Enhance an Angular Application with Progressive Web App (PWA) Capabilities

This challenge focuses on transforming a standard Angular web application into a Progressive Web App (PWA). By implementing PWA features, your application will gain offline capabilities, faster loading times, and an installable experience, significantly improving user engagement and accessibility across various devices and network conditions.

Problem Description

Your task is to take an existing Angular application and integrate PWA features to make it a fully functional Progressive Web App. This involves setting up a service worker to handle caching, enabling offline support, and ensuring the application can be installed on user devices.

Key Requirements:

Service Worker Integration: Implement and configure an Angular service worker to cache application assets (HTML, CSS, JavaScript, images, etc.).
Offline Support: Ensure the application remains functional and displays cached content when the user is offline or has a poor network connection.
App Shell Caching: Cache the "app shell" (the minimal UI required to power the user experience) to enable instant loading on repeat visits.
Manifest File: Create and configure a web app manifest file (manifest.webmanifest) that provides metadata about your application (name, icons, start URL, display mode, etc.) to enable installation.
HTTPS: Verify that the application is served over HTTPS, as this is a prerequisite for service workers and PWA installation.
Basic Functionality: The PWA should still support all the original functionalities of the base Angular application.

Expected Behavior:

First Visit: The application loads normally over the network.
Subsequent Visits (Online): The application should load almost instantly, leveraging cached assets from the service worker.
Offline Visit: The application should load the cached app shell and any pre-cached data, providing a usable experience even without an internet connection. A clear indication to the user that they are offline might be beneficial.
Installation Prompt: When the PWA is viewed on a compatible device and browser, a prompt should appear (or be triggerable through user interaction) allowing the user to "Add to Home Screen" or "Install" the application.

Edge Cases to Consider:

Cache Updates: How will new versions of the application be updated in the cache?
User Data: How should user-specific data be handled in an offline scenario? (For this challenge, assume basic data caching is sufficient, but acknowledge more advanced strategies exist).
Browser Compatibility: While not a primary focus for implementation, be aware that PWA features have varying levels of support across browsers.

Examples

Since this is an implementation task rather than a data transformation, specific input/output examples are less applicable. Instead, we'll describe successful outcomes.

Example Outcome 1: Successful Offline Access

Scenario: A user has visited your Angular application online. They then lose their internet connection.
Expected Behavior: Upon attempting to visit the application's URL while offline, the application loads quickly using cached resources. The core UI is displayed, and if the application has basic offline data capabilities (e.g., displaying a static "Welcome" message or cached list items), that functionality should work.

Example Outcome 2: Installability

Scenario: A user visits your PWA-enabled Angular application on a mobile device (e.g., Android via Chrome, iOS via Safari).
Expected Behavior: The browser automatically displays an "Add to Home Screen" banner or provides an option in its menu to "Install App". After installation, the application appears as an icon on the user's home screen and can be launched like a native application, often in its own window without browser UI.

Constraints

The base Angular application to be enhanced is assumed to be functional and built with a recent version of Angular CLI (v11 or later recommended).
The solution must use TypeScript.
The focus is on core PWA features (service worker, manifest, offline caching, installability). Advanced PWA features like push notifications or background sync are out of scope for this challenge.
The application should remain accessible via its original URL over HTTP during development, but the final deployed PWA must be served over HTTPS.

Notes

The Angular CLI provides built-in schematics to add PWA support, which is the recommended starting point for this challenge.
Familiarize yourself with the @angular/pwa package and its configuration options.
Consider using Chrome's DevTools (Application tab) to inspect service workers, cache storage, and the manifest.
Think about how the ngsw-config.json file is used to define caching strategies.
The primary goal is to demonstrate understanding of how to make an Angular app a PWA, not to build a complex offline-first application with intricate data synchronization.