//! Integration tests for TcpBridge over TCP localhost (D-030 Layer 2: IPC roundtrip).

use settled_reach_server::bridge::framing::{read_framed, write_framed};
use settled_reach_server::bridge::tcp::TcpBridge;
use settled_reach_server::bridge::types::*;
use settled_reach_server::bridge::{Inbound, SimBridge};
use settled_reach_server::simulation::time::{DayPhase, TickRate};
use std::net::{TcpListener, TcpStream};
use std::thread;

#[test]
fn snapshot_roundtrip_over_tcp() {
    // Bind listener first — port is guaranteed ready before spawning threads
    let listener = TcpListener::bind("127.0.0.1:0").expect("failed to bind");
    let server_addr = listener.local_addr().expect("failed to get local address");

    // Server thread: accept on pre-bound listener and send snapshot
    let server_handle = thread::spawn(move || {
        let bridge = TcpBridge::accept_on(listener).expect("failed to accept");

        let snapshot = ObserverSnapshot {
            tick: 42,
            game_time: GameTime {
                day: 0,
                time_of_day: 0,
                day_phase: DayPhase::Morning,
                tick_rate: TickRate::Full,
            },
            player_facing: FacingDirection::North,
            player_stance: MovementStance::default(),
            player_inventory: vec![],
            entities: vec![VisibleEntity {
                entity_id: 100,
                x: 10.5,
                y: 20.3,
                z: 0,
                kind: EntityKind::Npc,
                visibility: VisibilitySector::Forward,
                relationship: RelationshipState::Unknown,
                observation: EntityVisibility::Visible,
                tell_state: None,
            }],
            visible_tiles: vec![],
            nearby_interactions: vec![],
            current_monologue: None,
            pending_recognitions: vec![],
            dialogue_response: None,
            blocked_entities: vec![],
            scan_events: vec![],
            sound_events: vec![],
            follow_state: None,
            character_pressure: None,
            rng_seed: None,
            poi_list: vec![],
            examine_result: None,
            player_knowledge: None,
            save_result: None,
            triangle_crisis_events: vec![],
            state_hash: None,
            debug_response: None,
            sim_errors: vec![],
            current_ticker: None,
            settings_response: None,
            economy_snapshot: None,
            bookmark_catalog: None,
        };

        bridge
            .send_snapshot(&snapshot)
            .expect("failed to send snapshot");
    });

    // Client: connect and receive snapshot (no sleep needed — listener already bound)
    let stream = TcpStream::connect(server_addr).expect("failed to connect");
    let mut reader = std::io::BufReader::new(stream);

    let payload = read_framed(&mut reader)
        .expect("failed to read frame")
        .expect("unexpected EOF");

    let snapshot: ObserverSnapshot =
        rmp_serde::from_slice(&payload).expect("failed to deserialize");

    assert_eq!(snapshot.tick, 42);
    assert_eq!(snapshot.entities.len(), 1);
    assert_eq!(snapshot.entities[0].entity_id, 100);
    assert_eq!(snapshot.entities[0].x, 10.5);
    assert_eq!(snapshot.entities[0].y, 20.3);

    server_handle.join().expect("server thread panicked");
}

#[test]
fn input_roundtrip_over_tcp() {
    let listener = TcpListener::bind("127.0.0.1:0").expect("failed to bind");
    let server_addr = listener.local_addr().expect("failed to get local address");

    let server_handle = thread::spawn(move || {
        let bridge = TcpBridge::accept_on(listener).expect("failed to accept");

        // Non-blocking socket: retry until data arrives or timeout.
        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(5);
        let inputs = loop {
            match bridge.receive() {
                Ok(Some(Inbound::Inputs(inputs))) if !inputs.is_empty() => break inputs,
                Ok(_) => {
                    assert!(
                        std::time::Instant::now() < deadline,
                        "timed out waiting for inputs"
                    );
                    thread::sleep(std::time::Duration::from_millis(1));
                }
                Err(e) => panic!("failed to receive inputs: {}", e),
            }
        };

        assert_eq!(inputs.len(), 2);
        assert_eq!(inputs[0].tick, 10);
        assert_eq!(inputs[1].tick, 11);

        inputs
    });

