//! Error handling integration tests (#85).
//!
//! Tests the three error categories:
//! 1. Protocol errors: malformed input → SimError + server continues
//! 2. Desync detection: state_hash field populated in snapshots
//! 3. SimError wire format roundtrip

use bevy_app::prelude::*;
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::{BridgePlugin, BridgeResource, ServerRunning};
use settled_reach_server::knowledge::{KnowledgeGraph, KnowledgePlugin};
use settled_reach_server::npc::relationships::TrustEventQueue;
use settled_reach_server::simulation::interaction::NearbyInteractionBuffer;
use settled_reach_server::simulation::monologue::{MonologueBuffer, MonologueState};
use settled_reach_server::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
use settled_reach_server::simulation::SimulationPlugin;
use std::io::{BufReader, BufWriter};
use std::net::{TcpListener, TcpStream};
use std::sync::{Arc, Barrier};
use std::thread;

/// Acceptance test (#85): send a malformed message mid-session, assert the
/// server emits a SimError in the next snapshot and continues running.
///
/// Uses barriers to synchronize the server and client threads, ensuring
/// the malformed data arrives before the server's receive_inputs call.
#[test]
fn malformed_input_produces_sim_error_and_server_continues() {
    let listener = TcpListener::bind("127.0.0.1:0").expect("bind listener");
    let server_addr = listener.local_addr().expect("get local addr");

    // Barriers for tick synchronization between server and client.
    // Each barrier is used once: client signals "data sent", server proceeds to tick.
    let barrier_tick1 = Arc::new(Barrier::new(2));
    let barrier_tick2 = Arc::new(Barrier::new(2));
    let barrier_tick3 = Arc::new(Barrier::new(2));

    let b1_server = Arc::clone(&barrier_tick1);
    let b2_server = Arc::clone(&barrier_tick2);
    let b3_server = Arc::clone(&barrier_tick3);

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

        let mut app = App::new();
        app.add_plugins(SimulationPlugin);
        app.add_plugins(BridgePlugin);
        app.add_plugins(KnowledgePlugin);
        app.init_resource::<TrustEventQueue>();
        app.insert_resource(BridgeResource::new(bridge));
        app.insert_resource(WalkabilityMap::new(32, 32, 1));
        app.world_mut().spawn((
            PlayerCharacter,
            TilePosition::new(16, 16, 0),
            KnowledgeGraph::new(),
            NearbyInteractionBuffer::default(),
            MonologueBuffer::default(),
            MonologueState::default(),
        ));

        // Tick 1: wait for client to send valid input, then process
        b1_server.wait();
        app.update();
        assert!(
            app.world().resource::<ServerRunning>().0,
            "server should be running after tick 1"
        );

        // Tick 2: wait for client to send malformed input, then process
        b2_server.wait();
        app.update();
        assert!(
            app.world().resource::<ServerRunning>().0,
            "server must continue running after malformed input"
        );

        // Tick 3: wait for client to send valid input, then process
        b3_server.wait();
        app.update();
        assert!(
            app.world().resource::<ServerRunning>().0,
            "server should still be running after tick 3"
        );
    });

    // Client: connect and interact with synchronization
    let stream = TcpStream::connect(server_addr).expect("client connect");
    let mut reader = BufReader::new(stream.try_clone().expect("clone for reader"));
    let mut writer = BufWriter::new(stream);

    // --- Tick 1: send valid input ---
    let valid_inputs = vec![PlayerInput {
        tick: 0,
        action: PlayerAction::MoveNorth,
    }];
    let payload = rmp_serde::to_vec_named(&valid_inputs).expect("serialize");
    write_framed(&mut writer, &payload).expect("send valid input");
    barrier_tick1.wait(); // Signal: valid input sent

    // Read tick 1 snapshot
    let snap1_bytes = read_framed(&mut reader)
        .expect("read snapshot 1")
        .expect("not EOF");
    let snap1: ObserverSnapshot =
        rmp_serde::from_slice(&snap1_bytes).expect("deserialize snapshot 1");
    assert!(snap1.sim_errors.is_empty(), "no errors expected on tick 1");

    // --- Tick 2: send malformed input (properly framed but garbage payload) ---
    let garbage_payload: Vec<u8> = vec![0xFF, 0xFE, 0xFD, 0xFC, 0xAB, 0xCD, 0xEF];
    write_framed(&mut writer, &garbage_payload).expect("send malformed input");
    barrier_tick2.wait(); // Signal: malformed input sent

    // Read tick 2 snapshot — should contain SimError
    let snap2_bytes = read_framed(&mut reader)
        .expect("read snapshot 2")
        .expect("not EOF");
    let snap2: ObserverSnapshot =
        rmp_serde::from_slice(&snap2_bytes).expect("deserialize snapshot 2");
    assert!(
        !snap2.sim_errors.is_empty(),
        "sim_errors must contain the protocol error from malformed input"
    );
    assert_eq!(
        snap2.sim_errors[0].kind,
        SimErrorKind::ProtocolError,
        "error kind must be ProtocolError"
    );
    assert!(
        snap2.sim_errors[0]
            .message
            .contains("Malformed input frame")
            || snap2.sim_errors[0]
                .message
                .contains("Deserialization error"),
        "error message should describe the deserialization failure, got: {}",
        snap2.sim_errors[0].message,
    );

