lex-runtime 0.9.5

//! WebSocket server + chat-broadcast registry.
//!
//! `net.serve_ws(port, on_message)` blocks on a TCP listener, upgrades
//! each incoming connection to WebSocket, and runs a per-connection
//! worker thread that polls both inbound (calls Lex's `on_message`)
//! and outbound (drains broadcasts from a channel into the socket).
//!
//! `chat.broadcast(room, body)` looks up every connection in `room`
//! and pushes `body` onto its outbound channel. `chat.send(conn_id,
//! body)` is the same but to a single connection.
//!
//! The registry is an `Arc<Mutex<…>>` because Lex's immutability means
//! shared mutable state has to live in the host runtime. Lex code
//! stays pure: it receives an event, returns Nil, and any side
//! effects go through `chat.*` which is gated by the policy.

// tungstenite's `accept_hdr` callback takes/returns a tungstenite
// `ErrorResponse` which is large; we only ever return Ok so the
// large-Err warning is noise.
#![allow(clippy::result_large_err)]

use crate::policy::Policy;
use indexmap::IndexMap;
use lex_bytecode::vm::Vm;
use lex_bytecode::{Program, Value};
use std::net::TcpListener;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::mpsc;
use std::sync::{Arc, Mutex};
use std::thread;
use std::time::Duration;

/// Per-connection state held in the global registry.
struct Conn {
    room: String,
    /// Channel writer end. The connection's worker thread reads from
    /// the corresponding Receiver and writes each message to the
    /// WebSocket. Broadcasts push here.
    outbound: mpsc::Sender<String>,
}

/// Global chat registry. One per `net.serve_ws` invocation.
#[derive(Default)]
pub struct ChatRegistry {
    conns: Mutex<IndexMap<u64, Conn>>,
}

impl ChatRegistry {
    fn register(&self, room: String, outbound: mpsc::Sender<String>) -> u64 {
        static NEXT_ID: AtomicU64 = AtomicU64::new(1);
        let id = NEXT_ID.fetch_add(1, Ordering::SeqCst);
        self.conns.lock().unwrap().insert(id, Conn { room, outbound });
        id
    }
    fn unregister(&self, id: u64) {
        self.conns.lock().unwrap().shift_remove(&id);
    }
    fn broadcast(&self, room: &str, body: &str) {
        let conns = self.conns.lock().unwrap();
        for c in conns.values() {
            if c.room == room {
                let _ = c.outbound.send(body.to_string());
            }
        }
    }
    fn send_to(&self, id: u64, body: &str) -> bool {
        if let Some(c) = self.conns.lock().unwrap().get(&id) {
            let _ = c.outbound.send(body.to_string());
            true
        } else {
            false
        }
    }
}

/// `chat.broadcast(room, body)` — looked up at runtime by the
/// effect handler; called from inside the Lex VM.
pub fn chat_broadcast(reg: &Arc<ChatRegistry>, room: &str, body: &str) {
    reg.broadcast(room, body);
}

pub fn chat_send(reg: &Arc<ChatRegistry>, conn_id: u64, body: &str) -> bool {
    reg.send_to(conn_id, body)
}

/// Bind a WebSocket server. Blocks; returns Unit on shutdown (the
/// process is normally killed before that).
pub fn serve_ws(
    port: u16,
    handler_name: String,
    program: Arc<Program>,
    policy: Policy,
    registry: Arc<ChatRegistry>,
) -> Result<Value, String> {
    let listener = TcpListener::bind(("127.0.0.1", port))
        .map_err(|e| format!("net.serve_ws bind {port}: {e}"))?;
    eprintln!("net.serve_ws: listening on ws://127.0.0.1:{port}");
    for stream in listener.incoming() {
        let stream = match stream {
            Ok(s) => s,
            Err(e) => { eprintln!("net.serve_ws accept: {e}"); continue; }
        };
        let program = Arc::clone(&program);
        let policy = policy.clone();
        let handler_name = handler_name.clone();
        let registry = Arc::clone(&registry);
        thread::spawn(move || {
            if let Err(e) = handle_connection(stream, program, policy, handler_name, registry) {
                eprintln!("net.serve_ws connection error: {e}");
            }
        });
    }
    Ok(Value::Unit)
}

fn handle_connection(
    stream: std::net::TcpStream,
    program: Arc<Program>,
    policy: Policy,
    handler_name: String,
    registry: Arc<ChatRegistry>,
) -> Result<(), String> {
    use tungstenite::{accept_hdr, handshake::server::{Request, Response}};

    // Capture the request path during the handshake — used as the room name.
    let mut path = String::new();
    let path_ref = &mut path;
    let mut ws = accept_hdr(stream, |req: &Request, resp: Response| {
        *path_ref = req.uri().path().to_string();
        Ok(resp)
    }).map_err(|e| format!("ws handshake: {e}"))?;

    let room = path.trim_start_matches('/').to_string();

    // Outbound channel: broadcast/send pushes here, this thread writes
    // each message into the WebSocket.
    let (tx, rx) = mpsc::channel::<String>();
    let conn_id = registry.register(room.clone(), tx);

