mcp-pocket-memory 0.4.0

MCP server for durable AI memory backed by SQLite
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use std::{collections::BTreeSet, path::Path, time::Duration};

use rmcp::schemars;
use rusqlite::{Connection, OptionalExtension, Result, ToSql, params};
use serde::Serialize;

#[derive(Debug, Clone, Serialize, schemars::JsonSchema)]
pub struct Memory {
    pub key: String,
    pub repo: Option<String>,
    pub tags: Vec<String>,
    pub content: String,
    pub created_at: String,
    pub updated_at: String,
}

#[derive(Debug)]
pub struct Database {
    conn: Connection,
}

impl Database {
    pub fn open(path: impl AsRef<Path>) -> Result<Self> {
        let conn = Connection::open(path)?;
        conn.busy_timeout(Duration::from_secs(5))?;
        conn.pragma_update(None, "foreign_keys", "ON")?;
        conn.pragma_update(None, "journal_mode", "WAL")?;
        let db = Self { conn };
        db.init()?;
        Ok(db)
    }

    #[cfg(test)]
    fn open_in_memory() -> Result<Self> {
        let conn = Connection::open_in_memory()?;
        let db = Self { conn };
        db.init()?;
        Ok(db)
    }

    pub fn init(&self) -> Result<()> {
        self.conn.execute_batch(
            "
            CREATE TABLE IF NOT EXISTS memories (
                key TEXT PRIMARY KEY NOT NULL,
                repo TEXT,
                content TEXT NOT NULL,
                created_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
                updated_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now'))
            );

            CREATE TABLE IF NOT EXISTS memory_tags (
                memory_key TEXT NOT NULL,
                tag TEXT NOT NULL,
                PRIMARY KEY (memory_key, tag),
                FOREIGN KEY (memory_key) REFERENCES memories(key) ON DELETE CASCADE
            );
            ",
        )?;
        self.conn.execute_batch(
            "
            CREATE INDEX IF NOT EXISTS idx_memories_repo
                ON memories(repo, updated_at);

            CREATE INDEX IF NOT EXISTS idx_memories_updated_at
                ON memories(updated_at);

            CREATE INDEX IF NOT EXISTS idx_memory_tags_tag
                ON memory_tags(tag, memory_key);
            ",
        )
    }

    pub fn upsert_memory(
        &mut self,
        key: &str,
        repo: Option<&str>,
        tags: &[String],
        content: &str,
    ) -> Result<Memory> {
        let repo = normalize_repo(repo);
        let tags = normalize_tags(tags);
        let tx = self.conn.transaction()?;

        tx.execute("PRAGMA foreign_keys = ON", [])?;
        tx.execute(
            "
            INSERT INTO memories (key, repo, content)
            VALUES (?1, ?2, ?3)
            ON CONFLICT(key) DO UPDATE SET
                repo = excluded.repo,
                content = excluded.content,
                updated_at = strftime('%Y-%m-%dT%H:%M:%fZ', 'now')
            ",
            params![key, repo, content],
        )?;
        tx.execute(
            "DELETE FROM memory_tags WHERE memory_key = ?1",
            params![key],
        )?;

        for tag in tags {
            tx.execute(
                "INSERT INTO memory_tags (memory_key, tag) VALUES (?1, ?2)",
                params![key, tag],
            )?;
        }

        tx.commit()?;

        self.get_memory(key)?
            .ok_or(rusqlite::Error::QueryReturnedNoRows)
    }

    pub fn delete_memory(&mut self, key: &str) -> Result<bool> {
        let tx = self.conn.transaction()?;

        tx.execute(
            "DELETE FROM memory_tags WHERE memory_key = ?1",
            params![key],
        )?;
        let affected = tx.execute("DELETE FROM memories WHERE key = ?1", params![key])?;
        tx.commit()?;

