rto-graph 0.0.5

//! SQLite-backed graph store.

use std::path::Path;

use rusqlite::{Connection, OptionalExtension, params};

use crate::migrations;
use crate::model::{Direction, Edge, EdgeKind, FactSet, Node, NodeKind, Span};
use crate::provenance::Provenance;

/// Errors raised by the store.
#[derive(Debug, thiserror::Error)]
pub enum StoreError {
    /// Underlying `SQLite` failure.
    #[error("sqlite error: {0}")]
    Sqlite(#[from] rusqlite::Error),
    /// A node's `meta` could not be (de)serialized as JSON.
    #[error("json error: {0}")]
    Json(#[from] serde_json::Error),
    /// An edge referenced a node key that does not exist in the store.
    #[error("unknown node key: {0}")]
    UnknownNode(String),
    /// An edge violated the provenance/confidence invariant.
    #[error("invalid edge: {0}")]
    InvalidEdge(String),
    /// A stored value could not be interpreted (database corruption).
    #[error("corrupt store: {0}")]
    Corrupt(String),
}

/// Qualified node columns for `SELECT`s that alias the `nodes` table as `n`.
const NODE_COLS: &str =
    "n.key, n.kind, n.name, n.path, n.lang, n.blob_hash, n.span_start, n.span_end, n.meta";

/// `SELECT` prefix that yields an [`Edge`] row (endpoints resolved back to keys).
const EDGE_SELECT: &str = "SELECT ns.key AS src, nd.key AS dst, e.kind, e.provenance, \
     e.confidence, e.src_ref \
     FROM edges e JOIN nodes ns ON ns.id = e.src JOIN nodes nd ON nd.id = e.dst";

/// A Roteiro graph store backed by a single `SQLite` database.
pub struct Store {
    conn: Connection,
}

impl Store {
    /// Open (creating if absent) a store at `path` and apply pending migrations.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] if the database cannot be opened or a
    /// migration fails.
    pub fn open(path: &Path) -> Result<Self, StoreError> {
        let conn = Connection::open(path)?;
        Self::from_conn(conn)
    }

    /// Open an in-memory store (tests, previews).
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] if a migration fails.
    pub fn open_in_memory() -> Result<Self, StoreError> {
        let conn = Connection::open_in_memory()?;
        Self::from_conn(conn)
    }

    fn from_conn(mut conn: Connection) -> Result<Self, StoreError> {
        conn.execute_batch("PRAGMA foreign_keys = ON;")?;
        migrations::apply(&mut conn)?;
        Ok(Self { conn })
    }

    /// The schema version this store has been migrated to.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] on query failure.
    pub fn schema_version(&self) -> Result<u32, StoreError> {
        let v: i64 = self.conn.query_row(
            "SELECT COALESCE(MAX(version), 0) FROM schema_migrations",
            [],
            |r| r.get(0),
        )?;
        Ok(u32::try_from(v).unwrap_or(0))
    }

    /// Number of nodes currently in the store.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] on query failure.
    pub fn node_count(&self) -> Result<u64, StoreError> {
        let n: i64 = self
            .conn
            .query_row("SELECT COUNT(*) FROM nodes", [], |r| r.get(0))?;
        Ok(u64::try_from(n).unwrap_or(0))
    }

    /// Number of edges currently in the store.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] on query failure.
    pub fn edge_count(&self) -> Result<u64, StoreError> {
        let n: i64 = self
            .conn
            .query_row("SELECT COUNT(*) FROM edges", [], |r| r.get(0))?;
        Ok(u64::try_from(n).unwrap_or(0))
    }

    /// Insert or update a node, keyed by its natural [`Node::key`].
    ///
    /// # Errors
    /// Returns [`StoreError::Json`] if `meta` cannot be serialized, or
    /// [`StoreError::Sqlite`] on write failure.
    pub fn upsert_node(&self, node: &Node) -> Result<(), StoreError> {
        upsert_node(&self.conn, node)
    }

    /// Insert an edge. Both endpoints must already resolve to nodes.
    ///
    /// # Errors
    /// Returns [`StoreError::InvalidEdge`] if the provenance/confidence
    /// invariant is violated, [`StoreError::UnknownNode`] if an endpoint key is
    /// absent, or [`StoreError::Sqlite`] on write failure.
    pub fn insert_edge(&self, edge: &Edge) -> Result<(), StoreError> {
        insert_edge(&self.conn, edge)
    }

