refactor: type checking for BalanceAlert event

Author: sangaman

lib/alerts/Alerts.ts

@@ -1,9 +1,9 @@
 import { EventEmitter } from 'events';
-import { Alert, BalanceAlert } from './types';
-import SwapClientManager from '../swaps/SwapClientManager';
-import Logger from '../Logger';
-import { AlertType, ChannelSide } from '../constants/enums';
 import { satsToCoinsStr } from '../cli/utils';
+import { AlertType, ChannelSide } from '../constants/enums';
+import Logger from '../Logger';
+import SwapClientManager from '../swaps/SwapClientManager';
+import { Alert, BalanceAlertEvent } from './types';
 
 interface Alerts {
   on(event: 'alert', listener: (alert: Alert) => void): this;
@@ -35,20 +35,25 @@ class Alerts extends EventEmitter {
     swapClientManager.connextClient?.on('lowTradingBalance', this.onLowTradingBalance);
   }
 
-  private onLowTradingBalance = (balanceAlert: BalanceAlert) => {
+  private onLowTradingBalance = (balanceAlertEvent: BalanceAlertEvent) => {
     // TODO don't use JSON.stringify instead find a way to define unique ids per alert and keep in the map to avoid memory issues
-    const stringRepresentation = JSON.stringify(balanceAlert);
+    const stringRepresentation = JSON.stringify(balanceAlertEvent);
     this.logger.trace(`received low trading balance alert ${stringRepresentation}`);
     if (this.alerts.get(stringRepresentation) === undefined || this.checkAlertThreshold(stringRepresentation)) {
       this.logger.trace(`triggering low balance alert ${stringRepresentation}`);
 
-      balanceAlert.message = `${ChannelSide[balanceAlert.side || 0]} trading balance (${satsToCoinsStr(
-        balanceAlert.sideBalance || 0,
-      )} ${balanceAlert.currency}) is lower than 10% of trading capacity (${satsToCoinsStr(
-        balanceAlert.totalBalance || 0,
-      )} ${balanceAlert.currency})`;
-      balanceAlert.type = AlertType.LowTradingBalance;
-      balanceAlert.date = Date.now();
+      const message = `${ChannelSide[balanceAlertEvent.side || 0]} trading balance (${satsToCoinsStr(
+        balanceAlertEvent.sideBalance || 0,
+      )} ${balanceAlertEvent.currency}) is lower than 10% of trading capacity (${satsToCoinsStr(
+        balanceAlertEvent.totalBalance || 0,
+      )} ${balanceAlertEvent.currency})`;
+
+      const balanceAlert = {
+        ...balanceAlertEvent,
+        message,
+        type: AlertType.LowTradingBalance,
+        date: Date.now(),
+      };
 
       this.alerts.set(stringRepresentation, balanceAlert.date);
       this.emit('alert', balanceAlert);

lib/alerts/types.ts

@@ -1,8 +1,12 @@
 import { AlertType, ChannelSide } from '../constants/enums';
 
-export type Alert = BalanceAlert;
+type BaseAlert = {
+  type: AlertType;
+  message: string;
+  date: number;
+};
 
-export type BalanceAlert = BaseAlert & {
+export type BalanceAlertEvent = {
   /** The total balance of the channel when the alert is triggered. */
   totalBalance: number;
   /** The side of the balance either local or remote. */
@@ -14,9 +18,6 @@ export type BalanceAlert = BaseAlert & {
   /** The currency of the channel. */
   currency: string;
 };
+export type BalanceAlert = BaseAlert & BalanceAlertEvent;
 
-type BaseAlert = {
-  type: AlertType;
-  message: string;
-  date: number;
-};
+export type Alert = BalanceAlert;

lib/connextclient/ConnextClient.ts

@@ -3,9 +3,9 @@ import assert from 'assert';
 import http from 'http';
 import { combineLatest, defer, from, fromEvent, interval, Observable, of, Subscription, throwError, timer } from 'rxjs';
 import { catchError, distinctUntilChanged, filter, mergeMap, mergeMapTo, pluck, take, timeout } from 'rxjs/operators';
+import { BalanceAlertEvent } from '../alerts/types';
 import { SwapClientType, SwapRole, SwapState } from '../constants/enums';
 import { CurrencyInstance } from '../db/types';
-import { Alert } from '../alerts/types';
 import Logger from '../Logger';
 import swapErrors from '../swaps/errors';
 import SwapClient, {
@@ -51,15 +51,15 @@ interface ConnextClient {
   on(event: 'htlcAccepted', listener: (rHash: string, amount: number, currency: string) => void): this;
   on(event: 'connectionVerified', listener: (swapClientInfo: SwapClientInfo) => void): this;
   on(event: 'depositConfirmed', listener: (hash: string) => void): this;
-  on(event: 'lowTradingBalance', listener: (alert: Alert) => void): this;
+  on(event: 'lowTradingBalance', listener: (alert: BalanceAlertEvent) => void): this;
   once(event: 'initialized', listener: () => void): this;
   emit(event: 'htlcAccepted', rHash: string, amount: number, currency: string): boolean;
   emit(event: 'connectionVerified', swapClientInfo: SwapClientInfo): boolean;
   emit(event: 'initialized'): boolean;
   emit(event: 'preimage', preimageRequest: ProvidePreimageEvent): void;
   emit(event: 'transferReceived', transferReceivedRequest: TransferReceivedEvent): void;
   emit(event: 'depositConfirmed', hash: string): void;
-  emit(event: 'lowTradingBalance', alert: Alert): boolean;
+  emit(event: 'lowTradingBalance', alert: BalanceAlertEvent): boolean;
 }
 