    // Make WS reads non-blocking-ish so the same thread can also drain
    // the outbound channel. tungstenite reads through the underlying
    // TcpStream; setting a short read timeout lets us multiplex.
    let _ = ws.get_mut().set_read_timeout(Some(Duration::from_millis(50)));

    let result = run_loop(&mut ws, &rx, conn_id, &room, &program, &policy, &handler_name, &registry);
    registry.unregister(conn_id);
    let _ = ws.close(None);
    result
}

#[allow(clippy::too_many_arguments)]
fn run_loop(
    ws: &mut tungstenite::WebSocket<std::net::TcpStream>,
    rx: &mpsc::Receiver<String>,
    conn_id: u64,
    room: &str,
    program: &Arc<Program>,
    policy: &Policy,
    handler_name: &str,
    registry: &Arc<ChatRegistry>,
) -> Result<(), String> {
    use tungstenite::Message;
    use std::io::ErrorKind;
    loop {
        // 1) Try to read one inbound message. WouldBlock = no data yet.
        match ws.read() {
            Ok(Message::Text(body)) => {
                let ev = build_ws_event(conn_id, room, &body);
                let handler = crate::handler::DefaultHandler::new(policy.clone())
                    .with_program(Arc::clone(program))
                    .with_chat_registry(Arc::clone(registry));
                let mut vm = Vm::with_handler(program, Box::new(handler));
                if let Err(e) = vm.call(handler_name, vec![ev]) {
                    eprintln!("on_message {conn_id}: {e}");
                }
            }
            Ok(Message::Binary(_)) => { /* binary frames ignored in v1 */ }
            Ok(Message::Close(_)) | Err(tungstenite::Error::ConnectionClosed) => break,
            Ok(_) => {} // ping/pong/frame
            Err(tungstenite::Error::Io(ref e)) if e.kind() == ErrorKind::WouldBlock
                || e.kind() == ErrorKind::TimedOut => {}
            Err(e) => return Err(format!("ws read: {e}")),
        }
        // 2) Drain outbound channel. Doesn't block.
        loop {
            match rx.try_recv() {
                Ok(msg) => {
                    if let Err(e) = ws.send(Message::Text(msg.into())) {
                        return Err(format!("ws send: {e}"));
                    }
                }
                Err(mpsc::TryRecvError::Empty) => break,
                Err(mpsc::TryRecvError::Disconnected) => return Ok(()),
            }
        }
    }
    Ok(())
}

fn build_ws_event(conn_id: u64, room: &str, body: &str) -> Value {
    let mut rec = IndexMap::new();
    rec.insert("body".into(), Value::Str(body.into()));
    rec.insert("conn_id".into(), Value::Int(conn_id as i64));
    rec.insert("room".into(), Value::Str(room.into()));
    Value::Record(rec)
}

// ── Closure-based WebSocket server (#359) ────────────────────────────────────

/// Build a `WsConn` record value for the typed closure-based handler.
fn build_ws_conn(conn_id: u64, path: &str, subprotocol: &str) -> Value {
    let mut rec = IndexMap::new();
    rec.insert("id".into(), Value::Str(conn_id.to_string().into()));
    rec.insert("path".into(), Value::Str(path.into()));
    rec.insert("subprotocol".into(), Value::Str(subprotocol.into()));
    Value::Record(rec)
}

/// Build a `WsMessage` variant value.
fn build_ws_message_text(body: &str) -> Value {
    Value::Variant { name: "WsText".into(), args: vec![Value::Str(body.into())] }
}

fn build_ws_message_close() -> Value {
    Value::Variant { name: "WsClose".into(), args: vec![] }
}

fn build_ws_message_ping() -> Value {
    Value::Variant { name: "WsPing".into(), args: vec![] }
}

fn build_ws_message_binary(payload: &[u8]) -> Value {
    let bytes = payload.iter().map(|b| Value::Int(*b as i64)).collect();
    Value::Variant { name: "WsBinary".into(), args: vec![Value::List(bytes)] }
}

/// Interpret a `WsAction` variant and send the appropriate frame.
/// Generic over the stream so this serves both the plaintext-only
/// server path (`TcpStream`) and the dial path that may sit on top
/// of a TLS-wrapped stream (`MaybeTlsStream<TcpStream>`).
fn apply_ws_action<S: std::io::Read + std::io::Write>(
    action: &Value,
    ws: &mut tungstenite::WebSocket<S>,
) -> Result<(), String> {
    use tungstenite::Message;
    match action {
        Value::Variant { name, args } if name == "WsSend" => {
            let text = match args.first() {
                Some(Value::Str(s)) => s.clone(),
                _ => return Err("WsSend payload must be Str".into()),
            };
            ws.send(Message::Text(text.to_string().into()))
                .map_err(|e| format!("ws send: {e}"))
        }
        Value::Variant { name, args } if name == "WsSendBinary" => {
            let bytes: Vec<u8> = match args.first() {
                Some(Value::List(elems)) => elems
                    .iter()
                    .map(|v| match v {
                        Value::Int(n) => Ok(*n as u8),
                        _ => Err("WsSendBinary payload must be List[Int]".into()),
                    })
                    .collect::<Result<Vec<_>, String>>()?,
                _ => return Err("WsSendBinary payload must be List[Int]".into()),
            };
            ws.send(Message::Binary(bytes.into()))
                .map_err(|e| format!("ws send binary: {e}"))
        }
        Value::Variant { name, .. } if name == "WsNoOp" => Ok(()),
        other => Err(format!("unexpected WsAction: {other:?}")),
    }
}

