kranz-engine 0.2.2

//! Cross-process control inbox (design.md "Cross-process control").
//!
//! The single-writer rule (§4.3) means only the engine appends `events.jsonl`.
//! Other processes (CLI `kranz msg/pause/resume`, the server) talk to a
//! running engine by dropping [`ControlCommand`] JSON files into
//! `paths.control_dir()`. File names are `<zero-padded-nanos>-<8-hex>.json`
//! so lexicographic order == chronological order; writes go through a tmp
//! file + rename so a draining engine never observes a partial file. The
//! nanosecond prefix keeps back-to-back enqueues (e.g. `pause` immediately
//! followed by `resume`) in issue order — a millisecond prefix left same-ms
//! enqueues to be ordered by the random suffix.
//!
//! The engine [`drain`]s the inbox between worker runs, and a
//! [`ControlWatcher`] polls [`peek_interrupt`] so an `interrupt` message can
//! abort the active run.
//!
//! # Authenticity (audit 2026-09-01 C1)
//!
//! The inbox carries operator consent: `approve-grant`, `approve-revision`,
//! `answer-question`, and `config-change` all land as events that are
//! indistinguishable from a human decision. It used to be a plain directory
//! any process with write access to the repo could drop a file into, which
//! made forging consent a one-file operation for a worker, a validator, or
//! any gate command.
//!
//! Every file therefore carries a `sig`: a hex HMAC-SHA256 over the mission
//! id, the file name, and the canonical JSON of the command, keyed by the
//! repository authority key ([`crate::paths::authority_key_path`]). [`drain`]
//! and [`peek_interrupt`] verify it with a constant-time compare and
//! quarantine anything unsigned or wrongly signed to `.bad`, never applying
//! it. [`acknowledge`] records the acknowledged file's name as the mission's
//! control mark outside the repository, and any later file whose name is at
//! or below the mark is quarantined as a replay even when its signature
//! verifies.

use crate::error::{EngineError, Result};
use crate::paths::MissionPaths;
use crate::types::{ControlCommand, MissionStatus};
use chrono::Utc;
use std::ffi::{OsStr, OsString};
use std::io::{ErrorKind, Write};
use std::path::{Path, PathBuf};
use subtle::ConstantTimeEq as _;

/// Width of the zero-padded nanosecond prefix — the full `u64` decimal
/// width, so names sort lexicographically for any conceivable timestamp.
const TIMESTAMP_WIDTH: usize = 20;

/// Length of the random hex suffix (a `uuid` v4 `simple()` prefix).
const RAND_LEN: usize = 8;

/// JSON key holding the authenticity tag of a control file.
const SIG_FIELD: &str = "sig";

/// The bytes a control file's `sig` covers: the mission id and the FILE
/// NAME, each length-prefixed so no two fields can be re-cut into a
/// different pair, then the canonical JSON of the command.
///
/// Signing the re-serialized `ControlCommand` rather than the raw file bytes
/// binds the MEANING of the file, not its whitespace, and keeps the signer
/// and the verifier on one code path: both go `ControlCommand` -> canonical
/// JSON -> HMAC, so they cannot drift on key order or number formatting.
///
/// Binding the name makes a signed file single-use together with the
/// control mark (`paths::record_control_mark`): names order by creation
/// time, the engine records the last name it acknowledged, and a captured
/// file re-dropped later carries a name at or below that mark (follow-up
/// review F-1).
fn signed_payload(mission_id: &str, name: &str, cmd: &ControlCommand) -> Result<String> {
    let body = serde_json::to_string(cmd)?;
    Ok(format!(
        "{}:{mission_id}\n{}:{name}\n{body}",
        mission_id.len(),
        name.len()
    ))
}

/// Hex HMAC-SHA256 of [`signed_payload`] under the repository authority key.
fn sign(key: &[u8], mission_id: &str, name: &str, cmd: &ControlCommand) -> Result<String> {
    Ok(crate::hooks::hmac_sha256_hex(
        key,
        signed_payload(mission_id, name, cmd)?.as_bytes(),
    ))
}

/// A file whose name is at or below the recorded control mark was already
/// acknowledged once, or predates one that was: a replay, whatever its
/// signature says. Names are fixed-width, so string order is time order.
fn is_replayed(repo_root: &Path, mission_id: &str, name: &str) -> bool {
    crate::paths::read_control_mark(repo_root, mission_id).is_some_and(|mark| name <= mark.as_str())
}

/// Why a queued file was refused. Distinguishing the two matters: a forged or
/// unsigned file is quarantined, whereas an operator whose key is temporarily
/// unreadable must NOT have their inbox renamed away underneath them.
enum ControlRefusal {
    /// The file is not an authentic command; quarantine it.
    Quarantine(String),
    /// This process cannot verify right now; leave the file queued.
    Skip(String),
}

