Update change on each output or input change

lib/transaction/transaction.js

@@ -421,11 +421,11 @@ Transaction.prototype.addInput = function(input, outputScript, satoshis) {
  */
 Transaction.prototype.uncheckedAddInput = function(input) {
   $.checkArgumentType(input, Input, 'input');
-  this._changeSetup = false;
   this.inputs.push(input);
   if (input.output) {
     this._inputAmount += input.output.satoshis;
   }
+  this._updateChangeOutput();
   return this;
 };
 
@@ -450,7 +450,7 @@ Transaction.prototype.hasAllUtxoInfo = function() {
  */
 Transaction.prototype.fee = function(amount) {
   this._fee = amount;
-  this._changeSetup = false;
+  this._updateChangeOutput();
   return this;
 };
 
@@ -467,7 +467,7 @@ Transaction.prototype.fee = function(amount) {
  */
 Transaction.prototype.change = function(address) {
   this._change = new Address(address);
-  this._changeSetup = false;
+  this._updateChangeOutput();
   return this;
 };
 
@@ -509,8 +509,12 @@ Transaction.prototype.addData = function(value) {
 
 Transaction.prototype.addOutput = function(output) {
   $.checkArgumentType(output, Output, 'output');
+  this._addOutput(output);
+  this._updateChangeOutput();
+};
+
+Transaction.prototype._addOutput = function(output) {
   this.outputs.push(output);
-  this._changeSetup = false;
   this._outputAmount += output.satoshis;
 };
 
@@ -518,12 +522,7 @@ Transaction.prototype._updateChangeOutput = function() {
   if (!this._change) {
     return;
   }
-  if (this._changeSetup) {
-    return;
-  }
-  if (!_.isUndefined(this._changeSetup)) {
-    this._clearSignatures();
-  }
+  this._clearSignatures();
   if (!_.isUndefined(this._changeOutput)) {
     this.removeOutput(this._changeOutput);
   }
@@ -531,14 +530,13 @@ Transaction.prototype._updateChangeOutput = function() {
   var fee = this.getFee();
   if (available - fee > 0) {
     this._changeOutput = this.outputs.length;
-    this.addOutput(new Output({
+    this._addOutput(new Output({
       script: Script.fromAddress(this._change),
       satoshis: available - fee
     }));
   } else {
     this._changeOutput = undefined;
   }
-  this._changeSetup = true;
 };
 
 Transaction.prototype.getFee = function() {
@@ -606,7 +604,6 @@ Transaction.prototype.removeOutput = function(index) {
  */
 Transaction.prototype.sign = function(privateKey, sigtype) {
   $.checkState(this.hasAllUtxoInfo());
-  this._updateChangeOutput();
   var self = this;
   if (_.isArray(privateKey)) {
     _.each(privateKey, function(privateKey) {

test/transaction/transaction.js

@@ -260,7 +260,8 @@ describe('Transaction', function() {
       var transaction = new Transaction()
         .from(simpleUtxoWith1BTC)
         .change(changeAddress)
-        .to(toAddress, 1);
+        .fee(50000000)
+        .to(toAddress, 40000000);
       expect(function() {
         return transaction.serialize();
       }).to.throw(errors.Transaction.FeeError);