//! Harness-local todo store — the persistent, DB-backed half of the
//! "todos" (loose-ends v2) system, owned by the in-container harness.
//!
//! In-container subsystems (matrix, forge-notify, bash) push *todos* to
//! the harness over the in-agent socket instead of firing wakes directly.
//! The harness owns this store locally (one sqlite db under the harness
//! dir) and signals its own turn loop on a new/changed row — hive-c0re is
//! not involved (no broker round-trip, no marker files).
//!
//! Because the store lives inside a single agent's container, todos are
//! **not** agent-scoped here (unlike the old c0re store): every row
//! belongs to this agent. A todo is tagged with a `subsystem` marker plus
//! an optional `subsystem_key` (a matrix room id, a bash task id, …), and
//! `(subsystem, subsystem_key)` is the upsert/dedup key — re-pushing the
//! same item is idempotent, and a producer can list / clear / rebuild only
//! its own set (e.g. matrix wipes + recreates its todos on daemon restart).
//!
//! Removal/dismissal has two different paths. The **producing subsystem**
//! `clear`s a todo it has itself resolved (keyed by subsystem + key) — a
//! one-shot event has nothing left to represent once resolved, so this
//! hard-deletes the row. The **agent** `mark_done`s one by id (via
//! `cancel_loose_end`) — that only means "stop showing it to me", so it sets
//! `acked` instead of deleting: a *reconciled* producer like `disk_watch`
//! (re-derives its summary on a timer, not a one-shot event) needs the row
//! to survive ack so [`Todos::upsert`] can still tell "unchanged" from
//! "genuinely different". Acked rows stay out of [`Todos::list`] but keep
//! anchoring that comparison; a materially different summary un-acks +
//! wakes again. Acked rows are reaped after a retention window
//! (`vacuum.rs`) so the table doesn't grow unbounded.

use std::path::Path;
use std::sync::Mutex;

use anyhow::{Context, Result};
use chrono::{DateTime, Utc};
use hive_sh4re::wire_time;
use rusqlite::{Connection, params};

/// SQL bootstrap. `CREATE TABLE IF NOT EXISTS` so first-boot agents and
/// existing ones converge on the same base shape; additive columns land via
/// [`MIGRATIONS`] as try-and-ignore `ALTER TABLE`s so existing dbs catch up
/// without a hard schema-version bump.
const SCHEMA: &str = r"
CREATE TABLE IF NOT EXISTS todos (
    id            INTEGER PRIMARY KEY AUTOINCREMENT,
    subsystem     TEXT    NOT NULL,
    subsystem_key TEXT,
    summary       TEXT    NOT NULL,
    source        TEXT,
    updated_at    INTEGER NOT NULL
);
-- (subsystem, subsystem_key) is the upsert/dedup key. A NULL key never
-- conflicts (SQLite treats NULLs as distinct), so keyless todos always
-- insert as one-offs; keyed todos update in place.
CREATE UNIQUE INDEX IF NOT EXISTS idx_todos_dedup
    ON todos (subsystem, subsystem_key);
";

/// Additive column migrations — see `turn_stats.rs`'s identical pattern.
/// Each runs unconditionally and ignores `duplicate column name` errors, so
/// re-running on an already-migrated db is a silent no-op.
const MIGRATIONS: &[&str] = &[
    "ALTER TABLE todos ADD COLUMN acked INTEGER NOT NULL DEFAULT 0",
    // No default: only meaningful once `acked = 1`; NULL on every
    // pre-migration / never-acked row, which `reap_acked`'s `acked_at < ?`
    // comparison naturally excludes (NULL compares false, not true).
    "ALTER TABLE todos ADD COLUMN acked_at INTEGER",
];

