Media Player Refactoring Python Kata

Overview

This kata complements Clean Code: SOLID, Ep. 12 - Interface Segregation Principle.

The exercise involves refactoring a multimedia player system to adhere to this principle.

The problem we have at hand involves different types of media -- audio, video, and images. We start with a monolithic IMediaPlayer interface that handles all types of media. This will be your starting point.

Instructions

Exercise 1

In the first part, your task is to refactor the existing code such that each type of media player (audio, video, and image) has its own specific interface, instead of the monolithic IMediaPlayer interface. You should create IAudioPlayer, IVideoPlayer, and IImagePlayer interfaces, each with a relevant method, and update the AudioPlayer, VideoPlayer, and ImagePlayer classes to implement these new interfaces.

This part includes unit tests that ensure each type of media player is functioning correctly. After you have completed your refactoring, all unit tests should pass.

Exercise 2

In the second part, we will deal with the compatibility of different players with different file types.

Before, we had a separate player for each media type. We want to have media files that come in different formats (e.g., .mp3, .flac, .wav for audio, .jpeg, .png for images, and .mp4, .mkv for videos). And some players can only handle certain formats.

We have the MediaFile class to represent a media file, your task is to:

1. Update the player interfaces to take MediaFile objects, e.g.:

   class IMediaPlayer(ABC):
   
       @abstractmethod
       def play_audio(self, file):
           pass

2. Create specialized players that can only handle certain formats (i.e., Mp3Player, FlacPlayer, WavPlayer).

   class Mp3Player(IAudioPlayer):
   
       def play_audio(file):
           if file.format != "mp3":
               raise ValueError("Invalid file format for Mp3Player!")
   
           # Implementation...

   The same kind of specialization will be done for FlacPlayer, WavPlayer, and respective video and image players.

3. Add corresponding unit tests, e.g.:

   def test_mp3_player_handles_mp3():
       mp3_player = Mp3Player()
       mp3_file = MediaFile(format="mp3", filename="")
       mp3_player.play_audio(mp3_file)
   
   def test_mp3_player_rejects_non_mp3():
       mp3_player = Mp3Player()
       flac_file = MediaFile(format="flac", filename="")
       with pytest.raises(ValueError):
           mp3_player.play_audio(flac_file)

Exercise 3

In the third part, we introduce the concept of a MediaListPlayer. This class accepts a list of media files and a corresponding list of players. It checks if the player is compatible with the media file format before trying to play/display the file.

For the MediaListPlayer, we can update the play_list method to take a list of IAudioPlayer, IVideoPlayer, and IImagePlayer instead of IMediaPlayer.

In the play_list method, we should use the appropriate player based on the type of the media file. This may require additional checks or mappings from file type to player.

Your task is to refactor the code to segregate interfaces based on the different file formats and adapt the MediaListPlayer to work with the new classes and interfaces.

Usage

You can import this project into Replit, and it will handle all dependencies automatically.

Prerequisites

• Python 3.8+
• pytest

Run main

make run

Run tests

make test