Assignment

The task is to build a REST API that exposes data from our existing podcast feeds at DR, with the following requirements. You are very welcome to justify any choices or rejections, in case you do not complete everything.

• It should be able to expose JSON data for a podcast feed based on a given name/id, e.g., "tiden" or "orientering".
• For a podcast feed, at a minimum, it should expose the title, description, link, category, and contained items (episodes).
• For each item, at a minimum, it should expose the id (guid), title, description, and publication date.
• It should be able to filter podcast feed items so that only items from a given publication date (pubDate) onwards are exposed.
• It should be able to limit how many items are exposed for the given podcast feed.
• We would like to see an example of a unit test.

Examples of podcast feeds:

• https://api.dr.dk/podcasts/v1/feeds/tiden.xml?limit=500
• https://api.dr.dk/podcasts/v1/feeds/orientering.xml?limit=10

More podcasts can be found here: https://www.dr.dk/lyd, and you can find the actual podcast feed by clicking on a given podcast and selecting "RSS".

Solution

The Rest API is implemented in .Net 8 using C#. The solution is following Clean Architecture therefore divided into 5 source projects:

• DR.PodcastFeeds.Api: The REST API (built on minimal APIs acting as the presentation layer)
• DR.PodcastFeeds.Domain: The domain class models (in this case the Podcast, Episode and Category classes)
• DR.PodcastFeeds.Infrastructure: The infrastructure layer (in this case the MongoDB database and HttpClient)
• DR.PodcastFeeds.Contracts: The contracts for the REST API (in this case the DTOs)
• DR.PodcastFeeds.Application: The application layer (implemented as a mediator pattern using MediatR)

API Specification

The API specification is available at https://dr-podcasts.azurewebsites.net/swagger (currently disabled)

Client application

A client application that consumes the API is available at https://podcasts.malpou.dev/ (currently disabled)

This is built using https://kit.svelte.dev/

Categories

The categories can be retrieved using a GET request to the /categories endpoint.

Podcasts

The podcasts can be retrieved using a GET request to the /podcasts endpoint. The podcasts can be filtered by category using the /categories/{categorySlug}/podcasts endpoint.

Episodes

The episodes can be retrieved using a GET request to the /podcasts/{podcastSlug}/episodes endpoint or the /episodes endpoint.

Episode filtering (Query parameters)

The episodes can be filtered in 3 ways:

• Last n episodes: Will return the last n episodes, specified by the ?last=n parameter.
• Episodes in a date range: Will return the episodes in a date range, specified by the ?from=yyyy-MM-dd&to=yyyy-MM-dd parameters.
• Pagination: Will return episodes paginated, specified by the ?page=n&size=n parameters.

Examples

• https://dr-podcasts.azurewebsites.net/podcasts/tiden/episodes?last=10
• https://dr-podcasts.azurewebsites.net/podcasts/tiden/episodes?from=2023-11-01&to=2023-11-30
• https://dr-podcasts.azurewebsites.net/podcasts/tiden/episodes?page=5&size=5

Configuration

The system can add or remove podcast feeds using HTTP POST and DELETE requests to the /podcasts/{podcastSlug} endpoint. The endpoint is secured using basic authentication. The podcast slug is the slug of the podcast feed, e.g. tiden or orientering.

Example

• POST https://dr-podcasts.azurewebsites.net/podcasts/tiden
• DELETE https://dr-podcasts.azurewebsites.net/podcasts/tiden

Authentication

The system is using basic authentication for the /podcasts/{podcastSlug} endpoints. You get a Bearer token by calling the /login endpoint with the username and password as JSON in the body.

Packages

The solution is using the following packages:

• Azure.Security.KeyVault.Secrets: For accessing the Azure Key Vault secrets which are used to store passwords and other sensitive data.
• BCrypt.Net-Next: For hashing of passwords.
• Hangfire.AspNetCore: For background jobs.
• MediatR: For the mediator pattern.
• MongoDB.Driver: For the MongoDB database actions.
• Swashbuckle.AspNetCore: For the API documentation.

Testing

Unit tests have been added for the fetching of episodes to display how unit tests can be implemented in a project like this. The unit tests can be found in the following projects:

• DR.PodcastFeeds.Infrastructure.Tests
• DR.PodcastFeeds.Application.Tests
• DR.PodcastFeeds.Api.Tests

There are no unit tests for the domain classes as they are just simple POCOs.

Packages

The solution is using the following testing frameworks:

• xUnit: For unit testing.
• NSubstitute: For mocking.
• FluentAssertions: For assertions.
• Testcontainers.MongoDB: For integration testing of the database (running on Docker).