hyperhive/hive-bash-mcp/src/runner.rs

//! Bash subprocess runner: spawns `bash -c <cmd>` tasks, writes status
//! files under `harness/bash-tasks/`, and fires hyperhive wake signals
//! on completion.
//!
//! Files under `tasks_dir()`:
//! - `<id>.json`  — task metadata + status (pending → running → done)
//! - `<id>.out`   — captured stdout (streamed while running)
//! - `<id>.err`   — captured stderr (streamed while running)
//!
//! Tasks with status `running` on daemon boot are marked `interrupted`
//! (the process died with the previous daemon). A best-effort wake is
//! still sent so the agent is not silently blocked.
//!
//! The runner kills the child process on timeout — `tokio::process::Child::drop()`
//! does not kill children, so we explicitly call `child.kill().await`.

use std::collections::{HashMap, HashSet};
use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
use std::sync::{Arc, Mutex, OnceLock};
use std::time::{Duration, SystemTime, UNIX_EPOCH};

use anyhow::{Result, bail};
use tokio::io::AsyncWriteExt as _;
use tokio::sync::Notify;

use crate::paths;
use crate::protocol::{TaskFile, TaskStatus};

/// Poll interval for the runner background loop.
const POLL_INTERVAL: Duration = Duration::from_millis(200);

/// Soft cap on stdout/stderr captured in the done JSON summary.
/// Full output always lives in the `.out`/`.err` files.
pub const SUMMARY_BYTES: usize = 4096;

/// Maximum inline wait (cap on `wait_seconds`).
pub const MAX_WAIT_SECS: u64 = 30;

/// Poll interval used by the inline-wait loops.
const POLL_MS: u64 = 100;

static TASK_SEQ: AtomicU64 = AtomicU64::new(0);

// ---------------------------------------------------------------------------
// Running-task registry (for on-demand kill)
// ---------------------------------------------------------------------------

/// Handle to a currently-executing task, used by [`kill_task`] to signal it.
/// `exec_cmd` selects on `cancel`; when notified it signals the task's
/// process group with `SIGKILL` (if `force`) or `SIGINT`.
struct RunningHandle {
    cancel: Arc<Notify>,
    force: Arc<AtomicBool>,
}

/// Global registry of running tasks (id → handle). Populated by `run_task`
/// for the duration of execution and read by [`kill_task`] from the socket
/// dispatch path — a separate async context from the runner loop, so a
/// shared global (rather than the loop-local `claimed` set) is needed.
fn running() -> &'static Mutex<HashMap<String, RunningHandle>> {
    static RUNNING: OnceLock<Mutex<HashMap<String, RunningHandle>>> = OnceLock::new();
    RUNNING.get_or_init(|| Mutex::new(HashMap::new()))
}

/// Outcome of one `exec_cmd` run.
enum ExecOutcome {
    /// Process exited on its own with this status code.
    Exited(i32),
    /// Killed by the per-task timeout (`timeout_secs`).
    TimedOut,
    /// Killed on request via [`kill_task`]. `forced` = SIGKILL vs SIGINT.
    Killed { forced: bool },
}

/// Send `sig` to the task's process group. A negative pgid targets the whole
/// group, so `bash -c` plus any children it spawned all receive the signal.
/// No-op if the child had no pid (already reaped).
fn signal_group(pgid: Option<i32>, sig: i32) {
    if let Some(pgid) = pgid {
        // SAFETY: plain libc `kill(2)`; `-pgid` targets the child's own
        // process group (it called `setpgid(0, 0)` so it leads its group).
        unsafe {
            libc::kill(-pgid, sig);
        }
    }
}

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

use hive_sh4re::wire_time::now_unix;

/// Generate a task ID: `<timestamp_hex><seq_hex>`.
#[must_use]
pub fn new_task_id() -> String {
    let t = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap_or_default()
        .as_millis();
    let seq = TASK_SEQ.fetch_add(1, Ordering::Relaxed);
    format!("{t:013x}{seq:04x}")
}

/// Write a task file atomically (tmp + rename).
fn write_task(task: &TaskFile) -> std::io::Result<()> {
    let json = serde_json::to_string_pretty(task)
        .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;
    let dest = paths::task_json(&task.id);
    let tmp = dest.with_extension("json.tmp");
    std::fs::write(&tmp, &json)?;
    std::fs::rename(&tmp, &dest)
}

