//! End-to-end integration tests against a real Soulseek server (soulfind).
//!
//! These tests are SERVER-OPTIONAL so `cargo test` stays green everywhere:
//!   * If `SOULSEEK_TEST_SERVER=host:port` is set, they connect to it.
//!   * Else if a soulfind binary is found (via `SOULFIND_BIN`, or a sibling
//!     `../soulfind/bin/soulfind` checkout), they spawn it on an ephemeral port
//!     with a throwaway database.
//!   * Else they SKIP with a printed notice (the test still passes).
//!
//! To run them against a locally built soulfind:
//! ```sh
//! SOULFIND_BIN=/path/to/soulfind \
//!   cargo test -p soulseek-rs-lib --test e2e -- --nocapture
//! ```
//!
//! No external crates are used — the library forbids dependencies, so the
//! harness sticks to `std` and the library's own public API.

#![allow(clippy::doc_markdown)]

use std::io::{Read, Write};
use std::net::{TcpStream, ToSocketAddrs};
use std::path::PathBuf;
use std::process::{Child, Command, Stdio};
use std::sync::mpsc::Sender;
use std::time::{Duration, Instant};

use soulseek_rs::message::Message;
use soulseek_rs::{Client, ClientSettings, DownloadStatus, PeerAddress};

/// A Soulseek server to test against: either a child soulfind process we
/// spawned, or an external server referenced by `SOULSEEK_TEST_SERVER`.
struct TestServer {
    host: String,
    port: u16,
    child: Option<Child>,
    db: Option<PathBuf>,
}

impl TestServer {
    /// Resolve a server to test against, or `None` if the suite should skip.
    fn resolve() -> Option<Self> {
        if let Ok(addr) = std::env::var("SOULSEEK_TEST_SERVER") {
            let (host, port) = split_host_port(&addr)?;
            wait_until_listening(&host, port, Duration::from_secs(2))?;
            return Some(Self {
                host,
                port,
                child: None,
                db: None,
            });
        }
        Self::spawn()
    }

    /// Spawn a local soulfind on an ephemeral port with a throwaway database.
    fn spawn() -> Option<Self> {
        let bin = soulfind_binary()?;
        let port = free_port()?;
        let db = std::env::temp_dir().join(format!("soulfind-e2e-{port}.db"));
        let _ = std::fs::remove_file(&db);

        let mut child = Command::new(&bin)
            .arg("-p")
            .arg(port.to_string())
            .arg("-d")
            .arg(&db)
            .stdout(Stdio::null())
            .stderr(Stdio::null())
            .spawn()
            .ok()?;

        if wait_until_listening("127.0.0.1", port, Duration::from_secs(5))
            .is_none()
        {
            // Server never came up (e.g. a toolchain/SQLite issue); skip.
            let _ = child.kill();
            let _ = child.wait();
            return None;
        }

        Some(Self {
            host: "127.0.0.1".to_string(),
            port,
            child: Some(child),
            db: Some(db),
        })
    }

    fn settings(&self, username: &str, password: &str) -> ClientSettings {
        ClientSettings {
            username: username.to_string(),
            password: password.to_string(),
            server_address: PeerAddress::new(self.host.clone(), self.port),
            enable_listen: false,
            listen_port: 0,
            shared_directory: None,
        }
    }

    /// Settings with the peer listener enabled on `port`, exercising the
    /// `SetWaitPort` step of the post-login handshake.
    fn listening_settings(
        &self,
        username: &str,
        password: &str,
        port: u16,
    ) -> ClientSettings {
        ClientSettings {
            enable_listen: true,
            listen_port: port,
            ..self.settings(username, password)
        }
    }
}

impl Drop for TestServer {
    fn drop(&mut self) {
        if let Some(child) = self.child.as_mut() {
            let _ = child.kill();
            let _ = child.wait();
        }
        if let Some(db) = self.db.as_ref() {
            let _ = std::fs::remove_file(db);
        }
    }
}

fn split_host_port(addr: &str) -> Option<(String, u16)> {
    let (host, port) = addr.rsplit_once(':')?;
    Some((host.to_string(), port.parse().ok()?))
}

fn soulfind_binary() -> Option<PathBuf> {
    if let Ok(p) = std::env::var("SOULFIND_BIN") {
        let p = PathBuf::from(p);
        return p.exists().then_some(p);
    }
    // Fall back to a `soulfind/bin/soulfind` checkout somewhere above this
    // workspace (the workspace may be nested, e.g. under `.../src/rust/`).
    let manifest = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
    manifest
        .ancestors()
        .map(|dir| dir.join("soulfind/bin/soulfind"))
        .find(|candidate| candidate.exists())
}

fn free_port() -> Option<u16> {
    let listener = std::net::TcpListener::bind("127.0.0.1:0").ok()?;
    listener.local_addr().ok().map(|addr| addr.port())
}

fn wait_until_listening(
    host: &str,
    port: u16,
    timeout: Duration,
) -> Option<()> {
    let addr = format!("{host}:{port}");
    let deadline = Instant::now() + timeout;
    while Instant::now() < deadline {
        if let Ok(mut addrs) = addr.to_socket_addrs()
            && let Some(sa) = addrs.next()
            && TcpStream::connect_timeout(&sa, Duration::from_millis(200))
                .is_ok()
        {
            return Some(());
        }
        std::thread::sleep(Duration::from_millis(100));
    }
    None
}