/// Parse and authenticate one control file's contents.
///
/// Fails CLOSED on an unsigned file. A control file written by a kranz that
/// predates signing carries no `sig` and is refused for that reason: the
/// on-disk format is otherwise unchanged, but an unauthenticated command is
/// exactly the thing this guard exists to stop, so old files are quarantined
/// rather than grandfathered.
fn authenticate(
    repo_root: &Path,
    mission_id: &str,
    name: &str,
    content: &str,
) -> std::result::Result<ControlCommand, ControlRefusal> {
    if is_replayed(repo_root, mission_id, name) {
        return Err(ControlRefusal::Quarantine(
            "control command replays a file the engine already acknowledged".to_string(),
        ));
    }
    let mut value: serde_json::Value = serde_json::from_str(content)
        .map_err(|e| ControlRefusal::Quarantine(format!("unparseable control command: {e}")))?;
    let object = value.as_object_mut().ok_or_else(|| {
        ControlRefusal::Quarantine("control command is not a JSON object".to_string())
    })?;
    let Some(presented) = object.remove(SIG_FIELD) else {
        return Err(ControlRefusal::Quarantine(
            "control command carries no signature".to_string(),
        ));
    };
    let Some(presented) = presented.as_str().map(str::to_string) else {
        return Err(ControlRefusal::Quarantine(
            "control command signature is not a string".to_string(),
        ));
    };
    let cmd: ControlCommand = serde_json::from_value(value)
        .map_err(|e| ControlRefusal::Quarantine(format!("unparseable control command: {e}")))?;

    // No key means no verdict, not a pass: skip and stay loud. Quarantining
    // here would let a transient home-directory problem shred a real inbox.
    let Some(key) = crate::paths::load_authority_key(repo_root) else {
        return Err(ControlRefusal::Skip(
            "no repository authority key available to verify control commands".to_string(),
        ));
    };
    let expected = sign(&key, mission_id, name, &cmd)
        .map_err(|e| ControlRefusal::Skip(format!("could not recompute signature: {e}")))?;
    if bool::from(expected.as_bytes().ct_eq(presented.as_bytes())) {
        Ok(cmd)
    } else {
        Err(ControlRefusal::Quarantine(
            "control command signature does not verify".to_string(),
        ))
    }
}

/// Enqueue one command into the mission's control inbox.
///
/// Creates the mission tree and control directory if needed — no-follow (P1
/// mission-path-no-follow): a symlinked `.kranz`/`missions`/mission dir or
/// `control/` entry is refused, never followed, since an enqueue through a
/// symlink would route control commands into another repository's mission.
/// The JSON goes to a sibling tmp file, then atomically renames to
/// `<zero-padded-nanos>-<8-hex>.json` — readers never see partial files.
/// Returns the final file path.
///
/// The written object is the command plus a `sig` field ([`authenticate`]);
/// minting the repository authority key on first use is part of enqueuing, so
/// an operator never has to run a key-setup step before `kranz pause` works.
pub fn enqueue(paths: &MissionPaths, cmd: &ControlCommand) -> Result<PathBuf> {
    // Sign BEFORE touching the mission tree: a repo with no reachable
    // authority key must fail loudly at the CLI rather than leave an
    // unverifiable file the engine would quarantine minutes later.
    let key = crate::paths::load_or_create_authority_key(&paths.repo_root)?;

    let nanos = Utc::now().timestamp_nanos_opt().unwrap_or(0).max(0) as u64;
    let rand = uuid::Uuid::new_v4().simple().to_string();
    let name = format!(
        "{nanos:0width$}-{}.json",
        &rand[..RAND_LEN],
        width = TIMESTAMP_WIDTH
    );
    // The name is part of what is signed (see `signed_payload`).
    let signature = sign(&key, &paths.mission_id, &name, cmd)?;

    let mission_dir = paths.open_mission_dir_nofollow(true)?;
    let dir = paths.control_dir();
    let control_dir = crate::paths::open_real_subdir(&mission_dir, "control", &dir, true)?;

    let final_path = dir.join(&name);
    let tmp_name = format!("{name}.tmp");

    let json = {
        let mut value = serde_json::to_value(cmd)?;
        let object = value.as_object_mut().ok_or_else(|| {
            EngineError::InvalidState("control command is not a JSON object".to_string())
        })?;
        object.insert(SIG_FIELD.to_string(), serde_json::Value::String(signature));
        serde_json::to_string(&value)?
    };
    {
        use cap_fs_ext::OpenOptionsFollowExt as _;
        use cap_primitives::fs::FollowSymlinks;
        let mut options = cap_std::fs::OpenOptions::new();
        options
            .write(true)
            .create_new(true)
            .follow(FollowSymlinks::No);
        let mut file = control_dir.open_with(&tmp_name, &options)?.into_std();
        file.write_all(json.as_bytes())?;
        file.sync_data()?;
    }
    control_dir.rename(&tmp_name, &control_dir, &name)?;
    Ok(final_path)
}

