//! The active side: the server dials its configured peers and keeps
//! retrying.

use std::net::{Ipv4Addr, SocketAddr};
use std::time::Duration;

use bgp_integration_tests::test_peer::TestPeer;
use bgp_integration_tests::test_server::TestServer;
use bgp_packet::errors::{BgpError, OpenMsgSubcode};
use bgp_packet::message::Message;
use bgp_primitives::ip_prefix::IpPrefix;
use bgp_rib::{LocalRoute, LocalRouteAttrs};
use bgp_server::config::PeerConfig;
use bgp_server::session::DialState;
use eyre::Result;
use tokio::net::TcpListener;

const LOCAL_ASN: u32 = 65000;
const PEER_ASN: u32 = 65001;
const TIMEOUT: Duration = Duration::from_secs(5);

/// Starts a server configured to dial `listener`'s address as peer "lab".
async fn server_dialing(listener: &TcpListener, remote_asn: u32) -> Result<TestServer> {
    let endpoint: SocketAddr = listener.local_addr()?;
    TestServer::start_with(LOCAL_ASN, |c| {
        c.connect_retry = Duration::from_millis(200);
        c.peers = vec![PeerConfig { name: "lab".into(), endpoint, remote_asn, hold_time_secs: 90, local_address: None }];
    })
    .await
}

async fn accept(listener: &TcpListener) -> Result<TestPeer> {
    let (stream, _) = tokio::time::timeout(TIMEOUT, listener.accept()).await??;
    Ok(TestPeer::from_stream(stream))
}

#[tokio::test]
async fn test_server_dials_configured_peer_and_establishes() -> Result<()> {
    let listener = TcpListener::bind((Ipv4Addr::LOCALHOST, 0)).await?;
    let server = server_dialing(&listener, PEER_ASN).await?;

    let mut peer = accept(&listener).await?;
    // Both sides send OPEN on connect; the test peer's handshake order works
    // whichever side opened TCP.
    let open = peer.handshake(PEER_ASN, Ipv4Addr::new(10, 0, 0, 2), 90).await?;
    assert_eq!(open.asn, LOCAL_ASN as u16);

    let mut events = server.registry.subscribe();
    // Either the Up event is still queued or the session is already listed.
    let listed = tokio::time::timeout(TIMEOUT, async {
        loop {
            if let Some(s) = server.registry.list().first().cloned() {
                return s;
            }
            let _ = events.recv().await;
        }
    })
    .await?;
    assert_eq!(listed.name.as_deref(), Some("lab"));
    assert_eq!(listed.peer.asn, PEER_ASN);
    assert_eq!(listed.peer.addr, listener.local_addr()?);

    // Configured view reflects it; the dialer is not in backoff.
    let (cfg, state) = server.registry.configured_peers().into_iter().next().unwrap();
    assert_eq!(cfg.name, "lab");
    assert!(matches!(state, DialState::Connecting | DialState::Idle), "{state:?}");

    // Local routes flow over the dialled session too.
    server
        .local_rib
        .announce(LocalRoute::new(IpPrefix::try_from("10.100.1.0/24")?, "alice", LocalRouteAttrs::default()))
        .await?;
    let update = tokio::time::timeout(TIMEOUT, peer.recv_update()).await??;
    assert_eq!(update.announced_routes[0].to_string(), "10.100.1.0/24");
    Ok(())
}

#[tokio::test]
async fn test_server_reconnects_after_peer_closes() -> Result<()> {
    let listener = TcpListener::bind((Ipv4Addr::LOCALHOST, 0)).await?;
    let server = server_dialing(&listener, PEER_ASN).await?;

    let mut first = accept(&listener).await?;
    first.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(10)).await;
        }
    })
    .await?;
    drop(first);

    // Session goes away, then the dialer comes back.
    tokio::time::timeout(TIMEOUT, async {
        while !server.registry.list().is_empty() {
            tokio::time::sleep(Duration::from_millis(10)).await;
        }
    })
    .await?;
    let (_, state) = server.registry.configured_peers().into_iter().next().unwrap();
    assert!(matches!(state, DialState::Backoff { .. }), "{state:?}");

    let mut second = accept(&listener).await?;
    second.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(10)).await;
        }
    })
    .await?;
    Ok(())
}