    // Client: connect and send inputs
    let stream = TcpStream::connect(server_addr).expect("failed to connect");
    let mut writer = std::io::BufWriter::new(stream);

    let inputs = vec![
        PlayerInput {
            tick: 10,
            action: PlayerAction::MoveNorth,
        },
        PlayerInput {
            tick: 11,
            action: PlayerAction::Interact {
                target_entity_id: None,
                verb: None,
            },
        },
    ];

    let payload = rmp_serde::to_vec_named(&inputs).expect("failed to serialize");
    write_framed(&mut writer, &payload).expect("failed to write frame");

    // Drop writer to close connection and signal EOF to server
    drop(writer);

    let received_inputs = server_handle.join().expect("server thread panicked");

    match &received_inputs[0].action {
        PlayerAction::MoveNorth => {}
        _ => panic!("expected MoveNorth action"),
    }
    match &received_inputs[1].action {
        PlayerAction::Interact { .. } => {}
        _ => panic!("expected Interact action"),
    }
}

#[test]
fn tcp_bridge_eof_returns_error() {
    let listener = TcpListener::bind("127.0.0.1:0").expect("failed to bind");
    let server_addr = listener.local_addr().expect("failed to get local address");

    let server_handle = thread::spawn(move || {
        let bridge = TcpBridge::accept_on(listener).expect("failed to accept");

        // Non-blocking socket: retry until we get Disconnected or timeout.
        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(5);
        loop {
            match bridge.receive() {
                Ok(None) => {
                    // No data yet — client hasn't disconnected, retry
                    assert!(
                        std::time::Instant::now() < deadline,
                        "timed out waiting for EOF"
                    );
                    thread::sleep(std::time::Duration::from_millis(1));
                }
                Ok(Some(_)) => panic!("expected Disconnected error, got a message"),
                Err(settled_reach_server::bridge::BridgeError::Disconnected) => break,
                Err(e) => panic!("expected Disconnected error, got: {}", e),
            }
        }
    });

    // Client: connect and immediately disconnect without sending data
    let stream = TcpStream::connect(server_addr).expect("failed to connect");
    drop(stream);

    server_handle.join().expect("server thread panicked");
}

/// T-1045 regression: EOF *mid-frame* (peer dies after a partial write) must
/// escalate to `Disconnected` like clean EOF — not surface an Io error every
/// tick forever against a frame that can never complete.
#[test]
fn tcp_bridge_eof_mid_frame_escalates_to_disconnected() {
    let listener = TcpListener::bind("127.0.0.1:0").expect("failed to bind");
    let server_addr = listener.local_addr().expect("failed to get local address");

    let server_handle = thread::spawn(move || {
        let bridge = TcpBridge::accept_on(listener).expect("failed to accept");

        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(5);
        loop {
            match bridge.receive() {
                Ok(None) => {
                    assert!(
                        std::time::Instant::now() < deadline,
                        "timed out waiting for mid-frame EOF"
                    );
                    thread::sleep(std::time::Duration::from_millis(1));
                }
                Ok(Some(_)) => panic!("expected Disconnected, got a message"),
                Err(settled_reach_server::bridge::BridgeError::Disconnected) => break,
                Err(e) => panic!("expected Disconnected, got: {}", e),
            }
        }
    });

    // Client: write 2 of the 4 length-prefix bytes, then die.
    use std::io::Write;
    let mut stream = TcpStream::connect(server_addr).expect("failed to connect");
    stream
        .write_all(&[0x00, 0x00])
        .expect("partial write failed");
    stream.flush().expect("flush failed");
    thread::sleep(std::time::Duration::from_millis(50));
    drop(stream);

    server_handle.join().expect("server thread panicked");
}

/// Build a raw frame (4-byte BE length prefix + payload) for split-write tests.
fn raw_frame(payload: &[u8]) -> Vec<u8> {
    let mut frame = (payload.len() as u32).to_be_bytes().to_vec();
    frame.extend_from_slice(payload);
    frame
}