    /// Apply a fact set atomically: all nodes are upserted, then all edges are
    /// inserted, in a single transaction. On any error nothing is committed.
    ///
    /// # Errors
    /// Returns the first error encountered (see [`Store::upsert_node`] and
    /// [`Store::insert_edge`]); the transaction is rolled back.
    pub fn apply_factset(&mut self, facts: &FactSet) -> Result<(), StoreError> {
        let tx = self.conn.transaction()?;
        for node in &facts.nodes {
            upsert_node(&tx, node)?;
        }
        for edge in &facts.edges {
            insert_edge(&tx, edge)?;
        }
        tx.commit()?;
        Ok(())
    }

    /// The `HEAD` tree id recorded at the last successful [`Store::rebuild`], if
    /// any. Used by the sync engine to detect an unchanged tree.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] on query failure.
    pub fn sync_state(&self) -> Result<Option<String>, StoreError> {
        Ok(self
            .conn
            .query_row("SELECT tree FROM sync_state WHERE id = 0", [], |r| r.get(0))
            .optional()?)
    }

    /// Atomically replace the entire graph with `facts` and record `tree` as the
    /// synced state. All existing nodes and edges are deleted first, so the
    /// store reflects exactly the given fact set.
    ///
    /// # Errors
    /// Returns the first error encountered (see [`Store::apply_factset`]); on any
    /// error nothing is committed.
    pub fn rebuild(&mut self, facts: &FactSet, tree: &str) -> Result<(), StoreError> {
        let tx = self.conn.transaction()?;
        tx.execute("DELETE FROM edges", [])?;
        tx.execute("DELETE FROM nodes", [])?;
        for node in &facts.nodes {
            upsert_node(&tx, node)?;
        }
        for edge in &facts.edges {
            insert_edge(&tx, edge)?;
        }
        tx.execute(
            "INSERT INTO sync_state (id, tree) VALUES (0, ?1)
             ON CONFLICT(id) DO UPDATE SET tree = excluded.tree",
            [tree],
        )?;
        tx.commit()?;
        Ok(())
    }

    /// Fetch a node by its natural key.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`], [`StoreError::Json`], or
    /// [`StoreError::Corrupt`] if a stored value cannot be decoded.
    pub fn get_node(&self, key: &str) -> Result<Option<Node>, StoreError> {
        let sql = format!("SELECT {NODE_COLS} FROM nodes n WHERE n.key = ?1");
        let mut stmt = self.conn.prepare(&sql)?;
        let mut rows = stmt.query([key])?;
        match rows.next()? {
            Some(row) => Ok(Some(row_to_node(row)?)),
            None => Ok(None),
        }
    }

    /// All nodes of a given kind.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`], [`StoreError::Json`], or
    /// [`StoreError::Corrupt`] on decode failure.
    pub fn nodes_by_kind(&self, kind: &NodeKind) -> Result<Vec<Node>, StoreError> {
        let sql = format!("SELECT {NODE_COLS} FROM nodes n WHERE n.kind = ?1 ORDER BY n.key");
        let mut stmt = self.conn.prepare(&sql)?;
        let mut rows = stmt.query([kind.as_str()])?;
        collect_nodes(&mut rows)
    }

    /// Edges whose source is the node with the given key.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] or [`StoreError::Corrupt`] on failure.
    pub fn edges_from(&self, key: &str) -> Result<Vec<Edge>, StoreError> {
        let sql = format!("{EDGE_SELECT} WHERE ns.key = ?1 ORDER BY e.id");
        let mut stmt = self.conn.prepare(&sql)?;
        let mut rows = stmt.query([key])?;
        collect_edges(&mut rows)
    }

    /// Edges whose destination is the node with the given key.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] or [`StoreError::Corrupt`] on failure.
    pub fn edges_to(&self, key: &str) -> Result<Vec<Edge>, StoreError> {
        let sql = format!("{EDGE_SELECT} WHERE nd.key = ?1 ORDER BY e.id");
        let mut stmt = self.conn.prepare(&sql)?;
        let mut rows = stmt.query([key])?;
        collect_edges(&mut rows)
    }

    /// All edges with the given provenance.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`] or [`StoreError::Corrupt`] on failure.
    pub fn edges_by_provenance(&self, provenance: Provenance) -> Result<Vec<Edge>, StoreError> {
        let sql = format!("{EDGE_SELECT} WHERE e.provenance = ?1 ORDER BY e.id");
        let mut stmt = self.conn.prepare(&sql)?;
        let mut rows = stmt.query([provenance.as_str()])?;
        collect_edges(&mut rows)
    }

