Merge pull request #244 from dcousens/txbuilder

Transaction Builder

src/index.js

@@ -13,6 +13,7 @@ module.exports = {
   Script: require('./script'),
   scripts: require('./scripts'),
   Transaction: require('./transaction'),
+  TransactionBuilder: require('./transaction_builder'),
   networks: require('./networks'),
   Wallet: require('./wallet')
 }

src/transaction.js

@@ -162,7 +162,17 @@ Transaction.prototype.toHex = function() {
  * hashType, serializes and finally hashes the result. This hash can then be
  * used to sign the transaction input in question.
  */
-Transaction.prototype.hashForSignature = function(prevOutScript, inIndex, hashType) {
+Transaction.prototype.hashForSignature = function(inIndex, prevOutScript, hashType) {
+  // FIXME: remove in 2.x.y
+  if (arguments[0] instanceof Script) {
+    console.warn('hashForSignature(prevOutScript, inIndex, ...) has been deprecated. Use hashForSignature(inIndex, prevOutScript, ...)')
+
+    // swap the arguments (must be stored in tmp, arguments is special)
+    var tmp = arguments[0]
+    inIndex = arguments[1]
+    prevOutScript = tmp
+  }
+
   assert(inIndex >= 0, 'Invalid vin index')
   assert(inIndex < this.ins.length, 'Invalid vin index')
   assert(prevOutScript instanceof Script, 'Invalid Script object')
@@ -296,35 +306,39 @@ Transaction.fromHex = function(hex) {
   return Transaction.fromBuffer(new Buffer(hex, 'hex'))
 }
 
-/**
+Transaction.prototype.setInputScript = function(index, script) {
- * Signs a pubKeyHash output at some index with the given key
+  this.ins[index].script = script
- */
+}
+
+// FIXME: remove in 2.x.y
 Transaction.prototype.sign = function(index, privKey, hashType) {
+  console.warn("Transaction.prototype.sign is deprecated.  Use TransactionBuilder instead.")
+
   var prevOutScript = privKey.pub.getAddress().toOutputScript()
   var signature = this.signInput(index, prevOutScript, privKey, hashType)
 
-  // FIXME: Assumed prior TX was pay-to-pubkey-hash
   var scriptSig = scripts.pubKeyHashInput(signature, privKey.pub)
   this.setInputScript(index, scriptSig)
 }
 
+// FIXME: remove in 2.x.y
 Transaction.prototype.signInput = function(index, prevOutScript, privKey, hashType) {
+  console.warn("Transaction.prototype.signInput is deprecated.  Use TransactionBuilder instead.")
+
   hashType = hashType || Transaction.SIGHASH_ALL
 
-  var hash = this.hashForSignature(prevOutScript, index, hashType)
+  var hash = this.hashForSignature(index, prevOutScript, hashType)
   var signature = privKey.sign(hash)
 
   return signature.toScriptSignature(hashType)
 }
 
-Transaction.prototype.setInputScript = function(index, script) {
+// FIXME: remove in 2.x.y
-  this.ins[index].script = script
-}
-
-// FIXME: could be validateInput(index, prevTxOut, pub)
 Transaction.prototype.validateInput = function(index, prevOutScript, pubKey, buffer) {
+  console.warn("Transaction.prototype.validateInput is deprecated.  Use TransactionBuilder instead.")
+
   var parsed = ECSignature.parseScriptSignature(buffer)
-  var hash = this.hashForSignature(prevOutScript, index, parsed.hashType)
+  var hash = this.hashForSignature(index, prevOutScript, parsed.hashType)
 
