const EthQuery = require('ethjs-query') const { hexToBn, BnMultiplyByFraction, bnToHex, } = require('./util') const addHexPrefix = require('ethereumjs-util').addHexPrefix const SIMPLE_GAS_COST = '0x5208' // Hex for 21000, cost of a simple send. /* tx-utils are utility methods for Transaction manager its passed ethquery and used to do things like calculate gas of a tx. */ module.exports = class TxGasUtil { constructor (provider) { this.query = new EthQuery(provider) } async analyzeGasUsage (txMeta) { const block = await this.query.getBlockByNumber('latest', true) let estimatedGasHex try { estimatedGasHex = await this.estimateTxGas(txMeta, block.gasLimit) } catch (err) { const simulationFailed = ( err.message.includes('Transaction execution error.') || err.message.includes('gas required exceeds allowance or always failing transaction') ) if (simulationFailed) { txMeta.simulationFails = true return txMeta } } this.setTxGas(txMeta, block.gasLimit, estimatedGasHex) return txMeta } async estimateTxGas (txMeta, blockGasLimitHex) { const txParams = txMeta.txParams // check if gasLimit is already specified txMeta.gasLimitSpecified = Boolean(txParams.gas) // if it is, use that value if (txMeta.gasLimitSpecified) { return txParams.gas } // if recipient has no code, gas is 21k max: const recipient = txParams.to const hasRecipient = Boolean(recipient) const code = await this.query.getCode(recipient) if (hasRecipient && (!code || code === '0x')) { txParams.gas = SIMPLE_GAS_COST txMeta.simpleSend = true // Prevents buffer addition return SIMPLE_GAS_COST } // if not, fall back to block gasLimit const blockGasLimitBN = hexToBn(blockGasLimitHex) const saferGasLimitBN = BnMultiplyByFraction(blockGasLimitBN, 19, 20) txParams.gas = bnToHex(saferGasLimitBN) // run tx return await this.query.estimateGas(txParams) } setTxGas (txMeta, blockGasLimitHex, estimatedGasHex) { txMeta.estimatedGas = addHexPrefix(estimatedGasHex) const txParams = txMeta.txParams // if gasLimit was specified and doesnt OOG, // use original specified amount if (txMeta.gasLimitSpecified || txMeta.simpleSend) { txMeta.estimatedGas = txParams.gas return } // if gasLimit not originally specified, // try adding an additional gas buffer to our estimation for safety const recommendedGasHex = this.addGasBuffer(txMeta.estimatedGas, blockGasLimitHex) txParams.gas = recommendedGasHex return } addGasBuffer (initialGasLimitHex, blockGasLimitHex) { const initialGasLimitBn = hexToBn(initialGasLimitHex) const blockGasLimitBn = hexToBn(blockGasLimitHex) const upperGasLimitBn = blockGasLimitBn.muln(0.9) const bufferedGasLimitBn = initialGasLimitBn.muln(1.5) // if initialGasLimit is above blockGasLimit, dont modify it if (initialGasLimitBn.gt(upperGasLimitBn)) return bnToHex(initialGasLimitBn) // if bufferedGasLimit is below blockGasLimit, use bufferedGasLimit if (bufferedGasLimitBn.lt(upperGasLimitBn)) return bnToHex(bufferedGasLimitBn) // otherwise use blockGasLimit return bnToHex(upperGasLimitBn) } async validateTxParams (txParams) { this.validateRecipient(txParams) if ('value' in txParams) { const value = txParams.value.toString() if (value.includes('-')) { throw new Error(`Invalid transaction value of ${txParams.value} not a positive number.`) } if (value.includes('.')) { throw new Error(`Invalid transaction value of ${txParams.value} number must be in wei`) } } } validateRecipient (txParams) { if (txParams.to === '0x') { if (txParams.data) { delete txParams.to } else { throw new Error('Invalid recipient address') } } return txParams } }