customer of 3333, and 2121 too: both routes come
    // back, with the paths they were announced with.
    cache.set_aspas(vec![
        (15169, vec![3356]),
        (3356, vec![PEER_ASN]),
        (PEER_ASN, vec![0]),
        (2121, vec![1101, PEER_ASN]),
    ]);
    table_becomes(&server, &["194.0.0.0/24", "8.8.8.0/24"], 0).await?;
    let paths: BTreeSet<Vec<u32>> = server
        .received_routes()
        .iter()
        .flat_map(|route| &route.attributes)
        .filter_map(|attribute| match attribute {
            PathAttribute::AsPath(path) => Some(path.segments[0].path.clone()),
            _ => None,
        })
        .collect();
    assert_eq!(
        paths,
        [vec![PEER_ASN, 2121], vec![PEER_ASN, 3356, 15169]].into()
    );

    // The validator loses its ASPAs altogether: nothing is known about
    // any path, and nothing is refused.
    cache.set_aspas(vec![
        (15169, vec![3356]),
        (3356, vec![0]),
        (PEER_ASN, vec![0]),
    ]);
    table_becomes(&server, &["194.0.0.0/24"], 1).await?;
    cache.set_aspas(vec![]);
    table_becomes(&server, &["194.0.0.0/24", "8.8.8.0/24"], 0).await
}

/// A peer can be exempt: its routes with invalid paths are taken, and
/// shown for what they are.
#[tokio::test]
async fn test_a_peer_can_be_exempt_from_path_verification() -> Result<()> {
    let cache = TestCache::start_with(vec![], aspas()).await;
    let import = ImportPolicy {
        accept_aspa_invalid: true,
        ..default_policy()
    };
    let Setup { server, .. } = server_with(&cache, Some(PeerRole::Peer), import).await?;
    let (base, _http) = server.serve_http().await?;
    let mut peer = established(&server).await?;

    announce(&mut peer, &["8.8.8.0/24"], &[PEER_ASN, 3356, 15169]).await?;
    table_becomes(&server, &["8.8.8.0/24"], 0).await?;
    let routes: Value = reqwest::get(format!("{base}/api/routes/received"))
        .await?
        .json()
        .await?;
    assert_eq!(routes["routes"][0]["aspa"], "invalid");
    assert!(server.refusals.peers().is_empty());
    Ok(())
}

/// A route can fail both checks. It is taken only when it passes both.
#[tokio::test]
async fn test_a_route_is_held_until_origin_and_path_are_both_in_order() -> Result<()> {
    let google = |asn| bgp_rpki::Vrp {
        prefix: prefix("8.8.8.0/24"),
        max_length: 24,
        asn,
    };
    let cache = TestCache::start_with(vec![google(13335)], aspas()).await;
    let Setup { server, .. } = server_with(&cache, Some(PeerRole::Peer), default_policy()).await?;
    let mut peer = established(&server).await?;
    announce(&mut peer, &["8.8.8.0/24"], &[PEER_ASN, 3356, 15169]).await?;
    table_becomes(&server, &[], 1).await?;

    // The origin is put right; the path is still a leak.
    cache.set(vec![google(15169)]);
    tokio::time::sleep(Duration::from_millis(500)).await;
    table_becomes(&server, &[], 1).await?;

    cache.set_aspas(vec![(15169, vec![3356]), (3356, vec![PEER_ASN])]);
    table_becomes(&server, &["8.8.8.0/24"], 0).await
}