    // --- Tick 3: send valid input again — server must still work ---
    let valid_inputs2 = vec![PlayerInput {
        tick: 2,
        action: PlayerAction::MoveSouth,
    }];
    let payload2 = rmp_serde::to_vec_named(&valid_inputs2).expect("serialize");
    write_framed(&mut writer, &payload2).expect("send valid input after error");
    barrier_tick3.wait(); // Signal: valid input sent

    // Read tick 3 snapshot — no errors, server recovered
    let snap3_bytes = read_framed(&mut reader)
        .expect("read snapshot 3")
        .expect("not EOF");
    let snap3: ObserverSnapshot =
        rmp_serde::from_slice(&snap3_bytes).expect("deserialize snapshot 3");
    assert!(
        snap3.sim_errors.is_empty(),
        "no errors expected on tick 3 — server recovered"
    );

    // Clean up
    drop(reader);
    drop(writer);
    server_handle
        .join()
        .expect("server thread should not panic");
}

/// State hash is populated in every snapshot and is deterministic for same state.
#[test]
fn state_hash_populated_in_snapshot() {
    let listener = TcpListener::bind("127.0.0.1:0").expect("bind listener");
    let server_addr = listener.local_addr().expect("get local addr");

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

        let mut app = App::new();
        app.add_plugins(SimulationPlugin);
        app.add_plugins(BridgePlugin);
        app.add_plugins(KnowledgePlugin);
        app.init_resource::<TrustEventQueue>();
        app.insert_resource(BridgeResource::new(bridge));
        app.insert_resource(WalkabilityMap::new(32, 32, 1));
        app.world_mut().spawn((
            PlayerCharacter,
            TilePosition::new(16, 16, 0),
            KnowledgeGraph::new(),
            NearbyInteractionBuffer::default(),
            MonologueBuffer::default(),
            MonologueState::default(),
        ));

        // Run one tick
        app.update();
    });

    let stream = TcpStream::connect(server_addr).expect("client connect");
    let mut reader = BufReader::new(stream.try_clone().expect("clone for reader"));
    let mut writer = BufWriter::new(stream);

    // Send empty input batch (no movement)
    let inputs: Vec<PlayerInput> = vec![];
    let payload = rmp_serde::to_vec_named(&inputs).expect("serialize");
    write_framed(&mut writer, &payload).expect("send empty input");

    // Read snapshot
    let snap_bytes = read_framed(&mut reader)
        .expect("read snapshot")
        .expect("not EOF");
    let snap: ObserverSnapshot = rmp_serde::from_slice(&snap_bytes).expect("deserialize snapshot");

    assert!(
        snap.state_hash.is_some(),
        "state_hash must be populated in snapshot"
    );
    assert_ne!(
        snap.state_hash.unwrap(),
        0,
        "state_hash should be a non-trivial hash value"
    );

    drop(reader);
    drop(writer);
    server_handle
        .join()
        .expect("server thread should not panic");
}

/// SimError roundtrips through MessagePack serialization.
#[test]
fn sim_error_roundtrip() {
    let error = SimError {
        kind: SimErrorKind::ProtocolError,
        message: "test protocol error".into(),
        tick: 42,
    };

    let bytes = rmp_serde::to_vec_named(&error).expect("serialize SimError");
    let decoded: SimError = rmp_serde::from_slice(&bytes).expect("deserialize SimError");

    assert_eq!(decoded.kind, SimErrorKind::ProtocolError);
    assert_eq!(decoded.message, "test protocol error");
    assert_eq!(decoded.tick, 42);
}

/// SimErrorKind::Panic variant roundtrips.
#[test]
fn sim_error_panic_variant_roundtrip() {
    let error = SimError {
        kind: SimErrorKind::Panic,
        message: "simulation system panicked".into(),
        tick: 100,
    };

    let bytes = rmp_serde::to_vec_named(&error).expect("serialize");
    let decoded: SimError = rmp_serde::from_slice(&bytes).expect("deserialize");

    assert_eq!(decoded.kind, SimErrorKind::Panic);
    assert_eq!(decoded.message, "simulation system panicked");
    assert_eq!(decoded.tick, 100);
}

/// Snapshot with sim_errors populates correctly through serialization.
#[test]
fn snapshot_with_sim_errors_roundtrips() {
    use settled_reach_server::simulation::time::{DayPhase, TickRate};

    let snapshot = ObserverSnapshot {
        version: PROTOCOL_VERSION,
        tick: 10,
        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![],
        visible_tiles: vec![],
        nearby_interactions: vec![],
        current_monologue: None,
        pending_recognitions: vec![],
        dialogue_response: None,
        blocked_entities: vec![],
        scan_events: vec![],
        sound_events: vec![],
        conversation_events: vec![],
        conversation_ended: 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: Some(0xDEADBEEF),
        debug_response: None,
        sim_errors: vec![SimError {
            kind: SimErrorKind::ProtocolError,
            message: "bad frame".into(),
            tick: 10,
        }],
        current_ticker: None,
        settings_response: None,
    };

    let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
    let decoded: ObserverSnapshot = rmp_serde::from_slice(&bytes).expect("deserialize");

    assert_eq!(decoded.state_hash, Some(0xDEADBEEF));
    assert_eq!(decoded.sim_errors.len(), 1);
    assert_eq!(decoded.sim_errors[0].kind, SimErrorKind::ProtocolError);
    assert_eq!(decoded.sim_errors[0].message, "bad frame");
}