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Samruddhi90Samruddhi90
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added the VisibilityMonitor code
1 parent 36e19aa commit b758777

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3 files changed

+177
-3
lines changed

3 files changed

+177
-3
lines changed

‎packages/remote-config/src/client/EventEmitter.ts‎

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/**
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* @license
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* Copyright 2017 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { assert } from '@firebase/util';
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/**
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* Base class to be used if you want to emit events. Call the constructor with
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* the set of allowed event names.
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*/
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export abstract class EventEmitter {
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private listeners_: {
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[eventType: string]: Array<{
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callback(...args: unknown[]): void;
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context: unknown;
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}>;
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} = {};
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constructor(private allowedEvents_: string[]) {
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assert(
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Array.isArray(allowedEvents_) && allowedEvents_.length > 0,
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'Requires a non-empty array'
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);
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}
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/**
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* To be overridden by derived classes in order to fire an initial event when
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* somebody subscribes for data.
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*
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* @returns {Array.<*>} Array of parameters to trigger initial event with.
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*/
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abstract getInitialEvent(eventType: string): unknown[];
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/**
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* To be called by derived classes to trigger events.
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*/
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protected trigger(eventType: string, ...varArgs: unknown[]) {
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if (Array.isArray(this.listeners_[eventType])) {
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// Clone the list, since callbacks could add/remove listeners.
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const listeners = [...this.listeners_[eventType]];
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for (let i = 0; i < listeners.length; i++) {
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listeners[i].callback.apply(listeners[i].context, varArgs);
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}
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}
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}
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on(eventType: string, callback: (a: unknown) => void, context: unknown) {
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this.validateEventType_(eventType);
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this.listeners_[eventType] = this.listeners_[eventType] || [];
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this.listeners_[eventType].push({ callback, context });
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const eventData = this.getInitialEvent(eventType);
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if (eventData) {
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callback.apply(context, eventData);
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}
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}
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off(eventType: string, callback: (a: unknown) => void, context: unknown) {
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this.validateEventType_(eventType);
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const listeners = this.listeners_[eventType] || [];
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for (let i = 0; i < listeners.length; i++) {
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if (
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listeners[i].callback === callback &&
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(!context || context === listeners[i].context)
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) {
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listeners.splice(i, 1);
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return;
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}
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}
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}
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private validateEventType_(eventType: string) {
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assert(
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this.allowedEvents_.find(et => {
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return et === eventType;
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}),
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'Unknown event: ' + eventType
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);
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}
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}

‎packages/remote-config/src/client/VisibilityMonitor.ts‎

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/**
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* @license
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* Copyright 2025 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { assert } from '@firebase/util';
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import { EventEmitter } from './EventEmitter';
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declare const document: Document;
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export class VisibilityMonitor extends EventEmitter {
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private visible_: boolean;
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static getInstance() {
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return new VisibilityMonitor();
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}
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constructor() {
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super(['visible']);
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let hidden: string;
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let visibilityChange: string;
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if (
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typeof document !== 'undefined' &&
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typeof document.addEventListener !== 'undefined'
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) {
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if (typeof document['hidden'] !== 'undefined') {
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// Opera 12.10 and Firefox 18 and later support
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visibilityChange = 'visibilitychange';
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hidden = 'hidden';
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} else if (typeof document['mozHidden'] !== 'undefined') {
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visibilityChange = 'mozvisibilitychange';
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hidden = 'mozHidden';
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} else if (typeof document['msHidden'] !== 'undefined') {
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visibilityChange = 'msvisibilitychange';
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hidden = 'msHidden';
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} else if (typeof document['webkitHidden'] !== 'undefined') {
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visibilityChange = 'webkitvisibilitychange';
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hidden = 'webkitHidden';
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}
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}
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// Initially, we always assume we are visible. This ensures that in browsers
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// without page visibility support or in cases where we are never visible
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// (e.g. chrome extension), we act as if we are visible, i.e. don't delay
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// reconnects
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this.visible_ = true;
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if (visibilityChange) {
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document.addEventListener(
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visibilityChange,
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() => {
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const visible = !document[hidden];
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if (visible !== this.visible_) {
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this.visible_ = visible;
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this.trigger('visible', visible);
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}
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},
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false
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);
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}
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}
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getInitialEvent(eventType: string): boolean[] {
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assert(eventType === 'visible', 'Unknown event type: ' + eventType);
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return [this.visible_];
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}
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}

‎packages/remote-config/src/client/realtime_handler.ts‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -21,7 +21,7 @@ import { ERROR_FACTORY, ErrorCode } from '../errors';
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import { _FirebaseInstallationsInternal } from '@firebase/installations';
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import { Storage } from '../storage/storage';
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import { calculateBackoffMillis, FirebaseError } from '@firebase/util';
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import { VisibilityMonitor } from '@firebase/database/dist/src/core/util/VisibilityMonitor';
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import { VisibilityMonitor } from './VisibilityMonitor';
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export class RealtimeHandler {
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constructor(
@@ -33,7 +33,7 @@ export class RealtimeHandler {
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private readonly apiKey: string,
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private readonly appId: string
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) {
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VisibilityMonitor.getInstance().on('visible', this.onVisibilityChange_, this);
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VisibilityMonitor.getInstance().on('visible', this.onVisibilityChange, this);
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}
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private streamController?: AbortController;
@@ -268,7 +268,7 @@ export class RealtimeHandler {
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return new URL(urlString);
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}
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private onVisibilityChange_(visible: unknown) {
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private onVisibilityChange(visible: unknown) {
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const wasInBackground = this.isInBackground;
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this.isInBackground = !visible;
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if (wasInBackground !== this.isInBackground) {

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