/// Resolve a test server or return early with a skip notice.
///
/// Set `SOULSEEK_E2E_REQUIRED=1` (as CI does) to turn a missing server into a
/// hard failure instead of a silent skip, so the suite genuinely runs there.
macro_rules! server_or_skip {
    () => {
        match TestServer::resolve() {
            Some(server) => server,
            None => {
                let required = std::env::var("SOULSEEK_E2E_REQUIRED")
                    .is_ok_and(|v| v != "0" && !v.is_empty());
                assert!(
                    !required,
                    "SOULSEEK_E2E_REQUIRED is set but no soulfind server could \
                     be started (set SOULFIND_BIN or SOULSEEK_TEST_SERVER)"
                );
                println!(
                    "e2e skipped: no soulfind server (set SOULFIND_BIN or \
                     SOULSEEK_TEST_SERVER to run)"
                );
                return;
            }
        }
    };
}

#[test]
fn connect_and_login_succeed() {
    let server = server_or_skip!();
    let mut client =
        Client::with_settings(server.settings("e2e_user", "e2e_pw"));
    client.connect().expect("connect to soulfind");
    let logged_in = client.login().expect("login to soulfind");
    assert!(logged_in, "login should succeed (soulfind auto-registers)");
}

#[test]
fn search_round_trips_without_error() {
    let server = server_or_skip!();
    let mut client =
        Client::with_settings(server.settings("e2e_search", "e2e_pw"));
    client.connect().expect("connect");
    assert!(client.login().expect("login"));

    // A fresh server has no shared files, so the search simply has to
    // round-trip without error and leave an (empty) queryable result set.
    let query = "nonexistent query xyzzy";
    let _ = client.search(query, Duration::from_secs(2));
    assert!(client.get_search_results(query).is_empty());

    // The search must also be tracked in client state under its key, proving
    // the request was actually registered and not silently dropped.
    assert!(
        client.get_all_searches().contains_key(query),
        "the issued search should be registered under its query key"
    );
}

#[test]
fn a_search_is_forwarded_to_a_connected_peer() {
    let server = server_or_skip!();

    // The server distributes each search to other connected users, so a second
    // client exercises the *incoming* FileSearch handler. We can't observe that
    // handler's state directly, but if it mishandled the forwarded bytes it
    // would take the receiver's session down — so we prove the receiver is
    // still alive afterwards by round-tripping its own search.
    let mut searcher =
        Client::with_settings(server.settings("e2e_searcher", "pw"));
    let mut receiver =
        Client::with_settings(server.settings("e2e_receiver", "pw"));
    searcher.connect().expect("searcher connect");
    receiver.connect().expect("receiver connect");
    assert!(searcher.login().expect("searcher login"));
    assert!(receiver.login().expect("receiver login"));

    let _ = searcher.search("some shared song", Duration::from_secs(2));

    // Receiver stays functional after handling the forwarded search.
    let probe = "receiver still alive";
    let _ = receiver.search(probe, Duration::from_secs(2));
    assert!(receiver.get_all_searches().contains_key(probe));
}

#[test]
fn a_private_message_is_delivered_between_users() {
    let server = server_or_skip!();

    // Two logged-in users, one messages the other through the server.
    let mut alice =
        Client::with_settings(server.settings("e2e_alice_pm", "pw"));
    let mut bob = Client::with_settings(server.settings("e2e_bob_pm", "pw"));
    alice.connect().expect("alice connect");
    bob.connect().expect("bob connect");
    assert!(alice.login().expect("alice login"));
    assert!(bob.login().expect("bob login"));

    let body = "hello bob, this is alice";
    alice
        .send_private_message("e2e_bob_pm", body)
        .expect("send private message");

    // Delivery is asynchronous; poll Bob's inbox until the message arrives.
    let deadline = Instant::now() + Duration::from_secs(5);
    let mut received = Vec::new();
    while Instant::now() < deadline {
        received.extend(bob.take_private_messages());
        if !received.is_empty() {
            break;
        }
        std::thread::sleep(Duration::from_millis(100));
    }

    let message = received
        .iter()
        .find(|m| m.message() == body)
        .expect("bob should receive alice's message");
    assert_eq!(message.username(), "e2e_alice_pm");
}