/// Poll the non-blocking bridge until `count` input batches arrive.
fn collect_input_batches(bridge: &TcpBridge, count: usize) -> Vec<Vec<PlayerInput>> {
    let deadline = std::time::Instant::now() + std::time::Duration::from_secs(5);
    let mut batches = Vec::new();
    while batches.len() < count {
        match bridge.receive() {
            Ok(Some(Inbound::Inputs(inputs))) if !inputs.is_empty() => batches.push(inputs),
            Ok(_) => {
                assert!(
                    std::time::Instant::now() < deadline,
                    "timed out waiting for {} input batches (got {})",
                    count,
                    batches.len()
                );
                thread::sleep(std::time::Duration::from_millis(1));
            }
            Err(e) => panic!("failed to receive inputs: {}", e),
        }
    }
    batches
}

/// T-1045 regression: a frame delivered in two TCP writes (split at
/// `split_point(frame_len)`) must decode, and the NEXT frame must also decode
/// — i.e. a partial read mid-frame must not desync the stream. The server
/// polls receive() during the gap, so it observes WouldBlock mid-frame.
fn assert_split_frame_does_not_desync(split_point: impl Fn(usize) -> usize) {
    use std::io::Write;

    let listener = TcpListener::bind("127.0.0.1:0").expect("failed to bind");
    let server_addr = listener.local_addr().expect("failed to get local address");

    let server_handle = thread::spawn(move || {
        let bridge = TcpBridge::accept_on(listener).expect("failed to accept");
        collect_input_batches(&bridge, 2)
    });

    let mut stream = TcpStream::connect(server_addr).expect("failed to connect");

    let inputs1 = vec![PlayerInput {
        tick: 10,
        action: PlayerAction::MoveNorth,
    }];
    let payload1 = rmp_serde::to_vec_named(&inputs1).expect("failed to serialize");
    let frame1 = raw_frame(&payload1);
    let split = split_point(frame1.len());
    assert!(split > 0 && split < frame1.len(), "split must be mid-frame");

    // First half, then a gap long enough for the server to poll mid-frame.
    stream
        .write_all(&frame1[..split])
        .expect("write first half");
    stream.flush().expect("flush first half");
    thread::sleep(std::time::Duration::from_millis(50));
    stream
        .write_all(&frame1[split..])
        .expect("write second half");
    stream.flush().expect("flush second half");

    // A second frame in a single write — decodes only if the stream is in sync.
    let inputs2 = vec![PlayerInput {
        tick: 11,
        action: PlayerAction::MoveSouth,
    }];
    let payload2 = rmp_serde::to_vec_named(&inputs2).expect("failed to serialize");
    stream
        .write_all(&raw_frame(&payload2))
        .expect("write second frame");
    stream.flush().expect("flush second frame");

    let batches = server_handle.join().expect("server thread panicked");
    assert_eq!(batches[0].len(), 1);
    assert_eq!(batches[0][0].tick, 10);
    assert!(matches!(batches[0][0].action, PlayerAction::MoveNorth));
    assert_eq!(batches[1].len(), 1);
    assert_eq!(batches[1][0].tick, 11);
    assert!(matches!(batches[1][0].action, PlayerAction::MoveSouth));
}

#[test]
fn frame_split_inside_prefix_does_not_desync() {
    // Split inside the 4-byte length prefix.
    assert_split_frame_does_not_desync(|_| 2);
}

#[test]
fn frame_split_inside_payload_does_not_desync() {
    // Split midway through the payload (prefix is 4 bytes).
    assert_split_frame_does_not_desync(|frame_len| 4 + (frame_len - 4) / 2);
}

