const EthQuery = require('ethjs-query') const { hexToBn, BnMultiplyByFraction, bnToHex, } = require('./util') /* 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 txProvideUtil { 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) { if (err.message.includes('Transaction execution error.')) { 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 not, fallback to block gasLimit if (!txMeta.gasLimitSpecified) { 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 = estimatedGasHex const txParams = txMeta.txParams // if gasLimit was specified and doesnt OOG, // use original specified amount if (txMeta.gasLimitSpecified) { 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) { if (('value' in txParams) && txParams.value.indexOf('-') === 0) { throw new Error(`Invalid transaction value of ${txParams.value} not a positive number.`) } } }