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package main
import (
"database/sql"
"fmt"
"log"
"os"
"path/filepath"
"time"
_ "modernc.org/sqlite"
)
// Cache manages persistent storage of binary resources and sessions in SQLite
type Cache struct {
db *sql.DB
cacheDir string
}
// Session represents persisted MCP session state
type Session struct {
SessionID string
LastID int64
SessionDir string
ExpiresAt int64
}
// InitCache opens or creates the SQLite cache database
func InitCache(cacheDir string) (*Cache, error) {
// Create cache directory if it doesn't exist
if err := os.MkdirAll(cacheDir, 0755); err != nil {
return nil, fmt.Errorf("failed to create cache directory: %w", err)
}
// Open database
dbPath := filepath.Join(cacheDir, "resources.db")
// Pragmas travel in the DSN so they apply to every pooled connection:
// busy_timeout (a writer waits for the lock instead of failing with
// SQLITE_BUSY), and WAL so readers do not block the writer. A post-open
// db.Exec("PRAGMA …") would only configure whichever single pooled
// connection ran it, leaving the others at SQLite's defaults.
db, err := sql.Open("sqlite",
"file:"+dbPath+"?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)")
if err != nil {
return nil, fmt.Errorf("failed to open database: %w", err)
}
// Create schema
schema := `
CREATE TABLE IF NOT EXISTS resources (
id INTEGER PRIMARY KEY AUTOINCREMENT,
filename TEXT NOT NULL,
content_type TEXT,
size INTEGER NOT NULL,
content BLOB NOT NULL,
created_at INTEGER NOT NULL,
service TEXT NOT NULL,
method TEXT NOT NULL
);
CREATE INDEX IF NOT EXISTS idx_resources_created ON resources(created_at);
CREATE TABLE IF NOT EXISTS sessions (
session_id TEXT PRIMARY KEY,
last_id INTEGER NOT NULL,
session_dir TEXT NOT NULL,
expires_at INTEGER NOT NULL
);
CREATE INDEX IF NOT EXISTS idx_sessions_expires ON sessions(expires_at);
`
if _, err := db.Exec(schema); err != nil {
db.Close()
return nil, fmt.Errorf("failed to create schema: %w", err)
}
return &Cache{
db: db,
cacheDir: cacheDir,
}, nil
}
// Close closes the database connection
func (c *Cache) Close() error {
return c.db.Close()
}
// CleanOldResources deletes resources older than maxAgeSeconds
func (c *Cache) CleanOldResources(maxAgeSeconds int) error {
cutoff := time.Now().Unix() - int64(maxAgeSeconds)
result, err := c.db.Exec(`
DELETE FROM resources
WHERE created_at < ?
`, cutoff)
if err != nil {
return fmt.Errorf("failed to clean old resources: %w", err)
}
rowsAffected, _ := result.RowsAffected()
if rowsAffected > 0 {
log.Printf("Cleaned %d old resources from cache\n", rowsAffected)
}
return nil
}
// StoreResource stores a binary resource in the database
func (c *Cache) StoreResource(filename, contentType string, data []byte, service, method string) (int64, error) {
result, err := c.db.Exec(`
INSERT INTO resources (filename, content_type, size, content, created_at, service, method)
VALUES (?, ?, ?, ?, ?, ?, ?)
`, filename, contentType, len(data), data, time.Now().Unix(), service, method)
if err != nil {
return 0, fmt.Errorf("failed to store resource: %w", err)
}
id, err := result.LastInsertId()
if err != nil {
return 0, fmt.Errorf("failed to get resource ID: %w", err)
}
return id, nil
}
// ExportResourceToFile extracts a resource from the database to a temporary file
func (c *Cache) ExportResourceToFile(id int64, tempDir string) (string, error) {
var filename string
var content []byte
err := c.db.QueryRow(`
SELECT filename, content
FROM resources
WHERE id = ?
`, id).Scan(&filename, &content)
if err == sql.ErrNoRows {
return "", fmt.Errorf("resource not found: %d", id)
}
if err != nil {
return "", fmt.Errorf("failed to query resource: %w", err)
}
// Write to temp file
filePath := filepath.Join(tempDir, filename)
if err := os.WriteFile(filePath, content, 0644); err != nil {
return "", fmt.Errorf("failed to write temp file: %w", err)
}
return filePath, nil
}
// SaveSession stores or updates session state in the database
func (c *Cache) SaveSession(sessionID string, lastID int64, sessionDir string, expiresAt int64) error {
_, err := c.db.Exec(`
INSERT INTO sessions (session_id, last_id, session_dir, expires_at)
VALUES (?, ?, ?, ?)
ON CONFLICT(session_id) DO UPDATE SET
last_id = excluded.last_id,
session_dir = excluded.session_dir,
expires_at = excluded.expires_at
`, sessionID, lastID, sessionDir, expiresAt)
if err != nil {
return fmt.Errorf("failed to save session: %w", err)
}
// Clean expired sessions on every save
if err := c.CleanExpiredSessions(); err != nil {
log.Printf("Warning: failed to clean expired sessions: %v\n", err)
}
return nil
}
// LoadSession retrieves session state from the database
// Returns nil if session doesn't exist or is expired
func (c *Cache) LoadSession(sessionID string) (*Session, error) {
var session Session
err := c.db.QueryRow(`
SELECT session_id, last_id, session_dir, expires_at
FROM sessions
WHERE session_id = ? AND expires_at > ?
`, sessionID, time.Now().Unix()).Scan(
&session.SessionID,
&session.LastID,
&session.SessionDir,
&session.ExpiresAt,
)
if err == sql.ErrNoRows {
return nil, nil // Session not found or expired
}
if err != nil {
return nil, fmt.Errorf("failed to load session: %w", err)
}
return &session, nil
}
// CleanExpiredSessions deletes expired sessions and their directories
func (c *Cache) CleanExpiredSessions() error {
now := time.Now().Unix()
// Get expired session directories before deleting
rows, err := c.db.Query(`
SELECT session_dir
FROM sessions
WHERE expires_at <= ?
`, now)
if err != nil {
return fmt.Errorf("failed to query expired sessions: %w", err)
}
defer rows.Close()
var sessionDirs []string
for rows.Next() {
var dir string
if err := rows.Scan(&dir); err != nil {
continue
}
sessionDirs = append(sessionDirs, dir)
}
// Delete expired sessions from database
result, err := c.db.Exec(`
DELETE FROM sessions
WHERE expires_at <= ?
`, now)
if err != nil {
return fmt.Errorf("failed to delete expired sessions: %w", err)
}
// Delete session directories
for _, dir := range sessionDirs {
if err := os.RemoveAll(dir); err != nil {
log.Printf("Warning: failed to delete session directory %s: %v\n", dir, err)
}
}
rowsAffected, _ := result.RowsAffected()
if rowsAffected > 0 {
log.Printf("Cleaned %d expired session(s) and their directories\n", rowsAffected)
}
return nil
}
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