From 090935f90aa3c2589fee7bc038c8f4fcf77da03c Mon Sep 17 00:00:00 2001
From: Frances Pangilinan <frankie.diamond@gmail.com>
Date: Wed, 14 Dec 2016 12:55:41 -0800
Subject: Create a TxManager

---
 app/scripts/lib/provider-utils.js | 106 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 app/scripts/lib/provider-utils.js

(limited to 'app/scripts/lib/provider-utils.js')

diff --git a/app/scripts/lib/provider-utils.js b/app/scripts/lib/provider-utils.js
new file mode 100644
index 000000000..d1678c964
--- /dev/null
+++ b/app/scripts/lib/provider-utils.js
@@ -0,0 +1,106 @@
+const async = require('async')
+const EthQuery = require('eth-query')
+const ethUtil = require('ethereumjs-util')
+const BN = ethUtil.BN
+const ethBinToOps = require('eth-bin-to-ops')
+
+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)
+    })
+  }
+
+    // perform static analyis on the target contract code
+  analyzeForDelegateCall (txParams, cb) {
+    if (txParams.to) {
+      this.query.getCode(txParams.to, function (err, result) {
+        if (err) return cb(err)
+
+        var code = ethUtil.toBuffer(result)
+        if (code !== '0x') {
+          var ops = ethBinToOps(code)
+          var containsDelegateCall = ops.some((op) => op.name === 'DELEGATECALL')
+          cb(containsDelegateCall)
+        } else {
+          cb()
+        }
+      })
+    } else {
+      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()
+  }
+
+  handleFork (block) {
+
+  }
+
+  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))
+  }
+}
-- 
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