/// One dynamic, subsystem-pushed todo. The consumer derives `age_seconds`
/// from `updated_at`.
#[derive(Debug, Clone)]
pub struct Todo {
    pub id: i64,
    /// Producing subsystem marker (`"matrix"`, `"forge"`, `"bash"`, …).
    pub subsystem: String,
    /// Optional subsystem-specific dedup key (matrix room id, bash task
    /// id, …). `None` = a keyless one-off todo.
    pub subsystem_key: Option<String>,
    /// Human-readable one-line summary shown to the agent.
    pub summary: String,
    /// Optional free-text provenance (e.g. the room name / task label).
    pub source: Option<String>,
    pub updated_at: DateTime<Utc>,
}

/// The harness-local todo store. Cheap to share behind an `Arc`; the inner
/// connection is guarded by a `Mutex` (todo ops are short sqlite writes).
pub struct Todos {
    conn: Mutex<Connection>,
}

impl Todos {
    /// Open (creating if needed) the todo store at `path`.
    ///
    /// # Errors
    ///
    /// Propagates sqlite open / schema-apply failures.
    pub fn open(path: &Path) -> Result<Self> {
        let conn =
            Connection::open(path).with_context(|| format!("open todos db {}", path.display()))?;
        conn.execute_batch(SCHEMA).context("apply todos schema")?;
        for stmt in MIGRATIONS {
            // Ignore "duplicate column name" — the migration already ran.
            // Any other error is logged but doesn't fail open(): the base
            // schema still works and we'd rather keep the harness alive
            // than crash on an upgrade hiccup.
            if let Err(e) = conn.execute(stmt, []) {
                let msg = e.to_string();
                if !msg.contains("duplicate column name") {
                    tracing::warn!(error = %msg, stmt, "todos migration failed");
                }
            }
        }
        Ok(Self {
            conn: Mutex::new(conn),
        })
    }

    /// Insert a todo, or update the existing one for `(subsystem, key)`
    /// when `key` is `Some` and already present. A `None` key never
    /// conflicts, so it always inserts a fresh row.
    ///
    /// Returns `(id, changed)` where `changed` is `true` when the row is new
    /// OR its `summary`/`source` actually differed — the caller uses this to
    /// decide whether to signal the turn loop (re-pushing an identical keyed
    /// todo is a no-op and must not re-wake). This holds **regardless of
    /// whether the existing row is acked**: an identical re-push of an
    /// acked row stays quiet (and stays acked/hidden), while a genuinely
    /// different summary un-acks it and reports `changed = true` — the
    /// agent's earlier dismissal doesn't suppress a real re-deterioration.
    ///
    /// # Errors
    ///
    /// Propagates sqlite query / execute failures.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn upsert(
        &self,
        subsystem: &str,
        key: Option<&str>,
        summary: &str,
        source: Option<&str>,
    ) -> Result<(i64, bool)> {
        let conn = self.conn.lock().unwrap();
        let now = Utc::now().timestamp();
        let existing: Option<(i64, String, Option<String>)> = if key.is_some() {
            conn.query_row(
                "SELECT id, summary, source FROM todos \
                 WHERE subsystem = ?1 AND subsystem_key IS ?2",
                params![subsystem, key],
                |row| Ok((row.get(0)?, row.get(1)?, row.get(2)?)),
            )
            .ok()
        } else {
            None
        };
        if let Some((id, cur_summary, cur_source)) = existing {
            let unchanged = cur_summary == summary && cur_source.as_deref() == source;
            if unchanged {
                return Ok((id, false));
            }
            // A materially different summary clears any prior ack — this is
            // new information, not a re-announcement of what was dismissed.
            conn.execute(
                "UPDATE todos SET summary = ?1, source = ?2, updated_at = ?3, \
                        acked = 0, acked_at = NULL \
                 WHERE id = ?4",
                params![summary, source, now, id],
            )?;
            return Ok((id, true));
        }
        conn.execute(
            "INSERT INTO todos \
               (subsystem, subsystem_key, summary, source, updated_at) \
             VALUES (?1, ?2, ?3, ?4, ?5)",
            params![subsystem, key, summary, source, now],
        )?;
        Ok((conn.last_insert_rowid(), true))
    }

