Add fee to SendRequest again

Cherry pick 0dcd8ac

core/src/main/java/org/bitcoinj/wallet/SendRequest.java

@@ -77,6 +77,22 @@ public class SendRequest {
      */
     public Address changeAddress = null;
 
+    /**
+     * <p>A transaction can have a fee attached, which is defined as the difference between the input values
+     * and output values. Any value taken in that is not provided to an output can be claimed by a miner. This
+     * is how mining is incentivized in later years of the Bitcoin system when inflation drops. It also provides
+     * a way for people to prioritize their transactions over others and is used as a way to make denial of service
+     * attacks expensive.</p>
+     *
+     * <p>This is a constant fee (in satoshis) which will be added to the transaction. It is recommended that it be
+     * at least {@link Transaction#REFERENCE_DEFAULT_MIN_TX_FEE} if it is set, as default Bitcoin Core will
+     * otherwise simply treat the transaction as if there were no fee at all.</p>
+     *
+     * <p>You might also consider adding a {@link SendRequest#feePerKb} to set the fee per kb of transaction size
+     * (rounded down to the nearest kb) as that is how transactions are sorted when added to a block by miners.</p>
+     */
+    public Coin fee = null;
+
     /**
      * <p>A transaction can have a fee attached, which is defined as the difference between the input values
      * and output values. Any value taken in that is not provided to an output can be claimed by a miner. This
@@ -256,6 +272,7 @@ public String toString() {
         MoreObjects.ToStringHelper helper = MoreObjects.toStringHelper(this).omitNullValues();
         helper.add("emptyWallet", emptyWallet);
         helper.add("changeAddress", changeAddress);
+        helper.add("fee", fee);
         helper.add("feePerKb", feePerKb);
         helper.add("ensureMinRequiredFee", ensureMinRequiredFee);
         helper.add("signInputs", signInputs);

core/src/main/java/org/bitcoinj/wallet/Wallet.java

@@ -3983,8 +3983,9 @@ public void completeTx(SendRequest req) throws InsufficientMoneyException {
                 req.tx.addInput(output);
 
             if (req.emptyWallet) {
+                final Coin baseFee = req.fee == null ? Coin.ZERO : req.fee;
                 final Coin feePerKb = req.feePerKb == null ? Coin.ZERO : req.feePerKb;
-                if (!adjustOutputDownwardsForFee(req.tx, bestCoinSelection, feePerKb, req.ensureMinRequiredFee))
+                if (!adjustOutputDownwardsForFee(req.tx, bestCoinSelection, baseFee, feePerKb, req.ensureMinRequiredFee))
                     throw new CouldNotAdjustDownwards();
             }
 
@@ -4006,6 +4007,12 @@ public void completeTx(SendRequest req) throws InsufficientMoneyException {
             if (size > Transaction.MAX_STANDARD_TX_SIZE)
                 throw new ExceededMaxTransactionSize();
 
+            final Coin calculatedFee = req.tx.getFee();
+            if (calculatedFee != null)
+                log.info("  with a fee of {}/kB, {} for {} bytes",
+                        calculatedFee.multiply(1000).divide(size).toFriendlyString(), calculatedFee.toFriendlyString(),
+                        size);
+
             // Label the transaction as being self created. We can use this later to spend its change output even before
             // the transaction is confirmed. We deliberately won't bother notifying listeners here as there's not much
             // point - the user isn't interested in a confidence transition they made themselves.
@@ -4018,6 +4025,7 @@ public void completeTx(SendRequest req) throws InsufficientMoneyException {
             req.tx.setExchangeRate(req.exchangeRate);
             req.tx.setMemo(req.memo);
             req.completed = true;
+            req.fee = calculatedFee;
             log.info("  completed: {}", req.tx);
         } finally {
             lock.unlock();
@@ -4081,10 +4089,10 @@ public void signTransaction(SendRequest req) {
     }
 
     /** Reduce the value of the first output of a transaction to pay the given feePerKb as appropriate for its size. */
-    private boolean adjustOutputDownwardsForFee(Transaction tx, CoinSelection coinSelection, Coin feePerKb,
+    private boolean adjustOutputDownwardsForFee(Transaction tx, CoinSelection coinSelection, Coin baseFee, Coin feePerKb,
             boolean ensureMinRequiredFee) {
         final int size = tx.unsafeBitcoinSerialize().length + estimateBytesForSigning(coinSelection);
-        Coin fee = feePerKb.multiply(size).divide(1000);
+        Coin fee = baseFee.add(feePerKb.multiply(size).divide(1000));
         if (ensureMinRequiredFee && fee.compareTo(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE) < 0)
             fee = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE;
         TransactionOutput output = tx.getOutput(0);
@@ -4830,7 +4838,14 @@ public FeeCalculation calculateFee(SendRequest req, Coin value, List<Transaction
         while (true) {
             resetTxInputs(req, originalInputs);
 
-            Coin fees = req.feePerKb.multiply(lastCalculatedSize).divide(1000);
+            Coin fees = req.fee == null ? Coin.ZERO : req.fee;
+            if (lastCalculatedSize > 0) {
+                // If the size is exactly 1000 bytes then we'll over-pay, but this should be rare.
+                fees = fees.add(req.feePerKb.multiply(lastCalculatedSize).divide(1000));
+            } else {
+                fees = fees.add(req.feePerKb);  // First time around the loop.
+            }
+
             if (needAtLeastReferenceFee && fees.compareTo(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE) < 0)
                 fees = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE;
 
@@ -5245,7 +5260,7 @@ private Transaction rekeyOneBatch(long timeSecs, @Nullable KeyParameter aesKey,
             }
             // When not signing, don't waste addresses.
             rekeyTx.addOutput(toMove.valueGathered, sign ? freshReceiveAddress() : currentReceiveAddress());
-            if (!adjustOutputDownwardsForFee(rekeyTx, toMove, Transaction.DEFAULT_TX_FEE, true)) {
+            if (!adjustOutputDownwardsForFee(rekeyTx, toMove, Coin.ZERO, Transaction.DEFAULT_TX_FEE, true)) {
                 log.error("Failed to adjust rekey tx for fees.");
                 return null;
             }