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import {
AbiDefinition,
AbiType,
DecodedLogArgs,
EventAbi,
EventParameter,
LogEntry,
LogWithDecodedArgs,
RawLog,
SolidityTypes,
} from 'ethereum-types';
import * as ethers from 'ethers';
import * as _ from 'lodash';
import { addressUtils } from './address_utils';
import { BigNumber } from './configured_bignumber';
/**
* AbiDecoder allows you to decode event logs given a set of supplied contract ABI's. It takes the contract's event
* signature from the ABI and attempts to decode the logs using it.
*/
export class AbiDecoder {
private readonly _methodIds: { [signatureHash: string]: EventAbi } = {};
/**
* Instantiate an AbiDecoder
* @param abiArrays An array of contract ABI's
* @return AbiDecoder instance
*/
constructor(abiArrays: AbiDefinition[][]) {
_.forEach(abiArrays, this.addABI.bind(this));
}
/**
* Attempt to decode a log given the ABI's the AbiDecoder knows about.
* @param log The log to attempt to decode
* @return The decoded log if the requisite ABI was available. Otherwise the log unaltered.
*/
public tryToDecodeLogOrNoop<ArgsType extends DecodedLogArgs>(log: LogEntry): LogWithDecodedArgs<ArgsType> | RawLog {
const methodId = log.topics[0];
const event = this._methodIds[methodId];
if (_.isUndefined(event)) {
return log;
}
const ethersInterface = new ethers.Interface([event]);
const decodedParams: DecodedLogArgs = {};
let topicsIndex = 1;
let decodedData: any[];
try {
decodedData = ethersInterface.events[event.name].parse(log.data);
} catch (error) {
if (error.code === ethers.errors.INVALID_ARGUMENT) {
// Because we index events by Method ID, and Method IDs are derived from the method
// name and the input parameters, it's possible that the return value of the event
// does not match our ABI. If that's the case, then ethers will throw an error
// when we try to parse the event. We handle that case here by returning the log rather
// than throwing an error.
return log;
}
throw error;
}
let didFailToDecode = false;
_.forEach(event.inputs, (param: EventParameter, i: number) => {
// Indexed parameters are stored in topics. Non-indexed ones in decodedData
let value: BigNumber | string | number = param.indexed ? log.topics[topicsIndex++] : decodedData[i];
if (_.isUndefined(value)) {
didFailToDecode = true;
return;
}
if (param.type === SolidityTypes.Address) {
const baseHex = 16;
value = addressUtils.padZeros(new BigNumber(value).toString(baseHex));
} else if (param.type === SolidityTypes.Uint256 || param.type === SolidityTypes.Uint) {
value = new BigNumber(value);
} else if (param.type === SolidityTypes.Uint8) {
value = new BigNumber(value).toNumber();
}
decodedParams[param.name] = value;
});
if (didFailToDecode) {
return log;
} else {
return {
...log,
event: event.name,
args: decodedParams,
};
}
}
/**
* Add additional ABI definitions to the AbiDecoder
* @param abiArray An array of ABI definitions to add to the AbiDecoder
*/
public addABI(abiArray: AbiDefinition[]): void {
if (_.isUndefined(abiArray)) {
return;
}
const ethersInterface = new ethers.Interface(abiArray);
_.map(abiArray, (abi: AbiDefinition) => {
if (abi.type === AbiType.Event) {
const topic = ethersInterface.events[abi.name].topics[0];
this._methodIds[topic] = abi;
}
});
}
}
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