/// Read a task file. Returns `None` if the file doesn't exist or is
/// unparseable.
#[must_use]
pub fn read_task(id: &str) -> Option<TaskFile> {
    let s = std::fs::read_to_string(paths::task_json(id)).ok()?;
    serde_json::from_str(&s).ok()
}

// ---------------------------------------------------------------------------
// Loose-ends file (generic MCP loose-ends protocol)
// ---------------------------------------------------------------------------

/// Rewrite `mcp-loose-ends/bash.json` with a summary of all currently
/// active (Pending or Running) tasks. The harness scans this directory
/// generically in `get_loose_ends` — no bash-specific code needed there.
///
/// File format: a JSON array of plain-text summary strings, one per
/// loose-end item. The harness includes them verbatim in the output.
/// Atomic write (tmp + rename) so the harness never reads a partial file.
fn refresh_loose_ends() {
    let active = active_tasks();
    let dir = paths::mcp_loose_ends_dir();
    if let Err(e) = std::fs::create_dir_all(&dir) {
        tracing::warn!(error = ?e, "bash_runner: create mcp-loose-ends dir failed");
        return;
    }
    let items: Vec<String> = active
        .iter()
        .map(|t| {
            let age = now_unix() - t.created_at;
            format!(
                "bash task `{}` status={:?}, cmd: `{}`, age {}s",
                t.id, t.status, t.cmd, age
            )
        })
        .collect();
    let dest = dir.join("bash.json");
    let tmp = dest.with_extension("json.tmp");
    let json = serde_json::to_string(&items).unwrap_or_else(|_| "[]".to_owned());
    if let Err(e) = std::fs::write(&tmp, &json).and_then(|()| std::fs::rename(&tmp, &dest)) {
        tracing::warn!(error = ?e, "bash_runner: write mcp-loose-ends/bash.json failed");
    }
}

// ---------------------------------------------------------------------------
// Public API used by daemon dispatch
// ---------------------------------------------------------------------------

/// Longest accepted caller-chosen task name.
const MAX_TASK_NAME_LEN: usize = 64;

/// Validate a caller-chosen task name. The name doubles as the task id
/// and therefore as the `<name>.json` filename, so it must be a single
/// safe path segment. Allows ASCII alphanumerics plus `.`, `_`, `-`;
/// rejects empties, over-long names, `.`/`..`, and anything that could
/// escape the tasks dir or collide with the `.json.tmp` scratch suffix.
fn validate_task_name(name: &str) -> Result<()> {
    if name.is_empty() {
        bail!("task name must not be empty");
    }
    if name.len() > MAX_TASK_NAME_LEN {
        bail!("task name too long (max {MAX_TASK_NAME_LEN} chars)");
    }
    if name == "." || name == ".." {
        bail!("task name {name:?} is reserved");
    }
    if !name
        .chars()
        .all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '_' | '-'))
    {
        bail!("task name {name:?} may only contain ASCII letters, digits, '.', '_', '-'");
    }
    Ok(())
}

/// Submit a new pending task. Returns the task ID.
///
/// When `name` is `Some`, it is validated and used as the task id (so it
/// surfaces in the wake `from`, status lookups, and the loose-ends list).
/// A name may be reused once any prior task of that name has finished;
/// submitting a name whose task is still `Pending`/`Running` is rejected.
/// `None` falls back to the auto-generated timestamp id.
///
/// # Errors
///
/// Returns an error if the name is invalid, a task of that name is still
/// running, the tasks directory cannot be created, or the task file
/// cannot be written.
pub fn submit_task(cmd: String, timeout_secs: Option<u64>, name: Option<String>) -> Result<String> {
    std::fs::create_dir_all(paths::tasks_dir())?;
    let id = match name {
        Some(name) => {
            validate_task_name(&name)?;
            if let Some(existing) = read_task(&name)
                && matches!(existing.status, TaskStatus::Pending | TaskStatus::Running)
            {
                bail!(
                    "a bash task named `{name}` is already running — wait for it to finish or pick another name"
                );
            }
            name
        }
        None => new_task_id(),
    };
    let task = TaskFile {
        id: id.clone(),
        cmd,
        timeout_secs,
        status: TaskStatus::Pending,
        created_at: now_unix(),
        started_at: None,
        completed_at: None,
        exit_code: None,
        stdout_tail: None,
        stderr_tail: None,
    };
    write_task(&task)?;
    refresh_loose_ends();
    Ok(id)
}

