import { BigNumber } from '@0xproject/utils'; import * as _ from 'lodash'; import * as Web3 from 'web3'; import * as SolidityCoder from 'web3/lib/solidity/coder'; import { AbiType, ContractEventArgs, DecodedLogArgs, LogWithDecodedArgs, RawLog, SolidityTypes } from '../types'; export class AbiDecoder { private _savedABIs: Web3.AbiDefinition[] = []; private _methodIds: { [signatureHash: string]: Web3.EventAbi } = {}; private static _padZeros(address: string) { let formatted = address; if (_.startsWith(formatted, '0x')) { formatted = formatted.slice(2); } formatted = _.padStart(formatted, 40, '0'); return `0x${formatted}`; } constructor(abiArrays: Web3.AbiDefinition[][]) { _.map(abiArrays, this._addABI.bind(this)); } // This method can only decode logs from the 0x & ERC20 smart contracts public tryToDecodeLogOrNoop( log: Web3.LogEntry, ): LogWithDecodedArgs | RawLog { const methodId = log.topics[0]; const event = this._methodIds[methodId]; if (_.isUndefined(event)) { return log; } const logData = log.data; const decodedParams: DecodedLogArgs = {}; let dataIndex = 0; let topicsIndex = 1; const nonIndexedInputs = _.filter(event.inputs, input => !input.indexed); const dataTypes = _.map(nonIndexedInputs, input => input.type); const decodedData = SolidityCoder.decodeParams(dataTypes, logData.slice('0x'.length)); _.map(event.inputs, (param: Web3.EventParameter) => { // Indexed parameters are stored in topics. Non-indexed ones in decodedData let value = param.indexed ? log.topics[topicsIndex++] : decodedData[dataIndex++]; if (param.type === SolidityTypes.Address) { value = AbiDecoder._padZeros(new BigNumber(value).toString(16)); } else if ( param.type === SolidityTypes.Uint256 || param.type === SolidityTypes.Uint8 || param.type === SolidityTypes.Uint ) { value = new BigNumber(value); } decodedParams[param.name] = value; }); return { ...log, event: event.name, args: decodedParams, }; } private _addABI(abiArray: Web3.AbiDefinition[]): void { _.map(abiArray, (abi: Web3.AbiDefinition) => { if (abi.type === AbiType.Event) { const signature = `${abi.name}(${_.map(abi.inputs, input => input.type).join(',')})`; const signatureHash = new Web3().sha3(signature); this._methodIds[signatureHash] = abi; } }); this._savedABIs = this._savedABIs.concat(abiArray); } }