//! RFC 010 c7a — membership events and the view, at the manager.
//!
//! Same construction as the c6a lifecycle suite: the handshake is bypassed,
//! connections are built already-established over localhost TCP pairs with
//! fabricated `Peer`s, and the manager is started plainly so the test can
//! terminate. What is under test is the membership layer that c7 adds to the
//! manager: `node_up`/`node_down` events to subscribers (snapshot-then-stream),
//! the view, and NodeId identity — memoized per `(name, incarnation)`, so a
//! reconnect blip keeps its id and a restart (new incarnation) gets a fresh one.
#![cfg(feature = "cluster")]

use std::time::Duration;

use smarm::cluster::envelope::NodeMeta;
use smarm::cluster::handshake::Peer;
use smarm::cluster::manager::{Call, Manager, Reply, MANAGER};
use smarm::cluster::membership::{subscribe, view, MembershipEvents, NodeEvent};
use smarm::cluster::spawn_established;
use smarm::cluster::transport::tcp::TcpTransport;
use smarm::cluster::transport::{Conn, FramedConn, Transport};
use smarm::cluster::Timing;
use smarm::gen_server::{self, GenServerBuilder};
use smarm::pg::{Incarnation, NodeId};
use smarm::run;

/// A fabricated post-handshake peer identity, with the incarnation under the
/// test's control (it is identity-bearing here, unlike in the c6a suite).
fn peer(name: &str, inc: u32) -> Peer {
    Peer {
        node_name: name.to_string(),
        incarnation: Incarnation::new(inc),
        meta: NodeMeta {
            role: "test".to_string(),
            region: "test".to_string(),
        },
    }
}

/// One established transport pair over localhost (TCP backlog covers the
/// sequential dial-then-accept, as in the c3 conformance suite).
fn pair(t: &dyn Transport) -> (Box<dyn Conn>, Box<dyn Conn>) {
    let mut l = t.listen("127.0.0.1:0").unwrap();
    let a = t.dial(&l.local_addr()).unwrap();
    let b = l.accept().unwrap();
    (a, b)
}

/// The next event, or a panic naming the wait. The bound is generous against
/// a sub-millisecond real cost.
fn next_event(ev: &MembershipEvents, waiting_for: &str) -> NodeEvent {
    ev.rx
        .recv_timeout(Duration::from_secs(5))
        .unwrap_or_else(|e| panic!("timed out waiting for {waiting_for}: {e:?}"))
}

/// Assert the subscription is drained: no event is pending.
fn assert_quiet(ev: &MembershipEvents) {
    assert!(matches!(ev.rx.try_recv(), Ok(None)));
}

fn disconnect(name: &str) {
    assert!(matches!(
        gen_server::call(
            MANAGER,
            Call::Disconnect {
                name: name.to_string()
            }
        ),
        Ok(Reply::Disconnected)
    ));
}

/// Live subscription: an empty snapshot, then `NodeUp` on registration and
/// `NodeDown` (same id) on commanded disconnect and on peer EOF alike.
#[test]
fn subscriber_sees_up_and_down() {
    run(|| {
        let mgr = GenServerBuilder::new(Manager::new())
            .named(MANAGER)
            .start()
            .expect("manager name is free");

        let ev = subscribe().expect("manager is up");
        assert_quiet(&ev); // nothing live: the snapshot is empty

        let t = TcpTransport;
        let (a1, b1) = pair(&t);
        let (a2, b2) = pair(&t);
        spawn_established(FramedConn::new(a1), peer("node-b", 1), Timing::default())
            .expect("node-b registers");
        spawn_established(FramedConn::new(a2), peer("node-c", 1), Timing::default())
            .expect("node-c registers");

        let up_b = match next_event(&ev, "node_up(node-b)") {
            NodeEvent::NodeUp(info) => {
                assert_eq!(info.name, "node-b");
                assert_eq!(info.incarnation, Incarnation::new(1));
                assert_eq!(info.meta.role, "test");
                info
            }
            other => panic!("expected node_up(node-b), got {other:?}"),
        };
        let up_c = match next_event(&ev, "node_up(node-c)") {
            NodeEvent::NodeUp(info) => {
                assert_eq!(info.name, "node-c");
                info
            }
            other => panic!("expected node_up(node-c), got {other:?}"),
        };
        assert_ne!(up_b.node, up_c.node, "distinct peers get distinct ids");

        // Commanded disconnect: down with node-b's id.
        disconnect("node-b");
        assert_eq!(
            next_event(&ev, "node_down(node-b)"),
            NodeEvent::NodeDown(up_b.clone())
        );

