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import BigNumber from 'bignumber.js';
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${formatted}`;
}
constructor(abiArrays: Web3.AbiDefinition[][]) {
_.map(abiArrays, this._addABI.bind(this));
}
// This method can only decode logs from the 0x & ERC20 smart contracts
public tryToDecodeLogOrNoop<ArgsType extends ContractEventArgs>(
log: Web3.LogEntry,
): LogWithDecodedArgs<ArgsType> | RawLog {
const methodId = log.topics[0];
const event = this._methodIds[methodId];
if (_.isUndefined(event)) {
return log;
}
const logData = log.data;
const decodedParams: DecodedLogArgs = {};
let dataIndex = 0;
let topicsIndex = 1;
const nonIndexedInputs = _.filter(event.inputs, input => !input.indexed);
const dataTypes = _.map(nonIndexedInputs, input => input.type);
const decodedData = SolidityCoder.decodeParams(dataTypes, logData.slice('0x'.length));
_.map(event.inputs, (param: Web3.EventParameter) => {
// Indexed parameters are stored in topics. Non-indexed ones in decodedData
let value = param.indexed ? log.topics[topicsIndex++] : decodedData[dataIndex++];
if (param.type === SolidityTypes.Address) {
value = AbiDecoder._padZeros(new BigNumber(value).toString(16));
} else if (
param.type === SolidityTypes.Uint256 ||
param.type === SolidityTypes.Uint8 ||
param.type === SolidityTypes.Uint
) {
value = new BigNumber(value);
}
decodedParams[param.name] = value;
});
return {
...log,
event: event.name,
args: decodedParams,
};
}
private _addABI(abiArray: Web3.AbiDefinition[]): void {
_.map(abiArray, (abi: Web3.AbiDefinition) => {
if (abi.type === AbiType.Event) {
const signature = `${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);
}
}
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