Revert "mtx: allow multiple indicies for subtractIndex."

This reverts commit d489238711.

lib/primitives/mtx.js

@@ -1223,27 +1223,41 @@ MTX.prototype.selectCoins = function selectCoins(coins, options) {
 };
 
 /**
- * Attempt to subtract a fee from all outputs evenly.
+ * Attempt to subtract a fee from a single output.
+ * @param {Number} index
  * @param {Amount} fee
- * @param {Set|null} set
  */
 
-MTX.prototype.subtractFee = function subtractFee(fee, set) {
+MTX.prototype.subtractIndex = function subtractIndex(index, fee) {
+  assert(typeof index === 'number');
+  assert(typeof fee === 'number');
+
+  const output = this.outputs[index];
+
+  if (!output)
+    throw new Error('Subtraction index does not exist.');
+
+  if (output.value < fee + output.getDustThreshold())
+    throw new Error('Could not subtract fee.');
+
+  output.value -= fee;
+};
+
+/**
+ * Attempt to subtract a fee from all outputs evenly.
+ * @param {Amount} fee
+ */
+
+MTX.prototype.subtractFee = function subtractFee(fee) {
   assert(typeof fee === 'number');
 
   let outputs = 0;
 
-  for (let i = 0; i < this.outputs.length; i++) {
-    const output = this.outputs[i];
-
-    if (set && !set.has(i))
-      continue;
-
+  for (const output of this.outputs) {
     // Ignore nulldatas and
     // other OP_RETURN scripts.
     if (output.script.isUnspendable())
       continue;
-
     outputs += 1;
   }
 
@@ -1254,12 +1268,7 @@ MTX.prototype.subtractFee = function subtractFee(fee, set) {
   const share = (fee - left) / outputs;
 
   // First pass, remove even shares.
-  for (let i = 0; i < this.outputs.length; i++) {
-    const output = this.outputs[i];
-
-    if (set && !set.has(i))
-      continue;
-
+  for (const output of this.outputs) {
     if (output.script.isUnspendable())
       continue;
 
@@ -1271,12 +1280,7 @@ MTX.prototype.subtractFee = function subtractFee(fee, set) {
 
   // Second pass, remove the remainder
   // for the one unlucky output.
-  for (let i = 0; i < this.outputs.length; i++) {
-    const output = this.outputs[i];
-
-    if (set && !set.has(i))
-      continue;
-
+  for (const output of this.outputs) {
     if (output.script.isUnspendable())
       continue;
 
@@ -1309,8 +1313,13 @@ MTX.prototype.fund = async function fund(coins, options) {
     this.addCoin(coin);
 
   // Attempt to subtract fee.
-  if (select.subtractFee)
-    this.subtractFee(select.fee, select.subtractIndex);
+  if (select.subtractFee) {
+    const index = select.subtractIndex;
+    if (index !== -1)
+      this.subtractIndex(index, select.fee);
+    else
+      this.subtractFee(select.fee);
+  }
 
   // Add a change output.
   const output = new Output();
@@ -1545,7 +1554,7 @@ function CoinSelector(tx, options) {
 
   this.selection = 'value';
   this.subtractFee = false;
-  this.subtractIndex = null;
+  this.subtractIndex = -1;
   this.height = -1;
   this.depth = -1;
   this.hardFee = -1;
@@ -1601,32 +1610,22 @@ CoinSelector.prototype.fromOptions = function fromOptions(options) {
   }
 
   if (options.subtractFee != null) {
-    assert(typeof options.subtractFee === 'boolean');
-    this.subtractFee = options.subtractFee;
+    if (typeof options.subtractFee === 'number') {
+      assert(util.isInt(options.subtractFee));
+      assert(options.subtractFee >= -1);
+      this.subtractIndex = options.subtractFee;
+      this.subtractFee = this.subtractIndex !== -1;
+    } else {
+      assert(typeof options.subtractFee === 'boolean');
+      this.subtractFee = options.subtractFee;
+    }
   }
 
   if (options.subtractIndex != null) {
-    let indicies = null;
-
-    if (typeof options.subtractIndex === 'number') {
-      indicies = [options.subtractIndex];
-    } else {
-      assert(Array.isArray(options.subtractIndex));
-      indicies = options.subtractIndex;
-    }
-
-    if (indicies.length > 0) {
-      const set = new Set();
-
-      for (const index of indicies) {
-        assert(util.isU32(index));
-        assert(index < this.tx.outputs.length);
-        set.add(index);
-      }
-
-      this.subtractIndex = set;
-      this.subtractFee = true;
-    }
+    assert(util.isInt(options.subtractIndex));
+    assert(options.subtractIndex >= -1);
+    this.subtractIndex = options.subtractIndex;
+    this.subtractFee = this.subtractIndex !== -1;
   }
 
   if (options.height != null) {

lib/wallet/http.js

@@ -391,7 +391,7 @@ HTTPServer.prototype.initRouter = function initRouter() {
       selection: valid.str('selection'),
       smart: valid.bool('smart'),
       subtractFee: valid.bool('subtractFee'),
-      subtractIndex: valid.get('subtractIndex'),
+      subtractIndex: valid.i32('subtractIndex'),
       depth: valid.u32(['confirmations', 'depth']),
       outputs: []
     };
@@ -431,7 +431,7 @@ HTTPServer.prototype.initRouter = function initRouter() {
       selection: valid.str('selection'),
       smart: valid.bool('smart'),
       subtractFee: valid.bool('subtractFee'),
-      subtractIndex: valid.get('subtractIndex'),
+      subtractIndex: valid.i32('subtractIndex'),
       depth: valid.u32(['confirmations', 'depth']),
       outputs: []
     };