        // Peer EOF, no command: down with node-c's id.
        drop(b2);
        assert_eq!(
            next_event(&ev, "node_down(node-c)"),
            NodeEvent::NodeDown(up_c.clone())
        );
        assert_quiet(&ev);

        drop(b1);
        mgr.shutdown();
    });
}

/// Snapshot-then-stream: a subscriber arriving after connections established
/// receives one `NodeUp` per live peer before anything else, and the view
/// call agrees with it.
#[test]
fn late_subscriber_gets_snapshot_and_view_agrees() {
    run(|| {
        let mgr = GenServerBuilder::new(Manager::new())
            .named(MANAGER)
            .start()
            .expect("manager name is free");

        let t = TcpTransport;
        let (a1, b1) = pair(&t);
        let (a2, b2) = pair(&t);
        spawn_established(FramedConn::new(a1), peer("node-b", 1), Timing::default())
            .expect("node-b registers");
        spawn_established(FramedConn::new(a2), peer("node-c", 1), Timing::default())
            .expect("node-c registers");

        let ev = subscribe().expect("manager is up");
        let mut names = Vec::new();
        for _ in 0..2 {
            match next_event(&ev, "a snapshot node_up") {
                NodeEvent::NodeUp(info) => names.push(info.name),
                other => panic!("expected a snapshot node_up, got {other:?}"),
            }
        }
        names.sort();
        assert_eq!(names, ["node-b", "node-c"]);
        assert_quiet(&ev); // the snapshot is exactly the live set

        let mut v = view().expect("manager is up");
        v.sort_by(|a, b| a.name.cmp(&b.name));
        assert_eq!(v.len(), 2);
        assert_eq!(v[0].name, "node-b");
        assert_eq!(v[1].name, "node-c");

        disconnect("node-b");
        disconnect("node-c");
        drop((b1, b2));
        // Drain the two downs so the subscription ends quiet.
        let _ = next_event(&ev, "node_down");
        let _ = next_event(&ev, "node_down");
        mgr.shutdown();
    });
}

/// NodeId identity: a restart (same name, new incarnation) is a NEW id — the
/// ghost and its successor are distinguishable — while a reconnect blip (same
/// name, same incarnation) keeps its id.
#[test]
fn restart_gets_new_id_blip_keeps_id() {
    run(|| {
        let mgr = GenServerBuilder::new(Manager::new())
            .named(MANAGER)
            .start()
            .expect("manager name is free");
        let ev = subscribe().expect("manager is up");
        let t = TcpTransport;

        let id = |e: NodeEvent, what: &str| -> NodeId {
            match e {
                NodeEvent::NodeUp(info) => info.node,
                other => panic!("expected node_up ({what}), got {other:?}"),
            }
        };
        let down_id = |e: NodeEvent, what: &str| -> NodeId {
            match e {
                NodeEvent::NodeDown(info) => info.node,
                other => panic!("expected node_down ({what}), got {other:?}"),
            }
        };

        // Up at incarnation 1, then the peer dies (EOF).
        let (a1, b1) = pair(&t);
        spawn_established(FramedConn::new(a1), peer("node-b", 1), Timing::default())
            .expect("registers");
        let id1 = id(next_event(&ev, "node_up inc 1"), "inc 1");
        drop(b1);
        assert_eq!(down_id(next_event(&ev, "node_down inc 1"), "inc 1"), id1);

        // Restart: new incarnation, new id — the ghost's id is not reused.
        let (a2, b2) = pair(&t);
        spawn_established(FramedConn::new(a2), peer("node-b", 2), Timing::default())
            .expect("registers");
        let id2 = id(next_event(&ev, "node_up inc 2"), "inc 2");
        assert_ne!(
            id1, id2,
            "a restarted node must be distinguishable from its ghost"
        );

        // Blip: the same incarnation reconnects and keeps its id.
        disconnect("node-b");
        assert_eq!(down_id(next_event(&ev, "node_down inc 2"), "inc 2"), id2);
        let (a3, b3) = pair(&t);
        spawn_established(FramedConn::new(a3), peer("node-b", 2), Timing::default())
            .expect("registers");
        let id3 = id(next_event(&ev, "node_up after blip"), "blip");
        assert_eq!(
            id2, id3,
            "a reconnect at the same incarnation is the same node"
        );

        disconnect("node-b");
        let _ = next_event(&ev, "final node_down");
        drop((b2, b3));
        mgr.shutdown();
    });
}

/// A dropped subscriber is pruned on the next emit and never disturbs the
/// manager or a live subscriber.
#[test]
fn dead_subscriber_is_pruned() {
    run(|| {
        let mgr = GenServerBuilder::new(Manager::new())
            .named(MANAGER)
            .start()
            .expect("manager name is free");

        let dead = subscribe().expect("manager is up");
        drop(dead);
        let live = subscribe().expect("manager is up");

        let t = TcpTransport;
        let (a1, b1) = pair(&t);
        spawn_established(FramedConn::new(a1), peer("node-b", 1), Timing::default())
            .expect("registers");
        match next_event(&live, "node_up despite a dead co-subscriber") {
            NodeEvent::NodeUp(info) => assert_eq!(info.name, "node-b"),
            other => panic!("expected node_up, got {other:?}"),
        }

        disconnect("node-b");
        let _ = next_event(&live, "node_down");
        drop(b1);
        mgr.shutdown();
    });
}