/// Closure-based WebSocket server. Accepts a `Value::Closure` as the handler.
pub fn serve_ws_fn(
    port: u16,
    subprotocol: String,
    closure: Value,
    program: Arc<Program>,
    policy: Policy,
    registry: Arc<ChatRegistry>,
) -> Result<Value, String> {
    // Fail fast: a configured subprotocol that can't be a valid HTTP
    // header value would silently break every handshake later (the
    // accept_hdr callback's `HeaderValue::from_str` would always
    // return Err). Reject at startup with a clear message instead.
    if !subprotocol.is_empty() {
        if let Err(e) =
            tungstenite::http::HeaderValue::from_str(&subprotocol)
        {
            return Err(format!(
                "net.serve_ws_fn: subprotocol {subprotocol:?} is not a valid \
                 HTTP header value: {e}"
            ));
        }
    }
    let listener = TcpListener::bind(("127.0.0.1", port))
        .map_err(|e| format!("net.serve_ws_fn bind {port}: {e}"))?;
    eprintln!("net.serve_ws_fn: listening on ws://127.0.0.1:{port}");
    for stream in listener.incoming() {
        let stream = match stream {
            Ok(s) => s,
            Err(e) => { eprintln!("net.serve_ws_fn accept: {e}"); continue; }
        };
        let program = Arc::clone(&program);
        let policy = policy.clone();
        let closure = closure.clone();
        let subprotocol = subprotocol.clone();
        let registry = Arc::clone(&registry);
        thread::spawn(move || {
            if let Err(e) = handle_connection_fn(
                stream, program, policy, closure, subprotocol, registry,
            ) {
                eprintln!("net.serve_ws_fn connection error: {e}");
            }
        });
    }
    Ok(Value::Unit)
}

fn handle_connection_fn(
    stream: std::net::TcpStream,
    program: Arc<Program>,
    policy: Policy,
    closure: Value,
    subprotocol: String,
    registry: Arc<ChatRegistry>,
) -> Result<(), String> {
    use tungstenite::{accept_hdr, handshake::server::{Request, Response}};

    let mut path = String::new();
    let path_ref = &mut path;
    let subproto_for_handshake = subprotocol.clone();
    let mut ws = accept_hdr(stream, |req: &Request, mut resp: Response| {
        *path_ref = req.uri().path().to_string();
        maybe_echo_subprotocol(req, &mut resp, &subproto_for_handshake);
        Ok(resp)
    }).map_err(|e| format!("ws handshake: {e}"))?;

    let (tx, rx) = mpsc::channel::<String>();
    let conn_id = registry.register(path.trim_start_matches('/').to_string(), tx);
    let _ = ws.get_mut().set_read_timeout(Some(Duration::from_millis(50)));

    let result = run_loop_fn(
        &mut ws, &rx, conn_id, &path, &subprotocol,
        &program, &policy, &closure, &registry,
    );
    registry.unregister(conn_id);
    let _ = ws.close(None);
    result
}

/// RFC 6455 §4.1: the server MUST advertise the negotiated
/// subprotocol back in the handshake response, and MUST select one
/// of the values the client offered. Echo when (a) the server has
/// a non-empty subprotocol, (b) the client offered subprotocols,
/// and (c) the server's configured value is among the client's
/// offers. Empty server-side configuration → no echo (matches the
/// dial_ws contract). Shared by `handle_connection_fn` (the
/// always-accept variant) and `handle_connection_fn_auth` (the
/// pre-handshake-auth variant).
fn maybe_echo_subprotocol(
    req: &tungstenite::handshake::server::Request,
    resp: &mut tungstenite::handshake::server::Response,
    subprotocol: &str,
) {
    use tungstenite::http::HeaderValue;
    if subprotocol.is_empty() {
        return;
    }
    let offered = match req.headers().get("Sec-WebSocket-Protocol") {
        Some(v) => v,
        None    => return,
    };
    let offered_str = match offered.to_str() {
        Ok(s)  => s,
        Err(_) => return,
    };
    let matches = offered_str
        .split(',')
        .map(|p| p.trim())
        .any(|p| p == subprotocol);
    if !matches {
        return;
    }
    // from_str cannot fail here: serve_ws_fn[_auth] validated
    // `subprotocol` upfront. Belt-and-braces: skip silently if it
    // somehow does.
    if let Ok(h) = HeaderValue::from_str(subprotocol) {
        resp.headers_mut().insert("Sec-WebSocket-Protocol", h);
    }
}

