Merge pull request #1123 from maraoz/transaction/amounts

add Transaction#inputAmount and outputAmount

lib/errors/spec.js

@@ -56,6 +56,9 @@ module.exports = [{
     }, {
       name: 'UnsupportedScript',
       message: 'Unsupported input script type: {0}'
+    }, {
+      name: 'MissingPreviousOutput',
+      message: 'No previous output information.'
     }]
   }, {
     name: 'NeedMoreInfo',

lib/transaction/transaction.js

@@ -36,8 +36,8 @@ function Transaction(serialized) {
   }
   this.inputs = [];
   this.outputs = [];
-  this._inputAmount = 0;
-  this._outputAmount = 0;
+  this._inputAmount = undefined;
+  this._outputAmount = undefined;
 
   if (serialized) {
     if (serialized instanceof Transaction) {
@@ -109,6 +109,20 @@ var hashProperty = {
 Object.defineProperty(Transaction.prototype, 'hash', hashProperty);
 Object.defineProperty(Transaction.prototype, 'id', hashProperty);
 
+var ioProperty = {
+  configurable: false,
+  writeable: false,
+  enumerable: true,
+  get: function() {
+    return this._getInputAmount();
+  }
+};
+Object.defineProperty(Transaction.prototype, 'inputAmount', ioProperty);
+ioProperty.get = function() {
+  return this._getOutputAmount();
+};
+Object.defineProperty(Transaction.prototype, 'outputAmount', ioProperty);
+
 /**
  * Retrieve the little endian hash of the transaction (used for serialization)
  * @return {Buffer}
@@ -348,7 +362,7 @@ Transaction.prototype._checkConsistency = function() {
     $.checkState(this._changeScript);
     $.checkState(this.outputs[this._changeIndex]);
     $.checkState(this.outputs[this._changeIndex].script.toString() ===
-      this._changeScript.toString());
+                 this._changeScript.toString());
   }
   // TODO: add other checks
 };
@@ -509,7 +523,7 @@ Transaction.prototype._fromNonP2SH = function(utxo) {
 
 Transaction.prototype._fromMultisigUtxo = function(utxo, pubkeys, threshold) {
   $.checkArgument(threshold <= pubkeys.length,
-                  'Number of required signatures must be greater than the number of public keys');
+    'Number of required signatures must be greater than the number of public keys');
   utxo = new UnspentOutput(utxo);
   this.addInput(new MultiSigScriptHashInput({
     output: new Output({
@@ -559,9 +573,6 @@ Transaction.prototype.addInput = function(input, outputScript, satoshis) {
 Transaction.prototype.uncheckedAddInput = function(input) {
   $.checkArgumentType(input, Input, 'input');
   this.inputs.push(input);
-  if (input.output) {
-    this._inputAmount += input.output.satoshis;
-  }
   this._updateChangeOutput();
   return this;
 };
@@ -655,15 +666,60 @@ Transaction.prototype.addData = function(value) {
   return this;
 };
 
+
+/**
+ * Add an output to the transaction.
+ *
+ * @param {Output} output the output to add.
+ * @return {Transaction} this, for chaining
+ */
 Transaction.prototype.addOutput = function(output) {
   $.checkArgumentType(output, Output, 'output');
   this._addOutput(output);
   this._updateChangeOutput();
+  return this;
 };
 
 Transaction.prototype._addOutput = function(output) {
   this.outputs.push(output);
-  this._outputAmount += output.satoshis;
+  this._outputAmount = undefined;
+};
+
+
+/**
+ * Calculates or gets the total output amount in satoshis
+ *
+ * @return {Number} the transaction total output amount 
+ */
+Transaction.prototype._getOutputAmount = function() {
+  if (_.isUndefined(this._outputAmount)) {
+    var self = this;
+    this._outputAmount = 0;
+    _.each(this.outputs, function(output) {
+      self._outputAmount += output.satoshis;
+    });
+  }
+  return this._outputAmount;
+};
+
+
+/**
+ * Calculates or gets the total input amount in satoshis
+ *
+ * @return {Number} the transaction total input amount 
+ */
+Transaction.prototype._getInputAmount = function() {
+  if (_.isUndefined(this._inputAmount)) {
+    var self = this;
+    this._inputAmount = 0;
+    _.each(this.inputs, function(input) {
+      if (_.isUndefined(input.output)) {
+        throw new errors.Transaction.Input.MissingPreviousOutput();
+      }
+      self._inputAmount += input.output.satoshis;
+    });
+  }
+  return this._inputAmount;
 };
 
 Transaction.prototype._updateChangeOutput = function() {
@@ -714,7 +770,7 @@ Transaction.prototype._estimateFee = function() {
 };
 
 Transaction.prototype._getUnspentValue = function() {
-  return this._inputAmount - this._outputAmount;
+  return this._getInputAmount() - this._getOutputAmount();
 };
 
 Transaction.prototype._clearSignatures = function() {
@@ -744,7 +800,6 @@ Transaction.prototype._estimateSize = function() {
 
 Transaction.prototype._removeOutput = function(index) {
   var output = this.outputs[index];
-  this._outputAmount -= output.satoshis;
   this.outputs = _.without(this.outputs, output);
 };
 
@@ -766,7 +821,6 @@ Transaction.prototype.removeInput = function(txId, outputIndex) {
     throw new errors.Transaction.InvalidIndex(index, this.inputs.length);
   }
   var input = this.inputs[index];
-  this._inputAmount -= input.output.satoshis;
   this.inputs = _.without(this.inputs, input);
   this._updateChangeOutput();
 };