        Ok(affected > 0)
    }

    pub fn find_memories(
        &self,
        keyword: Option<&str>,
        repo: Option<&str>,
        tags: &[String],
        limit: usize,
    ) -> Result<Vec<Memory>> {
        let keyword_terms = normalize_keyword_terms(keyword);
        let repo = normalize_repo(repo);
        let tags = normalize_tags(tags);
        let limit = limit.clamp(1, 50) as i64;

        let keys = self.find_memory_keys(&keyword_terms, repo.as_deref(), &tags, limit)?;

        keys.into_iter()
            .map(|key| {
                self.get_memory(&key)?
                    .ok_or(rusqlite::Error::QueryReturnedNoRows)
            })
            .collect()
    }

    fn get_memory(&self, key: &str) -> Result<Option<Memory>> {
        self.conn
            .query_row(
                "
                SELECT key, repo, content, created_at, updated_at
                FROM memories
                WHERE key = ?1
                ",
                params![key],
                |row| self.map_memory(row),
            )
            .optional()
    }

    fn find_memory_keys(
        &self,
        keyword_terms: &[String],
        repo: Option<&str>,
        tags: &[String],
        limit: i64,
    ) -> Result<Vec<String>> {
        let mut sql = String::from("SELECT m.key FROM memories m WHERE 1 = 1");
        let mut params = Vec::<&dyn ToSql>::new();
        let patterns = keyword_terms
            .iter()
            .map(|term| format!("%{}%", escape_like(term)))
            .collect::<Vec<_>>();
        let repo_value = repo.map(str::to_owned);
        let tag_count = tags.len() as i64;

        if !patterns.is_empty() {
            sql.push_str(" AND (");
            for index in 0..patterns.len() {
                if index > 0 {
                    sql.push_str(" OR ");
                }
                sql.push_str(
                    "
                    m.key LIKE ? ESCAPE '\\'
                    OR m.content LIKE ? ESCAPE '\\'
                    OR m.repo LIKE ? ESCAPE '\\'
                    OR EXISTS (
                        SELECT 1
                        FROM memory_tags mt
                        WHERE mt.memory_key = m.key
                            AND mt.tag LIKE ? ESCAPE '\\'
                    )
                    ",
                );
            }
            sql.push(')');

            for pattern in &patterns {
                params.push(pattern);
                params.push(pattern);
                params.push(pattern);
                params.push(pattern);
            }
        }

        if let Some(repo) = repo_value.as_ref() {
            sql.push_str(" AND m.repo = ?");
            params.push(repo);
        }

        if !tags.is_empty() {
            sql.push_str(
                "
                AND m.key IN (
                    SELECT memory_key
                    FROM memory_tags
                    WHERE tag IN (",
            );
            append_placeholders(&mut sql, tags.len());
            sql.push_str(
                ")
                    GROUP BY memory_key
                    HAVING COUNT(DISTINCT tag) = ?
                )",
            );
            params.extend(tags.iter().map(|tag| tag as &dyn ToSql));
            params.push(&tag_count);
        }

        sql.push_str(" ORDER BY m.updated_at DESC, m.key ASC LIMIT ?");
        params.push(&limit);

        let mut stmt = self.conn.prepare(&sql)?;
        let rows = stmt.query_map(rusqlite::params_from_iter(params), |row| row.get(0))?;
        rows.collect()
    }

    fn map_memory(&self, row: &rusqlite::Row<'_>) -> Result<Memory> {
        let key = row.get::<_, String>(0)?;
        Ok(Memory {
            repo: row.get(1)?,
            tags: self.get_tags(&key)?,
            key,
            content: row.get(2)?,
            created_at: row.get(3)?,
            updated_at: row.get(4)?,
        })
    }

    fn get_tags(&self, key: &str) -> Result<Vec<String>> {
        let mut stmt = self.conn.prepare(
            "
            SELECT tag
            FROM memory_tags
            WHERE memory_key = ?1
            ORDER BY tag ASC
            ",
        )?;

        let rows = stmt.query_map(params![key], |row| row.get(0))?;
        rows.collect()
    }
}

fn append_placeholders(sql: &mut String, count: usize) {
    for index in 0..count {
        if index > 0 {
            sql.push_str(", ");
        }
        sql.push('?');
    }
}

fn normalize_tags(tags: &[String]) -> Vec<String> {
    tags.iter()
        .map(|tag| tag.trim().to_lowercase())
        .filter(|tag| !tag.is_empty())
        .collect::<BTreeSet<_>>()
        .into_iter()
        .collect()
}