   return pubKey.verify(hash, parsed.signature)
 }

src/transaction_builder.js

@@ -0,0 +1,260 @@
+var assert = require('assert')
+var scripts = require('./scripts')
+
+var ECPubKey = require('./ecpubkey')
+var ECSignature = require('./ecsignature')
+var Script = require('./script')
+var Transaction = require('./transaction')
+
+function TransactionBuilder() {
+  this.prevOutMap = {}
+  this.prevOutScripts = {}
+  this.prevOutTypes = {}
+
+  this.signatures = []
+  this.tx = new Transaction()
+}
+
+// Static constructors
+TransactionBuilder.fromTransaction = function(transaction) {
+  var txb = new TransactionBuilder()
+
+  // Extract/add inputs
+  transaction.ins.forEach(function(txin) {
+    txb.addInput(txin.hash, txin.index, txin.sequence)
+  })
+
+  // Extract/add outputs
+  transaction.outs.forEach(function(txout) {
+    txb.addOutput(txout.script, txout.value)
+  })
+
+  // Extract/add signatures
+  transaction.ins.forEach(function(txin) {
+    // Ignore empty scripts
+    if (txin.script.buffer.length === 0) return
+
+    var redeemScript
+    var scriptSig = txin.script
+    var scriptType = scripts.classifyInput(scriptSig)
+
+    // Re-classify if P2SH
+    if (scriptType === 'scripthash') {
+      redeemScript = Script.fromBuffer(scriptSig.chunks.slice(-1)[0])
+      scriptSig = Script.fromChunks(scriptSig.chunks.slice(0, -1))
+
+      scriptType = scripts.classifyInput(scriptSig)
+      assert.equal(scripts.classifyOutput(redeemScript), scriptType, 'Non-matching scriptSig and scriptPubKey in input')
+    }
+
+    // Extract hashType, pubKeys and signatures
+    var hashType, pubKeys, signatures
+
+    switch (scriptType) {
+      case 'pubkeyhash':
+        var parsed = ECSignature.parseScriptSignature(scriptSig.chunks[0])
+        var pubKey = ECPubKey.fromBuffer(scriptSig.chunks[1])
+
+        hashType = parsed.hashType
+        pubKeys = [pubKey]
+        signatures = [parsed.signature]
+
+        break
+
+      case 'multisig':
+        var scriptSigs = scriptSig.chunks.slice(1) // ignore OP_0
+        var parsed = scriptSigs.map(function(scriptSig) {
+          return ECSignature.parseScriptSignature(scriptSig)
+        })
+
+        hashType = parsed[0].hashType
+        pubKeys = []
+        signatures = parsed.map(function(p) { return p.signature })
+
+        break
+
+      case 'pubkey':
+        var parsed = ECSignature.parseScriptSignature(scriptSig.chunks[0])
+
+        hashType = parsed.hashType
+        pubKeys = []
+        signatures = [parsed.signature]
+
+        break
+
+      default:
+        assert(false, scriptType + ' not supported')
+    }
+
+    txb.signatures[txin.index] = {
+      hashType: hashType,
+      pubKeys: pubKeys,
+      redeemScript: redeemScript,
+      scriptType: scriptType,
+      signatures: signatures
+    }
+  })
+
+  return txb
+}
+
+// Operations
+TransactionBuilder.prototype.addInput = function(prevTx, index, sequence, prevOutScript) {
+  var prevOutHash
+
+  if (typeof prevTx === 'string') {
+    prevOutHash = new Buffer(prevTx, 'hex')
+
+    // TxId hex is big-endian, we want little-endian hash
+    Array.prototype.reverse.call(prevOutHash)
+
+  } else if (prevTx instanceof Transaction) {
+    prevOutHash = prevTx.getHash()
+    prevOutScript = prevTx.outs[index].script
+
+  } else {
+    prevOutHash = prevTx
+
+  }
+
+  var prevOutType
+  if (prevOutScript !== undefined) {
+    prevOutType = scripts.classifyOutput(prevOutScript)
+
+    assert.notEqual(prevOutType, 'nonstandard', 'PrevOutScript not supported (nonstandard)')
+  }
+
+  assert(this.signatures.every(function(input) {
+    return input.hashType & Transaction.SIGHASH_ANYONECANPAY
+  }), 'No, this would invalidate signatures')
+
+  var prevOut = prevOutHash.toString('hex') + ':' + index
+  assert(!(prevOut in this.prevOutMap), 'Transaction is already an input')
+
+  var vout = this.tx.addInput(prevOutHash, index, sequence)
+  this.prevOutMap[prevOut] = true
+  this.prevOutScripts[vout] = prevOutScript
+  this.prevOutTypes[vout] = prevOutType
+
+  return vout
+}
+
+TransactionBuilder.prototype.addOutput = function(scriptPubKey, value) {
+  assert(this.signatures.every(function(signature) {
+    return (signature.hashType & 0x1f) === Transaction.SIGHASH_SINGLE
+  }), 'No, this would invalidate signatures')
+
+  return this.tx.addOutput(scriptPubKey, value)
+}
+
+TransactionBuilder.prototype.build = function() {
+  return this.__build(false)
+}
+
+TransactionBuilder.prototype.buildIncomplete = function() {
+  return this.__build(true)
+}
+
+TransactionBuilder.prototype.__build = function(allowIncomplete) {
+  if (!allowIncomplete) {
+    assert(this.tx.ins.length > 0, 'Transaction has no inputs')
+    assert(this.tx.outs.length > 0, 'Transaction has no outputs')
+    assert(this.signatures.length > 0, 'Transaction has no signatures')
+    assert.equal(this.signatures.length, this.tx.ins.length, 'Transaction is missing signatures')
+  }
+
+  var tx = this.tx.clone()
+
+  // Create script signatures from signature meta-data
+  this.signatures.forEach(function(input, index) {
+    var scriptSig
+    var scriptType = input.scriptType
+
+    var signatures = input.signatures.map(function(signature) {
+      return signature.toScriptSignature(input.hashType)
+    })
+
+    switch (scriptType) {
+      case 'pubkeyhash':
+        var signature = signatures[0]
+        var pubKey = input.pubKeys[0]
+        scriptSig = scripts.pubKeyHashInput(signature, pubKey)
+
+        break
+
+      case 'multisig':
+        var redeemScript = allowIncomplete ? undefined : input.redeemScript
+        scriptSig = scripts.multisigInput(signatures, redeemScript)
+
+        break
+
+      case 'pubkey':
+        var signature = signatures[0]
+        scriptSig = scripts.pubKeyInput(signature)
+
+        break
+
+      default:
+        assert(false, scriptType + ' not supported')
+    }
+
+    if (input.redeemScript) {
+      scriptSig = scripts.scriptHashInput(scriptSig, input.redeemScript)
+    }
+
+    tx.setInputScript(index, scriptSig)
+  })
+
+  return tx
+}
+
+TransactionBuilder.prototype.sign = function(index, privKey, redeemScript, hashType) {
+  assert(this.tx.ins.length >= index, 'No input at index: ' + index)
+  hashType = hashType || Transaction.SIGHASH_ALL
+
+  var prevOutScript = this.prevOutScripts[index]
+  var prevOutType = this.prevOutTypes[index]
+
+  var scriptType, hash
+  if (redeemScript) {
+    prevOutScript = prevOutScript || scripts.scriptHashOutput(redeemScript.getHash())
+    prevOutType = prevOutType || 'scripthash'
+
+    assert.equal(prevOutType, 'scripthash', 'PrevOutScript must be P2SH')
+
+    scriptType = scripts.classifyOutput(redeemScript)
+
+    assert.notEqual(scriptType, 'scripthash', 'RedeemScript can\'t be P2SH')
+    assert.notEqual(scriptType, 'nonstandard', 'RedeemScript not supported (nonstandard)')
+
+    hash = this.tx.hashForSignature(index, redeemScript, hashType)
+
+  } else {
+    prevOutScript = prevOutScript || privKey.pub.getAddress().toOutputScript()
+    scriptType = prevOutType || 'pubkeyhash'
+
+    assert.notEqual(scriptType, 'scripthash', 'PrevOutScript requires redeemScript')
+
+    hash = this.tx.hashForSignature(index, prevOutScript, hashType)
+  }
+
+  if (!(index in this.signatures)) {
+    this.signatures[index] = {
+      hashType: hashType,
+      pubKeys: [],
+      redeemScript: redeemScript,
+      scriptType: scriptType,
+      signatures: []
+    }
+  }
+
+  var input = this.signatures[index]
+  assert.equal(input.hashType, hashType, 'Inconsistent hashType')
+  assert.deepEqual(input.redeemScript, redeemScript, 'Inconsistent redeemScript')
+
+  var signature = privKey.sign(hash)
+  input.pubKeys.push(privKey.pub)
+  input.signatures.push(signature)
+}
+
+module.exports = TransactionBuilder

