embark/lib/modules/profiler/gasEstimator.js

/*global web3*/
const async = require('async');
const ContractFuzzer = require('./fuzzer.js');

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) => {
      let fuzzMap = self.fuzzer.generateFuzz(3, contract);
      let contractObj = new web3.eth.Contract(contract.abiDefinition, contract.deployedAddress);
      async.each(contract.abiDefinition.filter((x) => x.type !== "event"), 
        (abiMethod, gasCb) => {
          let name = abiMethod.name;
          if (abiMethod.type === "constructor") {
            // already provided for us
            gasMap['constructor'] = contract.gasEstimates.creation.totalCost.toString();
            return gasCb(null, name, abiMethod.type);
          } else if (abiMethod.type === "fallback") {
            gasMap['fallback'] = contract.gasEstimates.external[""].toString();
            return gasCb(null, name, abiMethod.type);
          } else if (
            (abiMethod.inputs === null || abiMethod.inputs === undefined || abiMethod.inputs.length === 0)
          ) {
            // just run it and register it
            contractObj.methods[name]
            .apply(contractObj.methods[name], [])
            .estimateGas((err, gasAmount) => {
              if (err) return gasCb(err, name, abiMethod.type);
              gasMap[name] = gasAmount;
              return gasCb(null, name, abiMethod.type);              
            });
          } 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 (variance.every(v => v === variance[0])) {
                  gasMap[name] = variance[0];
                } else {
                  // get average
                  let sum = variance.reduce(function(memo, num) { return memo + num; });
                  gasMap[name] = sum / variance.length;
                }
                return gasCb(null, name, abiMethod.type);
              });    
          }
        },
        (err, name, type) => {
          if (err) {
            if (type === "constructor" || type === "fallback") name = type;
            return cb(err, null, name);
          }
          cb(null, gasMap, null);
        }
      );
    });
  }
}

module.exports = GasEstimator;