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import * as ethUtil from 'ethereumjs-util';
import * as jsSHA3 from 'js-sha3';
import * as _ from 'lodash';
import * as uuid from 'uuid/v4';
import * as Web3 from 'web3';
import {ContractEvents, IndexedFilterValues, SubscriptionOpts} from '../types';
const TOPIC_LENGTH = 32;
export const filterUtils = {
generateUUID(): string {
return uuid();
},
getFilter(address: string, eventName: ContractEvents,
indexFilterValues: IndexedFilterValues, abi: Web3.ContractAbi,
subscriptionOpts?: SubscriptionOpts): Web3.FilterObject {
const eventAbi = _.find(abi, {name: eventName}) as Web3.EventAbi;
const eventSignature = filterUtils.getEventSignatureFromAbiByName(eventAbi, eventName);
const topicForEventSignature = ethUtil.addHexPrefix(jsSHA3.keccak256(eventSignature));
const topicsForIndexedArgs = filterUtils.getTopicsForIndexedArgs(eventAbi, indexFilterValues);
const topics = [topicForEventSignature, ...topicsForIndexedArgs];
let filter: Web3.FilterObject = {
address,
topics,
};
if (!_.isUndefined(subscriptionOpts)) {
filter = {
...subscriptionOpts,
...filter,
};
}
return filter;
},
getEventSignatureFromAbiByName(eventAbi: Web3.EventAbi, eventName: ContractEvents): string {
const types = _.map(eventAbi.inputs, 'type');
const signature = `${eventAbi.name}(${types.join(',')})`;
return signature;
},
getTopicsForIndexedArgs(abi: Web3.EventAbi, indexFilterValues: IndexedFilterValues): Array<string|null> {
const topics: Array<string|null> = [];
for (const eventInput of abi.inputs) {
if (!eventInput.indexed) {
continue;
}
if (_.isUndefined(indexFilterValues[eventInput.name])) {
// Null is a wildcard topic in a JSON-RPC call
topics.push(null);
} else {
const value = indexFilterValues[eventInput.name] as string;
const buffer = ethUtil.toBuffer(value);
const paddedBuffer = ethUtil.setLengthLeft(buffer, TOPIC_LENGTH);
const topic = ethUtil.bufferToHex(paddedBuffer);
topics.push(topic);
}
}
return topics;
},
matchesFilter(log: Web3.LogEntry, filter: Web3.FilterObject): boolean {
if (!_.isUndefined(filter.address) && log.address !== filter.address) {
return false;
}
if (!_.isUndefined(filter.topics)) {
return filterUtils.matchesTopics(log.topics, filter.topics);
}
return true;
},
matchesTopics(logTopics: string[], filterTopics: Array<string[]|string|null>): boolean {
const matchesTopic = _.zipWith(logTopics, filterTopics, filterUtils.matchesTopic.bind(filterUtils));
const matchesTopics = _.every(matchesTopic);
return matchesTopics;
},
matchesTopic(logTopic: string, filterTopic: string[]|string|null): boolean {
if (_.isArray(filterTopic)) {
return _.includes(filterTopic, logTopic);
}
if (_.isString(filterTopic)) {
return filterTopic === logTopic;
}
// null topic is a wildcard
return true;
},
};
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