src/wallet.js

@@ -4,7 +4,7 @@ var networks = require('./networks')
 
 var Address = require('./address')
 var HDNode = require('./hdnode')
-var Transaction = require('./transaction')
+var TransactionBuilder = require('./transaction_builder')
 var Script = require('./script')
 
 function Wallet(seed, network, unspents) {
@@ -57,17 +57,17 @@ Wallet.prototype.createTx = function(to, value, fixedFee, changeAddress) {
   var subTotal = value
   var addresses = []
 
-  var tx = new Transaction()
+  var txb = new TransactionBuilder()
-  tx.addOutput(to, value)
+  txb.addOutput(to, value)
 
   for (var i = 0; i < utxos.length; ++i) {
     var utxo = utxos[i]
     addresses.push(utxo.address)
 
     var outpoint = utxo.from.split(':')
-    tx.addInput(outpoint[0], parseInt(outpoint[1]))
+    txb.addInput(outpoint[0], parseInt(outpoint[1]))
 
-    var fee = fixedFee === undefined ? estimatePaddedFee(tx, this.network) : fixedFee
+    var fee = fixedFee === undefined ? estimatePaddedFee(txb.buildIncomplete(), this.network) : fixedFee
 
     accum += utxo.value
     subTotal = value + fee
@@ -75,7 +75,7 @@ Wallet.prototype.createTx = function(to, value, fixedFee, changeAddress) {
       var change = accum - subTotal
 
       if (change > this.network.dustThreshold) {
-        tx.addOutput(changeAddress || this.getChangeAddress(), change)
+        txb.addOutput(changeAddress || this.getChangeAddress(), change)
       }
 
       break
@@ -84,8 +84,7 @@ Wallet.prototype.createTx = function(to, value, fixedFee, changeAddress) {
 
   assert(accum >= subTotal, 'Not enough funds (incl. fee): ' + accum + ' < ' + subTotal)
 
-  this.signWith(tx, addresses)
+  return this.signWith(txb, addresses).build()
-  return tx
 }
 
 Wallet.prototype.processPendingTx = function(tx){
@@ -219,16 +218,14 @@ Wallet.prototype.setUnspentOutputs = function(utxo) {
   this.outputs = processUnspentOutputs(utxo)
 }
 
-Wallet.prototype.signWith = function(tx, addresses) {
+Wallet.prototype.signWith = function(txb, addresses) {
-  assert.equal(tx.ins.length, addresses.length, 'Number of addresses must match number of transaction inputs')
-
   addresses.forEach(function(address, i) {
-    var key = this.getPrivateKeyForAddress(address)
+    var privKey = this.getPrivateKeyForAddress(address)
 
-    tx.sign(i, key)
+    txb.sign(i, privKey)
   }, this)
 
-  return tx
+  return txb
 }
 
 function outputToUnspentOutput(output){

test/bitcoin.core.js

@@ -183,7 +183,7 @@ describe('Bitcoin-core', function() {
 
         var actualHash
         try {
-          actualHash = transaction.hashForSignature(script, inIndex, hashType)
+          actualHash = transaction.hashForSignature(inIndex, script, hashType)
         } catch (e) {
           // don't fail if we don't support it yet, TODO
           if (!e.message.match(/not yet supported/)) throw e

