//! The world handshake over a real socket against a fake server: packets may precede
//! `SMSG_AUTH_RESPONSE`. Deviation: `SMSG_WARDEN_DATA` refuses the login, because benilla cannot
//! answer Warden and the server kicks a client that stays silent about 30 s later.

use std::io::{Read, Write};
use std::net::{TcpListener, TcpStream};
use std::thread;

use benilla_protocol::messages::opcode;
use benilla_protocol::{messages, WardenRequired, WorldSession};
use benilla_srp::vanilla_header::HeaderCrypto;
use benilla_srp::SESSION_KEY_LENGTH;

const SESSION_KEY: [u8; SESSION_KEY_LENGTH] = [7u8; SESSION_KEY_LENGTH];
const SERVER_SEED: u32 = 0xDEAD_BEEF;

/// Write one server packet: `u16` BE size (opcode plus body) and `u16` LE opcode, encrypted once
/// `crypto` is set, then the plaintext body.
fn send(stream: &mut TcpStream, crypto: Option<&mut HeaderCrypto>, opcode: u16, body: &[u8]) {
    let size = (body.len() + 2) as u16;
    let s = size.to_be_bytes();
    let o = opcode.to_le_bytes();
    let mut header = [s[0], s[1], o[0], o[1]];
    if let Some(c) = crypto {
        c.encrypter().encrypt(&mut header);
    }
    stream.write_all(&header).unwrap();
    stream.write_all(body).unwrap();
}

/// Read the client's unencrypted `CMSG_AUTH_SESSION` (6-byte header: BE size + LE u32 opcode).
fn read_auth_session(stream: &mut TcpStream) {
    let mut header = [0u8; 6];
    stream.read_exact(&mut header).unwrap();
    let size = u16::from_be_bytes([header[0], header[1]]) as usize;
    let mut body = vec![0u8; size - 4];
    stream.read_exact(&mut body).unwrap();
}

/// A fake world server that sends the `pre` packets, encrypted and in order, before a successful
/// `SMSG_AUTH_RESPONSE`; returns its address.
fn fake_server(pre: Vec<(u16, Vec<u8>)>) -> String {
    let listener = TcpListener::bind("127.0.0.1:0").unwrap();
    let addr = listener.local_addr().unwrap().to_string();
    thread::spawn(move || {
        let (mut stream, _) = listener.accept().unwrap();
        send(
            &mut stream,
            None,
            opcode::SMSG_AUTH_CHALLENGE,
            &SERVER_SEED.to_le_bytes(),
        );
        read_auth_session(&mut stream);
        let mut crypto = HeaderCrypto::from_session_key(SESSION_KEY);
        for (op, body) in pre {
            send(&mut stream, Some(&mut crypto), op, &body);
        }
        send(
            &mut stream,
            Some(&mut crypto),
            opcode::SMSG_AUTH_RESPONSE,
            &[messages::AUTH_OK],
        );
        // Hold the socket open so the client's reads never see a premature EOF.
        thread::sleep(std::time::Duration::from_secs(2));
    });
    addr
}

#[test]
fn auth_response_alone_completes_the_handshake() {
    let addr = fake_server(vec![]);
    assert!(WorldSession::connect(&addr, "one", SESSION_KEY).is_ok());
}

/// The server interleaves its own packets ahead of the auth response.
#[test]
fn packets_ahead_of_the_auth_response_are_skipped() {
    let addr = fake_server(vec![
        (opcode::SMSG_LOGIN_VERIFY_WORLD, vec![0u8; 20]),
        (opcode::SMSG_SET_FACTION_STANDING, vec![0u8; 12]),
    ]);
    assert!(WorldSession::connect(&addr, "one", SESSION_KEY).is_ok());
}

#[test]
fn a_warden_server_is_refused_at_the_handshake() {
    let addr = fake_server(vec![(opcode::SMSG_WARDEN_DATA, vec![0u8; 16])]);
    let Err(err) = WorldSession::connect(&addr, "one", SESSION_KEY) else {
        panic!("a Warden server must not yield a session");
    };
    assert!(
        err.downcast_ref::<WardenRequired>().is_some(),
        "expected WardenRequired, got: {err:#}"
    );
}

/// Every packet the observer saw, with the thread that wrote it: the tests of this file share one
/// process, so each filters for its own thread.
static SEEN: std::sync::Mutex<Vec<(thread::ThreadId, u16, usize)>> =
    std::sync::Mutex::new(Vec::new());

fn record(opcode: u16, len: usize) {
    SEEN.lock()
        .unwrap()
        .push((thread::current().id(), opcode, len));
}

/// A packet sent before the session splits (the handshake's `CMSG_AUTH_SESSION`, the world entry's
/// `CMSG_PLAYER_LOGIN`) reaches the observer in write order, ahead of the writer's own.
#[test]
fn sends_before_the_split_are_observed_in_order() {
    benilla_protocol::observe_sends(record);
    let addr = fake_server(vec![]);
    let mut session = WorldSession::connect(&addr, "one", SESSION_KEY).unwrap();
    session.player_login(0x2a).unwrap();
    let (_reader, mut writer) = session.into_split().unwrap();
    writer.complete_cinematic().unwrap();
    let me = thread::current().id();
    let mine: Vec<(u16, usize)> = SEEN
        .lock()
        .unwrap()
        .iter()
        .filter(|(t, ..)| *t == me)
        .map(|&(_, op, len)| (op, len))
        .collect();
    let auth_len = messages::auth_session(
        u32::from(benilla_protocol::CLIENT_BUILD),
        "ONE",
        0,
        &[0; 20],
        &messages::STOCK_SECURE_ADDONS,
    )
    .len();
    assert_eq!(
        mine,
        [
            (opcode::CMSG_AUTH_SESSION, auth_len),
            (opcode::CMSG_PLAYER_LOGIN, messages::full_guid(0x2a).len()),
            (opcode::CMSG_COMPLETE_CINEMATIC, 0),
        ]
    );
}