fn normalize_repo(repo: Option<&str>) -> Option<String> {
    repo.map(str::trim)
        .filter(|repo| !repo.is_empty())
        .map(str::to_lowercase)
}

fn normalize_keyword_terms(keyword: Option<&str>) -> Vec<String> {
    keyword
        .unwrap_or_default()
        .split_whitespace()
        .map(normalize_keyword_term)
        .filter(|term| !term.is_empty())
        .collect::<BTreeSet<_>>()
        .into_iter()
        .collect()
}

fn normalize_keyword_term(term: &str) -> String {
    term.trim()
        .trim_matches(|ch: char| ch.is_ascii_punctuation() && ch != '-' && ch != '_' && ch != '%')
        .to_lowercase()
}

fn escape_like(keyword: &str) -> String {
    keyword
        .replace('\\', "\\\\")
        .replace('%', "\\%")
        .replace('_', "\\_")
}

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

    #[test]
    fn upsert_inserts_and_updates_memory() {
        let mut db = Database::open_in_memory().unwrap();

        let inserted = db
            .upsert_memory("project-style", None, &[], "follow existing pattern")
            .unwrap();
        let updated = db
            .upsert_memory("project-style", None, &[], "keep implementation simple")
            .unwrap();

        assert_eq!(inserted.key, "project-style");
        assert_eq!(updated.key, "project-style");
        assert_eq!(updated.content, "keep implementation simple");
        assert_eq!(inserted.created_at, updated.created_at);
    }

    #[test]
    fn find_memories_matches_key_or_content() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory("rust", None, &[], "sqlite memory store")
            .unwrap();
        db.upsert_memory("mcp", None, &[], "tool server").unwrap();

        let by_key = db.find_memories(Some("rust"), None, &[], 10).unwrap();
        let by_content = db.find_memories(Some("tool"), None, &[], 10).unwrap();

        assert_eq!(by_key.len(), 1);
        assert_eq!(by_key[0].key, "rust");
        assert_eq!(by_content.len(), 1);
        assert_eq!(by_content[0].key, "mcp");
    }

    #[test]
    fn delete_memory_reports_whether_row_existed() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory("temp", None, &[], "delete me").unwrap();

        assert!(db.delete_memory("temp").unwrap());
        assert!(!db.delete_memory("temp").unwrap());
    }

    #[test]
    fn find_memories_matches_tags() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory(
            "rust-style",
            None,
            &["rust".into(), "style".into()],
            "use fmt",
        )
        .unwrap();
        db.upsert_memory(
            "mcp-style",
            None,
            &["mcp".into(), "style".into()],
            "tool schema",
        )
        .unwrap();

        let by_one_tag = db.find_memories(None, None, &["rust".into()], 10).unwrap();
        let by_all_tags = db
            .find_memories(None, None, &["style".into(), "mcp".into()], 10)
            .unwrap();

        assert_eq!(by_one_tag.len(), 1);
        assert_eq!(by_one_tag[0].key, "rust-style");
        assert_eq!(by_one_tag[0].tags, vec!["rust", "style"]);
        assert_eq!(by_all_tags.len(), 1);
        assert_eq!(by_all_tags[0].key, "mcp-style");
    }

    #[test]
    fn upsert_replaces_tags() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory("memory", None, &["old".into()], "value")
            .unwrap();
        db.upsert_memory("memory", None, &["new".into()], "value")
            .unwrap();

        assert!(
            db.find_memories(None, None, &["old".into()], 10)
                .unwrap()
                .is_empty()
        );
        assert_eq!(
            db.find_memories(None, None, &["new".into()], 10).unwrap()[0].key,
            "memory"
        );
    }