test/fixtures/transaction_builder.json

@@ -0,0 +1,152 @@
+{
+  "valid": {
+    "build": [
+      {
+        "description": "pubKeyHash->pubKeyHash 1:1 transaction",
+        "txid": "bd641f4b0aa8bd70189ab45e935c4762f0e1c49f294b4779d79887937b7cf42e",
+        "txhex": "0100000001ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff000000006b483045022100a3b254e1c10b5d039f36c05f323995d6e5a367d98dd78a13d5bbc3991b35720e022022fccea3897d594de0689601fbd486588d5bfa6915be2386db0397ee9a6e80b601210279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798ffffffff0110270000000000001976a914aa4d7985c57e011a8b3dd8e0e5a73aaef41629c588ac00000000",
+        "inputs": [
+          {
+            "index": 0,
+            "prevTx": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+            "privKeys": [
+              "KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU73sVHnoWn"
+            ]
+          }
+        ],
+        "outputs": [
+          {
+            "script": "OP_DUP OP_HASH160 aa4d7985c57e011a8b3dd8e0e5a73aaef41629c5 OP_EQUALVERIFY OP_CHECKSIG",
+            "value": 10000
+          }
+        ]
+      },
+      {
+        "description": "pubKey->pubKeyHash 1:1 transaction",
+        "txid": "a900dea133a3c51e9fe55d82bf4a4f50a4c3ac6e380c841f93651a076573320c",
+        "txhex": "0100000001ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00000000494830450221009833abb3ab49d7004c06bcc79eafd6905ada3eee91f3376ad388548034acd9a702202e84dda6ef2678c82256afcfc459aaa68e179b2bb0e6b2dc3f1410e132c5e6c301ffffffff0100f90295000000001976a914aa4d7985c57e011a8b3dd8e0e5a73aaef41629c588ac00000000",
+        "inputs": [
+          {
+            "index": 0,
+            "prevTx": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+            "prevTxScript": "0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 OP_CHECKSIG",
+            "privKeys": [
+              "KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU73sVHnoWn"
+            ]
+          }
+        ],
+        "outputs": [
+          {
+            "script": "OP_DUP OP_HASH160 aa4d7985c57e011a8b3dd8e0e5a73aaef41629c5 OP_EQUALVERIFY OP_CHECKSIG",
+            "value": 2500000000
+          }
+        ]
+      },
+      {
+        "description": "2-of-2 P2SH multisig -> pubKeyHash 1:1 Transaction",
+        "txid": "8c500ce6eef6c78a10de923b68394cf31120151bdc4600e4b12de865defa9d24",
+        "txhex": "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",
+        "inputs": [
+          {
+            "index": 0,
+            "prevTx": "4971f016798a167331bcbc67248313fbc444c6e92e4416efd06964425588f5cf",
+            "privKeys": [
+              "91avARGdfge8E4tZfYLoxeJ5sGBdNJQH4kvjJoQFacbgwmaKkrx",
+              "91avARGdfge8E4tZfYLoxeJ5sGBdNJQH4kvjJoQFacbgww7vXtT"
+            ],
+            "redeemScript": "OP_2 0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8 04c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee51ae168fea63dc339a3c58419466ceaeef7f632653266d0e1236431a950cfe52a OP_2 OP_CHECKMULTISIG"
+          }
+        ],
+        "outputs": [
+          {
+            "script": "OP_DUP OP_HASH160 faf1d99bf040ea9c7f8cc9f14ac6733ad75ce246 OP_EQUALVERIFY OP_CHECKSIG",
+            "value": 10000
+          }
+        ]
+      }
+    ]
+  },
+  "invalid": {
+    "build": [
+      {
+        "exception": "Transaction has no inputs",
+        "inputs": [],
+        "outputs": [
+          {
+            "script": "OP_DUP OP_HASH160 aa4d7985c57e011a8b3dd8e0e5a73aaef41629c5 OP_EQUALVERIFY OP_CHECKSIG",
+            "value": 1000
+          }
+        ]
+      },
+      {
+        "exception": "Transaction has no outputs",
+        "inputs": [
+          {
+            "index": 0,
+            "prevTx": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+            "privKeys": []
+          }
+        ],
+        "outputs": []
+      },
+      {
+        "exception": "Transaction has no signatures",
+        "inputs": [
+          {
+            "index": 0,
+            "prevTx": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+            "privKeys": []
+          }
+        ],
+        "outputs": [
+          {
+            "script": "OP_DUP OP_HASH160 aa4d7985c57e011a8b3dd8e0e5a73aaef41629c5 OP_EQUALVERIFY OP_CHECKSIG",
+            "value": 1000
+          }
+        ]
+      },
+      {
+        "exception": "Transaction is missing signatures",
+        "inputs": [
+          {
+            "index": 0,
+            "prevTx": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+            "privKeys": [
+              "KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU73sVHnoWn"
+            ]
+          },
+          {
+            "index": 1,
+            "prevTx": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+            "privKeys": []
+          }
+        ],
+        "outputs": [
+          {
+            "script": "OP_DUP OP_HASH160 aa4d7985c57e011a8b3dd8e0e5a73aaef41629c5 OP_EQUALVERIFY OP_CHECKSIG",
+            "value": 1000
+          }
+        ]
+      },
+      {
+        "exception": "nulldata not supported",
+        "inputs": [
+          {
+            "index": 0,
+            "prevTx": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+            "prevTxScript": "OP_RETURN 06deadbeef03f895a2ad89fb6d696497af486cb7c644a27aa568c7a18dd06113401115185474",
+            "privKeys": [
+              "KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU73sVHnoWn"
+            ]
+          }
+        ],
+        "outputs": [
+          {
+            "script": "OP_DUP OP_HASH160 aa4d7985c57e011a8b3dd8e0e5a73aaef41629c5 OP_EQUALVERIFY OP_CHECKSIG",
+            "value": 1000
+          }
+        ]
+      }
+    ]
+  }
+}

test/integration/p2sh.js

@@ -1,14 +1,12 @@
 var assert = require('assert')
 
 var bitcoin = require('../../')
-var crypto = bitcoin.crypto
 var networks = bitcoin.networks
 var scripts = bitcoin.scripts
 
 var Address = bitcoin.Address
 var ECKey = bitcoin.ECKey
-var Transaction = bitcoin.Transaction
+var TransactionBuilder = bitcoin.TransactionBuilder
-var Script = bitcoin.Script
 
 var helloblock = require('helloblock-js')({
   network: 'testnet'
@@ -43,35 +41,31 @@ describe('Bitcoin-js', function() {
     var targetAddress = ECKey.makeRandom().pub.getAddress(networks.testnet).toString()
 
