add less-than-dust to fee. recalculate fee after input scripts are templated.

lib/bcoin/tx.js

@@ -42,12 +42,13 @@ function TX(data, block) {
   // ps = Pending Since
   this.ps = this.ts === 0 ? +new Date() / 1000 : 0;
 
-  this.change = data.change || null;
-  this.fee = data.fee || 10000;
-  this.dust = 5460;
+  this.changeAddress = data.changeAddress || null;
 }
 module.exports = TX;
 
+TX.fee = 10000;
+TX.dust = 5460;
+
 TX.prototype.clone = function clone() {
   return new TX(this);
 };
@@ -155,6 +156,7 @@ TX.prototype.scriptInput = function(input, pub) {
   // P2PKH and simple tx
   if (bcoin.script.isPubkeyhash(s) || bcoin.script.isSimplePubkeyhash(s)) {
     input.script = [ [], pub ];
+    this._recalculateFee();
     return;
   }
 
@@ -171,6 +173,7 @@ TX.prototype.scriptInput = function(input, pub) {
       n = n[0] || 0;
     for (var i = 0; i < n; i++)
       input.script[i + 1] = [];
+    this._recalculateFee();
     return;
   }
 
@@ -187,6 +190,7 @@ TX.prototype.scriptInput = function(input, pub) {
       input.script[i + 1] = [];
     // P2SH requires the redeem script after signatures
     input.script.push(pub);
+    this._recalculateFee();
     return;
   }
 
@@ -568,7 +572,7 @@ TX.prototype.utxos = function utxos(unspent) {
   var fee = 1;
 
   // total = cost + fee
-  var total = cost.add(new bn(this.fee));
+  var total = cost.add(new bn(TX.fee));
 
   var inputs = this.inputs.slice();
   var utxos = [];
@@ -587,7 +591,7 @@ TX.prototype.utxos = function utxos(unspent) {
   // var unspent = wallet.unspent();
   unspent.every(addInput, this);
 
-  // Add dummy output (for `left`) to calculate maximum TX size
+  // Add dummy output (for `change`) to calculate maximum TX size
   this.output({ address: null, value: new bn(0) });
 
   // Change fee value if it is more than 1024 bytes
@@ -597,7 +601,7 @@ TX.prototype.utxos = function utxos(unspent) {
     var byteSize = this.maxSize();
 
     var addFee = Math.ceil(byteSize / 1024) - fee;
-    total.iadd(new bn(addFee * this.fee));
+    total.iadd(new bn(addFee * TX.fee));
     fee += addFee;
 
     // Failed to get enough funds, add more inputs
@@ -609,28 +613,31 @@ TX.prototype.utxos = function utxos(unspent) {
   if (this.funds('in').cmp(total) < 0) {
     this.inputs = inputs;
     this.outputs.pop();
-    this.cost = total;
+    this.total = total;
     return null;
   }
 
   // How much money is left after sending outputs
-  var left = this.funds('in').sub(total);
+  var change = this.funds('in').sub(total);
 
   // Clear the tx of everything we added.
   this.inputs = inputs;
   this.outputs.pop();
-  this.cost = total;
 
   // Return necessary utxos and change.
   return {
     utxos: utxos,
-    change: left,
-    cost: total
+    change: change,
+    cost: cost,
+    fee: total.sub(cost),
+    total: total
   };
 };
 
-TX.prototype.fillUnspent = function fillUnspent(unspent, change) {
-  var result = this.utxos(unspent);
+TX.prototype.fillUnspent = function fillUnspent(unspent, changeAddress) {
+  var result = unspent.utxos ? unspent : this.utxos(unspent);
+
+  this.changeAddress = changeAddress || this.changeAddress;
 
   if (!result)
     return result;
@@ -639,20 +646,63 @@ TX.prototype.fillUnspent = function fillUnspent(unspent, change) {
     this.input(utxo, null);
   }, this);
 
-  // Not enough money, transfer everything to owner
-  if (result.change.cmpn(this.dust) < 0) {
-    // NOTE: that this output is either `postCost` or one of the `dust` values
-    this.outputs[this.outputs.length - 1].value.iadd(result.change);
+  if (result.change.cmpn(TX.dust) < 0) {
+    // Do nothing. Change is added to fee.
+    assert(this.getFee().cmp(result.fee.add(result.change)) === 0);
+    // Adding change to outputs.
+    // this.outputs[this.outputs.length - 1].value.iadd(result.change);
+    this.changeOutput = null;
   } else {
     this.output({
-      address: change || this.change,
+      address: this.changeAddress,
       value: result.change
     });
+    this.changeOutput = this.outputs[this.outputs.length - 1];
   }
 
   return result;
 };
 
+TX.prototype._recalculateFee = function recalculateFee() {
+  var output = this.changeOutput;
+  if (!output) {
+    this.output({
+      address: this.changeAddress,
+      value: new bn(0)
+    });
+    output = this.outputs[this.outputs.length - 1];
+  }
+
+  var byteSize = this.maxSize();
+  var newFee = Math.ceil(byteSize / 1024) * TX.fee;
+  var currentFee = this.getFee().toNumber();
+
+  if (newFee === currentFee) {
+    if (!this.changeOutput)
+      this.outputs.pop();
+    return;
+  }
+
+  if (newFee > currentFee) {
+    if (output.value.cmpn(newFee - currentFee) < 0) {
+      this.outputs.pop();
+      this.changeOutput = null;
+      return;
+    }
+    output.value.isubn(newFee - currentFee);
+  } else {
+    output.value.iaddn(currentFee - newFee);
+  }
+
+  if (output.value.cmpn(TX.dust) < 0) {
+    this.outputs.pop();
+    this.changeOutput = null;
+    return;
+  }
+
+  this.changeOutput = output;
+};
+
 TX.prototype.inputAddrs = function inputAddrs() {
   return this.inputs.filter(function(input) {
     return bcoin.script.isPubkeyhashInput(input.script);
@@ -663,6 +713,10 @@ TX.prototype.inputAddrs = function inputAddrs() {
   });
 };
 
+TX.prototype.getFee = function getFee() {
+  return this.funds('in').sub(this.funds('out'));
+};
+
 TX.prototype.funds = function funds(side) {
   if (side === 'in') {
     var inputs = this.inputs.filter(function(input) {

lib/bcoin/wallet.js

@@ -406,7 +406,7 @@ Wallet.prototype.fill = function fill(tx, cb) {
   var result = tx.fillUnspent(this.unspent(), this.getAddress());
   if (!result) {
     var err = new Error('Not enough funds');
-    err.minBalance = tx.cost;
+    err.minBalance = tx.total;
     cb(err);
     return null;
   }

test/wallet-test.js

@@ -177,7 +177,10 @@ describe('Wallet', function() {
       assert(t2.verify());
 
       assert.equal(t2.funds('in').toString(10), 16380);
-      assert.equal(t2.funds('out').toString(10), 6380);
+      // If change < dust and is added to outputs:
+      // assert.equal(t2.funds('out').toString(10), 6380);
+      // If change < dust and is added to fee:
+      assert.equal(t2.funds('out').toString(10), 5460);
 
       // Create new transaction
       var t3 = bcoin.tx().out(w2, 15000);