Recently Viewed Courses

Sample Problem Solving Task: “Recently Viewed Courses Page”

Scenario:

The University wants a page on the website that shows:

• A cacheable block of curated "Popular Courses".

• A non-cacheable block of "Recently Viewed Courses" (tracked per user session).

• Clean separation of frontend logic using Twig templates and CSS classes.

• Accessibility in markup and semantic HTML.

---

Task Requirements:

1. Create a custom module called recently_viewed_courses.

2. On visiting /courses/recently-viewed, the page should:

• Display Popular Courses (static content for now).

• Display Recently Viewed Courses stored in user session.

3. Use render arrays and #lazy_builder for the non-cacheable part.

4. Write a service to handle session storage for recently viewed courses.

5. Ensure the page is accessible and responsive.

---

Features

• Adds a custom page at /courses/recently-viewed.
• Displays:
  • Popular Courses (cacheable content).
  • Recently Viewed Courses (user session-based, non-cacheable).
• Uses:
  • Render arrays and lazy builders (can be switched to direct block rendering).
  • Twig template for clean and accessible frontend output.
  • A custom service for session-based storage of recently viewed items.
• Accessibility support with ARIA labels and semantic HTML.

---

Installation

1. Clone the module or copy it into the modules/custom/ directory of your Drupal project.

cd web/modules/custom
git clone https://github.com/your-repo/recently_viewed_courses.git

2. Enable the module using Drush or the admin UI.

drush en recently_viewed_courses

3. Visit /courses/recently-viewed to test the feature.

---

How It Works

1. CoursePageController.php

   Defines the page route and render array.

   Uses #theme => 'course_page' to load the Twig template.

   Includes #lazy_builder to call a trusted service method to render the dynamic block.

2. RecentlyViewedBlock.php

   A custom block plugin that fetches recently viewed course names from the session using a service (CourseTracker).

   Returned block content is never cached (#cache => ['max-age' => 0]).

3. CourseTracker.php

   A custom service that adds and retrieves course names from PHP session.

   Limits the session history to 5 unique entries.

4. RecentlyViewedLazyBuilder.php

   A custom lazy builder service that securely loads and returns the RecentlyViewedBlock render array.

   Implements TrustedCallbackInterface to allow render() to be safely used with #lazy_builder.

---

Test

Now visit: https://my-first-drupal10-app.ddev.site:8443/course/view/psychology

https://my-first-drupal10-app.ddev.site:8443/course/view/ai

Then go back to: https://my-first-drupal10-app.ddev.site:8443/courses/recently-viewed