/// T-1045 drain: one receive_bridge_inputs run (= one 50 ms tick) must drain
/// every complete frame buffered on the socket, not one frame per tick.
#[test]
fn single_tick_drains_all_ready_inbound_frames() {
    use bevy_ecs::system::RunSystemOnce;
    use settled_reach_server::atlas::cascade::CascadeLayer;
    use settled_reach_server::atlas::layer_proxy::AtlasLayerRequest;
    use settled_reach_server::bridge::{
        receive_bridge_inputs, AtlasRequestBuffer, BridgeResource, CityNamesRequestBuffer,
        HandshakeState, ServerRunning, StarMapRequestBuffer,
    };
    use settled_reach_server::simulation::input::InputQueue;

    let listener = TcpListener::bind("127.0.0.1:0").expect("failed to bind");
    let server_addr = listener.local_addr().expect("failed to get local address");

    // Client: five frames back-to-back in one tick window — two input
    // batches plus one of EACH request shape (atlas, star-map, city-names:
    // the full D-225/T-949 demux surface over the real framing/poll path —
    // PR #176 review H6). Returns the stream so it stays open until
    // assertions complete (no EOF race).
    let client_handle = thread::spawn(move || {
        use settled_reach_server::atlas::atlas_data_proxy::{CityNamesRequest, StarMapRequest};

        let mut stream = TcpStream::connect(server_addr).expect("failed to connect");
        for tick in [20u64, 21] {
            let inputs = vec![PlayerInput {
                tick,
                action: PlayerAction::MoveNorth,
            }];
            let payload = rmp_serde::to_vec_named(&inputs).expect("failed to serialize");
            write_framed(&mut stream, &payload).expect("write input frame");
        }
        let req = AtlasLayerRequest {
            body_id: "GJ1c".into(),
            up_to: CascadeLayer::Topography,
        };
        let payload = rmp_serde::to_vec_named(&req).expect("failed to serialize");
        write_framed(&mut stream, &payload).expect("write atlas frame");
        let sm = StarMapRequest { star_map: true };
        let payload = rmp_serde::to_vec_named(&sm).expect("failed to serialize star map");
        write_framed(&mut stream, &payload).expect("write star map frame");
        let cn = CityNamesRequest {
            city_names: true,
            body_id: "GJ1c".into(),
        };
        let payload = rmp_serde::to_vec_named(&cn).expect("failed to serialize city names");
        write_framed(&mut stream, &payload).expect("write city names frame");
        stream
    });

    let bridge = TcpBridge::accept_on(listener).expect("failed to accept");
    let _stream = client_handle.join().expect("client thread panicked");
    // Writes are flushed and joined; small grace period for loopback delivery.
    thread::sleep(std::time::Duration::from_millis(100));

    let mut world = bevy_ecs::world::World::new();
    world.insert_resource(BridgeResource::new(bridge));
    world.init_resource::<InputQueue>();
    world.init_resource::<ServerRunning>();
    world.insert_resource(HandshakeState::Complete);
    world.init_resource::<SimErrorBuffer>();
    world.init_resource::<AtlasRequestBuffer>();
    world.init_resource::<StarMapRequestBuffer>();
    world.init_resource::<CityNamesRequestBuffer>();

    world
        .run_system_once(receive_bridge_inputs)
        .expect("receive_bridge_inputs failed to run");

    assert_eq!(
        world.resource::<InputQueue>().len(),
        2,
        "both input batches must drain in a single tick"
    );
    assert_eq!(
        world.resource::<AtlasRequestBuffer>().0.len(),
        1,
        "the atlas request must drain in the same tick"
    );
    assert_eq!(
        world.resource::<StarMapRequestBuffer>().0.len(),
        1,
        "the star-map request must drain in the same tick (H6: real wire path)"
    );
    let city_names = &world.resource::<CityNamesRequestBuffer>().0;
    assert_eq!(
        city_names.len(),
        1,
        "the city-names request must drain in the same tick (H6: real wire path)"
    );
    assert_eq!(city_names[0].body_id, "GJ1c");
    assert!(
        world.resource::<ServerRunning>().0,
        "draining must not shut the server down"
    );
}