notifications: server implementation

notifications/server.go

@@ -0,0 +1,58 @@
+package notifications
+
+import (
+	context "context"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"log"
+
+	"github.com/btcsuite/btcd/btcec/v2/ecdsa"
+)
+
+var ErrInvalidSignature = fmt.Errorf("invalid signature")
+var ErrInternal = fmt.Errorf("internal error")
+
+type server struct {
+	store Store
+	NotificationsServer
+}
+
+func NewNotificationsServer(store Store) NotificationsServer {
+	return &server{
+		store: store,
+	}
+}
+
+func (s *server) SubscribeNotifications(
+	ctx context.Context,
+	request *SubscribeNotificationsRequest,
+) (*SubscribeNotificationsReply, error) {
+	first := sha256.Sum256([]byte(request.Url))
+	second := sha256.Sum256(first[:])
+	pubkey, wasCompressed, err := ecdsa.RecoverCompact(
+		request.Signature,
+		second[:],
+	)
+	if err != nil {
+		return nil, ErrInvalidSignature
+	}
+
+	if !wasCompressed {
+		return nil, ErrInvalidSignature
+	}
+
+	err = s.store.Register(ctx, hex.EncodeToString(pubkey.SerializeCompressed()), request.Url)
+	if err != nil {
+		log.Printf(
+			"failed to register %x for notifications on url %s: %v",
+			pubkey.SerializeCompressed(),
+			request.Url,
+			err,
+		)
+
+		return nil, ErrInternal
+	}
+
+	return &SubscribeNotificationsReply{}, nil
+}