//! Layer 3 integration test: real subprocess IPC (D-030)
//!
//! Spawns the server binary as a child process with --test-mode --port 0,
//! parses the LISTENING:{port} handshake from stdout, connects via TCP,
//! sends a PlayerInput, and reads back an ObserverSnapshot.
//!
//! This is the highest-fidelity test layer: no mocks, no in-process bridge.
//! The server runs as a separate OS process, exactly as it does in production.
//!
//! Spec references: D-020 (subprocess IPC), D-030 (Layer 3 integration tests)

use settled_reach_server::bridge::framing::{read_framed, write_framed};
use settled_reach_server::bridge::types::*;
use std::io::{BufRead, BufReader, BufWriter};
use std::net::TcpStream;
use std::process::{Command, Stdio};
use std::time::{Duration, Instant};

/// Timeout for the server to emit LISTENING:{port} on stdout.
const LISTEN_TIMEOUT: Duration = Duration::from_secs(15);

/// Timeout for the client to receive a snapshot after sending input.
const SNAPSHOT_TIMEOUT: Duration = Duration::from_secs(10);

#[test]
fn server_subprocess_sends_snapshot_on_connect() {
    // 1. Spawn server binary with --test-mode --port 0
    let server_bin = env!("CARGO_BIN_EXE_settled-reach-server");
    let mut child = Command::new(server_bin)
        .args(["--test-mode", "--port", "0"])
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .spawn()
        .expect("failed to spawn server binary");

    let stdout = child.stdout.take().expect("stdout not captured");
    let mut stdout_reader = BufReader::new(stdout);

    // 2. Parse LISTENING:{port} from stdout
    let port = {
        let deadline = Instant::now() + LISTEN_TIMEOUT;
        let mut line = String::new();
        loop {
            line.clear();
            match stdout_reader.read_line(&mut line) {
                Ok(0) => panic!("server stdout closed before LISTENING signal"),
                Ok(_) => {
                    let trimmed = line.trim();
                    if let Some(port_str) = trimmed.strip_prefix("LISTENING:") {
                        break port_str
                            .parse::<u16>()
                            .unwrap_or_else(|e| panic!("invalid port '{}': {}", port_str, e));
                    }
                }
                Err(e) => panic!("failed to read server stdout: {}", e),
            }
            assert!(
                Instant::now() < deadline,
                "timed out waiting for LISTENING signal"
            );
        }
    };

    // 3. Connect to the server via TCP
    let addr = format!("127.0.0.1:{}", port);
    let stream = TcpStream::connect(&addr)
        .unwrap_or_else(|e| panic!("failed to connect to server at {}: {}", addr, e));
    stream
        .set_read_timeout(Some(SNAPSHOT_TIMEOUT))
        .expect("set read timeout");

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

    // 4. Send one PlayerInput (idle tick 0)
    let inputs = vec![PlayerInput {
        tick: 0,
        action: PlayerAction::MoveNorth,
    }];
    let payload = rmp_serde::to_vec_named(&inputs).expect("serialize PlayerInput");
    write_framed(&mut writer, &payload).expect("send PlayerInput to server");

    // 5. Read one ObserverSnapshot
    let response = read_framed(&mut reader)
        .expect("read snapshot frame")
        .expect("server closed connection before sending snapshot");
    let snapshot: ObserverSnapshot =
        rmp_serde::from_slice(&response).expect("deserialize ObserverSnapshot");

    // 6. Assert protocol correctness (D-020)
    assert_eq!(
        snapshot.version, PROTOCOL_VERSION,
        "protocol version mismatch: got {}, expected {}",
        snapshot.version, PROTOCOL_VERSION
    );
    assert!(
        snapshot.entities.len() > 0,
        "snapshot should contain at least one entity (the player), got 0"
    );

    // The proof room has a player + NPCs. Verify the player entity exists.
    let has_player = snapshot
        .entities
        .iter()
        .any(|e| matches!(e.kind, EntityKind::Player));
    assert!(has_player, "snapshot must contain a Player entity");

    // 7. Clean up: drop connection so the server exits its game loop
    drop(reader);
    drop(writer);

    // Wait for child to exit (with timeout)
    let exit_deadline = Instant::now() + Duration::from_secs(5);
    loop {
        match child.try_wait() {
            Ok(Some(_status)) => break,
            Ok(None) => {
                if Instant::now() > exit_deadline {
                    child.kill().ok();
                    child.wait().ok();
                    break;
                }
                std::thread::sleep(Duration::from_millis(50));
            }
            Err(e) => {
                eprintln!("error waiting for server process: {}", e);
                child.kill().ok();
                break;
            }
        }
    }
}