add funding function + fix estimate

accumulative.js

@@ -2,7 +2,7 @@ var utils = require('./utils')
 
 // add inputs until we reach or surpass the target value (or deplete)
 // worst-case: O(n)
-module.exports = function accumulative (utxos, outputs, feeRate) {
+module.exports = function accumulative (utxos, outputs, feeRate, changeAddress) {
   if (!isFinite(utils.uintOrNaN(feeRate))) return {}
   var bytesAccum = utils.transactionBytes([], outputs)
 
@@ -31,7 +31,7 @@ module.exports = function accumulative (utxos, outputs, feeRate) {
     // go again?
     if (inAccum < outAccum + fee) continue
 
-    return utils.finalize(inputs, outputs, feeRate)
+    return utils.finalize(inputs, outputs, feeRate, changeAddress)
   }
 
   return { fee: feeRate * bytesAccum }

blackjack.js

@@ -2,7 +2,7 @@ var utils = require('./utils')
 
 // only add inputs if they don't bust the target value (aka, exact match)
 // worst-case: O(n)
-module.exports = function blackjack (utxos, outputs, feeRate) {
+module.exports = function blackjack (utxos, outputs, feeRate, changeAddress) {
   if (!isFinite(utils.uintOrNaN(feeRate))) return {}
 
   var bytesAccum = utils.transactionBytes([], outputs)
@@ -28,7 +28,7 @@ module.exports = function blackjack (utxos, outputs, feeRate) {
     // go again?
     if (inAccum < outAccum + fee) continue
 
-    return utils.finalize(inputs, outputs, feeRate)
+    return utils.finalize(inputs, outputs, feeRate, changeAddress)
   }
 
   return { fee: feeRate * bytesAccum }

funding.d.ts

@@ -0,0 +1,9 @@
+// funding.d.ts
+import { Target, UTXO } from "./index";
+
+export default function funding(inputs: UTXO[], outputs: Target[], feeRate: number): {
+    funding: number,
+    totalOutput: number,
+    totalInput: number,
+    fee: number
+};

funding.js

@@ -0,0 +1,27 @@
+const utils = require('./utils')
+
+// given inputs, outputs and feerate, return sats needed to fund the transaction
+module.exports = function funding (inputs, outputs, feeRate) {
+  if (!isFinite(utils.uintOrNaN(feeRate))) return {}
+
+  let inAccum = 0
+  const outAccum = utils.sumOrNaN(outputs)
+
+  for (var i = 0; i < inputs.length; ++i) {
+    const utxo = inputs[i]
+    const utxoValue = utils.uintOrNaN(utxo.value)
+
+    inAccum += utxoValue
+  }
+
+  // use all inputs and outputs
+  const bytesAccum = utils.transactionBytes(inputs, outputs)
+  const fee = feeRate * bytesAccum
+
+  return {
+    funding: Math.ceil(outAccum + fee - inAccum), // negative if overfunded
+    totalOutput: outAccum,
+    totalInput: inAccum,
+    fee: fee
+  }
+}

index.d.ts

@@ -21,4 +21,4 @@ export interface SelectedUTXO {
     outputs?: Target[],
     fee: number
 }
-export default function coinSelect(utxos: UTXO[], outputs: Target[], feeRate: number): SelectedUTXO;
+export default function coinSelect(utxos: UTXO[], outputs: Target[], feeRate: number, changeAddress?: string): SelectedUTXO;

index.js

@@ -7,15 +7,15 @@ function utxoScore (x, feeRate) {
   return x.value - (feeRate * utils.inputBytes(x))
 }
 
-module.exports = function coinSelect (utxos, outputs, feeRate) {
+module.exports = function coinSelect (utxos, outputs, feeRate, changeAddress) {
   utxos = utxos.concat().sort(function (a, b) {
     return utxoScore(b, feeRate) - utxoScore(a, feeRate)
   })
 