     // get latest unspents from the multisigAddress
-    helloblock.addresses.getUnspents(multisigAddress, function(err, resp, resource) {
+    helloblock.addresses.getUnspents(multisigAddress, function(err, res, unspents) {
       if (err) return done(err)
 
       // use the oldest unspent
-      var unspent = resource[resource.length - 1]
+      var unspent = unspents[unspents.length - 1]
       var spendAmount = Math.min(unspent.value, outputAmount)
 
-      var tx = new Transaction()
+      var txb = new TransactionBuilder()
-      tx.addInput(unspent.txHash, unspent.index)
+      txb.addInput(unspent.txHash, unspent.index)
-      tx.addOutput(targetAddress, spendAmount)
+      txb.addOutput(targetAddress, spendAmount)
 
-      var signatures = privKeys.map(function(privKey) {
+      privKeys.forEach(function(privKey) {
-        return tx.signInput(0, redeemScript, privKey)
+        txb.sign(0, privKey, redeemScript)
       })
 
-      var redeemScriptSig = scripts.multisigInput(signatures)
-      var scriptSig = scripts.scriptHashInput(redeemScriptSig, redeemScript)
-      tx.setInputScript(0, scriptSig)
-
       // broadcast our transaction
-      helloblock.transactions.propagate(tx.toHex(), function(err, resp, resource) {
+      helloblock.transactions.propagate(txb.build().toHex(), function(err, res) {
         // no err means that the transaction has been successfully propagated
         if (err) return done(err)
 
         // Check that the funds (spendAmount Satoshis) indeed arrived at the intended address
-        helloblock.addresses.get(targetAddress, function(err, resp, resource) {
+        helloblock.addresses.get(targetAddress, function(err, res, addrInfo) {
           if (err) return done(err)
 
-          assert.equal(resource.balance, spendAmount)
+          assert.equal(addrInfo.balance, spendAmount)
           done()
         })
       })

test/transaction.js

@@ -221,7 +221,7 @@ describe('Transaction', function() {
   // TODO:
   //  hashForSignature: [Function],
 
-  // FIXME: could be better
+  // FIXME: remove in 2.x.y
   describe('signInput/validateInput', function() {
     it('works for multi-sig redeem script', function() {
       var tx = new Transaction()