#[tokio::test]
async fn test_wrong_asn_is_refused_with_bad_peer_as() -> Result<()> {
    let listener = TcpListener::bind((Ipv4Addr::LOCALHOST, 0)).await?;
    let _server = server_dialing(&listener, PEER_ASN).await?;

    let mut peer = accept(&listener).await?;
    peer.send_open(65099, Ipv4Addr::new(10, 0, 0, 2), 90).await?;
    let _ = peer.recv_open().await?;
    let notif = tokio::time::timeout(TIMEOUT, async {
        loop {
            match peer.recv().await? {
                Message::Notification(n) => return Ok::<_, eyre::Error>(n),
                Message::KeepAlive => {}
                other => eyre::bail!("unexpected {other:?}"),
            }
        }
    })
    .await??;
    assert!(matches!(notif.error, BgpError::OpenMsg(OpenMsgSubcode::BadPeerAs)), "{notif:?}");

    // The dialer retries rather than giving up.
    let _again = accept(&listener).await?;
    Ok(())
}

/// An inbound connection from a configured peer's address is also checked
/// against the configured ASN and gets the configured name.
#[tokio::test]
async fn test_inbound_from_configured_address_uses_config() -> Result<()> {
    // Configure a peer at the loopback address on a port nobody listens on,
    // so the dialer never succeeds; then connect inbound from loopback.
    let server = TestServer::start_with(LOCAL_ASN, |c| {
        c.connect_retry = Duration::from_secs(60);
        c.peers = vec![PeerConfig {
            name: "lab".into(),
            endpoint: SocketAddr::new(Ipv4Addr::LOCALHOST.into(), 1),
            remote_asn: PEER_ASN,
            hold_time_secs: 90,
            local_address: None,
        }];
    })
    .await?;

    // Wrong ASN inbound → refused.
    let mut bad = TestPeer::connect(server.addr).await?;
    bad.send_open(65099, Ipv4Addr::new(10, 0, 0, 2), 90).await?;
    let _ = bad.recv_open().await?;
    let msg = tokio::time::timeout(TIMEOUT, bad.recv()).await??;
    assert!(matches!(&msg, Message::Notification(n) if matches!(n.error, BgpError::OpenMsg(OpenMsgSubcode::BadPeerAs))), "{msg:?}");

    // Right ASN inbound → established, named.
    let mut good = TestPeer::connect(server.addr).await?;
    good.handshake(PEER_ASN, Ipv4Addr::new(10, 0, 0, 2), 90).await?;
    let listed = tokio::time::timeout(TIMEOUT, async {
        loop {
            if let Some(s) = server.registry.list().first().cloned() {
                return s;
            }
            tokio::time::sleep(Duration::from_millis(10)).await;
        }
    })
    .await?;
    assert_eq!(listed.name.as_deref(), Some("lab"));
    Ok(())
}

/// With `local_address` set the connection must come from that address (the
/// peer may identify us by it), and an address the host does not have is
/// reported as the reason for backing off rather than silently ignored.
#[tokio::test]
async fn test_local_address_is_used_as_the_source() -> Result<()> {
    let listener = TcpListener::bind((Ipv4Addr::LOCALHOST, 0)).await?;
    let endpoint: SocketAddr = listener.local_addr()?;
    let _server = TestServer::start_with(LOCAL_ASN, |c| {
        c.connect_retry = Duration::from_millis(200);
        c.peers = vec![PeerConfig {
            name: "lab".into(),
            endpoint,
            remote_asn: PEER_ASN,
            hold_time_secs: 90,
            local_address: Some(Ipv4Addr::LOCALHOST.into()),
        }];
    })
    .await?;
    let (_stream, from) = tokio::time::timeout(TIMEOUT, listener.accept()).await??;
    assert_eq!(from.ip(), std::net::IpAddr::from(Ipv4Addr::LOCALHOST));

    // 192.0.2.1 is documentation space; no host has it.
    let server = TestServer::start_with(LOCAL_ASN, |c| {
        c.connect_retry = Duration::from_millis(200);
        c.peers = vec![PeerConfig {
            name: "lab".into(),
            endpoint,
            remote_asn: PEER_ASN,
            hold_time_secs: 90,
            local_address: Some(Ipv4Addr::new(192, 0, 2, 1).into()),
        }];
    })
    .await?;
    let reason = tokio::time::timeout(TIMEOUT, async {
        loop {
            if let Some((_, DialState::Backoff { last_error, .. })) = server.registry.configured_peers().into_iter().next() {
                return last_error;
            }
            tokio::time::sleep(Duration::from_millis(20)).await;
        }
    })
    .await?;
    assert!(reason.contains("local_address 192.0.2.1"), "{reason}");
    Ok(())
}