/// Drain the inbox: parse every queued `.json` file, oldest first,
/// NON-destructively.
///
/// Each parsed command is returned together with the file it came from; the
/// caller deletes each file only AFTER the command has been durably applied
/// (e.g. appended to the event log). Deleting up front would lose commands if
/// the process crashed between the drain and the apply — re-processing a file
/// on the next drain is the safe failure mode (duplicates are tolerated
/// downstream).
///
/// A file that fails to parse, or fails to authenticate, is renamed to
/// `<name>.bad` (with a warning) and skipped so neither a corrupt file nor a
/// forged one can block the queue. Non-`.json` files (tmp files, `.bad`
/// quarantines) are ignored. Returns the commands in filename (==
/// chronological) order.
///
/// # Trust model
///
/// The authority key lives under the operator's `~/.kranz`, never in the
/// repository, and never inside a session's working tree. Under an enforced
/// sandbox it sits in `authority_read_deny_paths`, so a contained session
/// cannot read it and therefore cannot produce a `sig` this function accepts.
/// Under the default `sandbox.enforce = off` there is no OS boundary, and the
/// barrier is the agent CLI's own deny rules (`permissions::AUTHORITY_DENY`
/// denies `Read`/`Edit`/`Write` on `~/.kranz/**` and on every mission's
/// `control/**`). That is a weaker barrier than the sandbox and is stated as
/// such: a session that escapes its own CLI's permission layer can still read
/// the key. What no longer works is the one-file forgery this closes, where
/// merely being able to write inside the repo was enough.
pub fn drain(paths: &MissionPaths) -> Result<Vec<(PathBuf, ControlCommand)>> {
    let mut commands = Vec::new();
    let Some(control_dir) = control_dir(paths, false)? else {
        return Ok(commands);
    };
    for name in queued_files(&control_dir)? {
        let path = paths.control_dir().join(&name);
        let content = match read_control_file(&control_dir, &name) {
            Ok(c) => c,
            Err(e) => {
                // Transient (e.g. racing another drain); skip, never block.
                tracing::warn!(path = %path.display(), error = %e, "unreadable control file, skipping");
                continue;
            }
        };
        match authenticate(
            &paths.repo_root,
            &paths.mission_id,
            &name.to_string_lossy(),
            &content,
        ) {
            Ok(cmd) => commands.push((path, cmd)),
            Err(ControlRefusal::Quarantine(reason)) => {
                quarantine(&control_dir, &name, &path, &reason)
            }
            Err(ControlRefusal::Skip(reason)) => {
                tracing::warn!(path = %path.display(), reason = %reason, "cannot verify control file, leaving it queued");
            }
        }
    }
    Ok(commands)
}

/// True if any queued file AUTHENTICATES to `Msg { interrupt: true }`.
///
/// Non-destructive: nothing is consumed, deleted, or renamed — the engine's
/// run-watcher polls this cheaply while a later [`drain`] still returns the
/// message itself. Signature checking belongs here too, not only in [`drain`]:
/// an unsigned file that aborted the active run would be a denial of service
/// on every mission, delivered by the same one-file write.
pub fn peek_interrupt(paths: &MissionPaths) -> Result<bool> {
    let Some(control_dir) = control_dir(paths, false)? else {
        return Ok(false);
    };
    for name in queued_files(&control_dir)? {
        let Ok(content) = read_control_file(&control_dir, &name) else {
            continue;
        };
        match authenticate(
            &paths.repo_root,
            &paths.mission_id,
            &name.to_string_lossy(),
            &content,
        ) {
            Ok(ControlCommand::Msg {
                interrupt: true, ..
            }) => return Ok(true),
            Ok(_) | Err(ControlRefusal::Quarantine(_)) => {}
            Err(ControlRefusal::Skip(reason)) => {
                // The brake is unverifiable, not absent. Say so on every
                // poll: a silent `false` would hide a lost key behind a run
                // that simply never stops (follow-up review F-3).
                tracing::warn!(
                    path = %paths.control_dir().join(&name).display(),
                    reason = %reason,
                    "cannot verify a queued control file while checking for an interrupt"
                );
            }
        }
    }
    Ok(false)
}

