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import * as _ from 'lodash';
import * as WebSocket from 'websocket';
import {
OrderbookChannel,
OrderbookChannelHandler,
OrderbookChannelMessageTypes,
OrderbookChannelSubscriptionOpts,
WebsocketClientEventType,
WebsocketConnectionEventType,
} from './types';
import { assert } from './utils/assert';
import { orderbookChannelMessageParser } from './utils/orderbook_channel_message_parser';
interface Subscription {
subscriptionOpts: OrderbookChannelSubscriptionOpts;
handler: OrderbookChannelHandler;
}
/**
* This class includes all the functionality related to interacting with a websocket endpoint
* that implements the standard relayer API v0
*/
export class WebSocketOrderbookChannel implements OrderbookChannel {
private _client: WebSocket.w3cwebsocket;
private _subscriptions: Subscription[] = [];
/**
* Instantiates a new WebSocketOrderbookChannel instance
* @param url The relayer API base WS url you would like to interact with
* @return An instance of WebSocketOrderbookChannel
*/
constructor(client: WebSocket.w3cwebsocket) {
this._client = client;
this._client.onerror = err => {
this._alertAllHandlersToError(err);
};
this._client.onclose = () => {
this._alertAllHandlersToClose();
};
this._client.onmessage = message => {
this._handleWebSocketMessage(message);
};
}
/**
* Subscribe to orderbook snapshots and updates from the websocket
* @param subscriptionOpts An OrderbookChannelSubscriptionOpts instance describing which
* token pair to subscribe to
* @param handler An OrderbookChannelHandler instance that responds to various
* channel updates
*/
public subscribe(subscriptionOpts: OrderbookChannelSubscriptionOpts, handler: OrderbookChannelHandler): void {
assert.isOrderbookChannelSubscriptionOpts('subscriptionOpts', subscriptionOpts);
assert.isOrderbookChannelHandler('handler', handler);
assert.assert(this._client.readyState === WebSocket.w3cwebsocket.OPEN, 'WebSocket connection is closed');
const newSubscription: Subscription = {
subscriptionOpts,
handler,
};
this._subscriptions.push(newSubscription);
const subscribeMessage = {
type: 'subscribe',
channel: 'orderbook',
requestId: this._subscriptions.length - 1,
payload: subscriptionOpts,
};
this._client.send(JSON.stringify(subscribeMessage));
}
/**
* Close the websocket and stop receiving updates
*/
public close(): void {
this._client.close();
}
/**
* For use in cases where we need to alert all handlers of an error
*/
private _alertAllHandlersToError(error: Error): void {
_.forEach(this._subscriptions, subscription => {
subscription.handler.onError(this, subscription.subscriptionOpts, error);
});
}
private _alertAllHandlersToClose(): void {
_.forEach(this._subscriptions, subscription => {
subscription.handler.onClose(this, subscription.subscriptionOpts);
});
}
private _handleWebSocketMessage(message: any): void {
// if we get a message with no data, alert all handlers and return
if (_.isUndefined(message.data)) {
this._alertAllHandlersToError(new Error(`Message does not contain utf8Data`));
return;
}
// try to parse the message data and route it to the correct handler
try {
const utf8Data = message.data;
const parserResult = orderbookChannelMessageParser.parse(utf8Data);
const subscription = this._subscriptions[parserResult.requestId];
if (_.isUndefined(subscription)) {
this._alertAllHandlersToError(new Error(`Message has unknown requestId: ${utf8Data}`));
return;
}
const handler = subscription.handler;
const subscriptionOpts = subscription.subscriptionOpts;
switch (parserResult.type) {
case OrderbookChannelMessageTypes.Snapshot: {
handler.onSnapshot(this, subscriptionOpts, parserResult.payload);
break;
}
case OrderbookChannelMessageTypes.Update: {
handler.onUpdate(this, subscriptionOpts, parserResult.payload);
break;
}
default: {
handler.onError(
this,
subscriptionOpts,
new Error(`Message has unknown type parameter: ${utf8Data}`),
);
}
}
} catch (error) {
this._alertAllHandlersToError(error);
}
}
}
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