test/transaction_builder.js

@@ -0,0 +1,262 @@
+var assert = require('assert')
+var ecdsa = require('../src/ecdsa')
+var scripts = require('../src/scripts')
+
+var Address = require('../src/address')
+var BigInteger = require('bigi')
+var ECKey = require('../src/eckey')
+var Script = require('../src/script')
+var Transaction = require('../src/transaction')
+var TransactionBuilder = require('../src/transaction_builder')
+
+var fixtures = require('./fixtures/transaction_builder')
+
+describe('TransactionBuilder', function() {
+  var privAddress, privScript
+  var prevTx, prevTxHash
+  var privKey
+  var txb
+
+  beforeEach(function() {
+    txb = new TransactionBuilder()
+
+    prevTx = new Transaction()
+    prevTx.addOutput('1BgGZ9tcN4rm9KBzDn7KprQz87SZ26SAMH', 0)
+    prevTx.addOutput('1cMh228HTCiwS8ZsaakH8A8wze1JR5ZsP', 1)
+    prevTxHash = prevTx.getHash()
+    prevTxId = prevTx.getId()
+
+    privKey = new ECKey(BigInteger.ONE, false)
+    privAddress = privKey.pub.getAddress()
+    privScript = privAddress.toOutputScript()
+    value = 10000
+  })
+
+  describe('addInput', function() {
+    it('accepts a txHash, index [and sequence number]', function() {
+      var vin = txb.addInput(prevTxHash, 1, 54)
+      assert.equal(vin, 0)
+
+      var txin = txb.tx.ins[0]
+      assert.equal(txin.hash, prevTxHash)
+      assert.equal(txin.index, 1)
+      assert.equal(txin.sequence, 54)
+      assert.equal(txb.prevOutScripts[0], undefined)
+    })
+
+    it('accepts a txHash, index [, sequence number and scriptPubKey]', function() {
+      var vin = txb.addInput(prevTxHash, 1, 54, prevTx.outs[1].script)
+      assert.equal(vin, 0)
+
+      var txin = txb.tx.ins[0]
+      assert.equal(txin.hash, prevTxHash)
+      assert.equal(txin.index, 1)
+      assert.equal(txin.sequence, 54)
+      assert.equal(txb.prevOutScripts[0], prevTx.outs[1].script)
+    })
+
+    it('accepts a prevTx, index [and sequence number]', function() {
+      var vin = txb.addInput(prevTx, 1, 54)
+      assert.equal(vin, 0)
+
+      var txin = txb.tx.ins[0]
+      assert.deepEqual(txin.hash, prevTxHash)
+      assert.equal(txin.index, 1)
+      assert.equal(txin.sequence, 54)
+      assert.equal(txb.prevOutScripts[0], prevTx.outs[1].script)
+    })
+
+    it('returns the input index', function() {
+      assert.equal(txb.addInput(prevTxHash, 0), 0)
+      assert.equal(txb.addInput(prevTxHash, 1), 1)
+    })
+
+    it('throws if prevOutScript is not supported', function() {
+      assert.throws(function() {
+        txb.addInput(prevTxHash, 0, undefined, Script.EMPTY)
+      }, /PrevOutScript not supported \(nonstandard\)/)
+    })
+
+    it('throws if SIGHASH_ALL has been used to sign any existing scriptSigs', function() {
+      txb.addInput(prevTxHash, 0)
+      txb.sign(0, privKey)
+
+      assert.throws(function() {
+        txb.addInput(prevTxHash, 0)
+      }, /No, this would invalidate signatures/)
+    })
+  })
+
+  describe('addOutput', function() {
+    it('throws if SIGHASH_ALL has been used to sign any existing scriptSigs', function() {
+      txb.addInput(prevTxHash, 0)
+      txb.addOutput(privScript, value)
+      txb.sign(0, privKey)
+
+      assert.throws(function() {
+        txb.addOutput(privScript, 9000)
+      }, /No, this would invalidate signatures/)
+    })
+  })
+
+  describe('sign', function() {
+    describe('when prevOutScript is undefined', function() {
+      it('assumes pubKeyHash', function() {
+        txb.addInput(prevTxHash, 0)
+        txb.sign(0, privKey)
+
+        assert.strictEqual(txb.signatures[0].redeemScript, undefined)
+        assert.equal(txb.signatures[0].scriptType, 'pubkeyhash')
+      })
+    })
+
+    describe('when redeemScript is defined', function() {
+      it('assumes scriptHash', function() {
+        txb.addInput(prevTxHash, 0)
+        txb.sign(0, privKey, privScript)
+
+        assert.equal(txb.signatures[0].redeemScript, privScript)
+      })
+
+      it('throws if prevOutScript is not P2SH', function() {
+        txb.addInput(prevTx, 0)
+
+        assert.throws(function() {
+          txb.sign(0, privKey, privScript)
+        }, /PrevOutScript must be P2SH/)
+      })
+
