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import { intervalUtils, logUtils } from '@0xproject/utils';
import { marshaller, Web3Wrapper } from '@0xproject/web3-wrapper';
import { BlockParamLiteral, FilterObject, LogEntry, Provider, RawLogEntry } from 'ethereum-types';
import { Block, BlockAndLogStreamer, Log } from 'ethereumjs-blockstream';
import * as _ from 'lodash';
import { EventWatcherCallback, OrderWatcherError } from '../types';
import { assert } from '../utils/assert';
const DEFAULT_EVENT_POLLING_INTERVAL_MS = 200;
enum LogEventState {
Removed,
Added,
}
/**
* The EventWatcher watches for blockchain events at the specified block confirmation
* depth.
*/
export class EventWatcher {
private readonly _web3Wrapper: Web3Wrapper;
private readonly _isVerbose: boolean;
private _blockAndLogStreamerIfExists: BlockAndLogStreamer<Block, Log> | undefined;
private _blockAndLogStreamIntervalIfExists?: NodeJS.Timer;
private _onLogAddedSubscriptionToken: string | undefined;
private _onLogRemovedSubscriptionToken: string | undefined;
private readonly _pollingIntervalMs: number;
constructor(
provider: Provider,
pollingIntervalIfExistsMs: undefined | number,
stateLayer: BlockParamLiteral,
isVerbose: boolean,
) {
this._isVerbose = isVerbose;
this._web3Wrapper = new Web3Wrapper(provider);
this._pollingIntervalMs = _.isUndefined(pollingIntervalIfExistsMs)
? DEFAULT_EVENT_POLLING_INTERVAL_MS
: pollingIntervalIfExistsMs;
this._blockAndLogStreamerIfExists = undefined;
this._blockAndLogStreamIntervalIfExists = undefined;
this._onLogAddedSubscriptionToken = undefined;
this._onLogRemovedSubscriptionToken = undefined;
}
public subscribe(callback: EventWatcherCallback): void {
assert.isFunction('callback', callback);
if (!_.isUndefined(this._blockAndLogStreamIntervalIfExists)) {
throw new Error(OrderWatcherError.SubscriptionAlreadyPresent);
}
this._startBlockAndLogStream(callback);
}
public unsubscribe(): void {
if (_.isUndefined(this._blockAndLogStreamIntervalIfExists)) {
throw new Error(OrderWatcherError.SubscriptionNotFound);
}
this._stopBlockAndLogStream();
}
private _startBlockAndLogStream(callback: EventWatcherCallback): void {
if (!_.isUndefined(this._blockAndLogStreamerIfExists)) {
throw new Error(OrderWatcherError.SubscriptionAlreadyPresent);
}
this._blockAndLogStreamerIfExists = new BlockAndLogStreamer(
this._blockstreamGetBlockOrNullAsync.bind(this),
this._blockstreamGetLogsAsync.bind(this),
this._onBlockAndLogStreamerError.bind(this),
);
const catchAllLogFilter = {};
this._blockAndLogStreamerIfExists.addLogFilter(catchAllLogFilter);
this._blockAndLogStreamIntervalIfExists = intervalUtils.setAsyncExcludingInterval(
this._reconcileBlockAsync.bind(this),
this._pollingIntervalMs,
this._onBlockAndLogStreamerError.bind(this),
);
let isRemoved = false;
this._onLogAddedSubscriptionToken = this._blockAndLogStreamerIfExists.subscribeToOnLogAdded(
this._onLogStateChangedAsync.bind(this, callback, isRemoved),
);
isRemoved = true;
this._onLogRemovedSubscriptionToken = this._blockAndLogStreamerIfExists.subscribeToOnLogRemoved(
this._onLogStateChangedAsync.bind(this, callback, isRemoved),
);
}
// This method only exists in order to comply with the expected interface of Blockstream's constructor
private async _blockstreamGetBlockOrNullAsync(hash: string): Promise<Block | null> {
const shouldIncludeTransactionData = false;
const blockOrNull = await this._web3Wrapper.sendRawPayloadAsync<Block | null>({
method: 'eth_getBlockByHash',
params: [hash, shouldIncludeTransactionData],
});
return blockOrNull;
}
// This method only exists in order to comply with the expected interface of Blockstream's constructor
private async _blockstreamGetLatestBlockOrNullAsync(): Promise<Block | null> {
const shouldIncludeTransactionData = false;
const blockOrNull = await this._web3Wrapper.sendRawPayloadAsync<Block | null>({
method: 'eth_getBlockByNumber',
params: [BlockParamLiteral.Latest, shouldIncludeTransactionData],
});
return blockOrNull;
}
// This method only exists in order to comply with the expected interface of Blockstream's constructor
private async _blockstreamGetLogsAsync(filterOptions: FilterObject): Promise<RawLogEntry[]> {
const logs = await this._web3Wrapper.sendRawPayloadAsync<RawLogEntry[]>({
method: 'eth_getLogs',
params: [filterOptions],
});
return logs as RawLogEntry[];
}
private _stopBlockAndLogStream(): void {
if (_.isUndefined(this._blockAndLogStreamerIfExists)) {
throw new Error(OrderWatcherError.SubscriptionNotFound);
}
this._blockAndLogStreamerIfExists.unsubscribeFromOnLogAdded(this._onLogAddedSubscriptionToken as string);
this._blockAndLogStreamerIfExists.unsubscribeFromOnLogRemoved(this._onLogRemovedSubscriptionToken as string);
intervalUtils.clearAsyncExcludingInterval(this._blockAndLogStreamIntervalIfExists as NodeJS.Timer);
delete this._blockAndLogStreamerIfExists;
delete this._blockAndLogStreamIntervalIfExists;
}
private async _onLogStateChangedAsync(
callback: EventWatcherCallback,
isRemoved: boolean,
rawLog: RawLogEntry,
): Promise<void> {
const log: LogEntry = marshaller.unmarshalLog(rawLog);
await this._emitDifferencesAsync(log, isRemoved ? LogEventState.Removed : LogEventState.Added, callback);
}
private async _reconcileBlockAsync(): Promise<void> {
const latestBlockOrNull = await this._blockstreamGetLatestBlockOrNullAsync();
if (_.isNull(latestBlockOrNull)) {
return; // noop
}
// We need to coerce to Block type cause Web3.Block includes types for mempool blocks
if (!_.isUndefined(this._blockAndLogStreamerIfExists)) {
// If we clear the interval while fetching the block - this._blockAndLogStreamer will be undefined
await this._blockAndLogStreamerIfExists.reconcileNewBlock(latestBlockOrNull);
}
}
private async _emitDifferencesAsync(
log: LogEntry,
logEventState: LogEventState,
callback: EventWatcherCallback,
): Promise<void> {
const logEvent = {
removed: logEventState === LogEventState.Removed,
...log,
};
if (!_.isUndefined(this._blockAndLogStreamIntervalIfExists)) {
callback(null, logEvent);
}
}
private _onBlockAndLogStreamerError(err: Error): void {
// Since Blockstream errors are all recoverable, we simply log them if the verbose
// config is passed in.
if (this._isVerbose) {
logUtils.warn(err);
}
}
}
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