/// Remove a command returned by [`drain`] after its event has been durably
/// applied. The delete stays relative to the same no-follow mission/control
/// chain as enqueue and drain, so a swapped parent symlink cannot redirect
/// acknowledgement outside the mission.
pub fn acknowledge(paths: &MissionPaths, path: &Path) -> Result<()> {
    if path.parent() != Some(paths.control_dir().as_path()) {
        return Err(EngineError::InvalidState(format!(
            "refusing control acknowledgement outside {}: {}",
            paths.control_dir().display(),
            path.display()
        )));
    }
    let name = path.file_name().ok_or_else(|| {
        EngineError::InvalidState(format!("control path {} has no file name", path.display()))
    })?;
    let Some(control_dir) = control_dir(paths, false)? else {
        return Err(std::io::Error::from(ErrorKind::NotFound).into());
    };
    control_dir.remove_file(name)?;
    // The file is gone; move the mark up to its name so the same bytes can
    // never be drained twice (follow-up review F-1).
    if let Some(name) = path.file_name().and_then(|n| n.to_str()) {
        crate::paths::record_control_mark(&paths.repo_root, &paths.mission_id, name)?;
    }
    Ok(())
}

/// Fold one mission's status; `None` when its log is unreadable or absent.
fn mission_status(repo_root: &Path, id: &str) -> Option<MissionStatus> {
    let paths = MissionPaths::new(repo_root, id);
    let events = crate::event_log::EventLog::read_events(&paths.events_file()).ok()?;
    Some(crate::reducer::fold(&events).ok()?.mission.status)
}

/// Resolve the target mission for a mid-mission control command (config
/// change, pause, resume): an ACTIVE (non-terminal) mission, chosen
/// unambiguously. Shared by the Slack bridge (`/kranz config|pause|resume`)
/// and the CLI (`kranz config role`), so both surfaces refuse the same
/// hazardous targets:
///
/// - explicit id: must exist and be active. A terminal mission's control
///   inbox is never drained (run() refuses terminal missions), so enqueuing
///   there would be a silent no-op reported as success — reject it instead.
/// - no id: exactly one active mission → use it; none → error; several →
///   error listing the candidates and asking for an explicit id (an
///   mtime-based guess could hijack the wrong running mission).
pub fn resolve_active_mission(repo_root: &Path, explicit: Option<&str>) -> Result<String> {
    let is_terminal = crate::mission_catalog::is_terminal_status;
    if let Some(id) = explicit {
        if !MissionPaths::is_safe_id(id) {
            return Err(EngineError::Other(format!("unknown mission `{id}`")));
        }
        // A symlinked mission dir is refused (P1 mission-path-no-follow),
        // never followed into another repository's mission.
        if MissionPaths::new(repo_root, id)
            .require_no_follow()
            .is_err()
        {
            return Err(EngineError::Other(format!("unknown mission `{id}`")));
        }
        match mission_status(repo_root, id) {
            None => Err(EngineError::Other(format!("unknown mission `{id}`"))),
            Some(s) if is_terminal(s) => Err(EngineError::Other(format!(
                "mission `{id}` is {s:?}; this change applies only to active missions"
            ))),
            Some(_) => Ok(id.to_string()),
        }
    } else {
        let active: Vec<String> = MissionPaths::list_missions(repo_root)
            .into_iter()
            .filter(|id| mission_status(repo_root, id).is_some_and(|s| !is_terminal(s)))
            .collect();
        match active.len() {
            0 => Err(EngineError::Other(
                "no active mission — create one first".into(),
            )),
            1 => Ok(active.into_iter().next().expect("len == 1")),
            _ => Err(EngineError::Other(format!(
                "several active missions ({}); name one explicitly",
                active.join(", ")
            ))),
        }
    }
}

/// Open the control directory through the pinned mission capability. A
/// missing mission/control directory is an empty inbox when `create` is
/// false.
fn control_dir(paths: &MissionPaths, create: bool) -> Result<Option<cap_std::fs::Dir>> {
    let mission_dir = match paths.open_mission_dir_nofollow(create) {
        Ok(dir) => dir,
        Err(EngineError::Io(error)) if error.kind() == ErrorKind::NotFound && !create => {
            return Ok(None)
        }
        Err(error) => return Err(error),
    };
    match crate::paths::open_real_subdir(&mission_dir, "control", &paths.control_dir(), create) {
        Ok(dir) => Ok(Some(dir)),
        Err(EngineError::Io(error)) if error.kind() == ErrorKind::NotFound && !create => Ok(None),
        Err(error) => Err(error),
    }
}