    /// Neighbouring nodes reachable from `key` in the given direction. Returns
    /// an empty vector if the node does not exist.
    ///
    /// # Errors
    /// Returns [`StoreError::Sqlite`], [`StoreError::Json`], or
    /// [`StoreError::Corrupt`] on failure.
    pub fn neighbors(&self, key: &str, dir: Direction) -> Result<Vec<Node>, StoreError> {
        let out = format!(
            "SELECT {NODE_COLS} FROM nodes n JOIN edges e ON n.id = e.dst \
             JOIN nodes s ON s.id = e.src WHERE s.key = ?1"
        );
        let inc = format!(
            "SELECT {NODE_COLS} FROM nodes n JOIN edges e ON n.id = e.src \
             JOIN nodes d ON d.id = e.dst WHERE d.key = ?1"
        );
        // Order by output column 1 (the node key) so results are deterministic
        // across SQLite versions/plans. Positional ordering avoids both the
        // ambiguity of a bare `key` (present in every joined table) and the fact
        // that a table-qualified name cannot be used after the `Both` UNION.
        let sql = match dir {
            Direction::Outgoing => format!("{out} ORDER BY 1"),
            Direction::Incoming => format!("{inc} ORDER BY 1"),
            Direction::Both => format!("{out} UNION {inc} ORDER BY 1"),
        };
        let mut stmt = self.conn.prepare(&sql)?;
        let mut rows = stmt.query([key])?;
        collect_nodes(&mut rows)
    }
}

// --- Free helpers operating on a `Connection` (a `Transaction` derefs to one) ---

fn node_row_id(conn: &Connection, key: &str) -> rusqlite::Result<Option<i64>> {
    conn.query_row("SELECT id FROM nodes WHERE key = ?1", [key], |r| r.get(0))
        .optional()
}

fn upsert_node(conn: &Connection, node: &Node) -> Result<(), StoreError> {
    let meta = serde_json::to_string(&node.meta)?;
    let (span_start, span_end) = match node.span {
        Some(s) => (Some(i64::from(s.start)), Some(i64::from(s.end))),
        None => (None, None),
    };
    conn.execute(
        "INSERT INTO nodes (key, kind, name, path, lang, blob_hash, span_start, span_end, meta)
         VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9)
         ON CONFLICT(key) DO UPDATE SET
             kind = excluded.kind, name = excluded.name, path = excluded.path,
             lang = excluded.lang, blob_hash = excluded.blob_hash,
             span_start = excluded.span_start, span_end = excluded.span_end,
             meta = excluded.meta",
        params![
            node.key,
            node.kind.as_str(),
            node.name,
            node.path,
            node.lang,
            node.blob_hash,
            span_start,
            span_end,
            meta,
        ],
    )?;
    Ok(())
}

fn insert_edge(conn: &Connection, edge: &Edge) -> Result<(), StoreError> {
    if !edge.is_valid() {
        return Err(StoreError::InvalidEdge(format!(
            "confidence must be present iff provenance is inferred (src={}, dst={})",
            edge.src, edge.dst
        )));
    }
    let src_id =
        node_row_id(conn, &edge.src)?.ok_or_else(|| StoreError::UnknownNode(edge.src.clone()))?;
    let dst_id =
        node_row_id(conn, &edge.dst)?.ok_or_else(|| StoreError::UnknownNode(edge.dst.clone()))?;
    conn.execute(
        "INSERT INTO edges (src, dst, kind, provenance, confidence, src_ref)
         VALUES (?1, ?2, ?3, ?4, ?5, ?6)",
        params![
            src_id,
            dst_id,
            edge.kind.as_str(),
            edge.provenance.as_str(),
            edge.confidence,
            edge.src_ref,
        ],
    )?;
    Ok(())
}

fn collect_nodes(rows: &mut rusqlite::Rows) -> Result<Vec<Node>, StoreError> {
    let mut out = Vec::new();
    while let Some(row) = rows.next()? {
        out.push(row_to_node(row)?);
    }
    Ok(out)
}

fn collect_edges(rows: &mut rusqlite::Rows) -> Result<Vec<Edge>, StoreError> {
    let mut out = Vec::new();
    while let Some(row) = rows.next()? {
        out.push(row_to_edge(row)?);
    }
    Ok(out)
}

