allow 0-value UTXO in unspent list

zetaclient/bitcoin_client.go

@@ -940,9 +940,8 @@ func (ob *BitcoinChainClient) ValidateCctxParams(params *types.OutboundTxParams)
 	}
 
 	// validate amount
-	_, err = getSatoshis(float64(params.Amount.Uint64()) / 1e8)
-	if err != nil {
-		return fmt.Errorf("ValidateCctxParams: invalid amount %d", params.Amount)
+	if params.Amount.Uint64() == 0 {
+		return fmt.Errorf("ValidateCctxParams: zero amount not allowed in cctx")
 	}
 	return nil
 }

zetaclient/utils.go

@@ -16,7 +16,7 @@ const (
 func getSatoshis(btc float64) (int64, error) {
 	// The amount is only considered invalid if it cannot be represented
 	// as an integer type.  This may happen if f is NaN or +-Infinity.
-	// BTC max amount is 21 mil and its at least 10^(-8) or one satoshi.
+	// BTC max amount is 21 mil and its at least 0 (Note: bitcoin allows creating 0 value outputs)
 	switch {
 	case math.IsNaN(btc):
 		fallthrough
@@ -26,8 +26,8 @@ func getSatoshis(btc float64) (int64, error) {
 		return 0, errors.New("invalid bitcoin amount")
 	case btc > 21000000.0:
 		return 0, errors.New("exceeded max bitcoin amount")
-	case btc < 0.00000001:
-		return 0, errors.New("cannot be less than 1 satoshi")
+	case btc < 0.0:
+		return 0, errors.New("cannot be less than zero")
 	}
 	return round(btc * satoshiPerBitcoin), nil
 }