    /// Clear producer-resolved todo(s) by `(subsystem, key)`. `key =
    /// Some(k)` targets the one keyed row; `key = None` matches
    /// `subsystem_key IS NULL`, i.e. **all** keyless todos for that
    /// subsystem (clear a specific keyless one via [`Todos::mark_done`] by
    /// id instead). Returns the number of rows deleted.
    ///
    /// # Errors
    ///
    /// Propagates the sqlite delete failure.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn clear(&self, subsystem: &str, key: Option<&str>) -> Result<usize> {
        let conn = self.conn.lock().unwrap();
        let n = conn.execute(
            "DELETE FROM todos WHERE subsystem = ?1 AND subsystem_key IS ?2",
            params![subsystem, key],
        )?;
        Ok(n)
    }

    /// Clear every todo `subsystem` owns — used by a producer that rebuilds
    /// its whole set on restart (cancel-and-recreate). Returns the number
    /// of rows deleted.
    ///
    /// # Errors
    ///
    /// Propagates the sqlite delete failure.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn clear_subsystem(&self, subsystem: &str) -> Result<usize> {
        let conn = self.conn.lock().unwrap();
        let n = conn.execute("DELETE FROM todos WHERE subsystem = ?1", params![subsystem])?;
        Ok(n)
    }

    /// The agent marks one of its todos done, by id — i.e. dismisses it from
    /// its own list. Sets `acked` rather than deleting the row (see the
    /// module doc comment for why): the row stays intact so a reconciled
    /// producer's next `upsert` can still tell "unchanged" from "genuinely
    /// different" instead of seeing an empty table and treating a re-poll of
    /// the same condition as brand new. Returns the number of rows newly
    /// acked (0 when the id was unknown, already gone, or already acked —
    /// acking twice is not a new action).
    ///
    /// # Errors
    ///
    /// Propagates the sqlite update failure.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn mark_done(&self, id: i64) -> Result<usize> {
        let conn = self.conn.lock().unwrap();
        let n = conn.execute(
            "UPDATE todos SET acked = 1, acked_at = ?1 WHERE id = ?2 AND acked = 0",
            params![Utc::now().timestamp(), id],
        )?;
        Ok(n)
    }

    /// Bulk-ack a specific, explicit list of todo ids in one shot. Exists
    /// for the case a per-id `mark_done` loop isn't worth the round-trips:
    /// an agent that hasn't called `get_loose_ends` in a long stretch (or
    /// one whose producers pile up faster than it triages) can end up with
    /// a backlog large enough that clearing it one call at a time is
    /// impractical. Deliberately **explicit ids, not a `<= threshold`
    /// range** — a reviewer's call on the design: a range-based
    /// bulk-ack risks silently acking something the agent never actually
    /// looked at, since todos are heterogeneous unrelated items (bash /
    /// matrix / forge) rather than a sequentially-read stream the way inbox
    /// messages are. The caller is expected to have looked at each id
    /// (typically the ids `get_loose_ends` just rendered) before passing
    /// them here. Same `acked`-not-deleted semantics as [`Self::mark_done`]
    /// (a reconciled producer's next `upsert` still sees the row to compare
    /// against). Unknown/already-acked ids are silently skipped — same "not
    /// a new action" idempotence as the single-id path. Returns the number
    /// of rows newly acked.
    ///
    /// # Errors
    ///
    /// Propagates the sqlite update failure.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn mark_done_many(&self, ids: &[i64]) -> Result<usize> {
        if ids.is_empty() {
            return Ok(0);
        }
        let conn = self.conn.lock().unwrap();
        let now = Utc::now().timestamp();
        let mut total = 0usize;
        for id in ids {
            total += conn.execute(
                "UPDATE todos SET acked = 1, acked_at = ?1 WHERE acked = 0 AND id = ?2",
                params![now, id],
            )?;
        }
        Ok(total)
    }