// ── serve_ws_fn_auth — pre-handshake auth callback (#423) ─────────────────────
//
// Variant of `serve_ws_fn` that runs a Lex closure against the
// upgrade request's path + headers *before* accepting the WS
// handshake. The closure returns `Result[Unit, Str]`:
//
//   Ok(())  → handshake proceeds, on_message handler runs as usual
//   Err(msg) → respond `401 Unauthorized` with `msg` as the body;
//              the WS upgrade never completes, on_message is never
//              called for this connection
//
// This is the hook the OCPP Security Profile 2 (Basic Auth) and
// Profile 3 (Bearer JWT) flows need — both check an `Authorization`
// header that's present at the HTTP upgrade but not exposed to user
// code by `serve_ws_fn`. The crypto primitives (`argon2id`,
// `hs256`) live downstream in lex-crypto / lex-ocpp; this builtin
// is just the missing transport hook that lets them fire at the
// right time.
//
// Effect-polymorphic in the same row that `serve_ws_fn` is — the
// auth callback and the on_message handler share `[Eff]`, so a
// caller can use `[sql]` (look up the CP's password hash) in auth
// and the same `[sql]` in subsequent message handling without
// duplicating the row declaration.

/// Closure-based WebSocket server with a pre-handshake auth
/// callback. Calls `auth_closure(path, headers)` before completing
/// the WS upgrade; rejects with 401 Unauthorized when the closure
/// returns `Err(msg)`. See `serve_ws_fn` for the post-handshake
/// behaviour (identical once auth passes).
pub fn serve_ws_fn_auth(
    port: u16,
    subprotocol: String,
    auth_closure: Value,
    handler_closure: Value,
    program: Arc<Program>,
    policy: Policy,
    registry: Arc<ChatRegistry>,
) -> Result<Value, String> {
    if !subprotocol.is_empty() {
        if let Err(e) =
            tungstenite::http::HeaderValue::from_str(&subprotocol)
        {
            return Err(format!(
                "net.serve_ws_fn_auth: subprotocol {subprotocol:?} is not a \
                 valid HTTP header value: {e}"
            ));
        }
    }
    let listener = TcpListener::bind(("127.0.0.1", port))
        .map_err(|e| format!("net.serve_ws_fn_auth bind {port}: {e}"))?;
    eprintln!("net.serve_ws_fn_auth: listening on ws://127.0.0.1:{port}");
    for stream in listener.incoming() {
        let stream = match stream {
            Ok(s) => s,
            Err(e) => {
                eprintln!("net.serve_ws_fn_auth accept: {e}");
                continue;
            }
        };
        let program = Arc::clone(&program);
        let policy = policy.clone();
        let auth_closure = auth_closure.clone();
        let handler_closure = handler_closure.clone();
        let subprotocol = subprotocol.clone();
        let registry = Arc::clone(&registry);
        thread::spawn(move || {
            if let Err(e) = handle_connection_fn_auth(
                stream, program, policy, auth_closure, handler_closure,
                subprotocol, registry,
            ) {
                eprintln!("net.serve_ws_fn_auth connection error: {e}");
            }
        });
    }
    Ok(Value::Unit)
}

#[allow(clippy::too_many_arguments)]
fn handle_connection_fn_auth(
    stream: std::net::TcpStream,
    program: Arc<Program>,
    policy: Policy,
    auth_closure: Value,
    handler_closure: Value,
    subprotocol: String,
    registry: Arc<ChatRegistry>,
) -> Result<(), String> {
    use tungstenite::{accept_hdr, handshake::server::{Request, Response}};
    use tungstenite::http::StatusCode;

    let mut path = String::new();
    let path_ref = &mut path;
    let subproto_for_handshake = subprotocol.clone();
    // `accept_hdr`'s callback is `FnOnce`, so the closures + program
    // + policy + registry it needs are moved in directly (no clones
    // inside the closure body).
    let auth_program = Arc::clone(&program);
    let auth_policy = policy.clone();
    let auth_registry = Arc::clone(&registry);
    let auth_closure_for_cb = auth_closure;

    let mut ws = accept_hdr(stream, move |req: &Request, mut resp: Response| {
        *path_ref = req.uri().path().to_string();

        let headers_value = build_headers_value(req);
        let path_arg = Value::Str(path_ref.clone().into());

        let dh = crate::handler::DefaultHandler::new(auth_policy.clone())
            .with_program(Arc::clone(&auth_program))
            .with_chat_registry(Arc::clone(&auth_registry));
        let mut vm = Vm::with_handler(&auth_program, Box::new(dh));
        let auth_result = vm.invoke_closure_value(
            auth_closure_for_cb,
            vec![path_arg, headers_value],
        );

        match auth_result {
            Ok(Value::Variant { name, .. }) if name == "Ok" => {
                maybe_echo_subprotocol(req, &mut resp, &subproto_for_handshake);
                Ok(resp)
            }
            Ok(Value::Variant { name, args }) if name == "Err" => {
                let msg = match args.first() {
                    Some(Value::Str(s)) => s.to_string(),
                    _                   => "unauthorized".to_string(),
                };
                let err = build_unauthorized_response(StatusCode::UNAUTHORIZED, msg);
                Err(err)
            }
            Ok(other) => {
                let err = build_unauthorized_response(
                    StatusCode::INTERNAL_SERVER_ERROR,
                    format!(
                        "net.serve_ws_fn_auth: auth callback returned \
                         non-Result value: {other:?}"
                    ),
                );
                Err(err)
            }
            Err(e) => {
                let err = build_unauthorized_response(
                    StatusCode::INTERNAL_SERVER_ERROR,
                    format!("net.serve_ws_fn_auth: auth callback error: {e:?}"),
                );
                Err(err)
            }
        }
    }).map_err(|e| format!("ws handshake: {e}"))?;

