Merge pull request #353 from blockchain/max-available

fix(): max available amount

src/helpers.js

@@ -468,10 +468,29 @@ Helpers.isEmailInvited = function (email, fraction) {
 };
 
 Helpers.blockchainFee = (amount, options) =>
-  amount < options.min_tx_amount
+  amount <= options.min_tx_amount
     ? 0
     : Math.min(Math.floor(amount * options.percent), options.max_service_charge);
 
+Helpers.balanceMinusFee = (balance, options) => {
+  if (!options || options.max_service_charge === undefined ||
+                  options.percent === undefined ||
+                  options.min_tx_amount === undefined) {
+    return balance;
+  }
+  if (balance <= options.min_tx_amount) {
+    return balance;
+  }
+  const point = Math.floor(options.max_service_charge * ((1 / options.percent) + 1));
+  if (options.min_tx_amount < balance && balance <= point) {
+    const maxWithFee = Math.floor(balance / (1 + options.percent));
+    return Math.max(maxWithFee, options.min_tx_amount);
+  }
+  return point < balance
+    ? balance - options.max_service_charge
+    : balance;
+};
+
 Helpers.guidToGroup = (guid) => {
   let hashed = WalletCrypo.sha256(new Buffer(guid.replace(/-/g, ''), 'hex'));
   return hashed[0] & 1 ? 'b' : 'a';

src/payment.js

@@ -69,7 +69,8 @@ function Payment (wallet, payment) {
     confEstimation: 'unknown',
     txSize: 0, // transaciton size
     blockchainFee: 0,
-    blockchainAddress: null
+    blockchainAddress: null,
+    serviceChargeOptions: {}
   };
 
   var p = payment || initialState;
@@ -248,6 +249,7 @@ Payment.amount = function (amounts, absoluteFee, feeOptions) {
       console.log('No amounts set.');
   } // fi switch
   return function (payment) {
+    payment.serviceChargeOptions = feeOptions || {};
     payment.blockchainFee = feeOptions
       ? Helpers.blockchainFee(formatAmo.reduce(Helpers.add, 0), feeOptions)
       : 0;
@@ -376,7 +378,7 @@ Payment.prebuild = function (absoluteFee) {
 
     var usableCoins = Transaction.filterUsableCoins(payment.coins, payment.feePerKb);
     var max = Transaction.maxAvailableAmount(usableCoins, payment.feePerKb);
-    payment.sweepAmount = max.amount - payment.blockchainFee;
+    payment.sweepAmount = Helpers.balanceMinusFee(max.amount, payment.serviceChargeOptions);
     payment.sweepFee = max.fee;
     payment.balance = Transaction.sumOfCoins(payment.coins);
 

src/transaction.js

@@ -168,7 +168,6 @@ Transaction.sumOfCoins = function (coins) {
 
 Transaction.selectCoins = function (usableCoins, amounts, fee, isAbsoluteFee) {
   var amount = amounts.reduce(Helpers.add, 0);
-  var nouts = amounts.length;
   var sorted = usableCoins.sort(function (a, b) { return b.value - a.value; });
   var len = sorted.length;
   var sel = [];
@@ -186,7 +185,7 @@ Transaction.selectCoins = function (usableCoins, amounts, fee, isAbsoluteFee) {
     for (var ii = 0; ii < len; ii++) {
       var coin2 = sorted[ii];
       accAm = accAm + coin2.value;
-      accFee = Transaction.guessFee(ii + 1, nouts + 1, fee);
+      accFee = Transaction.guessFee(ii + 1, 2, fee);
       sel.push(coin2);
       if (accAm >= accFee + amount) { return {'coins': sel, 'fee': accFee}; }
     }

tests/transaction_spend_spec.js

@@ -413,7 +413,7 @@ describe('Transaction', () => {
       let fee = 10000;
       let isAbsFee = false;
       let s = Transaction.selectCoins(coins, amounts, fee, isAbsFee);
-      expect(s).toEqual({'coins': [{value: 40000}, {value: 30000}], 'fee': 4080});
+      expect(s).toEqual({'coins': [{value: 40000}, {value: 30000}], 'fee': 3740});
     });
 
     it('Transaction.selectCoins with absolute fee', () => {