    /// List todos, newest-updated first. `subsystem = Some(..)` filters to
    /// one producer's set; `None` returns all. Excludes acked rows — once
    /// the agent has dismissed a todo it stays out of its own list, even
    /// though the row itself survives (see `mark_done`).
    ///
    /// # Errors
    ///
    /// Propagates the sqlite prepare / query failures.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn list(&self, subsystem: Option<&str>) -> Result<Vec<Todo>> {
        let conn = self.conn.lock().unwrap();
        let mut stmt = conn.prepare(
            "SELECT id, subsystem, subsystem_key, summary, source, updated_at \
             FROM todos \
             WHERE acked = 0 AND (?1 IS NULL OR subsystem = ?1) \
             ORDER BY updated_at DESC, id DESC",
        )?;
        let rows = stmt
            .query_map(params![subsystem], |row| {
                let updated_at_secs: i64 = row.get(5)?;
                Ok(Todo {
                    id: row.get(0)?,
                    subsystem: row.get(1)?,
                    subsystem_key: row.get(2)?,
                    summary: row.get(3)?,
                    source: row.get(4)?,
                    updated_at: wire_time::from_secs(updated_at_secs),
                })
            })?
            .collect::<rusqlite::Result<Vec<_>>>()?;
        Ok(rows)
    }

    /// Cheap existence check — `true` when at least one un-acked todo row
    /// exists (across every subsystem). Used to gate a `todo_wake`
    /// notification against being turned into a turn when its payload has
    /// already been drained by an earlier turn (see the serve loop's
    /// `LocalTodo` arm): an `EXISTS` probe, not a full `list` + row
    /// materialization, since this runs on every wake.
    ///
    /// # Errors
    ///
    /// Propagates the sqlite query failure.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn has_any(&self) -> Result<bool> {
        let conn = self.conn.lock().unwrap();
        let any: bool = conn.query_row(
            "SELECT EXISTS(SELECT 1 FROM todos WHERE acked = 0)",
            [],
            |row| row.get(0),
        )?;
        Ok(any)
    }

    /// Reap acked rows whose `acked_at` is older than `cutoff` (a unix
    /// timestamp). Called by the harness's hourly vacuum sweep
    /// (`vacuum.rs`), not on any hot path — bounds the table against acked
    /// one-shot todos (bash/matrix/forge) that will never naturally be
    /// upserted again and so would otherwise sit forever. Never touches
    /// un-acked rows. Returns the number of rows deleted.
    ///
    /// # Errors
    ///
    /// Propagates the sqlite delete failure.
    ///
    /// # Panics
    ///
    /// Panics if the connection mutex is poisoned.
    pub fn reap_acked(&self, cutoff: i64) -> Result<usize> {
        let conn = self.conn.lock().unwrap();
        let n = conn.execute(
            "DELETE FROM todos WHERE acked = 1 AND acked_at < ?1",
            params![cutoff],
        )?;
        Ok(n)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    // Return the `TempDir` alongside the store so it outlives the test —
    // dropping it early deletes the dir and SQLite fails with
    // `SQLITE_READONLY_DBMOVED`.
    fn store() -> (tempfile::TempDir, Todos) {
        let dir = tempfile::tempdir().unwrap();
        let db = Todos::open(&dir.path().join("todos.sqlite")).unwrap();
        (dir, db)
    }

    #[test]
    fn keyed_upsert_dedups_and_reports_changed() {
        let (_dir, s) = store();
        let (id1, changed1) = s
            .upsert("matrix", Some("!room:x"), "1 unread", None)
            .unwrap();
        assert!(changed1, "first push is new → changed");
        // Same key + same summary → no-op, not changed (must not re-wake).
        let (id2, changed2) = s
            .upsert("matrix", Some("!room:x"), "1 unread", None)
            .unwrap();
        assert_eq!(id1, id2, "keyed upsert updates in place, same row");
        assert!(!changed2, "identical re-push is a no-op");
        // Same key, new summary → updates, changed.
        let (id3, changed3) = s
            .upsert("matrix", Some("!room:x"), "3 unread", None)
            .unwrap();
        assert_eq!(id1, id3);
        assert!(changed3);
        assert_eq!(s.list(Some("matrix")).unwrap().len(), 1);
    }