/// Queued `.json` command names in filename (== chronological) order.
fn queued_files(dir: &cap_std::fs::Dir) -> Result<Vec<OsString>> {
    let entries = dir.entries()?;
    let mut files = Vec::new();
    for entry in entries {
        let entry = entry?;
        let name = entry.file_name();
        let is_file = entry.file_type().map(|t| t.is_file()).unwrap_or(false);
        if is_file && Path::new(&name).extension().and_then(|e| e.to_str()) == Some("json") {
            files.push(name);
        }
    }
    files.sort();
    Ok(files)
}

fn read_control_file(dir: &cap_std::fs::Dir, name: &OsStr) -> Result<String> {
    use cap_fs_ext::OpenOptionsFollowExt as _;
    use cap_primitives::fs::FollowSymlinks;
    use std::io::Read;
    let mut options = cap_std::fs::OpenOptions::new();
    options.read(true).follow(FollowSymlinks::No);
    let mut file = dir.open_with(name, &options)?.into_std();
    let mut content = String::new();
    file.read_to_string(&mut content)?;
    Ok(content)
}

/// Rename an unparseable or inauthentic command file to `<name>.bad` so it
/// stops blocking the queue but stays on disk for diagnosis.
fn quarantine(dir: &cap_std::fs::Dir, name: &OsStr, path: &Path, reason: &str) {
    let bad_name = format!("{}.bad", name.to_string_lossy());
    tracing::warn!(
        path = %path.display(),
        error = %reason,
        "refused control command, quarantining as .bad"
    );
    if let Err(e) = dir.rename(name, dir, &bad_name) {
        tracing::warn!(path = %path.display(), error = %e, "failed to quarantine control file");
    }
}

/// Spawn-able helper that polls [`peek_interrupt`] and fires a
/// [`tokio::sync::Notify`] once an interrupt message is queued. The
/// orchestrator selects on the notify alongside the active worker run.
pub struct ControlWatcher;

impl ControlWatcher {
    /// Loop [`peek_interrupt`] every `poll` interval; when an interrupt is
    /// seen, fire `notify.notify_one()` once and return. Poll errors are
    /// logged and treated as "no interrupt yet" — the watcher never dies on a
    /// transient filesystem hiccup.
    ///
    /// `notify_one` (never `notify_waiters`) is load-bearing: it stores a
    /// permit when nobody is waiting, so a fire while the run loop is between
    /// `notified()` registrations (or still inside `backend.start()`) is
    /// consumed by the NEXT waiter instead of being lost forever. Tokio also
    /// re-stores/passes on the permit when a woken `Notified` future is
    /// dropped unconsumed, so a `select!` race cannot swallow it either.
    pub async fn wait_for_interrupt(
        paths: MissionPaths,
        poll: std::time::Duration,
        notify: std::sync::Arc<tokio::sync::Notify>,
    ) {
        loop {
            match peek_interrupt(&paths) {
                Ok(true) => {
                    notify.notify_one();
                    return;
                }
                Ok(false) => {}
                Err(e) => {
                    tracing::warn!(error = %e, "control watcher poll failed, retrying");
                }
            }
            tokio::time::sleep(poll).await;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::events::{Event, EventKind};
    use crate::types::MissionConfig;
    use tempfile::TempDir;

    /// Serialized `events.jsonl` lines for a `mission.created` event (and
    /// optionally a `mission.completed`) that fold like a real log.
    fn events_lines(mission_id: &str, completed: bool) -> String {
        let mut lines = String::new();
        let created = Event {
            seq: 1,
            ts: Utc::now(),
            mission_id: mission_id.to_string(),
            kind: EventKind::MissionCreated {
                goal: "goal".into(),
                base_branch: "main".into(),
                mission_branch: format!("kranz/mission-{mission_id}"),
                config: MissionConfig::default(),
            },
        };
        lines.push_str(&serde_json::to_string(&created).unwrap());
        lines.push('\n');
        if completed {
            let done = Event {
                seq: 2,
                ts: Utc::now(),
                mission_id: mission_id.to_string(),
                kind: EventKind::MissionCompleted {},
            };
            lines.push_str(&serde_json::to_string(&done).unwrap());
            lines.push('\n');
        }
        lines
    }

    /// Seed a mission's `events.jsonl` under the repo's missions dir.
    fn seed_mission(repo_root: &Path, mission_id: &str, completed: bool) {
        let paths = MissionPaths::new(repo_root, mission_id);
        std::fs::create_dir_all(paths.mission_dir()).unwrap();
        std::fs::write(paths.events_file(), events_lines(mission_id, completed)).unwrap();
    }

    // -- C1: the inbox authenticates ---------------------------------------

    /// Drop a raw JSON object into the inbox the way an agent process with
    /// ordinary write access to the repo would: no `enqueue`, no key.
    fn plant(paths: &MissionPaths, name: &str, body: serde_json::Value) {
        std::fs::create_dir_all(paths.control_dir()).unwrap();
        std::fs::write(
            paths.control_dir().join(name),
            serde_json::to_string(&body).unwrap(),
        )
        .unwrap();
    }

    fn quarantined(paths: &MissionPaths) -> Vec<String> {
        std::fs::read_dir(paths.control_dir())
            .unwrap()
            .flatten()
            .map(|e| e.file_name().to_string_lossy().into_owned())
            .filter(|n| n.ends_with(".bad"))
            .collect()
    }