fn row_to_node(row: &rusqlite::Row) -> Result<Node, StoreError> {
    let kind: String = row.get("kind")?;
    let span_start: Option<i64> = row.get("span_start")?;
    let span_end: Option<i64> = row.get("span_end")?;
    let span = match (span_start, span_end) {
        (Some(s), Some(e)) => Some(Span::new(to_u32(s)?, to_u32(e)?)),
        _ => None,
    };
    let meta: String = row.get("meta")?;
    Ok(Node {
        key: row.get("key")?,
        kind: NodeKind::from_token(&kind),
        name: row.get("name")?,
        path: row.get("path")?,
        lang: row.get("lang")?,
        blob_hash: row.get("blob_hash")?,
        span,
        meta: serde_json::from_str(&meta)?,
    })
}

fn row_to_edge(row: &rusqlite::Row) -> Result<Edge, StoreError> {
    let kind: String = row.get("kind")?;
    let provenance: String = row.get("provenance")?;
    let provenance = Provenance::from_token(&provenance)
        .ok_or_else(|| StoreError::Corrupt(format!("unknown provenance: {provenance}")))?;
    Ok(Edge {
        src: row.get("src")?,
        dst: row.get("dst")?,
        kind: EdgeKind::from_token(&kind),
        provenance,
        confidence: row.get("confidence")?,
        src_ref: row.get("src_ref")?,
    })
}

fn to_u32(v: i64) -> Result<u32, StoreError> {
    u32::try_from(v).map_err(|_| StoreError::Corrupt(format!("span offset out of range: {v}")))
}

#[cfg(test)]
mod tests {
    use super::Store;
    use crate::model::{Direction, Edge, EdgeKind, FactSet, Node, NodeKind, Span};
    use crate::provenance::Provenance;

    fn sample_node(key: &str) -> Node {
        Node {
            key: key.to_owned(),
            kind: NodeKind::Fn,
            name: "sample".to_owned(),
            path: Some("src/lib.rs".to_owned()),
            lang: Some("rust".to_owned()),
            blob_hash: Some("deadbeef".to_owned()),
            span: Some(Span::new(10, 42)),
            meta: serde_json::json!({"vis": "pub"}),
        }
    }

    #[test]
    fn open_in_memory_applies_schema() {
        let store = Store::open_in_memory().expect("open");
        assert_eq!(store.node_count().expect("count"), 0);
        assert_eq!(store.schema_version().expect("version"), 2);
    }

    #[test]
    fn upsert_and_get_round_trips_all_fields() {
        let store = Store::open_in_memory().expect("open");
        let node = sample_node("sym:rust:src/lib.rs#sample");
        store.upsert_node(&node).expect("upsert");
        let got = store.get_node(&node.key).expect("get").expect("present");
        assert_eq!(got, node);
    }

    #[test]
    fn upsert_updates_in_place() {
        let store = Store::open_in_memory().expect("open");
        let mut node = sample_node("k");
        store.upsert_node(&node).expect("insert");
        node.name = "renamed".to_owned();
        node.kind = NodeKind::Struct;
        store.upsert_node(&node).expect("update");
        assert_eq!(store.node_count().expect("count"), 1);
        let got = store.get_node("k").expect("get").expect("present");
        assert_eq!(got.name, "renamed");
        assert_eq!(got.kind, NodeKind::Struct);
    }

    #[test]
    fn edge_with_unknown_endpoint_is_rejected() {
        let store = Store::open_in_memory().expect("open");
        store
            .upsert_node(&Node::new("a", NodeKind::Fn, "a"))
            .expect("a");
        let edge = Edge::derived("a", "missing", EdgeKind::Calls);
        let err = store.insert_edge(&edge).expect_err("should reject");
        assert!(matches!(err, super::StoreError::UnknownNode(k) if k == "missing"));
    }

    #[test]
    fn inferred_edge_requires_confidence() {
        let store = Store::open_in_memory().expect("open");
        store
            .upsert_node(&Node::new("a", NodeKind::Fn, "a"))
            .expect("a");
        store
            .upsert_node(&Node::new("b", NodeKind::Fn, "b"))
            .expect("b");
        // Hand-build an inferred edge with no confidence to violate the invariant.
        let bad = Edge {
            src: "a".to_owned(),
            dst: "b".to_owned(),
            kind: EdgeKind::References,
            provenance: Provenance::Inferred,
            confidence: None,
            src_ref: None,
        };
        assert!(matches!(
            store.insert_edge(&bad).expect_err("reject"),
            super::StoreError::InvalidEdge(_)
        ));
    }

