1 files changed, 87 insertions, 0 deletions
diff --git a/app/scripts/lib/tx-utils.js b/app/scripts/lib/tx-utils.js
new file mode 100644
index 000000000..a976173f5
--- /dev/null
+++ b/app/scripts/lib/tx-utils.js
@@ -0,0 +1,87 @@
+const async = require('async')
+const EthQuery = require('eth-query')
+const ethUtil = require('ethereumjs-util')
+const BN = ethUtil.BN
+
+/*
+tx-utils are utility methods for Transaction manager
+its passed a provider and that is passed to ethquery
+and used to do things like calculate gas of a tx.
+*/
+
+module.exports = class txProviderUtils {
+  constructor (provider) {
+    this.provider = provider
+    this.query = new EthQuery(provider)
+  }
+  analyzeGasUsage (txData, cb) {
+    var self = this
+    this.query.getBlockByNumber('latest', true, (err, block) => {
+      if (err) return cb(err)
+      async.waterfall([
+        self.estimateTxGas.bind(self, txData, block.gasLimit),
+        self.checkForTxGasError.bind(self, txData),
+        self.setTxGas.bind(self, txData, block.gasLimit),
+      ], cb)
+    })
+  }
+
+  estimateTxGas (txData, blockGasLimitHex, cb) {
+    const txParams = txData.txParams
+    // check if gasLimit is already specified
+    txData.gasLimitSpecified = Boolean(txParams.gas)
+    // if not, fallback to block gasLimit
+    if (!txData.gasLimitSpecified) {
+      txParams.gas = blockGasLimitHex
+    }
+    // run tx, see if it will OOG
+    this.query.estimateGas(txParams, cb)
+  }
+
+  checkForTxGasError (txData, estimatedGasHex, cb) {
+    txData.estimatedGas = estimatedGasHex
+    // all gas used - must be an error
+    if (estimatedGasHex === txData.txParams.gas) {
+      txData.simulationFails = true
+    }
+    cb()
+  }
+
+  setTxGas (txData, blockGasLimitHex, cb) {
+    const txParams = txData.txParams
+    // if OOG, nothing more to do
+    if (txData.simulationFails) {
+      cb()
+      return
+    }
+    // if gasLimit was specified and doesnt OOG,
+    // use original specified amount
+    if (txData.gasLimitSpecified) {
+      txData.estimatedGas = txParams.gas
+      cb()
+      return
+    }
+    // if gasLimit not originally specified,
+    // try adding an additional gas buffer to our estimation for safety
+    const estimatedGasBn = new BN(ethUtil.stripHexPrefix(txData.estimatedGas), 16)
+    const blockGasLimitBn = new BN(ethUtil.stripHexPrefix(blockGasLimitHex), 16)
+    const estimationWithBuffer = new BN(this.addGasBuffer(estimatedGasBn), 16)
+    // added gas buffer is too high
+    if (estimationWithBuffer.gt(blockGasLimitBn)) {
+      txParams.gas = txData.estimatedGas
+    // added gas buffer is safe
+    } else {
+      const gasWithBufferHex = ethUtil.intToHex(estimationWithBuffer)
+      txParams.gas = gasWithBufferHex
+    }
+    cb()
+    return
+  }
+
+  addGasBuffer (gas) {
+    const gasBuffer = new BN('100000', 10)
+    const bnGas = new BN(ethUtil.stripHexPrefix(gas), 16)
+    const correct = bnGas.add(gasBuffer)
+    return ethUtil.addHexPrefix(correct.toString(16))
+  }
+}