From cbde3233df8a634d976db3c8c29c21a93f1662ae Mon Sep 17 00:00:00 2001
From: Ivan Socolsky <jungans@gmail.com>
Date: Mon, 7 Mar 2016 15:18:32 -0300
Subject: [PATCH] handle lots of small inputs causing the total balance after
 fees to decrease

---
 lib/server.js              | 28 +++++++++++++++++-----------
 test/integration/server.js | 21 +++++++++++++++++++--
 2 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/lib/server.js b/lib/server.js
index be9f80a..7acdd0f 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -1273,6 +1273,12 @@ WalletService.prototype._selectTxInputs = function(txp, utxosToExclude, cb) {
     return cb(self._checkTxAndEstimateFee(txp));
   }
 
+  var txpAmount = txp.getTotalAmount();
+  var baseTxpSize = txp.getEstimatedSize();
+  var baseTxpFee = baseTxpSize * txp.feePerKb / 1000.;
+  var sizePerInput = txp.getEstimatedSizeForSingleInput();
+  var feePerInput = sizePerInput * txp.feePerKb / 1000.;
+
   function excludeUtxos(utxos) {
     var excludeIndex = _.reduce(utxosToExclude, function(res, val) {
       res[val] = val;
@@ -1284,6 +1290,15 @@ WalletService.prototype._selectTxInputs = function(txp, utxosToExclude, cb) {
     });
   };
 
+  function sanitizeUtxos(utxos) {
+    return _.filter(utxos, function(utxo) {
+      if (utxo.locked) return false;
+      if (utxo.satoshis <= feePerInput) return false;
+      if (txp.excludeUnconfirmedUtxos && !utxo.confirmations) return false;
+      return true;
+    });
+  };
+
   function partitionUtxos(utxos) {
     return _.groupBy(utxos, function(utxo) {
       if (utxo.confirmations == 0) return '0'
@@ -1293,14 +1308,9 @@ WalletService.prototype._selectTxInputs = function(txp, utxosToExclude, cb) {
   };
 
   function select(utxos, cb) {
-    var txpAmount = txp.getTotalAmount();
-    var baseTxpSize = txp.getEstimatedSize();
-    var baseTxpFee = baseTxpSize * txp.feePerKb / 1000.;
-    var sizePerInput = txp.getEstimatedSizeForSingleInput();
-    var feePerInput = sizePerInput * txp.feePerKb / 1000.;
-
     var totalValueInUtxos = _.sum(utxos, 'satoshis');
     var netValueInUtxos = totalValueInUtxos - baseTxpFee - (utxos.length * feePerInput);
+
     if (totalValueInUtxos < txpAmount) {
       log.debug('Total value in all utxos (' + Utils.formatAmountInBtc(totalValueInUtxos) + ') is insufficient to cover for txp amount (' + Utils.formatAmountInBtc(txpAmount) + ')');
       return cb(Errors.INSUFFICIENT_FUNDS);
@@ -1422,11 +1432,7 @@ WalletService.prototype._selectTxInputs = function(txp, utxosToExclude, cb) {
     if (totalAmount < txp.getTotalAmount()) return cb(Errors.INSUFFICIENT_FUNDS);
     if (availableAmount < txp.getTotalAmount()) return cb(Errors.LOCKED_FUNDS);
 
-    // Prepare UTXOs list
-    utxos = _.reject(utxos, 'locked');
-    if (txp.excludeUnconfirmedUtxos) {
-      utxos = _.filter(utxos, 'confirmations');
-    }
+    utxos = sanitizeUtxos(utxos);
 
     log.debug('Considering ' + utxos.length + ' utxos (' + Utils.formatUtxos(utxos) + ')');
 
diff --git a/test/integration/server.js b/test/integration/server.js
index e12ddcb..1b78eed 100644
--- a/test/integration/server.js
+++ b/test/integration/server.js
@@ -3412,8 +3412,6 @@ describe('Wallet service', function() {
             feePerKb: 100e2,
           };
           server.createTx(txOpts, function(err, txp) {
-            console.log('*** [server.js ln3417] err:', err); // TODO
-
             should.not.exist(err);
             should.exist(txp);
             txp.inputs.length.should.equal(1);
@@ -3422,6 +3420,25 @@ describe('Wallet service', function() {
           });
         });
       });
+      it('should ignore utxos too small to pay for fee', function(done) {
+        helpers.stubUtxos(server, wallet, ['1c200bit', '200bit'].concat(_.times(20, function() {
+          return '1bit';
+        })), function() {
+          var txOpts = {
+            outputs: [{
+              toAddress: '18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7',
+              amount: 200e2,
+            }],
+            feePerKb: 90e2,
+          };
+          server.createTx(txOpts, function(err, txp) {
+            should.not.exist(err);
+            should.exist(txp);
+            txp.inputs.length.should.equal(2);
+            done();
+          });
+        });
+      });
     });
   });