Add sqlite backend

sqlite/save.go

@@ -0,0 +1,61 @@
+package sqlite
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+
+	"fiatjaf.com/nostr"
+	"fiatjaf.com/nostr/eventstore"
+)
+
+func (s *SqliteBackend) SaveEvent(evt nostr.Event) error {
+	s.Lock()
+	defer s.Unlock()
+
+	// Check if event already exists
+	var existingID string
+	err := s.db.QueryRow("SELECT id FROM events WHERE id = ?", evt.ID.Hex()).Scan(&existingID)
+	if err == nil {
+		// Event already exists
+		return eventstore.ErrDupEvent
+	}
+
+	// Serialize tags to JSON
+	tagsJSON, err := json.Marshal(evt.Tags)
+	if err != nil {
+		return fmt.Errorf("failed to marshal tags: %w", err)
+	}
+
+	// Insert the event
+	query := `INSERT INTO events (id, created_at, kind, pubkey, content, tags, sig)
+              VALUES (?, ?, ?, ?, ?, ?, ?)`
+
+	_, err = s.db.Exec(query,
+		evt.ID.Hex(),
+		int64(evt.CreatedAt),
+		int(evt.Kind),
+		evt.PubKey.Hex(),
+		evt.Content,
+		string(tagsJSON),
+		hex.EncodeToString(evt.Sig[:]),
+	)
+
+	if err != nil {
+		return fmt.Errorf("failed to save event '%s': %w", evt.ID, err)
+	}
+
+	// Insert single-letter tags into event_tags table
+	for _, tag := range evt.Tags {
+		if len(tag) >= 2 && len(tag[0]) == 1 {
+			_, err := s.db.Exec("INSERT INTO event_tags (event_id, key, value) VALUES (?, ?, ?)",
+				evt.ID.Hex(), tag[0], tag[1])
+			if err != nil {
+				// Log error but don't fail the entire save operation
+				continue
+			}
+		}
+	}
+
+	return nil
+}