   // attempt to use the blackjack strategy first (no change output)
-  var base = blackjack(utxos, outputs, feeRate)
+  var base = blackjack(utxos, outputs, feeRate, changeAddress)
   if (base.inputs) return base
 
   // else, try the accumulative strategy
-  return accumulative(utxos, outputs, feeRate)
+  return accumulative(utxos, outputs, feeRate, changeAddress)
 }

package.json

@@ -26,13 +26,48 @@
     "accumulative.js",
     "blackjack.js",
     "break.js",
+    "funding.js",
+    "funding.d.ts",
     "index.js",
     "split.js",
     "utils.js",
+    "utils.d.ts",
     "index.d.ts"
   ],
   "main": "index.js",
   "types": "index.d.ts",
+  "exports": {
+    ".": {
+      "import": "./index.js",
+      "require": "./index.js"
+    },
+    "./accumulative": {
+      "import": "./accumulative.js",
+      "require": "./accumulative.js"
+    },
+    "./blackjack": {
+      "import": "./blackjack.js",
+      "require": "./blackjack.js"
+    },
+    "./break": {
+      "import": "./break.js",
+      "require": "./break.js"
+    },
+    "./funding": {
+      "import": "./funding.js",
+      "require": "./funding.js",
+      "types": "./funding.d.ts"
+    },
+    "./split": {
+      "import": "./split.js",
+      "require": "./split.js"
+    },
+    "./utils": {
+      "import": "./utils.js",
+      "require": "./utils.js",
+      "types": "./utils.d.ts"
+    }
+  },
   "repository": {
     "type": "git",
     "url": "https://github.com/ChrisCho-H/bitcoinselect.git"

test/fixtures/funding.json

@@ -0,0 +1,68 @@
+[
+  {
+    "description": "valid funding with 1 input and 2 outputs",
+    "feeRate": 1,
+    "inputs": [
+      1000
+    ],
+    "outputs": [
+      1000,
+      600
+    ],
+    "expected": {
+      "funding": 826,
+      "totalOutput": 1600,
+      "totalInput": 1000,
+      "fee": 226
+    }
+  },
+  {
+    "description": "valid funding with 1 input (+witnessUtxo) and 2 outputs",
+    "feeRate": 1,
+    "inputs": [
+      {
+        "value": 1000,
+        "witnessUtxo": {}
+      }
+    ],
+    "outputs": [
+      1000,
+      600
+    ],
+    "expected": {
+      "funding": 746,
+      "totalOutput": 1600,
+      "totalInput": 1000,
+      "fee": 146
+    }
+  },
+  {
+    "description": "negative funding when inputs > outputs",
+    "feeRate": 1,
+    "inputs": [
+      2000
+    ],
+    "outputs": [
+      1000,
+      600
+    ],
+    "expected": {
+      "funding": -174,
+      "totalOutput": 1600,
+      "totalInput": 2000,
+      "fee": 226
+    }
+  },
+  {
+    "description": "bad feerate",
+    "feeRate": 1.5,
+    "inputs": [
+      2000
+    ],
+    "outputs": [
+      1000,
+      600
+    ],
+    "expected": {}
+  }
+]

test/funding.js

@@ -0,0 +1,20 @@
+const fixtures = require('./fixtures/funding.json')
+const utils = require('./_utils')
+const tape = require('tape')
+const funding = require('../funding')
+
+fixtures.forEach(function (f) {
+  tape(f.description, function (t) {
+    var inputs = utils.expand(f.inputs, true)
+    var outputs = utils.expand(f.outputs)
+    var actual = funding(inputs, outputs, f.feeRate)
+
+    t.same(actual, f.expected)
+    if (actual.inputs) {
+      var feedback = funding(actual.inputs, actual.outputs, f.feeRate)
+      t.same(feedback, f.expected)
+    }
+
+    t.end()
+  })
+})

