zero-session 0.1.2

//! The `Store` handle — owns the SQLite connection, runs
//! migrations, and exposes append/list/milestone ops.
//!
//! Writes are synchronous on the caller's thread. With WAL
//! journalling and our <1 kB event rows, a commit lands in
//! microseconds on modern hardware; a thread-boundary would cost
//! more than the write itself. If that becomes untrue under
//! plugin-heavy loads, see the commented-out `spawn_blocking`
//! skeleton at the bottom of this file.

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

use chrono::{DateTime, Utc};
use rusqlite::{Connection, OptionalExtension, params};

use crate::SessionError;
use crate::event::{EventKind, SessionRow, StoredEvent};

mod migrations {
    // Embed the SQL files in `../migrations/` at compile time.
    refinery::embed_migrations!("./migrations");
}

/// Session-store handle.
pub struct Store {
    conn: Mutex<Connection>,
}

impl std::fmt::Debug for Store {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Store").finish_non_exhaustive()
    }
}

impl Store {
    /// Open or create a database at `path`, running migrations.
    ///
    /// # Errors
    /// Returns a `SessionError` if the parent directory cannot be
    /// created, the connection cannot be opened, or migrations fail.
    pub fn open(path: impl AsRef<Path>) -> Result<Self, SessionError> {
        let path = path.as_ref();
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent)?;
        }
        let mut conn = Connection::open(path)?;
        Self::configure(&conn)?;
        migrations::migrations::runner()
            .run(&mut conn)
            .map_err(|e| SessionError::Migration(e.to_string()))?;
        Ok(Self {
            conn: Mutex::new(conn),
        })
    }

    /// In-memory store for tests.
    ///
    /// # Errors
    /// Returns a `SessionError` if the in-memory connection or
    /// migrations fail.
    pub fn open_in_memory() -> Result<Self, SessionError> {
        let mut conn = Connection::open_in_memory()?;
        Self::configure(&conn)?;
        migrations::migrations::runner()
            .run(&mut conn)
            .map_err(|e| SessionError::Migration(e.to_string()))?;
        Ok(Self {
            conn: Mutex::new(conn),
        })
    }

    fn configure(conn: &Connection) -> Result<(), SessionError> {
        // WAL survives a hard kill mid-write; `synchronous=NORMAL`
        // keeps fsync'ing for durability without the latency of FULL.
        // `foreign_keys=ON` makes ON DELETE CASCADE actually cascade.
        conn.pragma_update(None, "journal_mode", "WAL")?;
        conn.pragma_update(None, "synchronous", "NORMAL")?;
        conn.pragma_update(None, "foreign_keys", "ON")?;
        Ok(())
    }

    /// Start a new session. `ulid` should be freshly generated by
    /// the caller (keeps this crate ulid-free) — any short unique
    /// string works. Returns the row id for subsequent `append`s.
    ///
    /// # Errors
    /// Returns a `SessionError::Sql` on insert failure (e.g. ulid
    /// collision).
    pub fn start_session(
        &self,
        ulid: &str,
        engine_base_url: Option<&str>,
        cli_version: &str,
        parent_ulid: Option<&str>,
    ) -> Result<i64, SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        let now = Utc::now().to_rfc3339();
        conn.execute(
            "INSERT INTO sessions (ulid, started_at, engine_base_url, cli_version, parent_ulid)
             VALUES (?1, ?2, ?3, ?4, ?5)",
            params![ulid, now, engine_base_url, cli_version, parent_ulid],
        )?;
        Ok(conn.last_insert_rowid())
    }

    /// Mark a session as ended. Idempotent — re-ending is a no-op.
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn end_session(&self, session_id: i64) -> Result<(), SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        let now = Utc::now().to_rfc3339();
        conn.execute(
            "UPDATE sessions SET ended_at = COALESCE(ended_at, ?1) WHERE id = ?2",
            params![now, session_id],
        )?;
        Ok(())
    }