    #[test]
    fn keyless_todos_always_insert() {
        let (_dir, s) = store();
        let (a, _) = s.upsert("bash", None, "task done", None).unwrap();
        let (b, _) = s.upsert("bash", None, "task done", None).unwrap();
        assert_ne!(a, b, "keyless pushes are distinct one-offs");
        assert_eq!(s.list(Some("bash")).unwrap().len(), 2);
    }

    #[test]
    fn clear_deletes_and_mark_done_hides_from_list() {
        let (_dir, s) = store();
        s.upsert("matrix", Some("!a:x"), "unread", None).unwrap();
        let (id, _) = s.upsert("forge", Some("pr-1"), "review", None).unwrap();
        assert_eq!(s.clear("matrix", Some("!a:x")).unwrap(), 1, "clear deletes");
        assert_eq!(
            s.mark_done(id).unwrap(),
            1,
            "mark_done acks, doesn't delete"
        );
        assert!(
            s.list(None).unwrap().is_empty(),
            "both are gone from the agent-visible list either way"
        );
    }

    #[test]
    fn has_any_reflects_emptiness() {
        let (_dir, s) = store();
        assert!(!s.has_any().unwrap(), "fresh store has no todos");
        let (id, _) = s.upsert("bash", None, "task done", None).unwrap();
        assert!(s.has_any().unwrap());
        s.mark_done(id).unwrap();
        assert!(
            !s.has_any().unwrap(),
            "empty again after draining the only row"
        );
    }

    #[test]
    fn clear_subsystem_wipes_only_its_own() {
        let (_dir, s) = store();
        s.upsert("matrix", Some("!a:x"), "u", None).unwrap();
        s.upsert("matrix", Some("!b:x"), "u", None).unwrap();
        s.upsert("forge", Some("pr-1"), "r", None).unwrap();
        assert_eq!(s.clear_subsystem("matrix").unwrap(), 2);
        let left = s.list(None).unwrap();
        assert_eq!(left.len(), 1);
        assert_eq!(left[0].subsystem, "forge");
    }

    /// The whole point of the fix: acking a reconciled todo must not defeat
    /// the producer's own anti-nag comparison. A re-push with an identical
    /// summary after ack stays quiet AND stays out of the list — the `disk_watch`
    /// bug this closes.
    #[test]
    fn acked_row_survives_unchanged_reupsert_and_stays_hidden() {
        let (_dir, s) = store();
        let (id, changed1) = s.upsert("disk", Some("usage"), "over 85%", None).unwrap();
        assert!(changed1);
        assert_eq!(s.mark_done(id).unwrap(), 1, "first ack succeeds");
        assert!(s.list(None).unwrap().is_empty(), "acked row is hidden");

        // Same producer, same reconcile tick, identical summary — must NOT
        // look like a new todo just because the agent dismissed it.
        let (id2, changed2) = s.upsert("disk", Some("usage"), "over 85%", None).unwrap();
        assert_eq!(id, id2, "same row, not a fresh insert");
        assert!(!changed2, "identical summary stays quiet even though acked");
        assert!(
            s.list(None).unwrap().is_empty(),
            "still hidden — an unchanged re-push does not un-ack"
        );
    }