utils.d.ts

@@ -0,0 +1,13 @@
+// utils.d.ts
+import {SelectedUTXO, Target, UTXO} from "./index";
+
+declare module "bitcoinselect/utils" {
+    export function inputBytes(input: UTXO): number;
+    export function outputBytes(output: Target): number;
+    export function dustThreshold(output: Target, feeRate: number): number;
+    export function transactionBytes(inputs: UTXO[], outputs: Target[]): number;
+    export function uintOrNaN(v: any): number;
+    export function sumForgiving(range: any[]): number;
+    export function sumOrNaN(range: any[]): number;
+    export function finalize(inputs: UTXO[], outputs: Target[], feeRate: number, changeAddress?: string): SelectedUTXO;
+}

utils.js

@@ -1,9 +1,9 @@
 // baseline estimates, used to improve performance
-var TX_EMPTY_SIZE = 4 + 1 + 1 + 4
-var TX_INPUT_BASE = 32 + 4 + 1 + 4
+var TX_EMPTY_SIZE = 4 + 1 + 1 + 4 + 0.5 // version + inputcount + outputcount + locktime + marker-flag (segwit)
+var TX_INPUT_BASE = 32 + 4 + 1 + 4 // txid + vout + scriptsigsize + sequence
 var TX_INPUT_PUBKEYHASH = 107
 var TX_INPUT_SEGWIT = 27
-var TX_INPUT_TAPROOT = 17 // round up 16.5 bytes
+var TX_INPUT_TAPROOT = 16.5 // round up 16.5 bytes - witness sig for key path spend
 var TX_OUTPUT_BASE = 8 + 1
 var TX_OUTPUT_PUBKEYHASH = 25
 var TX_OUTPUT_SCRIPTHASH = 23
@@ -20,8 +20,8 @@ function inputBytes (input) {
 
 function outputBytes (output) {
   return TX_OUTPUT_BASE + (output.script ? output.script.length
-    : output.address?.startsWith('bc1') || output.address?.startsWith('tb1')
-      ? output.address?.length === 42 ? TX_OUTPUT_SEGWIT : TX_OUTPUT_SEGWIT_SCRIPTHASH
+    : output.address?.startsWith('bc1') || output.address?.startsWith('tb1') || output.address?.startsWith('bcrt1')
+      ? output.address?.length === 42 || output.address?.length === 44 ? TX_OUTPUT_SEGWIT : TX_OUTPUT_SEGWIT_SCRIPTHASH
       : output.address?.startsWith('3') || output.address?.startsWith('2')
         ? TX_OUTPUT_SCRIPTHASH : TX_OUTPUT_PUBKEYHASH
   )
@@ -41,7 +41,6 @@ function transactionBytes (inputs, outputs) {
 function uintOrNaN (v) {
   if (typeof v !== 'number') return NaN
   if (!isFinite(v)) return NaN
-  if (Math.floor(v) !== v) return NaN
   if (v < 0) return NaN
   return v
 }
@@ -56,14 +55,15 @@ function sumOrNaN (range) {
 
 var BLANK_OUTPUT = outputBytes({})
 
-function finalize (inputs, outputs, feeRate) {
+function finalize (inputs, outputs, feeRate, changeAddress) {
   var bytesAccum = transactionBytes(inputs, outputs)
-  var feeAfterExtraOutput = feeRate * (bytesAccum + BLANK_OUTPUT)
+  const changeOutputBytes = changeAddress ? outputBytes({address:changeAddress}): BLANK_OUTPUT
+  var feeAfterExtraOutput = Math.ceil(feeRate * (bytesAccum + changeOutputBytes))
   var remainderAfterExtraOutput = sumOrNaN(inputs) - (sumOrNaN(outputs) + feeAfterExtraOutput)
 
   // is it worth a change output?
   if (remainderAfterExtraOutput > dustThreshold({}, feeRate)) {
-    outputs = outputs.concat({ value: remainderAfterExtraOutput })
+    outputs = outputs.concat({ value: Math.ceil(remainderAfterExtraOutput) })
   }
 
   var fee = sumOrNaN(inputs) - sumOrNaN(outputs)