implement Replacer for sqlite3.

sqlite3/replace.go

@@ -0,0 +1,65 @@
+package sqlite3
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+
+	"github.com/fiatjaf/eventstore/internal"
+	"github.com/nbd-wtf/go-nostr"
+)
+
+func (b *SQLite3Backend) ReplaceEvent(ctx context.Context, evt *nostr.Event) error {
+	txn, err := b.DB.BeginTx(ctx, nil)
+	if err != nil {
+		return fmt.Errorf("fail to start txn: %w", err)
+	}
+
+	filter := nostr.Filter{Limit: 1, Kinds: []int{evt.Kind}, Authors: []string{evt.PubKey}}
+	if nostr.IsAddressableKind(evt.Kind) {
+		// when addressable, add the "d" tag to the filter
+		filter.Tags = nostr.TagMap{"d": []string{evt.Tags.GetD()}}
+	}
+
+	query, params, err := b.queryEventsSql(filter, false)
+	if err != nil {
+		return err
+	}
+
+	rows, err := txn.QueryContext(ctx, query, params...)
+	if err != nil && err != sql.ErrNoRows {
+		return fmt.Errorf("failed to fetch older events using query %q: %w", query, err)
+	}
+
+	shouldStore := true
+	defer rows.Close()
+	for rows.Next() {
+		var previous nostr.Event
+		var timestamp int64
+		err := rows.Scan(&previous.ID, &previous.PubKey, &timestamp,
+			&previous.Kind, &previous.Tags, &previous.Content, &previous.Sig)
+		if err != nil {
+			return fmt.Errorf("failed to scan older event row: %w", err)
+		}
+		previous.CreatedAt = nostr.Timestamp(timestamp)
+		if internal.IsOlder(&previous, evt) {
+			if _, err := txn.ExecContext(ctx, "DELETE FROM event WHERE id = $1", evt.ID); err != nil {
+				return fmt.Errorf("failed to delete event %s for replacing: %w", previous.ID, err)
+			}
+		} else {
+			// there is a newer event already stored, so we won't store this
+			shouldStore = false
+		}
+	}
+
+	if shouldStore {
+		tagsj, _ := json.Marshal(evt.Tags)
+		_, err = txn.ExecContext(ctx, `
+        INSERT OR IGNORE INTO event (id, pubkey, created_at, kind, tags, content, sig)
+        VALUES ($1, $2, $3, $4, $5, $6, $7)
+    `, evt.ID, evt.PubKey, evt.CreatedAt, evt.Kind, tagsj, evt.Content, evt.Sig)
+	}
+
+	return err
+}