edda-ask 0.6.0

//! Cross-machine mirror provenance at the **read** end (GH-671).
//!
//! `edda sync --from-mirror` warns about a dead mirror at import time. That
//! signal dies with the command: once the rows are in the ledger, `edda ask`
//! on machine B renders a decision that arrived over a three-week-old mirror
//! exactly like one decided here this morning. The doneWhen clause this module
//! answers is "讀端過期時 `edda ask` 輸出有標示" — the marking belongs at the
//! read end, not only at the write end.
//!
//! Mechanism: the mirror import stamps `payload["mirror"]` on its
//! `decision_import` event (`edda_ledger::sync::make_import_event`), and the
//! imported row's `event_id` **is** that event's id, so a hit resolves its own
//! provenance with one `get_event`. Nothing is written at query time — the
//! same query-time-derivation contract [`crate::staleness`] follows.
//!
//! Staleness matches [`edda_ledger::sync::MirrorFreshness::is_stale`]: older
//! than the threshold, **or unreadable**. Unknown freshness must be visible,
//! never silently fresh.
//!
//! **Provenance is frozen; freshness is live.** Which machine a decision came
//! over is a fact about the past and is read from the import event. How stale
//! that is cannot be, because an already-imported decision is *skipped* on
//! every later import (`sync_from_mirror`'s self-import guard), so the stamp on
//! its import event is never rewritten. Ageing that frozen stamp meant every
//! mirrored decision on a perfectly current machine read stale 24 hours after
//! it first arrived, forever, and the hint's own remedy — re-export and pull —
//! could not clear it. So freshness is taken from the mirror **in this
//! checkout at query time**, which is what "讀端過期" names and what pulling a
//! fresh mirror actually changes — but only when that mirror is the *same
//! machine's*. A checkout's `docs/decisions/` is rewritten by whichever machine
//! last ran the wave-close export, routinely this one, and that says nothing
//! about how current a peer's rulings are. So the frozen stamp is not a rare
//! fallback: it stands for every decision whose origin machine is not the one
//! the local mirror belongs to, which in a fleet is most of them.

use crate::DecisionHit;
use edda_ledger::sync::DEFAULT_MIRROR_STALE_HOURS;
use edda_ledger::Ledger;
use serde::Serialize;
use std::path::Path;
use time::format_description::well_known::Rfc3339;
use time::OffsetDateTime;

/// Repo-relative mirror directory, fixed by `ledger.cross-machine-projection`
/// clause (1). Kept in step with `edda_bridge_claude::mirror_import`.
const MIRROR_INDEX: &str = "docs/decisions/INDEX.md";

/// The only event type that can carry `payload["mirror"]`.
///
/// `edda_ledger::sync::make_import_event` is the sole writer of that stamp and
/// always writes it onto a `decision_import` event, which is what makes "this
/// ledger has no `decision_import` events" a sound proxy for "no hit here can
/// have mirror provenance". A future writer that stamps some other event type
/// has to be taught to this constant too.
const MIRROR_STAMP_EVENT_TYPE: &str = "decision_import";

/// The mirror a decision arrived over, and how dead it was.
#[derive(Debug, Clone, Serialize)]
pub struct MirrorOrigin {
    /// Exporting machine from the mirror's `INDEX.md`, or the directory name
    /// when the stamp named none.
    pub machine: String,
    /// The `- **Exported at**:` stamp freshness was judged against: the mirror
    /// in this checkout **when that mirror is [`Self::machine`]'s own**,
    /// otherwise the stamp this row was imported under. Another machine's
    /// mirror — including this box's own re-export — never speaks for a peer's
    /// rulings. Absent when neither could be read.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub exported_at: Option<String>,
    /// Age of that stamp in hours at query time; `None` when unparseable.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub age_hours: Option<f64>,
    pub is_stale: bool,
    pub threshold_hours: i64,
}