+      it('throws if redeemScript is P2SH', function() {
+        txb.addInput(prevTxHash, 0)
+
+        var privScriptP2SH = scripts.scriptHashOutput(privScript.getHash())
+
+        assert.throws(function() {
+          txb.sign(0, privKey, privScriptP2SH)
+        }, /RedeemScript can\'t be P2SH/)
+      })
+
+      it('throws if redeemScript not supported', function() {
+        txb.addInput(prevTxHash, 0)
+
+        assert.throws(function() {
+          txb.sign(0, privKey, Script.EMPTY)
+        }, /RedeemScript not supported \(nonstandard\)/)
+      })
+    })
+  })
+
+  describe('build', function() {
+    fixtures.valid.build.forEach(function(f) {
+      it('builds the correct transaction', function() {
+        f.inputs.forEach(function(input) {
+          var prevTxScript
+
+          if (input.prevTxScript) {
+            prevTxScript = Script.fromASM(input.prevTxScript)
+          }
+
+          txb.addInput(input.prevTx, input.index, input.sequence, prevTxScript)
+        })
+
+        f.outputs.forEach(function(output) {
+          var script = Script.fromASM(output.script)
+
+          txb.addOutput(script, output.value)
+        })
+
+        f.inputs.forEach(function(input, index) {
+          var redeemScript
+
+          if (input.redeemScript) {
+            redeemScript = Script.fromASM(input.redeemScript)
+          }
+
+          input.privKeys.forEach(function(wif) {
+            var privKey = ECKey.fromWIF(wif)
+
+            txb.sign(index, privKey, redeemScript)
+          })
+        })
+
+        var tx = txb.build()
+
+        assert.equal(tx.getId(), f.txid)
+      })
+    })
+
+    fixtures.invalid.build.forEach(function(f) {
+      it('throws on ' + f.exception, function() {
+        f.inputs.forEach(function(input) {
+          var prevTxScript
+
+          if (input.prevTxScript) {
+            prevTxScript = Script.fromASM(input.prevTxScript)
+          }
+
+          txb.addInput(input.prevTx, input.index, input.sequence, prevTxScript)
+        })
+
+        f.outputs.forEach(function(output) {
+          var script = Script.fromASM(output.script)
+
+          txb.addOutput(script, output.value)
+        })
+
+        f.inputs.forEach(function(input, index) {
+          var redeemScript
+
+          if (input.redeemScript) {
+            redeemScript = Script.fromASM(input.redeemScript)
+          }
+
+          input.privKeys.forEach(function(wif) {
+            var privKey = ECKey.fromWIF(wif)
+
+            txb.sign(index, privKey, redeemScript)
+          })
+        })
+
+        assert.throws(function() {
+          txb.build()
+        }, new RegExp(f.exception))
+      })
+    })
+  })
+
+  describe('fromTransaction', function() {
+    fixtures.valid.build.forEach(function(f) {
+      it('builds the correct TransactionBuilder for ' + f.description, function() {
+        var tx = Transaction.fromHex(f.txhex)
+        var txb = TransactionBuilder.fromTransaction(tx)
+
+        assert.equal(txb.build().toHex(), f.txhex)
+      })
+    })
+
+    it('works for the P2SH multisig case', function() {
+      var privKeys = [
+        "91avARGdfge8E4tZfYLoxeJ5sGBdNJQH4kvjJoQFacbgwmaKkrx",
+        "91avARGdfge8E4tZfYLoxeJ5sGBdNJQH4kvjJoQFacbgww7vXtT"
+      ].map(function(wif) { return ECKey.fromWIF(wif) })
+      var redeemScript = Script.fromASM("OP_2 0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8 04c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee51ae168fea63dc339a3c58419466ceaeef7f632653266d0e1236431a950cfe52a OP_2 OP_CHECKMULTISIG")
+
+      txb.addInput("4971f016798a167331bcbc67248313fbc444c6e92e4416efd06964425588f5cf", 0)
+      txb.addOutput("1BgGZ9tcN4rm9KBzDn7KprQz87SZ26SAMH", 10000)
+      txb.sign(0, privKeys[0], redeemScript)
+
+      var tx = txb.buildIncomplete()
+
+      // in another galaxy...
+      // ... far, far away
+      var txb2 = TransactionBuilder.fromTransaction(tx)
+
+      // [you should] verify that Transaction is what you want...
+      // ... then sign it
+      txb2.sign(0, privKeys[1], redeemScript)
+      var tx2 = txb2.build()
+
+      assert.equal(tx2.toHex(), '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')
+    })
+  })
+})