/// Return all tasks currently in `Pending` or `Running` state.
#[must_use]
pub fn active_tasks() -> Vec<TaskFile> {
    let Ok(rd) = std::fs::read_dir(paths::tasks_dir()) else {
        return Vec::new();
    };
    let mut out = Vec::new();
    for entry in rd.flatten() {
        let path = entry.path();
        if path.extension().and_then(|e| e.to_str()) != Some("json") {
            continue;
        }
        let Some(id) = path.file_stem().and_then(|s| s.to_str()).map(str::to_owned) else {
            continue;
        };
        let Some(task) = read_task(&id) else { continue };
        if matches!(task.status, TaskStatus::Pending | TaskStatus::Running) {
            out.push(task);
        }
    }
    out
}

/// Inline wait: poll `read_task(id)` until terminal state or deadline.
/// Returns the final task on success, or `None` if it never completed.
pub async fn wait_for_task(id: &str, wait_secs: u64) -> Option<TaskFile> {
    let cap = wait_secs.min(MAX_WAIT_SECS);
    if cap == 0 {
        return read_task(id);
    }
    let deadline = tokio::time::Instant::now() + Duration::from_secs(cap);
    loop {
        match read_task(id) {
            None => break,
            Some(task) => {
                if matches!(
                    task.status,
                    TaskStatus::Done
                        | TaskStatus::TimedOut
                        | TaskStatus::Interrupted
                        | TaskStatus::Killed
                ) {
                    return Some(task);
                }
            }
        }
        if tokio::time::Instant::now() >= deadline {
            break;
        }
        tokio::time::sleep(Duration::from_millis(POLL_MS)).await;
    }
    read_task(id)
}

/// Kill a running or still-pending task.
///
/// Fire-and-forget: this **sends a signal and returns** — it does not wait
/// for the process to actually exit.
///
/// - **Running** (in the registry): signals its process group via the
///   `exec_cmd` cancel path — `SIGKILL` if `force`, else `SIGINT`. If the
///   process ignores `SIGINT`, the caller re-invokes with `force` to send
///   `SIGKILL` (no daemon-side auto-escalation). The task transitions to
///   [`TaskStatus::Killed`] once the process exits and a completion wake fires.
/// - **Pending** (queued, not yet started): marked `Killed` directly so the
///   runner loop never starts it. No process exists yet, so `force` is moot.
/// - **Terminal or unknown id**: no-op.
///
/// Returns `(killed, was_running)`: `killed` = a kill was issued (signal sent
/// or pending task cancelled); `was_running` = the task was actively running.
///
/// # Panics
///
/// Panics if the running-task registry mutex is poisoned (a prior holder
/// panicked) — unrecoverable, consistent with the rest of the daemon's
/// `Mutex` usage.
#[must_use]
pub fn kill_task(id: &str, force: bool) -> (bool, bool) {
    // Running task: signal via the registry.
    {
        let guard = running().lock().unwrap();
        if let Some(handle) = guard.get(id) {
            handle.force.store(force, Ordering::SeqCst);
            handle.cancel.notify_one();
            return (true, true);
        }
    }
    // Pending task: mark Killed so the poll loop never starts it.
    if let Some(mut task) = read_task(id)
        && task.status == TaskStatus::Pending
    {
        task.status = TaskStatus::Killed;
        task.completed_at = Some(now_unix());
        let _ = write_task(&task);
        refresh_loose_ends();
        return (true, false);
    }
    (false, false)
}

// ---------------------------------------------------------------------------
// Runner background loop
// ---------------------------------------------------------------------------

/// Spawn the background runner loop as a detached tokio task. `socket`
/// is the path to the per-agent broker socket used to deliver completion
/// wake signals. Call once at daemon startup.
pub fn spawn_loop(socket: PathBuf) {
    tokio::spawn(async move {
        run_loop(socket).await;
    });
}

async fn run_loop(socket: PathBuf) {
    if let Err(e) = std::fs::create_dir_all(paths::tasks_dir()) {
        tracing::warn!(error = ?e, "bash_runner: create tasks dir failed");
    }
    mark_interrupted(&socket).await;

    let claimed: Arc<Mutex<HashSet<String>>> = Arc::new(Mutex::new(HashSet::new()));

    loop {
        poll_once(&socket, &claimed);
        tokio::time::sleep(POLL_INTERVAL).await;
    }
}