    /// A materially different summary on an acked row is real information —
    /// it must un-ack, re-surface in `list`, and report `changed = true`.
    #[test]
    fn acked_row_resurfaces_on_genuine_change() {
        let (_dir, s) = store();
        let (id, _) = s.upsert("disk", Some("usage"), "over 85%", None).unwrap();
        s.mark_done(id).unwrap();
        assert!(s.list(None).unwrap().is_empty());

        let (id2, changed) = s.upsert("disk", Some("usage"), "over 90%", None).unwrap();
        assert_eq!(id, id2);
        assert!(changed, "a genuine re-deterioration must not be silenced");
        let visible = s.list(None).unwrap();
        assert_eq!(visible.len(), 1, "un-acked row is visible again");
        assert_eq!(visible[0].summary, "over 90%");
    }

    /// Acking an already-acked (or unknown) id is a no-op, not a new action.
    #[test]
    fn mark_done_twice_is_idempotent() {
        let (_dir, s) = store();
        let (id, _) = s.upsert("bash", None, "task done", None).unwrap();
        assert_eq!(s.mark_done(id).unwrap(), 1);
        assert_eq!(s.mark_done(id).unwrap(), 0, "already acked");
        assert_eq!(s.mark_done(999_999).unwrap(), 0, "unknown id");
    }

    /// `has_any` must also treat an acked-only table as empty — it gates a
    /// wake against a payload the agent has already drained.
    #[test]
    fn has_any_excludes_acked_rows() {
        let (_dir, s) = store();
        let (id, _) = s.upsert("bash", None, "task done", None).unwrap();
        assert!(s.has_any().unwrap());
        s.mark_done(id).unwrap();
        assert!(!s.has_any().unwrap(), "acked-only table reads as empty");
    }

    /// `mark_done_many` acks exactly the ids passed, leaves the rest
    /// untouched — no threshold/range semantics.
    #[test]
    fn mark_done_many_acks_only_the_listed_ids() {
        let (_dir, s) = store();
        let (id1, _) = s.upsert("bash", None, "task 1", None).unwrap();
        let (id2, _) = s.upsert("bash", None, "task 2", None).unwrap();
        let (id3, _) = s.upsert("bash", None, "task 3", None).unwrap();
        assert_eq!(
            s.mark_done_many(&[id1, id3]).unwrap(),
            2,
            "acks id1 and id3, not id2 — not a range"
        );
        let left = s.list(None).unwrap();
        assert_eq!(left.len(), 1);
        assert_eq!(left[0].id, id2);
        // Idempotent: re-running over the same ids acks nothing new.
        assert_eq!(s.mark_done_many(&[id1, id3]).unwrap(), 0);
        // Empty input is a no-op, not an error.
        assert_eq!(s.mark_done_many(&[]).unwrap(), 0);
    }

    /// `reap_acked` only removes acked rows past the cutoff — a recent ack
    /// and any un-acked row both survive.
    #[test]
    fn reap_acked_only_removes_old_acked_rows() {
        let (dir, s) = store();
        let (old_id, _) = s.upsert("bash", None, "old task", None).unwrap();
        let (recent_id, _) = s.upsert("bash", None, "recent task", None).unwrap();
        let (never_acked_id, _) = s.upsert("forge", Some("pr-1"), "review", None).unwrap();
        s.mark_done(old_id).unwrap();
        s.mark_done(recent_id).unwrap();

        // Backdate the old row's ack past the cutoff directly — mark_done
        // always acks "now", so simulate age via the raw connection.
        {
            let conn = s.conn.lock().unwrap();
            conn.execute(
                "UPDATE todos SET acked_at = ?1 WHERE id = ?2",
                params![Utc::now().timestamp() - 1000, old_id],
            )
            .unwrap();
        }

        let removed = s.reap_acked(Utc::now().timestamp() - 500).unwrap();
        assert_eq!(removed, 1, "only the backdated row is past the cutoff");

        let conn = Connection::open(dir.path().join("todos.sqlite")).unwrap();
        let remaining: i64 = conn
            .query_row("SELECT COUNT(*) FROM todos", [], |r| r.get(0))
            .unwrap();
        assert_eq!(
            remaining, 2,
            "recent ack + never-acked row both survive the reap"
        );
        let _ = never_acked_id;
    }
}