/// Resolve each hit's mirror provenance. Non-mirror decisions map to `None`,
/// which is every decision in a single-machine project.
///
/// Best-effort by construction: a hit whose event cannot be read maps to
/// `None` rather than failing the query — an unreadable event is not evidence
/// that a decision came from a mirror.
pub fn origins_for_hits(
    ledger: &Ledger,
    hits: &[DecisionHit],
    repo_root: Option<&Path>,
) -> Vec<Option<MirrorOrigin>> {
    // `edda ask` runs this twice per query (decisions + timeline) and once more
    // per project under `--fleet`, so the per-hit `get_event` below is paid ~2N
    // times — for a field that is `None` on every row of a single-machine
    // project, because such a project has no `decision_import` events for a
    // lookup to find. One index-backed probe (`idx_events_type`) answers that
    // for the whole list, so N primary-key lookups collapse into one seek that
    // reads no rows at all. A ledger that does have imports takes exactly the
    // per-hit path it took before.
    if hits.is_empty() || !may_hold_mirror_origins(ledger) {
        return vec![None; hits.len()];
    }
    let now = OffsetDateTime::now_utc();
    // Read once for the whole list: it is the same mirror for every hit.
    let live = repo_root.and_then(live_mirror);
    hits.iter()
        .map(|h| {
            ledger.get_event(&h.event_id).ok().flatten().and_then(|e| {
                origin_from_payload(
                    &e.payload,
                    now,
                    live.as_ref().map(|(s, m)| (s.as_str(), m.as_str())),
                )
            })
        })
        .collect()
}

/// The committed mirror in this checkout: its stamp **and whose it is**.
///
/// Both halves matter. A checkout's `docs/decisions/` is rewritten by this
/// machine's own wave-close export (`scripts/fleet/ratify-merged.sh`), so its
/// stamp routinely belongs to a *different* machine than the one a given
/// decision arrived from. Ageing a decision from `4090` against this box's own
/// fresh export would clear the marker for a mirror nobody re-pulled, and print
/// `from 4090 — exported <this box's timestamp>`, which is simply false.
///
/// Prefixes and trimming match `edda_ledger::sync::parse_index_meta` and
/// `edda_bridge_claude::mirror_import::read_stamp` — three readers of one file,
/// which only stay in agreement if they all strip it the same way.
fn live_mirror(repo_root: &Path) -> Option<(String, String)> {
    let text = std::fs::read_to_string(repo_root.join(MIRROR_INDEX)).ok()?;
    let field = |name: &str| {
        text.lines()
            .find_map(|l| l.strip_prefix(name))
            .map(|v| v.trim().to_string())
            .filter(|v| !v.is_empty())
    };
    Some((
        field("- **Exported at**:")?,
        field("- **Exporting machine**:")?,
    ))
}

/// Whether a per-hit lookup could find any provenance at all.
///
/// Same best-effort rule as the lookups it guards: a probe that could not be
/// read answers `true`, because failing to read the ledger is not evidence that
/// nothing arrived over a mirror. The cost of being wrong that way is the
/// per-hit path that ran before this short-circuit existed.
fn may_hold_mirror_origins(ledger: &Ledger) -> bool {
    match ledger.iter_events_by_type(MIRROR_STAMP_EVENT_TYPE) {
        Ok(imports) => !imports.is_empty(),
        Err(_) => true,
    }
}

/// Annotate an in-memory hit list with the origins from [`origins_for_hits`].
pub fn annotate_hits(hits: &mut [DecisionHit], origins: &[Option<MirrorOrigin>]) {
    for (hit, origin) in hits.iter_mut().zip(origins.iter()) {
        hit.mirror = origin.clone();
    }
}

