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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, pending ] = results
if (!balance) return undefined
const pendingValue = pending.reduce((total, tx) => {
return total.add(this.calculateMaxCost(tx))
}, new BN(0))
return `0x${balance.sub(pendingValue).toString(16)}`
}
calculateMaxCost (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
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