From 7b27f5dc9bf60c5ae8d04fec184d321bdd75b139 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Tue, 12 Jan 2016 04:08:25 -0800
Subject: [PATCH] hard fee calculation.

---
 lib/bcoin/tx.js | 72 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 45 insertions(+), 27 deletions(-)

diff --git a/lib/bcoin/tx.js b/lib/bcoin/tx.js
index 44e7ed81..32df2726 100644
--- a/lib/bcoin/tx.js
+++ b/lib/bcoin/tx.js
@@ -41,6 +41,10 @@ function TX(data, block) {
 
   this._lock = this.lock;
 
+  this._fee = !(data instanceof bcoin.tx)
+    ? data.fee
+    : data._fee;
+
   if (data.inputs) {
     data.inputs.forEach(function(input) {
       this.input(input, null);
@@ -781,7 +785,7 @@ TX.prototype.maxSize = function maxSize() {
   return total;
 };
 
-TX.prototype.getUnspent = function getUnspent(unspent) {
+TX.prototype.getUnspent = function getUnspent(unspent, hardFee) {
   var tx = this.clone();
   var cost = tx.funds('out');
   var fee = 1;
@@ -790,48 +794,59 @@ TX.prototype.getUnspent = function getUnspent(unspent) {
   var lastAdded = 0;
   var size, addFee, change;
 
+  if (!hardFee)
+    hardFee = this._fee;
+
+  if (hardFee) {
+    total = cost.add(hardFee);
+    this._fee = hardFee;
+  }
+
   function addInput(unspent) {
-    // Add new inputs until TX will have enough funds to cover both
-    // minimum post cost and fee
+    // Add new inputs until TX will have enough
+    // funds to cover both minimum post cost
+    // and fee.
     var index = tx._input(unspent);
     inputs.push(tx.inputs[index]);
     lastAdded++;
     return tx.funds('in').cmp(total) < 0;
   }
 
-  // Transfer `total` funds maximum
-  // var unspent = wallet.unspent();
+  // Transfer `total` funds maximum.
   unspent.every(addInput);
 
-  // Add dummy output (for `change`) to calculate maximum TX size
-  tx.output({
-    script: [],
-    value: new bn(0)
-  });
+  if (!hardFee) {
+    // Add dummy output (for `change`) to
+    // calculate maximum TX size.
+    tx.output({
+      script: [],
+      value: new bn(0)
+    });
 
-  // Change fee value if it is more than 1024 bytes
-  // (10000 satoshi for every 1024 bytes)
-  do {
-    // Calculate maximum possible size after signing
-    size = tx.maxSize();
+    // Change fee value if it is more than 1024
+    // bytes (10000 satoshi for every 1024 bytes).
+    do {
+      // Calculate max possible size after signing.
+      size = tx.maxSize();
 
-    addFee = Math.ceil(size / 1024) - fee;
-    total.iaddn(addFee * constants.tx.fee);
-    fee += addFee;
+      addFee = Math.ceil(size / 1024) - fee;
+      total.iaddn(addFee * constants.tx.fee);
+      fee += addFee;
 
-    // Failed to get enough funds, add more inputs
-    if (tx.funds('in').cmp(total) < 0)
-      unspent.slice(lastAdded).every(addInput);
-  } while (tx.funds('in').cmp(total) < 0 && lastAdded < unspent.length);
+      // Failed to get enough funds, add more inputs.
+      if (tx.funds('in').cmp(total) < 0)
+        unspent.slice(lastAdded).every(addInput);
+    } while (tx.funds('in').cmp(total) < 0 && lastAdded < unspent.length);
+  }
 
-  // Expose `total`
+  // Expose `total`. Useful for error messages.
   this.total = total;
 
-  // Still failing to get enough funds
+  // Still failing to get enough funds.
   if (tx.funds('in').cmp(total) < 0)
     return null;
 
-  // How much money is left after sending outputs
+  // How much money is left after filling outputs.
   change = tx.funds('in').sub(total);
 
   // Return necessary inputs and change.
@@ -844,8 +859,8 @@ TX.prototype.getUnspent = function getUnspent(unspent) {
   };
 };
 
-TX.prototype.fillUnspent = function fillUnspent(unspent, changeAddress) {
-  var result = unspent.cost ? unspent : this.getUnspent(unspent);
+TX.prototype.fillUnspent = function fillUnspent(unspent, changeAddress, fee) {
+  var result = this.getUnspent(unspent, fee);
 
   if (!result)
     return result;
@@ -884,6 +899,9 @@ TX.prototype._recalculateFee = function recalculateFee() {
   var output = this.changeOutput;
   var size, real, fee;
 
+  if (this._fee)
+    return;
+
   if (!output) {
     this.output({
       address: this.changeAddress,