 const getRouterNodeIdentifier = (network: string): string => {
@@ -343,7 +343,7 @@ class ConnextClient extends SwapClient {
         const totalBalance = remoteBalance + localBalance;
         const alertThreshold = totalBalance * 0.1;
 
-        this.checkLowBalance(remoteBalance, localBalance, totalBalance, alertThreshold, currency, this.emit.bind(this));
+        this.checkLowBalance(remoteBalance, localBalance, totalBalance, alertThreshold, currency);
       }
     } catch (e) {
       this.logger.error('failed to update total outbound capacity', e);

lib/lndclient/LndClient.ts

@@ -2,6 +2,7 @@ import assert from 'assert';
 import crypto from 'crypto';
 import { promises as fs, watch } from 'fs';
 import grpc, { ChannelCredentials, ClientReadableStream } from 'grpc';
+import { BalanceAlertEvent } from 'lib/alerts/types';
 import path from 'path';
 import { SwapClientType, SwapRole, SwapState } from '../constants/enums';
 import Logger from '../Logger';
@@ -27,15 +28,14 @@ import { deriveChild } from '../utils/seedutil';
 import { base64ToHex, hexToUint8Array } from '../utils/utils';
 import errors from './errors';
 import { Chain, ChannelCount, ClientMethods, LndClientConfig, LndInfo } from './types';
-import { Alert } from '../alerts/types';
 
 interface LndClient {
   on(event: 'connectionVerified', listener: (swapClientInfo: SwapClientInfo) => void): this;
   on(event: 'htlcAccepted', listener: (rHash: string, amount: number) => void): this;
   on(event: 'channelBackup', listener: (channelBackup: Uint8Array) => void): this;
   on(event: 'channelBackupEnd', listener: () => void): this;
   on(event: 'locked', listener: () => void): this;
-  on(event: 'lowTradingBalance', listener: (alert: Alert) => void): this;
+  on(event: 'lowTradingBalance', listener: (alert: BalanceAlertEvent) => void): this;
 
   once(event: 'initialized', listener: () => void): this;
 
@@ -45,7 +45,7 @@ interface LndClient {
   emit(event: 'channelBackupEnd'): boolean;
   emit(event: 'locked'): boolean;
   emit(event: 'initialized'): boolean;
-  emit(event: 'lowTradingBalance', alert: Alert): boolean;
+  emit(event: 'lowTradingBalance', alert: BalanceAlertEvent): boolean;
 }
 
 const GRPC_CLIENT_OPTIONS = {
@@ -257,7 +257,6 @@ class LndClient extends SwapClient {
           totalBalance,
           alertThreshold,
           this.currency,
-          this.emit.bind(this),
         );
       })
       .catch(async (err) => {

lib/swaps/SwapClient.ts

@@ -1,4 +1,5 @@
 import { EventEmitter } from 'events';
+import { BalanceAlertEvent } from 'lib/alerts/types';
 import { ChannelSide, SwapClientType } from '../constants/enums';
 import Logger from '../Logger';
 import { setTimeoutPromise } from '../utils/utils';
@@ -71,8 +72,10 @@ export type WithdrawArguments = {
 
 interface SwapClient {
   on(event: 'connectionVerified', listener: (swapClientInfo: SwapClientInfo) => void): this;
+  on(event: 'lowTradingBalance', listener: (alert: BalanceAlertEvent) => void): this;
   once(event: 'initialized', listener: () => void): this;
   emit(event: 'connectionVerified', swapClientInfo: SwapClientInfo): boolean;
+  emit(event: 'lowTradingBalance', alert: BalanceAlertEvent): boolean;
   emit(event: 'initialized'): boolean;
 }
 
@@ -234,10 +237,9 @@ abstract class SwapClient extends EventEmitter {
     totalBalance: number,
     alertThreshold: number,
     currency: string,
-    emit: Function,
   ) => {
     if (localBalance < alertThreshold) {
-      emit('lowTradingBalance', {
+      this.emit('lowTradingBalance', {
         totalBalance,
         currency,
         side: ChannelSide.Local,
@@ -247,7 +249,7 @@ abstract class SwapClient extends EventEmitter {
     }
 
     if (remoteBalance < alertThreshold) {
-      emit('lowTradingBalance', {
+      this.emit('lowTradingBalance', {
         totalBalance,
         currency,
         side: ChannelSide.Remote,