selectUnspent function and tests

Transaction.js

@@ -679,6 +679,56 @@ Transaction.prototype.parse = function (parser) {
   this.calcHash();
 };
 
+/*
+ * selectUnspent
+ *
+ *  Selects some unspend outputs for later usage in tx inputs
+ *
+ * @unspentArray: unspent array (UTXO) avaible on the form:
+ * [{
+ *       address: "mqSjTad2TKbPcKQ3Jq4kgCkKatyN44UMgZ",
+ *       hash: "2ac165fa7a3a2b535d106a0041c7568d03b531e58aeccdd3199d7289ab12cfc1",
+ *       scriptPubKey: "76a9146ce4e1163eb18939b1440c42844d5f0261c0338288ac",
+ *       vout: 1,
+ *       amount: 0.01,                
+ *       }, [...]
+ * ]
+ * This is compatible con insight's /utxo API. 
+ * NOTE that amount is in BTCs! (as returned in insight and bitcoind.
+ *
+ * @totalNeededAmount: output transaction amount in BTC, including fee
+ *
+ *
+ * Return the selected outputs or null if there are not enough funds.
+ * It does not check for confirmations. The unspendArray should be filtered.
+ *
+ */
+Transaction.selectUnspent = function (unspentArray, totalNeededAmount) {
+
+  // TODO we could randomize or select the selection
+  
+  var selected = [];
+  var l = unspentArray.length;
+  var totalSat = bignum(0);
+  var totalNeededAmountSat = bignum(totalNeededAmount * util.COIN);
+  var fullfill  = false;
+
+  for(var i = 0; i<l; i++) {
+    var u = unspentArray[i];
+    var sat = bignum(u.amount * util.COIN);
+    totalSat = totalSat.add(sat);
+    selected.push(u);
+    if(totalSat.cmp(totalNeededAmountSat) >= 0) {
+      fullfill = true;
+      break;
+    }
+  }
+  if (!fullfill) return [];
+  return selected;
+}
+
+
+
 var TransactionInputsCache = exports.TransactionInputsCache =
 function TransactionInputsCache(tx)
 {

test/data/unspends.json

@@ -0,0 +1,24 @@
+[
+  {
+    "address": "mqSjTad2TKbPcKQ3Jq4kgCkKatyN44UMgZ",
+    "txid": "2ac165fa7a3a2b535d106a0041c7568d03b531e58aeccdd3199d7289ab12cfc1",
+    "scriptPubKey": "76a9146ce4e1163eb18939b1440c42844d5f0261c0338288ac",
+    "vout": 1,
+    "amount": 0.01
+  },
+  {
+    "address": "mqSjTad2TKbPcKQ3Jq4kgCkKatyN44UMgZ",
+    "txid": "2ac165fa7a3a2b535d106a0041c7568d03b531e58aeccdd3199d7289ab12cfc2",
+    "scriptPubKey": "76a9146ce4e1163eb18939b1440c42844d5f0261c0338288ad",
+    "vout": 1,
+    "amount": 0.1
+  },
+  {
+    "address": "mqSjTad2TKbPcKQ3Jq4kgCkKatyN44UMgZ",
+    "txid": "2ac165fa7a3a2b535d106a0041c7568d03b531e58aeccdd3199d7289ab12cfc3",
+    "scriptPubKey": "76a9146ce4e1163eb18939b1440c42844d5f0261c0338288ae",
+    "vout": 3,
+    "amount": 1
+  }
+]
+

test/test.Transaction.js

@@ -25,11 +25,40 @@ describe('Transaction', function() {
     should.exist(In);
     should.exist(Out);
   });
+
+
   it('should be able to create instance', function() {
     var t = new Transaction();
     should.exist(t);
   });
 
+
+  it('should be able to select unspents', function() {
+    var u = Transaction.selectUnspent(testdata.dataUnspends,1.0);
+    u.length.should.equal(3);
+    u = Transaction.selectUnspent(testdata.dataUnspends,0.5);
+    u.length.should.equal(3);
+    u = Transaction.selectUnspent(testdata.dataUnspends,0.1);
+    u.length.should.equal(2);
+    u = Transaction.selectUnspent(testdata.dataUnspends,0.05);
+    u.length.should.equal(2);
+    u = Transaction.selectUnspent(testdata.dataUnspends,0.015);
+    u.length.should.equal(2);
+    u = Transaction.selectUnspent(testdata.dataUnspends,0.01);
+    u.length.should.equal(1);
+    should.exist(u[0].amount);
+    should.exist(u[0].txid);
+    should.exist(u[0].scriptPubKey);
+    should.exist(u[0].vout);
+  });
+
+
+  it.skip('should be able to create instance thru #create', function() {
+    var t = Transaction.create({
+    });
+    should.exist(t);
+  });
+
   // Read tests from test/data/tx_valid.json
   // Format is an array of arrays
   // Inner arrays are either [ "comment" ]

test/testdata.js

@@ -7,6 +7,8 @@ var dataTxValid = JSON.parse(fs.readFileSync('test/data/tx_valid.json'));
 var dataTxInvalid = JSON.parse(fs.readFileSync('test/data/tx_invalid.json'));
 var dataScriptValid = JSON.parse(fs.readFileSync('test/data/script_valid.json'));
 var dataScriptInvalid = JSON.parse(fs.readFileSync('test/data/script_invalid.json'));
+var dataUnspends = JSON.parse(fs.readFileSync('test/data/unspends.json'));
+ 
 
 module.exports.dataValid = dataValid;
 module.exports.dataInvalid = dataInvalid;
@@ -16,3 +18,4 @@ module.exports.dataTxInvalid = dataTxInvalid;
 module.exports.dataScriptValid = dataScriptValid;
 module.exports.dataScriptInvalid = dataScriptInvalid;
 module.exports.dataScriptAll = dataScriptValid.concat(dataScriptInvalid);
+module.exports.dataUnspends = dataUnspends;