#[test]
fn login_succeeds_with_listener_enabled() {
    let server = server_or_skip!();

    // With the listener enabled the client also sends SetWaitPort during the
    // post-login handshake; the server must accept it and keep the session.
    let port = free_port().expect("free listener port");
    let mut client = Client::with_settings(server.listening_settings(
        "e2e_listener",
        "pw",
        port,
    ));
    client.connect().expect("connect with listener");
    assert!(
        client.login().expect("login with listener enabled"),
        "the handshake including SetWaitPort should still log in"
    );
}

#[test]
fn wrong_password_is_rejected() {
    let server = server_or_skip!();

    // soulfind auto-registers a username on first login and binds it to that
    // password, so a second login with a different password must be rejected.
    let user = "e2e_pw_user";
    let mut first =
        Client::with_settings(server.settings(user, "correct-horse"));
    first.connect().expect("connect (registering login)");
    assert!(
        first.login().expect("first login"),
        "registration should log in"
    );
    drop(first);

    let mut second =
        Client::with_settings(server.settings(user, "wrong-password"));
    second.connect().expect("connect (wrong password)");
    // The server may signal rejection either as a non-success status or as an
    // authentication error; both mean "not logged in", only `Ok(true)` accepts.
    assert!(
        !matches!(second.login(), Ok(true)),
        "a mismatched password must not be accepted"
    );
}

#[test]
fn two_clients_can_be_logged_in_together() {
    let server = server_or_skip!();

    // The server must handle several independent sessions at once — this is
    // the precondition for any peer-to-peer feature routed through it.
    let mut alice = Client::with_settings(server.settings("e2e_alice", "pw_a"));
    let mut bob = Client::with_settings(server.settings("e2e_bob", "pw_b"));

    alice.connect().expect("alice connect");
    bob.connect().expect("bob connect");

    assert!(alice.login().expect("alice login"));
    assert!(bob.login().expect("bob login"));
}

// ---------------------------------------------------------------------------
// Peer-to-peer download coverage.
//
// The client cannot serve files (the upload side is not implemented), so a real
// download is exercised with a minimal in-process "mock uploader" that speaks
// the peer protocol using the library's own public `Message` wire format. It
// drives the same path a real peer would after a search: a `P` control
// connection to our listener, a `QueueUpload` → `TransferRequest` →
// `TransferResponse` negotiation, then an `F` connection that streams the bytes.
// ---------------------------------------------------------------------------

/// Configuration for a one-shot mock uploader.
struct MockUpload {
    listen_addr: String,
    peer_username: String,
    filename: String,
    content: Vec<u8>,
    token: u32,
    ready: Sender<()>,
}

/// Build a `PeerInit` (peer code 1) frame: `[len][1][username][conn_type][token]`.
fn peer_init_bytes(username: &str, conn_type: &str, token: u32) -> Vec<u8> {
    let mut m = Message::new();
    m.write_int8(1)
        .write_string(username)
        .write_string(conn_type)
        .write_int32(token);
    m.get_buffer()
}

/// Read one length-prefixed peer message (`[len:4 LE][payload]`) from a blocking
/// stream. The returned `Message` keeps the length prefix, so `get_message_code`
/// and `set_pointer(8)` behave exactly as they do inside the library.
fn read_framed(stream: &mut TcpStream) -> std::io::Result<Message> {
    let mut len_buf = [0u8; 4];
    stream.read_exact(&mut len_buf)?;
    let len = u32::from_le_bytes(len_buf) as usize;
    let mut payload = vec![0u8; len];
    stream.read_exact(&mut payload)?;
    let mut data = len_buf.to_vec();
    data.extend_from_slice(&payload);
    Ok(Message::new_with_data(data))
}

fn connect_retry(addr: &str, timeout: Duration) -> std::io::Result<TcpStream> {
    let deadline = Instant::now() + timeout;
    loop {
        match TcpStream::connect(addr) {
            Ok(stream) => return Ok(stream),
            Err(e) => {
                if Instant::now() >= deadline {
                    return Err(e);
                }
                std::thread::sleep(Duration::from_millis(50));
            }
        }
    }
}

fn run_mock_uploader(cfg: &MockUpload) -> std::io::Result<()> {
    // 1. P (control) connection: register ourselves with the downloader.
    let mut p = connect_retry(&cfg.listen_addr, Duration::from_secs(5))?;
    p.set_read_timeout(Some(Duration::from_secs(10)))?;
    p.write_all(&peer_init_bytes(&cfg.peer_username, "P", 0))?;
    p.flush()?;
    let _ = cfg.ready.send(());

