Cache

server/cache.go

@@ -0,0 +1,61 @@
+package server
+
+import (
+	"database/sql"
+	"time"
+	_ "github.com/mattn/go-sqlite3" // SQLite driver
+)
+
+const (
+	createTableQuery = `CREATE TABLE IF NOT EXISTS messages (
+		id VARCHAR(20) PRIMARY KEY,
+		time INT NOT NULL,
+		topic VARCHAR(64) NOT NULL,
+		message VARCHAR(1024) NOT NULL
+	)`
+	insertQuery         = `INSERT INTO messages (id, time, topic, message) VALUES (?, ?, ?, ?)`
+	pruneOlderThanQuery = `DELETE FROM messages WHERE time < ?`
+)
+
+type cache struct {
+	db *sql.DB
+	insert *sql.Stmt
+	prune *sql.Stmt
+}
+
+func newCache(filename string) (*cache, error) {
+	db, err := sql.Open("sqlite3", filename)
+	if err != nil {
+		return nil, err
+	}
+	if _, err := db.Exec(createTableQuery); err != nil {
+		return nil, err
+	}
+	insert, err := db.Prepare(insertQuery)
+	if err != nil {
+		return nil, err
+	}
+	prune, err := db.Prepare(pruneOlderThanQuery)
+	if err != nil {
+		return nil, err
+	}
+	return &cache{
+		db:     db,
+		insert: insert,
+		prune:  prune,
+	}, nil
+}
+
+func (c *cache) Load() (map[string]*topic, error) {
+
+}
+
+func (c *cache) Add(m *message) error {
+	_, err := c.insert.Exec(m.ID, m.Time, m.Topic, m.Message)
+	return err
+}
+
+func (c *cache) Prune(olderThan time.Duration) error {
+	_, err := c.prune.Exec(time.Now().Add(-1 * olderThan).Unix())
+	return err
+}