    let (tx, rx) = mpsc::channel::<String>();
    let conn_id = registry.register(path.trim_start_matches('/').to_string(), tx);
    let _ = ws.get_mut().set_read_timeout(Some(Duration::from_millis(50)));

    let result = run_loop_fn(
        &mut ws, &rx, conn_id, &path, &subprotocol,
        &program, &policy, &handler_closure, &registry,
    );
    registry.unregister(conn_id);
    let _ = ws.close(None);
    result
}

/// Project the upgrade request headers into a Lex value of type
/// `List[{ name :: Str, value :: Str }]`. Non-UTF-8 header values
/// are skipped (the HTTP spec allows them, the Lex `Str` type
/// doesn't — and OCPP Auth / JWT headers are ASCII by construction
/// so a strict drop is safe here).
fn build_headers_value(req: &tungstenite::handshake::server::Request) -> Value {
    let mut items: std::collections::VecDeque<Value> = std::collections::VecDeque::new();
    for (name, val) in req.headers().iter() {
        let v = match val.to_str() {
            Ok(s)  => s.to_string(),
            Err(_) => continue,
        };
        let mut rec = IndexMap::new();
        rec.insert("name".into(), Value::Str(name.as_str().into()));
        rec.insert("value".into(), Value::Str(v.into()));
        items.push_back(Value::Record(rec));
    }
    Value::List(items)
}

fn build_unauthorized_response(
    status: tungstenite::http::StatusCode,
    msg: String,
) -> tungstenite::handshake::server::ErrorResponse {
    tungstenite::http::Response::builder()
        .status(status)
        .header("Content-Type", "text/plain; charset=utf-8")
        .body(Some(msg))
        .expect("ErrorResponse builder")
}

#[allow(clippy::too_many_arguments)]
fn run_loop_fn(
    ws: &mut tungstenite::WebSocket<std::net::TcpStream>,
    rx: &mpsc::Receiver<String>,
    conn_id: u64,
    path: &str,
    subprotocol: &str,
    program: &Arc<Program>,
    policy: &Policy,
    closure: &Value,
    registry: &Arc<ChatRegistry>,
) -> Result<(), String> {
    use tungstenite::Message;
    use std::io::ErrorKind;

    let ws_conn = build_ws_conn(conn_id, path, subprotocol);

    loop {
        let ws_msg = match ws.read() {
            Ok(Message::Text(body)) => Some(build_ws_message_text(&body)),
            Ok(Message::Binary(_)) => None,
            Ok(Message::Ping(_)) => Some(build_ws_message_ping()),
            Ok(Message::Close(_)) | Err(tungstenite::Error::ConnectionClosed) => {
                // Notify handler then exit.
                let handler = crate::handler::DefaultHandler::new(policy.clone())
                    .with_program(Arc::clone(program))
                    .with_chat_registry(Arc::clone(registry));
                let mut vm = Vm::with_handler(program, Box::new(handler));
                let _ = vm.invoke_closure_value(
                    closure.clone(),
                    vec![ws_conn.clone(), build_ws_message_close()],
                );
                break;
            }
            Ok(_) => None, // pong / frame
            Err(tungstenite::Error::Io(ref e))
                if e.kind() == ErrorKind::WouldBlock || e.kind() == ErrorKind::TimedOut => None,
            Err(e) => return Err(format!("ws read: {e}")),
        };

        if let Some(msg) = ws_msg {
            let handler = crate::handler::DefaultHandler::new(policy.clone())
                .with_program(Arc::clone(program))
                .with_chat_registry(Arc::clone(registry));
            let mut vm = Vm::with_handler(program, Box::new(handler));
            match vm.invoke_closure_value(closure.clone(), vec![ws_conn.clone(), msg]) {
                Ok(action) => {
                    if let Err(e) = apply_ws_action(&action, ws) {
                        eprintln!("ws action {conn_id}: {e}");
                    }
                }
                Err(e) => eprintln!("ws handler {conn_id}: {e}"),
            }
        }

        // Drain broadcast/send outbound channel.
        loop {
            match rx.try_recv() {
                Ok(msg) => {
                    if let Err(e) = ws.send(Message::Text(msg.into())) {
                        return Err(format!("ws send: {e}"));
                    }
                }
                Err(mpsc::TryRecvError::Empty) => break,
                Err(mpsc::TryRecvError::Disconnected) => return Ok(()),
            }
        }
    }
    Ok(())
}