    #[test]
    fn find_memories_matches_repo() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory(
            "gateway-login",
            Some("infinity-gateway"),
            &["login".into()],
            "sync contact from access",
        )
        .unwrap();
        db.upsert_memory(
            "kira-session",
            Some("kira"),
            &["session".into()],
            "persist reasoning",
        )
        .unwrap();

        let gateway = db
            .find_memories(None, Some("infinity-gateway"), &[], 10)
            .unwrap();
        let kira = db
            .find_memories(Some("persist"), Some("kira"), &[], 10)
            .unwrap();

        assert_eq!(gateway.len(), 1);
        assert_eq!(gateway[0].key, "gateway-login");
        assert_eq!(gateway[0].repo.as_deref(), Some("infinity-gateway"));
        assert_eq!(kira.len(), 1);
        assert_eq!(kira[0].key, "kira-session");
    }

    #[test]
    fn find_memories_matches_repo_and_tags() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory(
            "gateway-login",
            Some("infinity-gateway"),
            &["login".into(), "contact".into()],
            "sync contact from access",
        )
        .unwrap();
        db.upsert_memory(
            "gateway-token",
            Some("infinity-gateway"),
            &["auth".into()],
            "token refresh",
        )
        .unwrap();
        db.upsert_memory(
            "kira-contact",
            Some("kira"),
            &["contact".into()],
            "unrelated repo",
        )
        .unwrap();

        let memories = db
            .find_memories(None, Some("infinity-gateway"), &["contact".into()], 10)
            .unwrap();

        assert_eq!(memories.len(), 1);
        assert_eq!(memories[0].key, "gateway-login");
    }

    #[test]
    fn find_memories_without_filters_returns_recent_context() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory(
            "first-memory",
            Some("repo-a"),
            &["decision".into()],
            "first context",
        )
        .unwrap();
        db.upsert_memory(
            "second-memory",
            Some("repo-b"),
            &["bug".into()],
            "second context",
        )
        .unwrap();

        let memories = db.find_memories(None, None, &[], 10).unwrap();

        assert_eq!(memories.len(), 2);
    }

    #[test]
    fn find_memories_matches_keyword_terms_across_content_repo_and_tags() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory(
            "gateway-token",
            Some("infinity-gateway"),
            &["auth".into()],
            "token refresh rule",
        )
        .unwrap();
        db.upsert_memory(
            "kira-session",
            Some("kira"),
            &["persistence".into()],
            "reasoning must be restored",
        )
        .unwrap();

        let memories = db
            .find_memories(Some("gateway reasoning"), None, &[], 10)
            .unwrap();
        let keys = memories
            .into_iter()
            .map(|memory| memory.key)
            .collect::<BTreeSet<_>>();

        assert!(keys.contains("gateway-token"));
        assert!(keys.contains("kira-session"));
    }

    #[test]
    fn find_memories_matches_quoted_keyword_terms() {
        let mut db = Database::open_in_memory().unwrap();
        db.upsert_memory(
            "duplicate-tags",
            Some("mcp-pocket-memory"),
            &["edge-case".into()],
            "Memory dengan duplicate tags di array",
        )
        .unwrap();

        let memories = db
            .find_memories(Some("\"duplicate tags\""), None, &[], 10)
            .unwrap();

        assert_eq!(memories.len(), 1);
        assert_eq!(memories[0].key, "duplicate-tags");
    }

    #[test]
    fn file_connections_support_parallel_writes() {
        let db_path = std::env::temp_dir().join(format!(
            "mcp-pocket-memory-parallel-{}.sqlite3",
            std::process::id()
        ));
        let _ = std::fs::remove_file(&db_path);
        Database::open(&db_path).unwrap();

        std::thread::scope(|scope| {
            for index in 0..8 {
                let db_path = db_path.clone();
                scope.spawn(move || {
                    let mut db = Database::open(&db_path).unwrap();
                    db.upsert_memory(
                        &format!("parallel-memory-{index}"),
                        Some("parallel-repo"),
                        &["parallel".into()],
                        &format!("parallel content {index}"),
                    )
                    .unwrap();
                });
            }
        });

        let db = Database::open(&db_path).unwrap();
        let memories = db
            .find_memories(None, Some("parallel-repo"), &[], 20)
            .unwrap();
        let _ = std::fs::remove_file(&db_path);
        let _ = std::fs::remove_file(db_path.with_extension("sqlite3-wal"));
        let _ = std::fs::remove_file(db_path.with_extension("sqlite3-shm"));

        assert_eq!(memories.len(), 8);
    }
}