1 files changed, 51 insertions, 0 deletions
diff --git a/app/scripts/lib/pending-balance-calculator.js b/app/scripts/lib/pending-balance-calculator.js
new file mode 100644
index 000000000..474ed3261
--- /dev/null
+++ b/app/scripts/lib/pending-balance-calculator.js
@@ -0,0 +1,51 @@
+const BN = require('ethereumjs-util').BN
+const normalize = require('eth-sig-util').normalize
+
+class PendingBalanceCalculator {
+
+  // Must be initialized with two functions:
+  // getBalance => Returns a promise of a BN of the current balance in Wei
+  // getPendingTransactions => Returns an array of TxMeta Objects,
+  // which have txParams properties, which include value, gasPrice, and gas,
+  // all in a base=16 hex format.
+  constructor ({ getBalance, getPendingTransactions }) {
+    this.getPendingTransactions = getPendingTransactions
+    this.getNetworkBalance = getBalance
+  }
+
+  async getBalance() {
+    const results = await Promise.all([
+      this.getNetworkBalance(),
+      this.getPendingTransactions(),
+    ])
+
+    const balance = results[0]
+    const pending = results[1]
+
+    const pendingValue = pending.reduce((total, tx) => {
+      return total.add(this.valueFor(tx))
+    }, new BN(0))
+
+    return `0x${balance.sub(pendingValue).toString(16)}`
+  }
+
+  valueFor (tx) {
+    const txValue = tx.txParams.value
+    const value = this.hexToBn(txValue)
+    const gasPrice = this.hexToBn(tx.txParams.gasPrice)
+
+    const gas = tx.txParams.gas
+    const gasLimit = tx.txParams.gasLimit
+    const gasLimitBn = this.hexToBn(gas || gasLimit)
+
+    const gasCost = gasPrice.mul(gasLimitBn)
+    return value.add(gasCost)
+  }
+
+  hexToBn (hex) {
+    return new BN(normalize(hex).substring(2), 16)
+  }
+
+}
+
+module.exports = PendingBalanceCalculator