//! Who may connect: only the addresses of configured peers, and each of
//! them only so many times at once.

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_server::config::PeerConfig;
use bgp_server::family::FamilySet;
use bgp_server::policy::ImportPolicy;
use eyre::Result;
use tokio::net::TcpListener;

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

fn peer_at(endpoint: SocketAddr) -> PeerConfig {
    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: ImportPolicy::permissive(),
        role: None,
        require_role: false,
        import_hook: None,
        export_hook: None,
    }
}

/// Whether the server closed the connection without sending anything.
async fn closed_unanswered(peer: &mut TestPeer) -> bool {
    matches!(tokio::time::timeout(TIMEOUT, peer.recv()).await, Ok(Err(_)))
}

/// A host that is not a configured peer gets nothing: no OPEN to answer,
/// no session, no routes taken from it. Any host used to be able to open a
/// session as any AS it named.
#[tokio::test]
async fn test_a_host_that_is_not_a_configured_peer_is_refused() -> Result<()> {
    // The only peer configured is somewhere else (documentation space).
    let server = TestServer::start_with(LOCAL_ASN, |c| {
        c.accept_unconfigured_peers = false;
        c.peers = vec![peer_at("192.0.2.9:179".parse().unwrap())];
    })
    .await?;

    let mut stranger = TestPeer::connect(server.addr).await?;
    assert!(closed_unanswered(&mut stranger).await);
    assert!(server.registry.list().is_empty());
    Ok(())
}

/// The address of a configured peer is let in, and held to what is
/// configured for that peer.
#[tokio::test]
async fn test_a_configured_peer_is_let_in() -> Result<()> {
    // Somewhere for the server's own dialling to go; never answered.
    let listener = TcpListener::bind((Ipv4Addr::LOCALHOST, 0)).await?;
    let endpoint = listener.local_addr()?;
    let server = TestServer::start_with(LOCAL_ASN, |c| {
        c.accept_unconfigured_peers = false;
        c.peers = vec![peer_at(endpoint)];
    })
    .await?;

    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(10)).await;
        }
    })
    .await?;
    assert_eq!(server.registry.list()[0].name.as_deref(), Some("r1"));
    Ok(())
}

/// One address may hold only a few connections at a time, so that one host
/// cannot use up the server's sockets with connections that never get as
/// far as a session.
#[tokio::test]
async fn test_one_address_may_open_only_a_few_connections() -> Result<()> {
    let server = TestServer::start(LOCAL_ASN).await?;

    // Four that say nothing: each is sent the server's OPEN and waited on.
    let mut held = Vec::new();
    for _ in 0..4 {
        let mut peer = TestPeer::connect(server.addr).await?;
        tokio::time::timeout(TIMEOUT, peer.recv_open()).await??;
        held.push(peer);
    }
    let mut one_too_many = TestPeer::connect(server.addr).await?;
    assert!(closed_unanswered(&mut one_too_many).await);

    // When one of them goes, there is room again.
    held.pop();
    tokio::time::timeout(TIMEOUT, async {
        loop {
            let mut peer = TestPeer::connect(server.addr).await?;
            if peer.recv_open().await.is_ok() {
                return Ok::<_, eyre::Report>(());
            }
            tokio::time::sleep(Duration::from_millis(20)).await;
        }
    })
    .await??;
    Ok(())
}