    #[test]
    fn unsigned_approve_grant_is_quarantined_and_never_drained() {
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-1");
        // Enqueue one real command first so the repo's authority key exists;
        // without it drain would SKIP rather than quarantine, and the test
        // would pass for the wrong reason.
        enqueue(&paths, &ControlCommand::Pause).unwrap();
        plant(
            &paths,
            "00000000000000000001-aaaaaaaa.json",
            serde_json::json!({ "kind": "approve-grant", "command": "cargo publish" }),
        );

        let drained = drain(&paths).unwrap();
        assert!(
            drained
                .iter()
                .all(|(_, cmd)| !matches!(cmd, ControlCommand::ApproveGrant { .. })),
            "an unsigned approve-grant must never reach the engine"
        );
        assert_eq!(
            quarantined(&paths),
            vec!["00000000000000000001-aaaaaaaa.json.bad".to_string()],
        );
    }

    #[test]
    fn wrong_key_signature_is_quarantined() {
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-1");
        enqueue(&paths, &ControlCommand::Pause).unwrap();
        let cmd = ControlCommand::ApproveGrant {
            command: "cargo publish".to_string(),
        };
        let forged = sign(
            b"not the repository authority key",
            &paths.mission_id,
            "00000000000000000002-bbbbbbbb.json",
            &cmd,
        )
        .unwrap();
        plant(
            &paths,
            "00000000000000000002-bbbbbbbb.json",
            serde_json::json!({
                "kind": "approve-grant",
                "command": "cargo publish",
                "sig": forged,
            }),
        );

        assert!(drain(&paths)
            .unwrap()
            .iter()
            .all(|(_, cmd)| !matches!(cmd, ControlCommand::ApproveGrant { .. })));
        assert_eq!(
            quarantined(&paths),
            vec!["00000000000000000002-bbbbbbbb.json.bad".to_string()],
        );
    }

    #[test]
    fn a_correctly_signed_command_drains() {
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-1");
        enqueue(
            &paths,
            &ControlCommand::ApproveGrant {
                command: "cargo publish".to_string(),
            },
        )
        .unwrap();

        let drained = drain(&paths).unwrap();
        assert_eq!(drained.len(), 1);
        assert!(
            matches!(&drained[0].1, ControlCommand::ApproveGrant { command } if command == "cargo publish"),
            "{:?}",
            drained[0].1
        );
        assert!(quarantined(&paths).is_empty());
    }

    #[test]
    fn signed_fractional_config_values_keep_their_bits() {
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-fractional");
        let costs = [
            0.3917785_f64,
            f64::from_bits(0.3917785_f64.to_bits() + 1),
            0.095758,
        ];
        for cost in costs {
            enqueue(
                &paths,
                &ControlCommand::ConfigChange {
                    patch: serde_json::json!({"worker": {"maxBudgetUsd": cost}}),
                },
            )
            .unwrap();
        }
        let drained = drain(&paths).unwrap();
        assert_eq!(drained.len(), costs.len());
        for ((_, command), expected) in drained.iter().zip(costs) {
            let ControlCommand::ConfigChange { patch } = command else {
                panic!("wrong command")
            };
            assert_eq!(
                patch["worker"]["maxBudgetUsd"].as_f64().unwrap().to_bits(),
                expected.to_bits()
            );
        }
        assert!(quarantined(&paths).is_empty());
    }

    #[test]
    fn a_signature_from_another_mission_does_not_transfer() {
        // The mission id is inside the signed payload, so lifting a valid
        // file out of mission A's inbox into mission B's must not carry the
        // approval with it.
        let tmp = TempDir::new().unwrap();
        let source = MissionPaths::new(tmp.path(), "m-a");
        let target = MissionPaths::new(tmp.path(), "m-b");
        let cmd = ControlCommand::ApproveGrant {
            command: "cargo publish".to_string(),
        };
        let file = enqueue(&source, &cmd).unwrap();
        let body = std::fs::read_to_string(&file).unwrap();
        std::fs::create_dir_all(target.control_dir()).unwrap();
        let name = "00000000000000000003-cccccccc.json";
        std::fs::write(target.control_dir().join(name), body).unwrap();

        assert!(drain(&target).unwrap().is_empty());
        assert_eq!(quarantined(&target), vec![format!("{name}.bad")]);
    }

    #[test]
    fn an_unsigned_interrupt_never_aborts_the_run() {
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-1");
        enqueue(&paths, &ControlCommand::Pause).unwrap();
        plant(
            &paths,
            "00000000000000000004-dddddddd.json",
            serde_json::json!({ "kind": "msg", "text": "stop", "interrupt": true }),
        );
        assert!(!peek_interrupt(&paths).unwrap());
    }

