feat(whatsapp): add legacy server retry logic for message sending failures

Author: MinecraftFuns

internal/messaging/whatsapp_service.go

@@ -94,6 +94,14 @@ func (s *WhatsAppService) resolveRecipientAddress(canonicalPhone string) string
 	return canonicalPhone
 }
 
+func shouldRetryWithLegacyServer(err error) bool {
+	if err == nil {
+		return false
+	}
+	msg := err.Error()
+	return strings.Contains(msg, "failed to get user info") || strings.Contains(msg, "rate-overlimit")
+}
+
 // ValidateAndCanonicalizeRecipient validates and canonicalizes a WhatsApp phone number.
 // It removes all non-numeric characters and validates the result has at least 6 digits.
 func (s *WhatsAppService) ValidateAndCanonicalizeRecipient(recipient string) (string, error) {
@@ -186,6 +194,19 @@ func (s *WhatsAppService) SendMessage(ctx context.Context, to string, body strin
 	}
 	err = s.client.SendMessage(ctx, sendTo, body)
 	if err != nil {
+		if sendTo == canonicalTo && shouldRetryWithLegacyServer(err) {
+			legacyTo := fmt.Sprintf("%s@%s", canonicalTo, types.LegacyUserServer)
+			slog.Warn("WhatsAppService SendMessage retrying with legacy server", "to", legacyTo, "phone", canonicalTo)
+			retryErr := s.client.SendMessage(ctx, legacyTo, body)
+			if retryErr == nil {
+				s.safeEmitReceipt(models.Receipt{To: canonicalTo, Status: models.MessageStatusSent, Time: time.Now().Unix()})
+				slog.Info("WhatsAppService message sent via legacy server", "to", legacyTo, "phone", canonicalTo)
+				return nil
+			}
+			slog.Error("WhatsAppService SendMessage legacy retry failed", "error", retryErr, "to", legacyTo, "phone", canonicalTo)
+			return retryErr
+		}
+
 		slog.Error("WhatsAppService SendMessage error", "error", err, "to", sendTo, "phone", canonicalTo)
 		return err
 	}