chore: wrapTimer function types (#8428)

This gives us better types for our wrapTimer function.

Maybe the type `(args: any) => any` could also be improved

---------

Co-authored-by: Nuno Góis <nuno@getunleash.io>

src/lib/features/frontend-api/client-feature-toggle-read-model.ts

@@ -22,7 +22,7 @@ export default class ClientFeatureToggleReadModel
 
     constructor(db: Db, eventBus: EventEmitter) {
         this.db = db;
-        this.timer = (action) =>
+        this.timer = (action: string) =>
             metricsHelper.wrapTimer(eventBus, DB_TIME, {
                 store: 'client-feature-toggle-read-model',
                 action,

src/lib/features/frontend-api/frontend-api-controller.ts

@@ -49,7 +49,7 @@ export default class FrontendAPIController extends Controller {
         this.logger = config.getLogger('frontend-api-controller.ts');
         this.services = services;
 
-        this.timer = (functionName) =>
+        this.timer = (functionName: string) =>
             metricsHelper.wrapTimer(config.eventBus, FUNCTION_TIME, {
                 className: 'FrontendAPIController',
                 functionName,

src/lib/util/metrics-helper.ts

@@ -1,20 +1,31 @@
-/* eslint-disable no-param-reassign */
+import type EventEmitter from 'events';
 import timer from './timer';
 
 // wrapTimer keeps track of the timing of a async operation and emits
 // a event on the given eventBus once the operation is complete
 //
-// the returned function is designed to be used as a .then(<func>) argument.
-// It transparently passes the data to the following .then(<func>)
+// the returned function is designed to stop the timer and emit the event
 //
-// usage: promise.then(wrapTimer(bus, type, { payload: 'ok' }))
-const wrapTimer: (EventEmitter, string, object) => (any) => any = (
-    eventBus,
-    event,
-    args = {},
+// Usage:
+// Define the timer function. It can  be done once per class.
+// this.timer = (action: string) =>
+//     metricsHelper.wrapTimer(eventBus, DB_TIME, {
+//         store: 'client-feature-toggle-read-model',
+//         action,
+//     });
+//
+// Before performing an operation, start the timer:
+// const stopTimer = this.timer(`timer-name`);
+// // perform operation and then stop timer
+// stopTimer();
+
+const wrapTimer = (
+    eventBus: EventEmitter,
+    event: string,
+    args: Record<string, unknown> = {},
 ) => {
     const t = timer.new();
-    return (data) => {
+    return (data: unknown) => {
         args.time = t();
         eventBus.emit(event, args);
         return data;