/// The pure half: read `payload["mirror"]` for provenance, and age the mirror
/// this checkout actually holds — falling back to the frozen import stamp only
/// when there is no live mirror to read.
fn origin_from_payload(
    payload: &serde_json::Value,
    now: OffsetDateTime,
    live: Option<(&str, &str)>,
) -> Option<MirrorOrigin> {
    let mirror = payload.get("mirror")?.as_object()?;
    let machine = mirror
        .get("machine")
        .and_then(|v| v.as_str())
        .unwrap_or("?")
        .to_string();
    let frozen = mirror
        .get("exported_at")
        .and_then(|v| v.as_str())
        .map(str::to_string);
    // The live stamp only speaks for this decision if the mirror in the
    // checkout is the same machine's. Anyone else's — including this box's own
    // re-export — says nothing about how current `machine`'s rulings are.
    let exported_at = live
        .filter(|(_, live_machine)| *live_machine == machine)
        .map(|(stamp, _)| stamp.to_string())
        .or(frozen);
    let age_hours = exported_at.as_deref().and_then(|ts| {
        OffsetDateTime::parse(ts, &Rfc3339)
            .ok()
            .map(|t| (now - t).as_seconds_f64() / 3600.0)
    });
    Some(MirrorOrigin {
        machine,
        exported_at,
        // Same rule as the import-time warning: unknown age is stale.
        is_stale: match age_hours {
            Some(h) => h >= DEFAULT_MIRROR_STALE_HOURS as f64,
            None => true,
        },
        age_hours,
        threshold_hours: DEFAULT_MIRROR_STALE_HOURS,
    })
}

/// The human line `edda ask` prints under a decision that rode a dead mirror.
pub fn stale_hint(origin: &MirrorOrigin) -> String {
    let age = match origin.age_hours {
        Some(h) => format!("{h:.1}h old"),
        None => "stamp missing or unreadable".to_string(),
    };
    format!(
        "⚠ stale-mirror hint: from {} — exported {} ({age}, threshold {}h). Re-export on the source machine and pull.",
        origin.machine,
        origin.exported_at.as_deref().unwrap_or("?"),
        origin.threshold_hours,
    )
}

#[cfg(test)]
mod tests {
    use super::*;
    use edda_core::event::{finalize_event, new_note_event};
    use edda_core::Event;
    use edda_ledger::ledger::{init_branches_json, init_head, init_workspace};
    use edda_ledger::paths::EddaPaths;
    use std::sync::atomic::{AtomicU64, Ordering};

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

    /// A real on-disk ledger — this workspace does not mock internal crates,
    /// and the short-circuit below is a claim about what SQLite holds.
    fn setup() -> Ledger {
        let n = TEST_COUNTER.fetch_add(1, Ordering::SeqCst);
        let tmp = std::env::temp_dir().join(format!("edda_ask_mirror_{}_{n}", std::process::id()));
        let _ = std::fs::remove_dir_all(&tmp);
        let paths = EddaPaths::discover(&tmp);
        init_workspace(&paths).unwrap();
        init_head(&paths, "main").unwrap();
        init_branches_json(&paths, "main").unwrap();
        Ledger::open(&tmp).unwrap()
    }

    fn append(ledger: &Ledger, event: &Event) -> String {
        let mut chained = event.clone();
        chained.parent_hash = ledger.last_event_hash().unwrap();
        finalize_event(&mut chained).unwrap();
        ledger.append_event(&chained).unwrap();
        chained.event_id
    }

    fn note(text: &str) -> Event {
        new_note_event("main", None, "system", text, &[]).unwrap()
    }

    /// A `decision_import` carrying the stamp `sync::make_import_event` writes.
    fn mirror_import(machine: &str, exported_at: &str) -> Event {
        let mut e = note("[sync] imported db.engine=sqlite");
        e.event_type = "decision_import".to_string();
        e.payload["mirror"] = serde_json::json!({
            "machine": machine,
            "exported_at": exported_at,
        });
        e
    }

    fn hit(event_id: &str) -> DecisionHit {
        DecisionHit {
            event_id: event_id.to_string(),
            key: "db.engine".to_string(),
            value: "sqlite".to_string(),
            reason: String::new(),
            domain: "db".to_string(),
            branch: "main".to_string(),
            ts: "2026-09-07T00:00:00Z".to_string(),
            is_active: true,
            governance: crate::DecisionGovernance::default(),
            tags: Vec::new(),
            village_id: None,
            staleness: None,
            mirror: None,
        }
    }

    fn at(ts: &str) -> OffsetDateTime {
        OffsetDateTime::parse(ts, &Rfc3339).unwrap()
    }

    fn payload(exported_at: Option<&str>) -> serde_json::Value {
        match exported_at {
            Some(ts) => serde_json::json!({"mirror": {"machine": "4090", "exported_at": ts}}),
            None => serde_json::json!({"mirror": {"machine": "4090", "exported_at": null}}),
        }
    }