// ── serve_ws_fn_actor — outbound-bridge actor registration (#459) ────────────
//
// Variant of `serve_ws_fn` that registers each connection as a named
// actor in `conc_registry`, so non-WS callers (HTTP webhooks, scheduled
// tasks, broadcast loops) can push frames into the socket via
// `conc.lookup(name) |> conc.tell(frame)`.
//
// Signature:
//
//   net.serve_ws_fn_actor(
//     port        :: Int,
//     subprotocol :: Str,
//     name_of     :: (WsConn) -> Str,                       # per-connection name
//     on_message  :: (WsConn, WsMessage) -> [E] WsAction    # same as serve_ws_fn
//   ) -> [net, concurrent, io] Unit
//
// On each accepted connection, the runtime:
//   1. Builds the WsConn record (same shape as serve_ws_fn) and calls
//      `name_of(conn)`. An empty-string return means "don't register
//      this connection" — the socket still accepts inbound frames and
//      runs `on_message`, but no outbound handle is exposed.
//   2. Builds an `ActorHandler::Native` bridge whose `send` closure
//      writes the message body to the per-connection `mpsc::Sender<String>`
//      that already exists for the broadcast path.
//   3. Registers the bridge actor under the name. Name collisions
//      (`AlreadyRegistered`) abort the connection — surface the bug at
//      the source level rather than silently overwriting an existing
//      session.
//   4. On disconnect, unregisters the name and tears down the socket.
//
// The inbound half (read frame → call `on_message` → apply `WsAction`)
// is identical to `serve_ws_fn`.
//
// Out-of-scope for v1: binary message dispatch from a non-WS task. The
// native bridge only accepts `Value::Str`; binary frames need a tagged
// message type (`WsOut::Text(Str) | WsOut::Binary(List[Int])`) that the
// native handler can match on. Filed as a follow-up.
pub fn serve_ws_fn_actor(
    port: u16,
    subprotocol: String,
    name_of_closure: Value,
    on_message_closure: Value,
    program: Arc<Program>,
    policy: Policy,
    registry: Arc<ChatRegistry>,
) -> Result<Value, String> {
    if !subprotocol.is_empty() {
        if let Err(e) =
            tungstenite::http::HeaderValue::from_str(&subprotocol)
        {
            return Err(format!(
                "net.serve_ws_fn_actor: subprotocol {subprotocol:?} is not a valid \
                 HTTP header value: {e}"
            ));
        }
    }
    let listener = TcpListener::bind(("127.0.0.1", port))
        .map_err(|e| format!("net.serve_ws_fn_actor bind {port}: {e}"))?;
    eprintln!("net.serve_ws_fn_actor: listening on ws://127.0.0.1:{port}");
    for stream in listener.incoming() {
        let stream = match stream {
            Ok(s) => s,
            Err(e) => { eprintln!("net.serve_ws_fn_actor accept: {e}"); continue; }
        };
        let program = Arc::clone(&program);
        let policy = policy.clone();
        let name_of_closure = name_of_closure.clone();
        let on_message_closure = on_message_closure.clone();
        let subprotocol = subprotocol.clone();
        let registry = Arc::clone(&registry);
        thread::spawn(move || {
            if let Err(e) = handle_connection_fn_actor(
                stream, program, policy, name_of_closure, on_message_closure,
                subprotocol, registry,
            ) {
                eprintln!("net.serve_ws_fn_actor connection error: {e}");
            }
        });
    }
    Ok(Value::Unit)
}

#[allow(clippy::too_many_arguments)]
fn handle_connection_fn_actor(
    stream: std::net::TcpStream,
    program: Arc<Program>,
    policy: Policy,
    name_of_closure: Value,
    on_message_closure: Value,
    subprotocol: String,
    registry: Arc<ChatRegistry>,
) -> Result<(), String> {
    use tungstenite::{accept_hdr, handshake::server::{Request, Response}};

    let mut path = String::new();
    let path_ref = &mut path;
    let subproto_for_handshake = subprotocol.clone();
    let mut ws = accept_hdr(stream, |req: &Request, mut resp: Response| {
        *path_ref = req.uri().path().to_string();
        maybe_echo_subprotocol(req, &mut resp, &subproto_for_handshake);
        Ok(resp)
    }).map_err(|e| format!("ws handshake: {e}"))?;

    let (tx, rx) = mpsc::channel::<String>();
    let conn_id = registry.register(path.trim_start_matches('/').to_string(), tx.clone());
    let _ = ws.get_mut().set_read_timeout(Some(Duration::from_millis(50)));

    // Build the WsConn record and ask the user's name_of closure what
    // name to register this connection under. Empty string is the
    // documented opt-out (inbound still works, no outbound handle is
    // exposed). Type mismatch or runtime error aborts the connection —
    // the same "surface the bug at the source level" reasoning as a
    // `conc.register` name collision below; silently degrading to an
    // unregistered connection would have a non-WS caller's
    // `conc.lookup` return None and conclude the session is offline.
    let ws_conn = build_ws_conn(conn_id, &path, &subprotocol);
    let registered_name: Option<String> = {
        let handler = crate::handler::DefaultHandler::new(policy.clone())
            .with_program(Arc::clone(&program))
            .with_chat_registry(Arc::clone(&registry));
        let mut vm = Vm::with_handler(&program, Box::new(handler));
        match vm.invoke_closure_value(name_of_closure.clone(), vec![ws_conn.clone()]) {
            Ok(Value::Str(s)) if !s.is_empty() => Some(s.to_string()),
            Ok(Value::Str(_)) => None,
            Ok(other) => {
                registry.unregister(conn_id);
                let _ = ws.close(None);
                return Err(format!(
                    "net.serve_ws_fn_actor: name_of must return Str, got {other:?}"
                ));
            }
            Err(e) => {
                registry.unregister(conn_id);
                let _ = ws.close(None);
                return Err(format!(
                    "net.serve_ws_fn_actor: name_of error: {e:?}"
                ));
            }
        }
    };