    // 2. Wait for the downloader's QueueUpload (peer code 43).
    loop {
        let mut msg = read_framed(&mut p)?;
        if msg.get_message_code() == 43 {
            msg.set_pointer(8);
            let _requested = msg.read_string();
            break;
        }
    }

    // 3. Offer the transfer with a TransferRequest (peer code 40). The size here
    //    becomes the download's expected size, so it must match the content.
    let mut tr = Message::new();
    tr.write_int32(40)
        .write_int32(1) // direction: upload
        .write_int32(cfg.token)
        .write_string(&cfg.filename)
        .write_int64(cfg.content.len() as u64);
    p.write_all(&tr.get_buffer())?;
    p.flush()?;

    // 4. Wait for the downloader to allow it (TransferResponse, peer code 41).
    loop {
        let msg = read_framed(&mut p)?;
        if msg.get_message_code() == 41 {
            break;
        }
    }

    // 5. F (file) connection. PeerInit(F) and the 4-byte transfer token go in a
    //    single write so the token lands in the listener's read buffer, where
    //    the download is looked up by token.
    let mut f = connect_retry(&cfg.listen_addr, Duration::from_secs(5))?;
    f.set_read_timeout(Some(Duration::from_secs(10)))?;
    let mut init = peer_init_bytes(&cfg.peer_username, "F", cfg.token);
    init.extend_from_slice(&cfg.token.to_le_bytes());
    f.write_all(&init)?;
    f.flush()?;

    // 6. The downloader replies with an 8-byte START_DOWNLOAD offset, then we
    //    stream the file bytes.
    let mut start = [0u8; 8];
    f.read_exact(&mut start)?;
    f.write_all(&cfg.content)?;
    f.flush()?;

    // Keep the connection open briefly so the reader drains everything.
    std::thread::sleep(Duration::from_millis(500));
    Ok(())
}

fn unique_download_dir() -> PathBuf {
    let dir = std::env::temp_dir().join(format!(
        "soulseek-e2e-dl-{}-{:?}",
        std::process::id(),
        std::thread::current().id()
    ));
    let _ = std::fs::create_dir_all(&dir);
    dir
}

#[test]
fn a_file_downloads_from_a_peer_over_p_and_f_connections() {
    let server = server_or_skip!();

    // Downloader: connected to the server with its peer listener enabled.
    let listen_port = free_port().expect("free listen port");
    let mut client = Client::with_settings(server.listening_settings(
        "e2e_downloader",
        "pw",
        listen_port,
    ));
    client.connect().expect("connect");
    assert!(client.login().expect("login"));

    let filename = "mock_song.mp3";
    let content: Vec<u8> = (0..2000u32).map(|i| (i % 251) as u8).collect();
    let size = content.len() as u64;
    let token = 424_242_u32;
    let download_dir = unique_download_dir();

    // Start the mock uploader; it signals once its P connection is established.
    let (ready_tx, ready_rx) = std::sync::mpsc::channel();
    let cfg = MockUpload {
        listen_addr: format!("127.0.0.1:{listen_port}"),
        peer_username: "e2e_mockpeer".to_string(),
        filename: filename.to_string(),
        content: content.clone(),
        token,
        ready: ready_tx,
    };
    let uploader = std::thread::spawn(move || {
        if let Err(e) = run_mock_uploader(&cfg) {
            eprintln!("[mock uploader] {e}");
        }
    });

    ready_rx
        .recv_timeout(Duration::from_secs(5))
        .expect("mock uploader P connection");

    // The listener registers an incoming peer under "<username>:direct"; give
    // that registration a moment to complete before queuing the download.
    std::thread::sleep(Duration::from_millis(1500));

    let (_download, status_rx) = client
        .download(
            filename.to_string(),
            "e2e_mockpeer:direct".to_string(),
            size,
            download_dir.display().to_string(),
        )
        .expect("start download");

    // Wait for completion via the per-download status channel.
    let mut completed = false;
    let deadline = Instant::now() + Duration::from_secs(20);
    while Instant::now() < deadline {
        match status_rx.recv_timeout(Duration::from_millis(500)) {
            Ok(DownloadStatus::Completed) => {
                completed = true;
                break;
            }
            Ok(DownloadStatus::Failed | DownloadStatus::TimedOut) => {
                break;
            }
            _ => {}
        }
        if client
            .get_all_downloads()
            .iter()
            .any(|d| matches!(d.status, DownloadStatus::Completed))
        {
            completed = true;
            break;
        }
    }
    let _ = uploader.join();

    assert!(completed, "the download should reach Completed");

    let written = std::fs::read(download_dir.join(filename))
        .expect("downloaded file should exist");
    assert_eq!(written, content, "downloaded bytes should match the source");

    let _ = std::fs::remove_dir_all(&download_dir);
}