/// On boot, flip any `running` tasks to `interrupted` and fire a wake.
async fn mark_interrupted(socket: &Path) {
    let Ok(rd) = std::fs::read_dir(paths::tasks_dir()) else {
        return;
    };
    for entry in rd.flatten() {
        let path = entry.path();
        if path.extension().and_then(|e| e.to_str()) != Some("json") {
            continue;
        }
        let Some(id) = path.file_stem().and_then(|s| s.to_str()).map(str::to_owned) else {
            continue;
        };
        let Some(mut task) = read_task(&id) else {
            continue;
        };
        if task.status != TaskStatus::Running {
            continue;
        }
        tracing::warn!(id = %id, "bash_runner: marking interrupted task");
        task.status = TaskStatus::Interrupted;
        task.completed_at = Some(now_unix());
        if let Err(e) = write_task(&task) {
            tracing::warn!(id = %id, error = ?e, "bash_runner: write interrupted state failed");
        }
        refresh_loose_ends();
        send_wake(socket, &id, "interrupted (daemon restarted)", None).await;
    }
}

fn poll_once(socket: &Path, claimed: &Arc<Mutex<HashSet<String>>>) {
    let Ok(rd) = std::fs::read_dir(paths::tasks_dir()) else {
        return;
    };
    for entry in rd.flatten() {
        let path = entry.path();
        if path.extension().and_then(|e| e.to_str()) != Some("json") {
            continue;
        }
        let Some(id) = path.file_stem().and_then(|s| s.to_str()).map(str::to_owned) else {
            continue;
        };
        {
            let guard = claimed.lock().unwrap();
            if guard.contains(&id) {
                continue;
            }
        }
        let Some(task) = read_task(&id) else { continue };
        if task.status != TaskStatus::Pending {
            continue;
        }
        // Claim before spawning to avoid double-spawn across poll iterations.
        claimed.lock().unwrap().insert(id.clone());
        let socket = socket.to_path_buf();
        let claimed = claimed.clone();
        tokio::spawn(async move {
            run_task(task, &socket).await;
            claimed.lock().unwrap().remove(&id);
        });
    }
}

// ---------------------------------------------------------------------------
// Task execution
// ---------------------------------------------------------------------------

async fn run_task(mut task: TaskFile, socket: &Path) {
    let id = task.id.clone();
    tracing::info!(id = %id, cmd = %task.cmd, "bash_runner: starting task");

    task.status = TaskStatus::Running;
    task.started_at = Some(now_unix());
    if let Err(e) = write_task(&task) {
        tracing::warn!(id = %id, error = ?e, "bash_runner: write running state failed");
    }
    refresh_loose_ends();
    // Best-effort: tally the normalised command head for the /stats
    // "favorite tools" view. Counted once per execution, regardless of
    // exit status. Never fails the task.
    crate::stats::record_command(&task.cmd);

    let out_path = paths::task_out(&id);
    let err_path = paths::task_err(&id);

    // Register a kill handle for the duration of execution so `kill_task`
    // (called from the socket dispatch path) can signal this task.
    let cancel = Arc::new(Notify::new());
    let force = Arc::new(AtomicBool::new(false));
    running().lock().unwrap().insert(
        id.clone(),
        RunningHandle {
            cancel: cancel.clone(),
            force: force.clone(),
        },
    );

    let outcome = exec_cmd(
        &task.cmd,
        &out_path,
        &err_path,
        task.timeout_secs,
        &cancel,
        &force,
    )
    .await;

    // Deregister before writing terminal state — the task is no longer killable.
    running().lock().unwrap().remove(&id);

    let stdout_tail = tail_file(&out_path, SUMMARY_BYTES);
    let stderr_tail = tail_file(&err_path, SUMMARY_BYTES);

    let (status, exit_code, summary) = match outcome {
        Ok(ExecOutcome::Exited(code)) => (TaskStatus::Done, Some(code), format!("exit={code}")),
        Ok(ExecOutcome::TimedOut) => {
            tracing::warn!(id = %id, "bash_runner: task timed out");
            let secs = task.timeout_secs.unwrap_or(0);
            (
                TaskStatus::TimedOut,
                None,
                format!("timed out after {secs}s"),
            )
        }
        Ok(ExecOutcome::Killed { forced }) => {
            let sig = if forced { "SIGKILL" } else { "SIGINT" };
            tracing::warn!(id = %id, sig, "bash_runner: task killed");
            (TaskStatus::Killed, None, format!("killed ({sig})"))
        }
        Err(e) => {
            tracing::warn!(id = %id, error = ?e, "bash_runner: exec error");
            (TaskStatus::Done, None, "exec error".to_owned())
        }
    };