    #[test]
    fn a_decision_that_never_rode_a_mirror_has_no_origin() {
        // The single-machine case: every decision, and the reason the marker
        // does not become noise in a solo project.
        let local = serde_json::json!({"role": "system", "decision": {"key": "db.engine"}});
        assert!(origin_from_payload(&local, at("2026-09-07T00:00:00Z"), None).is_none());
    }

    #[test]
    fn a_fresh_mirror_is_not_marked() {
        let o = origin_from_payload(
            &payload(Some("2026-09-07T00:00:00Z")),
            at("2026-09-07T06:00:00Z"),
            None,
        )
        .expect("mirror payload");
        assert_eq!(o.machine, "4090");
        assert!(!o.is_stale, "6h < 24h threshold");
        assert!((o.age_hours.expect("parsed stamp") - 6.0).abs() < 0.001);
    }

    #[test]
    fn a_mirror_past_the_threshold_is_marked_stale() {
        let o = origin_from_payload(
            &payload(Some("2026-09-01T00:00:00Z")),
            at("2026-09-07T00:00:00Z"),
            None,
        )
        .expect("mirror payload");
        assert!(o.is_stale, "144h >= 24h threshold");
        assert!(stale_hint(&o).contains("4090"));
        assert!(stale_hint(&o).contains("144.0h old"));
    }

    #[test]
    fn exactly_at_the_threshold_is_stale() {
        // Boundary matches `MirrorFreshness::is_stale`: `>=`, not `>`.
        let o = origin_from_payload(
            &payload(Some("2026-09-06T00:00:00Z")),
            at("2026-09-07T00:00:00Z"),
            None,
        )
        .expect("mirror payload");
        assert!(o.is_stale);
    }

    #[test]
    fn a_fresh_checkout_clears_a_marker_the_frozen_stamp_would_hold_forever() {
        // The round-3 P1. An already-imported decision is skipped on every
        // later import, so `payload["mirror"]["exported_at"]` is frozen at
        // whatever it was the first time. Ageing that meant a machine that
        // pulls faithfully still read stale after 24h, permanently, and the
        // hint's own remedy could not clear it. Freshness is the mirror this
        // checkout holds now.
        let frozen_and_ancient = payload(Some("2026-08-01T00:00:00Z"));
        let now = at("2026-09-07T00:00:00Z");

        let without_live =
            origin_from_payload(&frozen_and_ancient, now, None).expect("mirror payload");
        assert!(
            without_live.is_stale,
            "no live mirror to read ⇒ the frozen stamp is all we have"
        );

        let with_live = origin_from_payload(
            &frozen_and_ancient,
            now,
            Some(("2026-09-06T18:00:00Z", "4090")),
        )
        .expect("mirror payload");
        assert!(
            !with_live.is_stale,
            "a mirror re-exported 6h ago is not stale, whatever the import stamp said"
        );
        assert_eq!(
            with_live.exported_at.as_deref(),
            Some("2026-09-06T18:00:00Z"),
            "the stamp reported is the one freshness was judged against"
        );
        assert_eq!(
            with_live.machine, "4090",
            "provenance still comes from the import event, not the live index"
        );
    }

    #[test]
    fn another_machines_fresh_export_does_not_clear_this_ones_marker() {
        // Round 4. The checkout's `docs/decisions/` is rewritten by whichever
        // machine last ran the wave-close export — routinely this box, not the
        // one a given decision came from. Taking its stamp unconditionally
        // cleared the marker for a mirror nobody re-pulled and printed
        // "from 4090 — exported <this box's timestamp>", which is false.
        let from_4090 = payload(Some("2026-08-01T00:00:00Z"));
        let now = at("2026-09-07T00:00:00Z");

        let foreign =
            origin_from_payload(&from_4090, now, Some(("2026-09-06T23:00:00Z", "docs-box")))
                .expect("mirror payload");
        assert!(
            foreign.is_stale,
            "a fresh export by docs-box says nothing about how current 4090's rulings are"
        );
        assert_eq!(
            foreign.exported_at.as_deref(),
            Some("2026-08-01T00:00:00Z"),
            "the frozen stamp is reported, never another machine's"
        );

