Transaction: add `removeInput` member

lib/errors/spec.js

@@ -54,6 +54,9 @@ module.exports = [{
   }, {
     name: 'NeedMoreInfo',
     message: '{0}'
+  }, {
+    name: 'InvalidIndex',
+    message: 'Invalid index: {0} is not between 0, {1}'
   }, {
     name: 'UnableToVerifySignature',
     message: 'Unable to verify signature: {0}'

lib/transaction/transaction.js

@@ -529,7 +529,7 @@ Transaction.prototype._updateChangeOutput = function() {
   }
   this._clearSignatures();
   if (!_.isUndefined(this._changeOutput)) {
-    this.removeOutput(this._changeOutput);
+    this._removeOutput(this._changeOutput);
   }
   var available = this._getUnspentValue();
   var fee = this.getFee();
@@ -589,10 +589,33 @@ Transaction.prototype._estimateSize = function() {
   return result;
 };
 
-Transaction.prototype.removeOutput = function(index) {
+Transaction.prototype._removeOutput = function(index) {
   var output = this.outputs[index];
   this._outputAmount -= output.satoshis;
-  this.outputs = _.without(this.outputs, this.outputs[this._changeOutput]);
+  this.outputs = _.without(this.outputs, output);
+};
+
+Transaction.prototype.removeOutput = function(index) {
+  this._removeOutput(index);
+  this._updateChangeOutput();
+};
+
+Transaction.prototype.removeInput = function(txId, outputIndex) {
+  var index;
+  if (!outputIndex && _.isNumber(txId)) {
+    index = txId;
+  } else {
+    index = _.findIndex(this.inputs, function(input) {
+      return input.prevTxId.toString('hex') === txId && input.outputIndex === outputIndex;
+    });
+  }
+  if (index < 0 || index >= this.inputs.length) {
+    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();
 };
 
 /* Signature handling */

test/transaction/transaction.js

@@ -357,6 +357,40 @@ describe('Transaction', function() {
       }).to.not.throw();
     });
   });
+
+  describe('removeInput and removeOutput', function() {
+    it('can remove an input by index', function() {
+      var transaction = new Transaction()
+        .from(simpleUtxoWith1BTC);
+      transaction.inputs.length.should.equal(1);
+      transaction.removeInput(0);
+      transaction._inputAmount.should.equal(0);
+      transaction.inputs.length.should.equal(0);
+    });
+    it('can remove an input by transaction id', function() {
+      var transaction = new Transaction()
+        .from(simpleUtxoWith1BTC);
+      transaction.inputs.length.should.equal(1);
+      transaction.removeInput(simpleUtxoWith1BTC.txId, simpleUtxoWith1BTC.outputIndex);
+      transaction._inputAmount.should.equal(0);
+      transaction.inputs.length.should.equal(0);
+    });
+    it('fails if the index provided is invalid', function() {
+      var transaction = new Transaction()
+        .from(simpleUtxoWith1BTC);
+      expect(function() {
+        transaction.removeInput(2);
+      }).to.throw(errors.Transaction.InvalidIndex);
+    });
+    it('an output can be removed by index', function() {
+      var transaction = new Transaction()
+        .to(toAddress, 40000000)
+        .to(toAddress, 40000000);
+      transaction.outputs.length.should.equal(2);
+      transaction.removeOutput(0);
+      transaction.outputs.length.should.equal(1);
+    });
+  });
 });
 
 var tx_empty_hex = '01000000000000000000';