    task.status = status;
    task.completed_at = Some(now_unix());
    task.exit_code = exit_code;
    task.stdout_tail = stdout_tail.clone().filter(|s| !s.is_empty());
    task.stderr_tail = stderr_tail.clone().filter(|s| !s.is_empty());

    if let Err(e) = write_task(&task) {
        tracing::warn!(id = %id, error = ?e, "bash_runner: write done state failed");
    }
    refresh_loose_ends();

    let out_snippet = stdout_tail.as_deref().unwrap_or("").trim();
    let err_snippet = stderr_tail.as_deref().unwrap_or("").trim();
    send_wake(socket, &id, &summary, Some((out_snippet, err_snippet))).await;
}

/// Run `bash -c cmd` in its own process group, streaming output to files.
/// `timeout_secs = None` means no timeout — run until natural exit.
///
/// Tasks run under `bash`, not `sh` (on NixOS `/bin/sh` is bash in POSIX
/// mode, which disables bashisms — arrays, `[[ … ]]`, `local`, process
/// substitution), invoked via `/usr/bin/env bash`.
///
/// The task is cancellable via `cancel` (set `force` first): on cancel the
/// whole process group is signalled — `SIGKILL` if `force`, else `SIGINT` —
/// so children of the shell die too, not just the shell. The timeout path
/// likewise `SIGKILL`s the group.
async fn exec_cmd(
    cmd: &str,
    out_path: &Path,
    err_path: &Path,
    timeout_secs: Option<u64>,
    cancel: &Notify,
    force: &AtomicBool,
) -> Result<ExecOutcome> {
    use tokio::process::Command;
    // `/usr/bin/env bash` rather than a bare `bash`: `/usr/bin/env` is at a
    // fixed absolute path (coreutils, present on NixOS), and it resolves
    // `bash` via PATH — the same controlled PATH the daemon's systemd unit
    // sets. Avoids hardcoding a nix store / generation path in the binary.
    let mut cmd_builder = Command::new("/usr/bin/env");
    cmd_builder
        .arg("bash")
        .arg("-c")
        .arg(cmd)
        .stdout(std::process::Stdio::piped())
        .stderr(std::process::Stdio::piped());
    // SAFETY: `setpgid`/`nice` are async-signal-safe and only touch the
    // calling (child) process before exec — no allocations, no locks.
    // `setpgid(0, 0)` makes the child its own process-group leader so the
    // whole subtree can be signalled as a group (`kill(-pgid, …)`).
    unsafe {
        cmd_builder.pre_exec(|| {
            libc::setpgid(0, 0);
            libc::nice(10);
            Ok(())
        });
    }
    let mut child = cmd_builder.spawn()?;
    // With `setpgid(0, 0)` the child's pgid equals its pid.
    let pgid = child.id().map(u32_to_i32);

    let stdout = child.stdout.take().expect("stdout piped");
    let stderr = child.stderr.take().expect("stderr piped");

    let out_path = out_path.to_path_buf();
    let err_path = err_path.to_path_buf();

    let copy_out = tokio::spawn(copy_stream_to_file(
        tokio::io::BufReader::new(stdout),
        out_path,
    ));
    let copy_err = tokio::spawn(copy_stream_to_file(
        tokio::io::BufReader::new(stderr),
        err_path,
    ));

    // A future that fires when the timeout elapses, or never if `None`.
    let timeout_fut = async {
        match timeout_secs {
            Some(secs) => tokio::time::sleep(Duration::from_secs(secs)).await,
            None => std::future::pending::<()>().await,
        }
    };

    let mut timed_out = false;
    let mut killed: Option<bool> = None;
    let wait_res = {
        let wait = child.wait();
        tokio::pin!(wait);
        tokio::pin!(timeout_fut);
        loop {
            tokio::select! {
                res = &mut wait => break res,
                () = &mut timeout_fut => {
                    // Per-task timeout: hard-kill the whole group and reap.
                    signal_group(pgid, libc::SIGKILL);
                    timed_out = true;
                    break (&mut wait).await;
                }
                () = cancel.notified() => {
                    // A kill was requested: send the signal and keep waiting.
                    // `kill` is fire-and-forget — we do NOT block-for-exit or
                    // auto-escalate. If the process ignores SIGINT the caller
                    // re-invokes kill with `force`, which re-fires this arm
                    // with SIGKILL. `killed` tracks the last signal sent.
                    let forced = force.load(Ordering::SeqCst);
                    signal_group(pgid, if forced { libc::SIGKILL } else { libc::SIGINT });
                    killed = Some(forced);
                }
            }
        }
    };

    let _ = copy_out.await;
    let _ = copy_err.await;

    let status = wait_res?;
    let outcome = if let Some(forced) = killed {
        ExecOutcome::Killed { forced }
    } else if timed_out {
        ExecOutcome::TimedOut
    } else {
        ExecOutcome::Exited(status.code().unwrap_or(-1))
    };
    Ok(outcome)
}