        // Same stamp, same machine: that is the pull the marker exists to
        // reward, and it must still clear.
        let ours = origin_from_payload(&from_4090, now, Some(("2026-09-06T23:00:00Z", "4090")))
            .expect("mirror payload");
        assert!(!ours.is_stale);
        assert_eq!(ours.exported_at.as_deref(), Some("2026-09-06T23:00:00Z"));
    }

    #[test]
    fn an_unreadable_stamp_is_stale_not_silently_fresh() {
        // Death visibility: unknown freshness must be visible.
        let missing = origin_from_payload(&payload(None), at("2026-09-07T00:00:00Z"), None)
            .expect("mirror payload");
        assert!(missing.is_stale);
        assert!(missing.age_hours.is_none());
        assert!(stale_hint(&missing).contains("stamp missing or unreadable"));

        let garbage = origin_from_payload(
            &payload(Some("not-a-timestamp")),
            at("2026-09-07T00:00:00Z"),
            None,
        )
        .expect("mirror payload");
        assert!(garbage.is_stale);
        assert!(garbage.age_hours.is_none());
    }

    /// The half of the short-circuit that must NOT fire: a ledger holding a
    /// mirror import still resolves provenance one hit at a time. The
    /// locally-decided row beside it stays `None`, so a passing probe cannot be
    /// mistaken for a blanket "everything here came over a mirror".
    #[test]
    fn a_ledger_with_a_mirror_import_annotates_exactly_the_imported_hit() {
        let ledger = setup();
        let local = append(&ledger, &note("decided here this morning"));
        let imported = append(&ledger, &mirror_import("4090", "2026-01-01T00:00:00Z"));

        let mut hits = vec![hit(&imported), hit(&local), hit("evt_not_in_this_ledger")];
        let origins = origins_for_hits(&ledger, &hits, None);
        annotate_hits(&mut hits, &origins);

        let o = hits[0].mirror.as_ref().expect("the import carries a stamp");
        assert_eq!(o.machine, "4090");
        assert_eq!(o.exported_at.as_deref(), Some("2026-01-01T00:00:00Z"));
        assert!(o.is_stale, "a stamp from 2026-01-01 is long past 24h");
        assert!(
            hits[1].mirror.is_none(),
            "a locally-decided row in a mirror-fed ledger did not ride a mirror"
        );
        assert!(
            hits[2].mirror.is_none(),
            "an event that cannot be read is not evidence of a mirror"
        );
    }

    /// The single-machine case the short-circuit exists for. The `None`s here
    /// have to be the same `None`s the per-hit path produced, so the test pins
    /// both halves: the events really are in the ledger (a lookup would have
    /// found them and still answered `None`), and there is no
    /// `decision_import` for one to find.
    #[test]
    fn a_ledger_with_no_mirror_import_answers_none_for_every_hit() {
        let ledger = setup();
        let local = append(&ledger, &note("decided here this morning"));

        assert!(
            ledger.get_event(&local).unwrap().is_some(),
            "the row is present, so `None` below is the short-circuit's answer \
             and not a lookup that missed"
        );
        assert!(
            ledger
                .iter_events_by_type(MIRROR_STAMP_EVENT_TYPE)
                .unwrap()
                .is_empty(),
            "the condition the short-circuit keys on"
        );

        let mut hits = vec![hit(&local), hit("evt_not_in_this_ledger")];
        let origins = origins_for_hits(&ledger, &hits, None);
        assert_eq!(
            origins.len(),
            hits.len(),
            "one answer per hit, short-circuit or not — `annotate_hits` zips \
             the two and would silently drop the tail"
        );
        assert!(origins.iter().all(Option::is_none));
        annotate_hits(&mut hits, &origins);
        assert!(hits.iter().all(|h| h.mirror.is_none()));

        assert!(
            origins_for_hits(&ledger, &[], None).is_empty(),
            "no hits, no probe: a query that matched nothing did no ledger \
             work before this short-circuit and must do none after"
        );
    }
}