    /// Append an event. The `seq` is allocated here so callers
    /// don't race on numbering. Returns the new `seq`.
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn append(
        &self,
        session_id: i64,
        kind: EventKind,
        text: &str,
    ) -> Result<i64, SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        let seq: i64 = conn.query_row(
            "SELECT COALESCE(MAX(seq), 0) + 1 FROM events WHERE session_id = ?1",
            params![session_id],
            |r| r.get(0),
        )?;
        let now = Utc::now().to_rfc3339();
        conn.execute(
            "INSERT INTO events (session_id, seq, at, kind, text) VALUES (?1, ?2, ?3, ?4, ?5)",
            params![session_id, seq, now, kind.as_str(), text],
        )?;
        Ok(seq)
    }

    /// List events in replay order, newest last. `limit` caps the
    /// returned set from the tail (most recent `limit` entries).
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn list_events(
        &self,
        session_id: i64,
        limit: u32,
    ) -> Result<Vec<StoredEvent>, SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        let mut stmt = conn.prepare(
            "SELECT id, session_id, seq, at, kind, text
             FROM events
             WHERE session_id = ?1
             ORDER BY seq DESC
             LIMIT ?2",
        )?;
        let rows = stmt.query_map(params![session_id, limit], |r| {
            let at_str: String = r.get(3)?;
            let kind_str: String = r.get(4)?;
            Ok(StoredEvent {
                id: r.get(0)?,
                session_id: r.get(1)?,
                seq: r.get(2)?,
                at: parse_rfc3339(&at_str),
                kind: EventKind::parse_str(&kind_str).unwrap_or(EventKind::System),
                text: r.get(5)?,
            })
        })?;
        // We asked DESC to cap from the tail; flip back to
        // ascending so the caller can append straight into the log.
        let mut out: Vec<_> = rows.collect::<Result<_, _>>()?;
        out.reverse();
        Ok(out)
    }

    /// Fetch the N most recent sessions (by `started_at` desc).
    /// `limit == 0` returns an empty vec without hitting the DB.
    ///
    /// Used by `/sessions` to paint a navigable list; the `cli_version`
    /// and `engine_base_url` columns are pulled through so the listing
    /// can show mismatches (e.g. an old session from a different
    /// engine base URL) without a follow-up round-trip.
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn list_sessions(&self, limit: u32) -> Result<Vec<SessionRow>, SessionError> {
        if limit == 0 {
            return Ok(Vec::new());
        }
        let conn = self.conn.lock().expect("store mutex poisoned");
        let mut stmt = conn.prepare(
            "SELECT id, ulid, started_at, ended_at, engine_base_url, cli_version, parent_ulid
             FROM sessions
             ORDER BY started_at DESC
             LIMIT ?1",
        )?;
        let rows = stmt.query_map(params![limit], parse_session_row)?;
        rows.collect::<Result<_, _>>().map_err(Into::into)
    }

    /// Look up a session by its `ulid`. Returns `None` when no row
    /// matches; `Err` only on SQL failure.
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn get_session_by_ulid(&self, ulid: &str) -> Result<Option<SessionRow>, SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        conn.query_row(
            "SELECT id, ulid, started_at, ended_at, engine_base_url, cli_version, parent_ulid
             FROM sessions
             WHERE ulid = ?1",
            params![ulid],
            parse_session_row,
        )
        .optional()
        .map_err(Into::into)
    }

    /// Cheap `COUNT(*)` for a session's events. Handy for the
    /// `/sessions` list so it can render `42 event(s)` without
    /// pulling every row.
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn count_events(&self, session_id: i64) -> Result<i64, SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        conn.query_row(
            "SELECT COUNT(*) FROM events WHERE session_id = ?1",
            params![session_id],
            |r| r.get(0),
        )
        .map_err(Into::into)
    }

    /// Fetch the most recent session (by `started_at`).
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn last_session(&self) -> Result<Option<SessionRow>, SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        conn.query_row(
            "SELECT id, ulid, started_at, ended_at, engine_base_url, cli_version, parent_ulid
             FROM sessions
             ORDER BY started_at DESC
             LIMIT 1",
            [],
            parse_session_row,
        )
        .optional()
        .map_err(Into::into)
    }