    #[test]
    fn resolve_explicit_active_mission_is_accepted() {
        let tmp = TempDir::new().unwrap();
        seed_mission(tmp.path(), "m-a", false);
        assert_eq!(
            resolve_active_mission(tmp.path(), Some("m-a")).unwrap(),
            "m-a"
        );
    }

    #[test]
    fn resolve_unknown_mission_is_an_error() {
        let tmp = TempDir::new().unwrap();
        let err = resolve_active_mission(tmp.path(), Some("m-nope"))
            .unwrap_err()
            .to_string();
        assert!(
            err.contains("m-nope"),
            "error names the unknown mission: {err}"
        );
    }

    #[test]
    fn resolve_explicit_mission_rejects_path_traversal_before_reading() {
        let tmp = TempDir::new().unwrap();
        let repo_root = tmp.path().join("nested").join("repo");
        std::fs::create_dir_all(repo_root.join(".kranz").join("missions")).unwrap();
        // Seed a real, foldable ACTIVE mission log at the traversal TARGET:
        // from `<repo>/.kranz/missions/<id>`, the `../../..` id below lands
        // in `<tmp>/nested/outside-target/`. An empty repo would mask a
        // reverted guard — every traversal id would fail as "unknown mission"
        // for the wrong reason.
        let outside = tmp.path().join("nested").join("outside-target");
        std::fs::create_dir_all(&outside).unwrap();
        std::fs::write(
            outside.join("events.jsonl"),
            events_lines("outside-target", false),
        )
        .unwrap();
        let traversal_id = "../../../outside-target";
        // Fixture liveness: the traversal id really folds to an active
        // mission, so a reverted `is_safe_id` guard would ACCEPT it.
        assert!(
            mission_status(&repo_root, traversal_id)
                .is_some_and(|status| !crate::mission_catalog::is_terminal_status(status)),
            "fixture: traversal target must fold as an active mission"
        );

        for id in [traversal_id, "a/b", r"a\b", "C:escape"] {
            let error = resolve_active_mission(&repo_root, Some(id))
                .unwrap_err()
                .to_string();
            assert!(error.contains("unknown mission"), "{id}: {error}");
        }
    }

    #[test]
    fn resolve_terminal_mission_is_an_error() {
        let tmp = TempDir::new().unwrap();
        seed_mission(tmp.path(), "m-done", true);
        let err = resolve_active_mission(tmp.path(), Some("m-done"))
            .unwrap_err()
            .to_string();
        assert!(
            err.contains("active missions"),
            "honest error, not false success: {err}"
        );
    }

    #[test]
    fn resolve_bare_uses_the_single_active_mission() {
        let tmp = TempDir::new().unwrap();
        seed_mission(tmp.path(), "m-only", false);
        // A terminal sibling does not make the bare form ambiguous.
        seed_mission(tmp.path(), "m-done", true);
        assert_eq!(resolve_active_mission(tmp.path(), None).unwrap(), "m-only");
    }

    #[test]
    fn resolve_bare_with_no_active_mission_is_an_error() {
        let tmp = TempDir::new().unwrap();
        assert!(resolve_active_mission(tmp.path(), None).is_err());
    }

    #[test]
    fn resolve_bare_with_several_active_missions_refuses_and_lists_them() {
        let tmp = TempDir::new().unwrap();
        seed_mission(tmp.path(), "m-a", false);
        seed_mission(tmp.path(), "m-b", false);
        let err = resolve_active_mission(tmp.path(), None)
            .unwrap_err()
            .to_string();
        assert!(err.contains("several active missions"), "{err}");
        assert!(
            err.contains("m-a") && err.contains("m-b"),
            "candidates listed: {err}"
        );
    }

    // Symlink-creating tests are unix-only, exactly like the lessons guard's
    // tests; Windows needs privileges to create symlinks.

    #[cfg(unix)]
    #[test]
    fn resolve_explicit_mission_refuses_a_symlinked_mission_dir() {
        use std::os::unix::fs::symlink;
        let tmp = TempDir::new().unwrap();
        let elsewhere = TempDir::new().unwrap();
        // The symlink target holds a foldable ACTIVE mission, so a reverted
        // guard would ACCEPT the id instead of refusing it.
        seed_mission(elsewhere.path(), "m-evil", false);
        let missions = tmp.path().join(".kranz").join("missions");
        std::fs::create_dir_all(&missions).unwrap();
        symlink(
            elsewhere
                .path()
                .join(".kranz")
                .join("missions")
                .join("m-evil"),
            missions.join("m-evil"),
        )
        .unwrap();
        let err = resolve_active_mission(tmp.path(), Some("m-evil"))
            .unwrap_err()
            .to_string();
        assert!(err.contains("unknown mission"), "{err}");
    }

