feat: implement SQLite storage for state messages and add message retrieval endpoint

internal/storage/sqlite.go

@@ -0,0 +1,86 @@
+package storage
+
+import (
+	"database/sql"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+// DB wraps sql.DB
+type DB struct {
+	conn *sql.DB
+}
+
+// Default is the package-level DB used by handlers
+var Default *DB
+
+// Init opens the sqlite database at path and ensures the table exists
+func Init(path string) (*DB, error) {
+	conn, err := sql.Open("sqlite3", path)
+	if err != nil {
+		return nil, err
+	}
+	// set reasonable pragmas
+	if _, err := conn.Exec("PRAGMA journal_mode=WAL;"); err != nil {
+		// ignore
+	}
+	schema := `CREATE TABLE IF NOT EXISTS messages (
+        message TEXT NOT NULL,
+        timestamp TEXT NOT NULL
+    );`
+	if _, err := conn.Exec(schema); err != nil {
+		conn.Close()
+		return nil, err
+	}
+	return &DB{conn: conn}, nil
+}
+
+// SetDefault sets the package default DB
+func SetDefault(d *DB) {
+	Default = d
+}
+
+// Close closes the underlying connection
+func (d *DB) Close() error {
+	if d == nil || d.conn == nil {
+		return nil
+	}
+	return d.conn.Close()
+}
+
+// InsertMessage inserts a message with timestamp into the DB
+func (d *DB) InsertMessage(msg string, ts time.Time) error {
+	if d == nil || d.conn == nil {
+		return nil
+	}
+	_, err := d.conn.Exec("INSERT INTO messages(message, timestamp) VALUES(?, ?)", msg, ts.Format(time.RFC3339))
+	return err
+}
+
+// Message is the returned message shape
+type Message struct {
+	Message   string `json:"message"`
+	Timestamp string `json:"timestamp"`
+}
+
+// QueryMessages returns messages ordered by newest first
+func (d *DB) QueryMessages(limit, offset int) ([]Message, error) {
+	if d == nil || d.conn == nil {
+		return nil, nil
+	}
+	rows, err := d.conn.Query("SELECT message, timestamp FROM messages ORDER BY rowid DESC LIMIT ? OFFSET ?", limit, offset)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	res := []Message{}
+	for rows.Next() {
+		var m Message
+		if err := rows.Scan(&m.Message, &m.Timestamp); err != nil {
+			return nil, err
+		}
+		res = append(res, m)
+	}
+	return res, nil
+}