    /// Set (upsert) a milestone flag.
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn set_milestone(&self, key: &str, value: &str) -> Result<(), SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        let now = Utc::now().to_rfc3339();
        conn.execute(
            "INSERT INTO milestones (key, value, at) VALUES (?1, ?2, ?3)
             ON CONFLICT(key) DO UPDATE SET value = excluded.value, at = excluded.at",
            params![key, value, now],
        )?;
        Ok(())
    }

    /// Read a milestone. Returns `None` if it has never been set.
    ///
    /// # Errors
    /// Propagates underlying SQL failures.
    pub fn get_milestone(&self, key: &str) -> Result<Option<String>, SessionError> {
        let conn = self.conn.lock().expect("store mutex poisoned");
        conn.query_row(
            "SELECT value FROM milestones WHERE key = ?1",
            params![key],
            |r| r.get::<_, String>(0),
        )
        .optional()
        .map_err(Into::into)
    }
}

fn parse_session_row(r: &rusqlite::Row<'_>) -> rusqlite::Result<SessionRow> {
    let started: String = r.get(2)?;
    let ended: Option<String> = r.get(3)?;
    Ok(SessionRow {
        id: r.get(0)?,
        ulid: r.get(1)?,
        started_at: parse_rfc3339(&started),
        ended_at: ended.as_deref().map(parse_rfc3339),
        engine_base_url: r.get(4)?,
        cli_version: r.get(5)?,
        parent_ulid: r.get(6)?,
    })
}

fn parse_rfc3339(s: &str) -> DateTime<Utc> {
    DateTime::parse_from_rfc3339(s).map_or_else(|_| Utc::now(), |dt| dt.with_timezone(&Utc))
}

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

    #[test]
    fn migrations_are_idempotent() {
        // Open twice — second open should replay migrations against
        // the already-migrated DB without errors.
        let s1 = Store::open_in_memory().unwrap();
        drop(s1);
        let _s2 = Store::open_in_memory().unwrap();
    }

    #[test]
    fn append_and_list_round_trip() {
        let s = Store::open_in_memory().unwrap();
        let sid = s
            .start_session("01HTEST", Some("http://x"), "0.3.0", None)
            .unwrap();
        let seq1 = s.append(sid, EventKind::Prompt, "> hello").unwrap();
        let seq2 = s.append(sid, EventKind::System, "welcome").unwrap();
        let seq3 = s.append(sid, EventKind::Command, "status ok").unwrap();
        assert_eq!((seq1, seq2, seq3), (1, 2, 3));

        let events = s.list_events(sid, 100).unwrap();
        assert_eq!(events.len(), 3);
        assert_eq!(events[0].kind, EventKind::Prompt);
        assert_eq!(events[2].text, "status ok");
    }

    #[test]
    fn list_events_returns_tail_in_order() {
        let s = Store::open_in_memory().unwrap();
        let sid = s.start_session("01HTAIL", None, "0.3.0", None).unwrap();
        for i in 0..10 {
            s.append(sid, EventKind::System, &format!("line {i}"))
                .unwrap();
        }
        let tail = s.list_events(sid, 3).unwrap();
        assert_eq!(tail.len(), 3);
        assert_eq!(tail[0].text, "line 7");
        assert_eq!(tail[2].text, "line 9");
    }

    #[test]
    fn last_session_is_most_recent() {
        let s = Store::open_in_memory().unwrap();
        s.start_session("01HA", None, "0.3.0", None).unwrap();
        // Sleep one ms so started_at differs. Chrono's RFC-3339
        // output has ms granularity; same-ms rows would sort by id.
        std::thread::sleep(std::time::Duration::from_millis(2));
        s.start_session("01HB", None, "0.3.0", None).unwrap();

        let last = s.last_session().unwrap().unwrap();
        assert_eq!(last.ulid, "01HB");
    }