test/wallet.js

@@ -7,6 +7,7 @@ var scripts = require('../src/scripts')
 var Address = require('../src/address')
 var HDNode = require('../src/hdnode')
 var Transaction = require('../src/transaction')
+var TransactionBuilder = require('../src/transaction_builder')
 var Wallet = require('../src/wallet')
 
 var fixtureTxes = require('./fixtures/mainnet_tx')
@@ -623,17 +624,17 @@ describe('Wallet', function() {
 
     describe('signing', function(){
       afterEach(function(){
-        Transaction.prototype.sign.restore()
+        TransactionBuilder.prototype.sign.restore()
       })
 
       it('signs the inputs with respective keys', function(){
         var fee = 30000
-        sinon.stub(Transaction.prototype, "sign")
+        sinon.spy(TransactionBuilder.prototype, "sign")
 
         var tx = wallet.createTx(to, value, fee)
 
-        assert(Transaction.prototype.sign.calledWith(0, wallet.getPrivateKeyForAddress(address2)))
+        assert(TransactionBuilder.prototype.sign.calledWith(0, wallet.getPrivateKeyForAddress(address2)))
-        assert(Transaction.prototype.sign.calledWith(1, wallet.getPrivateKeyForAddress(address1)))
+        assert(TransactionBuilder.prototype.sign.calledWith(1, wallet.getPrivateKeyForAddress(address1)))
       })
     })