embark-area-51/lib/modules/gasEstimator/index.js

const async = require('async');
const _ = require('underscore');
const ContractFuzzer = require('../fuzzer');

/*global web3*/

class GasEstimator {
  constructor(embark) {
    this.embark = embark;
    this.logger = embark.logger;
    this.events = embark.events;
    this.fuzzer = new ContractFuzzer(embark);
  }

  estimateGas(contractName, cb) {
    const self = this;
    let gasMap = {};
    self.events.request('contracts:contract', contractName, (contract) => {
      self.logger.info("Generating three rounds of fuzz for contract -- ", contractName);
      let fuzzMap = self.fuzzer.generateFuzz(3, contract);
      self.logger.info("--  Beginning gastimation for contract -- " + contractName);
      let contractObj = new web3.eth.Contract(contract.abiDefinition, contract.deployedAddress);
      async.each(contract.abiDefinition, 
        (abiMethod, gasCb) => {
          let name = abiMethod.name;
          if (abiMethod.type === "constructor") {
            // already provided for us
             gasCb(null, 'constructor', contract.gasEstimates.creation.totalCost);
          } else if (abiMethod.inputs === []) {
            // just run it and register it
            contractObj.methods[name]
            .apply(contractObj.methods[name], [])
            .estimateGas((err, gasAmount) => {
              if (err) gasCb(err);
              gasMap[name] = gasAmount;
              gasCb(err, gasAmount, name);
            });
          } else {
            // async concatenate all the fuzz values and their gas cost outputs and check for equality
            async.concat(fuzzMap[name], (values, getVarianceCb) => {
              contractObj.methods[name]
                .apply(contractObj.methods[name], values)
                .estimateGas((err, gasAmount) => {
                  getVarianceCb(err, [gasAmount]);
                });
              }, (err, variance) => {
                if (err) {
                  gasCb(err) 
                } else if (variance.reduce(_.isEqual, variance[2])) {
                  gasMap[name] = variance[0];
                } else {
                  gasMap[name] = 'variable';
                }
                gasCb();
              });    
          };
        },
        (err) => {
          if (err) return cb(err);
          cb(null, gasMap);
        }
      );
    });
  }
}

module.exports = GasEstimator;