Add MaybeSilentPayment helper

Author: Sjors

src/common/bip352.cpp

@@ -151,6 +151,18 @@ std::optional<PublicData> CreateInputPubkeysTweak(
     return public_data;
 }
 
+bool MaybeSilentPayment(const CTransactionRef &tx) {
+    if (tx->IsCoinBase()) return false;
+
+    if (std::none_of(tx->vout.begin(), tx->vout.end(), [](const CTxOut& txout) {
+        return txout.scriptPubKey.IsPayToTaproot();
+    })) {
+        return false;
+    }
+
+    return true;
+}
+
 std::optional<PublicData> GetSilentPaymentsPublicData(const std::vector<CTxIn>& vin, const std::map<COutPoint, Coin>& coins)
 {
     // Extract the keys from the inputs

src/common/bip352.h

@@ -117,6 +117,17 @@ std::pair<CPubKey, uint256> CreateLabelTweak(const CKey& scan_key, const int m);
  */
 V0SilentPaymentDestination GenerateSilentPaymentLabeledAddress(const V0SilentPaymentDestination& recipient, const uint256& label);
 
+/**
+ * @brief: Check if a transaction could be a silent payment.
+ *
+ * A coinbase transaction can't be a silent payment.
+ * A transaction with no Taproot outputs can't be a silent payment.
+ *
+ * @param tx                        The transaction to check
+ * @return false if a transaction can't be a silent payment, true otherwise.
+ */
+bool MaybeSilentPayment(const CTransactionRef &tx);
+
 /**
  * @brief Get silent payment public data from transaction inputs.
  *