    #[test]
    fn apply_factset_is_atomic() {
        let mut store = Store::open_in_memory().expect("open");
        // Second edge references a missing node, so the whole set must roll back.
        let facts = FactSet::new()
            .with_node(Node::new("a", NodeKind::Fn, "a"))
            .with_node(Node::new("b", NodeKind::Fn, "b"))
            .with_edge(Edge::derived("a", "b", EdgeKind::Calls))
            .with_edge(Edge::derived("a", "ghost", EdgeKind::Calls));
        assert!(store.apply_factset(&facts).is_err());
        assert_eq!(store.node_count().expect("count"), 0, "rolled back");
        assert_eq!(store.edge_count().expect("count"), 0, "rolled back");
    }

    #[test]
    fn neighbors_and_provenance_queries() {
        let mut store = Store::open_in_memory().expect("open");
        let facts = FactSet::new()
            .with_node(Node::new("a", NodeKind::Fn, "a"))
            .with_node(Node::new("b", NodeKind::Fn, "b"))
            .with_node(Node::new("c", NodeKind::Fn, "c"))
            .with_edge(Edge::derived("a", "b", EdgeKind::Calls))
            .with_edge(Edge::inferred("a", "c", EdgeKind::References, 0.5));
        store.apply_factset(&facts).expect("apply");

        let out = store.neighbors("a", Direction::Outgoing).expect("out");
        let mut keys: Vec<_> = out.iter().map(|n| n.key.clone()).collect();
        keys.sort();
        assert_eq!(keys, ["b", "c"]);

        assert!(
            store
                .neighbors("b", Direction::Outgoing)
                .expect("b out")
                .is_empty()
        );
        assert_eq!(
            store
                .neighbors("b", Direction::Incoming)
                .expect("b in")
                .len(),
            1
        );

        let inferred = store
            .edges_by_provenance(Provenance::Inferred)
            .expect("inf");
        assert_eq!(inferred.len(), 1);
        assert_eq!(inferred[0].confidence, Some(0.5));
    }

    #[test]
    fn neighbors_of_absent_node_is_empty() {
        let store = Store::open_in_memory().expect("open");
        assert!(
            store
                .neighbors("nope", Direction::Both)
                .expect("q")
                .is_empty()
        );
    }

    #[test]
    fn get_missing_node_is_none() {
        let store = Store::open_in_memory().expect("open");
        assert!(store.get_node("absent").expect("get").is_none());
    }

    #[test]
    fn nodes_by_kind_and_edges_to() {
        let mut store = Store::open_in_memory().expect("open");
        let facts = FactSet::new()
            .with_node(Node::new("f1", NodeKind::Fn, "f1"))
            .with_node(Node::new("f2", NodeKind::Fn, "f2"))
            .with_node(Node::new("s1", NodeKind::Struct, "s1"))
            .with_edge(Edge::derived("f1", "s1", EdgeKind::References))
            .with_edge(Edge::derived("f2", "s1", EdgeKind::References));
        store.apply_factset(&facts).expect("apply");

        let fns = store.nodes_by_kind(&NodeKind::Fn).expect("fns");
        assert_eq!(
            fns.iter().map(|n| n.key.as_str()).collect::<Vec<_>>(),
            ["f1", "f2"]
        );
        assert!(
            store
                .nodes_by_kind(&NodeKind::Enum)
                .expect("enums")
                .is_empty()
        );

        let into_s1 = store.edges_to("s1").expect("edges_to");
        assert_eq!(into_s1.len(), 2);
        assert!(into_s1.iter().all(|e| e.dst == "s1"));
    }

    #[test]
    fn open_persists_across_reopen() {
        let path =
            std::env::temp_dir().join(format!("roteiro-open-test-{}.db", std::process::id()));
        std::fs::remove_file(&path).ok();
        {
            let store = Store::open(&path).expect("open");
            store
                .upsert_node(&sample_node("persisted"))
                .expect("upsert");
        }
        {
            let store = Store::open(&path).expect("reopen");
            assert_eq!(store.node_count().expect("count"), 1);
            assert_eq!(store.schema_version().expect("version"), 2);
            assert!(store.get_node("persisted").expect("get").is_some());
        }
        std::fs::remove_file(&path).expect("cleanup");
    }
}