    // Register the native bridge actor in the conc registry. The
    // bridge captures `tx` and writes any inbound message body to the
    // outbound channel, which the run loop drains into the socket.
    if let Some(ref name) = registered_name {
        let tx_for_bridge = tx.clone();
        let bridge = lex_bytecode::value::NativeActorHandler {
            send: Box::new(move |msg: Value| -> Result<Value, String> {
                match msg {
                    Value::Str(s) => {
                        tx_for_bridge.send(s.to_string()).map_err(|e| {
                            format!("net.serve_ws_fn_actor: outbound channel closed: {e}")
                        })?;
                        Ok(Value::Unit)
                    }
                    other => Err(format!(
                        "net.serve_ws_fn_actor: native bridge accepts Str messages only, got {other:?}"
                    )),
                }
            }),
        };
        let cell = Value::Actor(Arc::new(Mutex::new(lex_bytecode::value::ActorCell {
            state: Value::Unit,
            handler: lex_bytecode::value::ActorHandler::Native(Arc::new(bridge)),
        })));
        if let Err(e) = lex_bytecode::conc_registry::register(name, cell) {
            // Name collision: abort the connection. Surfacing the
            // duplicate immediately is more useful than silently
            // overwriting whichever session was registered first.
            registry.unregister(conn_id);
            let _ = ws.close(None);
            return Err(format!(
                "net.serve_ws_fn_actor: conc.register({name:?}) failed: {e:?}"
            ));
        }
    }

    let result = run_loop_fn(
        &mut ws, &rx, conn_id, &path, &subprotocol,
        &program, &policy, &on_message_closure, &registry,
    );

    // Tear down: unregister from both the conc registry (so a subsequent
    // `conc.lookup(name)` returns None) and the chat registry.
    if let Some(ref name) = registered_name {
        let _ = lex_bytecode::conc_registry::unregister(name);
    }
    registry.unregister(conn_id);
    let _ = ws.close(None);
    result
}

// ── Closure-based WebSocket client (#390) ────────────────────────────────────
//
// Inverse of `serve_ws_fn`: open a connection to a remote WS server and
// run two Lex callbacks against it.
//
// - `on_open : () -> [E] WsAction` is invoked once after the handshake
//   completes. The returned `WsAction` (typically `WsSend(boot_frame)`)
//   is applied to the socket immediately. This is the hook for
//   protocols like OCPP where the client sends a `BootNotification`
//   the moment it connects.
// - `on_message : (WsMessage) -> [E] WsAction` is invoked for every
//   inbound frame. Same `WsAction` semantics as the server-side
//   handler. A `WsClose` message is delivered once before the loop
//   exits so handlers can run shutdown logic.
//
// Multi-frame sends from `on_open` (e.g. a charger that wants to
// also kick off a heartbeat scheduler at connect-time) aren't
// expressible in v1 — the issue's `send :: (Str) -> [net]
// Result[Unit, Str]` closure would let users push outbound frames
// from arbitrary `[net]` code, but that requires representing
// Rust-native closures as Lex `Value`s, which is a separate
// runtime change. v1 covers the BootNotification + reactive reply
// pattern that motivates the issue.

fn build_dial_result(ok: Result<(), String>) -> Value {
    match ok {
        Ok(()) => Value::Variant {
            name: "Ok".into(),
            args: vec![Value::Unit],
        },
        Err(msg) => Value::Variant {
            name: "Err".into(),
            args: vec![Value::Str(msg.into())],
        },
    }
}

/// `net.dial_ws(url, subprotocol, on_open, on_message) -> [net, E]
/// Result[Unit, Str]`. Blocks for the lifetime of the connection;
/// returns `Ok(())` on a clean close from the server, `Err(reason)`
/// on dial failure, handshake failure, read error, or write error.
pub fn dial_ws(
    url: String,
    subprotocol: String,
    on_open: Value,
    on_message: Value,
    program: Arc<Program>,
    policy: Policy,
) -> Result<Value, String> {
    use tungstenite::client::IntoClientRequest;
    use tungstenite::http::HeaderValue;