    #[test]
    fn end_session_is_idempotent() {
        let s = Store::open_in_memory().unwrap();
        let sid = s.start_session("01HEND", None, "0.3.0", None).unwrap();
        s.end_session(sid).unwrap();
        let first_ended = s.last_session().unwrap().unwrap().ended_at;
        s.end_session(sid).unwrap();
        let second_ended = s.last_session().unwrap().unwrap().ended_at;
        assert_eq!(first_ended, second_ended);
    }

    #[test]
    fn milestones_upsert_and_read() {
        let s = Store::open_in_memory().unwrap();
        assert_eq!(s.get_milestone("welcome_shown").unwrap(), None);
        s.set_milestone("welcome_shown", "true").unwrap();
        assert_eq!(
            s.get_milestone("welcome_shown").unwrap().as_deref(),
            Some("true")
        );
        // Overwrite.
        s.set_milestone("welcome_shown", "skipped").unwrap();
        assert_eq!(
            s.get_milestone("welcome_shown").unwrap().as_deref(),
            Some("skipped")
        );
    }

    #[test]
    fn unknown_event_kind_is_rejected_by_schema() {
        let s = Store::open_in_memory().unwrap();
        let sid = s.start_session("01HBAD", None, "0.3.0", None).unwrap();
        let conn = s.conn.lock().unwrap();
        let res = conn.execute(
            "INSERT INTO events (session_id, seq, at, kind, text) VALUES (?1, 1, ?2, ?3, ?4)",
            params![sid, Utc::now().to_rfc3339(), "bogus", "x"],
        );
        assert!(res.is_err(), "CHECK constraint should reject unknown kind");
    }

    #[test]
    fn list_sessions_honors_limit_and_is_newest_first() {
        let s = Store::open_in_memory().unwrap();
        s.start_session("01HA", None, "0.3.0", None).unwrap();
        std::thread::sleep(std::time::Duration::from_millis(2));
        s.start_session("01HB", None, "0.3.0", None).unwrap();
        std::thread::sleep(std::time::Duration::from_millis(2));
        s.start_session("01HC", None, "0.3.0", None).unwrap();

        let all = s.list_sessions(10).unwrap();
        assert_eq!(all.len(), 3);
        assert_eq!(
            all.iter().map(|r| r.ulid.as_str()).collect::<Vec<_>>(),
            vec!["01HC", "01HB", "01HA"],
            "list_sessions must be newest-first",
        );

        let top = s.list_sessions(1).unwrap();
        assert_eq!(top.len(), 1);
        assert_eq!(top[0].ulid, "01HC");

        // Zero limit is a no-op — must not hit the DB or produce rows.
        assert!(s.list_sessions(0).unwrap().is_empty());
    }

    #[test]
    fn get_session_by_ulid_round_trips_and_misses_cleanly() {
        let s = Store::open_in_memory().unwrap();
        s.start_session("01HFOUND", Some("http://e"), "0.3.0", None)
            .unwrap();
        let hit = s.get_session_by_ulid("01HFOUND").unwrap();
        assert!(hit.is_some());
        assert_eq!(hit.unwrap().ulid, "01HFOUND");
        // Missing ulid returns Ok(None), not an error — callers should
        // format a friendly "no such session" line, not crash.
        assert!(s.get_session_by_ulid("01HMISSING").unwrap().is_none());
    }

    #[test]
    fn count_events_matches_append_count() {
        let s = Store::open_in_memory().unwrap();
        let sid = s.start_session("01HCNT", None, "0.3.0", None).unwrap();
        assert_eq!(s.count_events(sid).unwrap(), 0);
        for i in 0..5 {
            s.append(sid, EventKind::System, &format!("line {i}"))
                .unwrap();
        }
        assert_eq!(s.count_events(sid).unwrap(), 5);
    }

    #[test]
    fn parent_ulid_records_fork_link() {
        let s = Store::open_in_memory().unwrap();
        let _parent = s.start_session("01HP", None, "0.3.0", None).unwrap();
        let _child = s
            .start_session("01HC", None, "0.3.0", Some("01HP"))
            .unwrap();
        let last = s.last_session().unwrap().unwrap();
        assert_eq!(last.parent_ulid.as_deref(), Some("01HP"));
    }
}