KIP9 basic wallet compatibility (kaspanet#2276)

* introduce min change target

* clarify wallet help messages for from-address and send-all

cmd/kaspawallet/config.go

@@ -58,9 +58,9 @@ type sendConfig struct {
 	Password                 string   `long:"password" short:"p" description:"Wallet password"`
 	DaemonAddress            string   `long:"daemonaddress" short:"d" description:"Wallet daemon server to connect to"`
 	ToAddress                string   `long:"to-address" short:"t" description:"The public address to send Kaspa to" required:"true"`
-	FromAddresses            []string `long:"from-address" short:"a" description:"Specific public address to send Kaspa from. Use multiple times to accept several addresses" required:"false"`
+	FromAddresses            []string `long:"from-address" short:"a" description:"Specific public address to send Kaspa from. Repeat multiple times (adding -a before each) to accept several addresses" required:"false"`
 	SendAmount               string   `long:"send-amount" short:"v" description:"An amount to send in Kaspa (e.g. 1234.12345678)"`
-	IsSendAll                bool     `long:"send-all" description:"Send all the Kaspa in the wallet (mutually exclusive with --send-amount)"`
+	IsSendAll                bool     `long:"send-all" description:"Send all the Kaspa in the wallet (mutually exclusive with --send-amount). If --from-address was used, will send all only from the specified addresses."`
 	UseExistingChangeAddress bool     `long:"use-existing-change-address" short:"u" description:"Will use an existing change address (in case no change address was ever used, it will use a new one)"`
 	Verbose                  bool     `long:"show-serialized" short:"s" description:"Show a list of hex encoded sent transactions"`
 	config.NetworkFlags

cmd/kaspawallet/daemon/server/create_unsigned_transaction.go

@@ -14,6 +14,11 @@ import (
 // TODO: Implement a better fee estimation mechanism
 const feePerInput = 10000
 
+// The minimal change amount to target in order to avoid large storage mass (see KIP9 for more details).
+// By having at least 0.2KAS in the change output we make sure that every transaction with send value >= 0.2KAS
+// should succeed (at most 50K storage mass for each output, thus overall lower than standard mass upper bound which is 100K gram)
+const minChangeTarget = constants.SompiPerKaspa / 5
+
 func (s *server) CreateUnsignedTransactions(_ context.Context, request *pb.CreateUnsignedTransactionsRequest) (
 	*pb.CreateUnsignedTransactionsResponse, error,
 ) {
@@ -124,9 +129,10 @@ func (s *server) selectUTXOs(spendAmount uint64, isSendAll bool, feePerInput uin
 		totalSpend := spendAmount + fee
 		// Two break cases (if not send all):
 		// 		1. totalValue == totalSpend, so there's no change needed -> number of outputs = 1, so a single input is sufficient
-		// 		2. totalValue > totalSpend, so there will be change and 2 outputs, therefor in order to not struggle with new dust
-		// 		   rules we try and find at least 2 inputs (even though the next one is not necessary in terms of spend value)
-		if !isSendAll && (totalValue == totalSpend || (totalValue > totalSpend && len(selectedUTXOs) > 1)) {
+		// 		2. totalValue > totalSpend, so there will be change and 2 outputs, therefor in order to not struggle with --
+		//		   2.1 go-nodes dust patch we try and find at least 2 inputs (even though the next one is not necessary in terms of spend value)
+		// 		   2.2 KIP9 we try and make sure that the change amount is not too small
+		if !isSendAll && (totalValue == totalSpend || (totalValue >= totalSpend+minChangeTarget && len(selectedUTXOs) > 1)) {
 			break
 		}
 	}