    // Build the request — when `subprotocol` is non-empty, attach the
    // Sec-WebSocket-Protocol header so the server's accept-handler
    // can match on it. Empty subprotocol → header omitted (the same
    // contract as `serve_ws_fn`'s subprotocol arg).
    //
    // Caller-controlled inputs (URL syntax, subprotocol header value)
    // surface as a Lex `Err(reason)`, not a Rust panic / handler
    // error, so `match net.dial_ws(...) { Err(_) => ..., Ok(_) => ... }`
    // works at the Lex level.
    let mut req = match url.as_str().into_client_request() {
        Ok(r) => r,
        Err(e) => {
            return Ok(build_dial_result(Err(format!(
                "net.dial_ws: bad URL `{url}`: {e}"
            ))));
        }
    };
    if !subprotocol.is_empty() {
        let header = match HeaderValue::from_str(&subprotocol) {
            Ok(h) => h,
            Err(e) => {
                return Ok(build_dial_result(Err(format!(
                    "net.dial_ws: invalid subprotocol `{subprotocol}`: {e}"
                ))));
            }
        };
        req.headers_mut().insert("Sec-WebSocket-Protocol", header);
    }

    let (mut ws, _resp) = match tungstenite::connect(req) {
        Ok(pair) => pair,
        Err(e) => {
            return Ok(build_dial_result(Err(format!(
                "net.dial_ws: connect to `{url}`: {e}"
            ))));
        }
    };

    // Non-blocking-ish reads so we don't tie up the thread on an idle
    // socket, mirroring the server's read-timeout multiplexing.
    if let Some(stream) = stream_for(&mut ws) {
        let _ = stream.set_read_timeout(Some(Duration::from_millis(50)));
    }

    // 1. Fire on_open once and apply its action.
    {
        let handler = crate::handler::DefaultHandler::new(policy.clone())
            .with_program(Arc::clone(&program));
        let mut vm = Vm::with_handler(&program, Box::new(handler));
        match vm.invoke_closure_value(on_open.clone(), vec![]) {
            Ok(action) => {
                if let Err(e) = apply_ws_action(&action, &mut ws) {
                    return Ok(build_dial_result(Err(format!(
                        "net.dial_ws: on_open action: {e}"
                    ))));
                }
            }
            Err(e) => {
                return Ok(build_dial_result(Err(format!(
                    "net.dial_ws: on_open: {e}"
                ))));
            }
        }
    }

    // 2. Run the read loop, dispatching each inbound frame to on_message.
    let loop_result = dial_run_loop(&mut ws, &on_message, &program, &policy);
    let _ = ws.close(None);
    Ok(build_dial_result(loop_result))
}

/// Pull the underlying TCP stream out of a `MaybeTlsStream` so we can
/// set a read timeout. For plaintext connections this is the
/// `TcpStream` directly; for `rustls`-wrapped streams it's the inner
/// socket. Returns `None` if the wrapping is some other variant —
/// in that case we just skip the timeout and rely on blocking reads.
fn stream_for(
    ws: &mut tungstenite::WebSocket<tungstenite::stream::MaybeTlsStream<std::net::TcpStream>>,
) -> Option<&mut std::net::TcpStream> {
    use tungstenite::stream::MaybeTlsStream;
    match ws.get_mut() {
        MaybeTlsStream::Plain(s) => Some(s),
        MaybeTlsStream::Rustls(s) => Some(s.get_mut()),
        _ => None,
    }
}

fn dial_run_loop(
    ws: &mut tungstenite::WebSocket<tungstenite::stream::MaybeTlsStream<std::net::TcpStream>>,
    on_message: &Value,
    program: &Arc<Program>,
    policy: &Policy,
) -> Result<(), String> {
    use std::io::ErrorKind;
    use tungstenite::Message;

    loop {
        let ws_msg = match ws.read() {
            Ok(Message::Text(body)) => Some(build_ws_message_text(&body)),
            Ok(Message::Binary(payload)) => Some(build_ws_message_binary(&payload)),
            Ok(Message::Ping(_)) => Some(build_ws_message_ping()),
            Ok(Message::Close(_)) | Err(tungstenite::Error::ConnectionClosed) => {
                // Deliver WsClose so the handler can do shutdown work.
                let handler = crate::handler::DefaultHandler::new(policy.clone())
                    .with_program(Arc::clone(program));
                let mut vm = Vm::with_handler(program, Box::new(handler));
                let _ = vm.invoke_closure_value(
                    on_message.clone(),
                    vec![build_ws_message_close()],
                );
                return Ok(());
            }
            Ok(_) => None, // pong / raw frame
            Err(tungstenite::Error::Io(ref e))
                if e.kind() == ErrorKind::WouldBlock || e.kind() == ErrorKind::TimedOut =>
            {
                None
            }
            Err(e) => return Err(format!("net.dial_ws: read: {e}")),
        };

        if let Some(msg) = ws_msg {
            let handler = crate::handler::DefaultHandler::new(policy.clone())
                .with_program(Arc::clone(program));
            let mut vm = Vm::with_handler(program, Box::new(handler));
            match vm.invoke_closure_value(on_message.clone(), vec![msg]) {
                Ok(action) => {
                    if let Err(e) = apply_ws_action(&action, ws) {
                        return Err(format!("net.dial_ws: action: {e}"));
                    }
                }
                Err(e) => return Err(format!("net.dial_ws: on_message: {e}")),
            }
        }
    }
}