/// `u32` pid → `i32` for `kill(2)`. Pids fit in `i32`; saturates defensively.
fn u32_to_i32(v: u32) -> i32 {
    i32::try_from(v).unwrap_or(i32::MAX)
}

async fn copy_stream_to_file<R>(mut reader: R, path: PathBuf)
where
    R: tokio::io::AsyncRead + Unpin,
{
    match tokio::fs::File::create(&path).await {
        Ok(mut f) => {
            let _ = tokio::io::copy(&mut reader, &mut f).await;
            let _ = f.flush().await;
        }
        Err(e) => {
            tracing::warn!(path = %path.display(), error = ?e, "bash_runner: open output file failed");
        }
    }
}

fn tail_file(path: &Path, max_bytes: usize) -> Option<String> {
    let data = std::fs::read(path).ok()?;
    let slice = if data.len() > max_bytes {
        &data[data.len() - max_bytes..]
    } else {
        &data
    };
    Some(String::from_utf8_lossy(slice).into_owned())
}

// ---------------------------------------------------------------------------
// Wake delivery
// ---------------------------------------------------------------------------

pub(crate) async fn send_wake(
    socket: &Path,
    id: &str,
    summary: &str,
    output: Option<(&str, &str)>,
) {
    use tokio::io::{AsyncBufReadExt as _, BufReader};
    use tokio::net::UnixStream;
    let mut body = format!("bash task `{id}` finished: {summary}");
    if let Some((stdout, stderr)) = output {
        if !stdout.is_empty() {
            body.push_str("\n\nstdout:\n```\n");
            body.push_str(stdout);
            body.push_str("\n```");
        }
        if !stderr.is_empty() {
            body.push_str("\n\nstderr:\n```\n");
            body.push_str(stderr);
            body.push_str("\n```");
        }
    }
    let req = hive_sh4re::AgentRequest::Wake {
        from: format!("bash-task-{id}"),
        body,
    };

    match UnixStream::connect(socket).await {
        Ok(stream) => {
            let (read, mut write) = stream.into_split();
            let line = match serde_json::to_string(&req) {
                Ok(mut s) => {
                    s.push('\n');
                    s
                }
                Err(e) => {
                    tracing::warn!(id = %id, error = ?e, "bash_runner: serialise wake failed");
                    return;
                }
            };
            if write.write_all(line.as_bytes()).await.is_err() {
                tracing::warn!(id = %id, "bash_runner: write wake failed");
                return;
            }
            let _ = write.shutdown().await;
            // Drain the response so the server doesn't get ECONNRESET.
            let mut resp = String::new();
            let _ = BufReader::new(read).read_line(&mut resp).await;
            tracing::info!(id = %id, "bash_runner: wake delivered");
        }
        Err(e) => {
            tracing::warn!(id = %id, error = ?e, "bash_runner: connect wake socket failed");
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{MAX_TASK_NAME_LEN, validate_task_name};

    #[test]
    fn accepts_reasonable_names() {
        for ok in ["build", "ci-check", "nix_flake.check", "t1", "A.B-C_9"] {
            assert!(validate_task_name(ok).is_ok(), "{ok} should be valid");
        }
    }

    #[test]
    fn rejects_unsafe_names() {
        // Empty, traversal, separators, control/space, and over-long.
        for bad in [
            "",
            ".",
            "..",
            "a/b",
            "../escape",
            "has space",
            "tab\tname",
            "slash\\back",
        ] {
            assert!(
                validate_task_name(bad).is_err(),
                "{bad:?} should be rejected"
            );
        }
        assert!(validate_task_name(&"x".repeat(MAX_TASK_NAME_LEN + 1)).is_err());
        // Exactly at the cap is allowed.
        assert!(validate_task_name(&"x".repeat(MAX_TASK_NAME_LEN)).is_ok());
    }
}