    #[cfg(unix)]
    #[test]
    fn enqueue_refuses_a_symlinked_mission_dir_without_touching_the_target() {
        use std::os::unix::fs::symlink;
        let tmp = TempDir::new().unwrap();
        let elsewhere = TempDir::new().unwrap();
        let missions = tmp.path().join(".kranz").join("missions");
        std::fs::create_dir_all(&missions).unwrap();
        symlink(elsewhere.path(), missions.join("m-evil")).unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-evil");
        let err = enqueue(&paths, &ControlCommand::Pause).unwrap_err();
        assert!(err.to_string().contains("refusing"), "{err}");
        // Nothing was routed into the target tree.
        assert!(!elsewhere.path().join("control").exists());
    }

    #[cfg(unix)]
    #[test]
    fn enqueue_refuses_a_symlinked_control_dir_without_touching_the_target() {
        use std::os::unix::fs::symlink;
        let tmp = TempDir::new().unwrap();
        seed_mission(tmp.path(), "m-1", false);
        let paths = MissionPaths::new(tmp.path(), "m-1");
        let elsewhere = TempDir::new().unwrap();
        symlink(elsewhere.path(), paths.control_dir()).unwrap();
        let err = enqueue(&paths, &ControlCommand::Pause).unwrap_err();
        assert!(err.to_string().contains("refusing"), "{err}");
        // Nothing was written into the target dir.
        assert!(std::fs::read_dir(elsewhere.path())
            .unwrap()
            .next()
            .is_none());
    }

    #[test]
    fn rapid_back_to_back_enqueues_drain_in_issue_order() {
        // Failure-mode fixture for the 2026-07-23 CI flake: with a
        // millisecond filename prefix, two commands enqueued in the same
        // millisecond were drained in random-suffix order (resume sorted
        // before pause and red the run). The nanosecond prefix must keep
        // rapid back-to-back enqueues in issue order.
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-1");
        for cmd in [
            ControlCommand::Pause,
            ControlCommand::Resume,
            ControlCommand::Pause,
            ControlCommand::Resume,
            ControlCommand::Pause,
        ] {
            enqueue(&paths, &cmd).unwrap();
        }
        let order: Vec<bool> = drain(&paths)
            .unwrap()
            .iter()
            .map(|(_, cmd)| matches!(cmd, ControlCommand::Pause))
            .collect();
        assert_eq!(
            order,
            vec![true, false, true, false, true],
            "rapid enqueues must drain in issue order, never random-suffix order"
        );
    }
}

#[cfg(test)]
mod replay_tests {
    use super::*;
    use tempfile::TempDir;

    /// A captured, correctly signed control file re-dropped after the engine
    /// acknowledged it must not drain again (follow-up review F-1).
    #[test]
    fn an_acknowledged_control_file_cannot_be_replayed() {
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-1");
        let cmd = ControlCommand::ApproveGrant {
            command: "cargo publish".to_string(),
        };
        let path = enqueue(&paths, &cmd).unwrap();
        let captured = std::fs::read(&path).unwrap();

        let drained = drain(&paths).unwrap();
        assert_eq!(drained.len(), 1);
        acknowledge(&paths, &path).unwrap();

        std::fs::write(&path, &captured).unwrap();
        let again = drain(&paths).unwrap();
        assert!(
            again.is_empty(),
            "a replayed control file drained: {again:?}"
        );
        let bad = std::fs::read_dir(paths.control_dir())
            .unwrap()
            .flatten()
            .filter(|e| e.file_name().to_string_lossy().ends_with(".bad"))
            .count();
        assert_eq!(bad, 1, "the replay must be quarantined");

        // A fresh enqueue after the mark still works: the mark is a floor,
        // not a lock.
        let fresh = enqueue(&paths, &ControlCommand::Pause).unwrap();
        assert!(
            fresh.file_name().unwrap().to_string_lossy()
                > path.file_name().unwrap().to_string_lossy()
        );
        assert_eq!(drain(&paths).unwrap().len(), 1);
    }

    /// The signature binds the file name: the same signed body under a newer
    /// name does not verify.
    #[test]
    fn a_signed_body_moved_to_a_new_name_does_not_verify() {
        let tmp = TempDir::new().unwrap();
        let paths = MissionPaths::new(tmp.path(), "m-1");
        let path = enqueue(&paths, &ControlCommand::Pause).unwrap();
        let captured = std::fs::read(&path).unwrap();
        std::fs::remove_file(&path).unwrap();
        std::fs::write(
            paths
                .control_dir()
                .join("99999999999999999999-ffffffff.json"),
            &captured,
        )
        .unwrap();
        assert!(drain(&paths).unwrap().is_empty());
    }
}