song-of-the-day/song_of_the_day/SongValidators/SongResolver.cs

using Microsoft.Extensions.Logging;

public class SongResolver
{
    private readonly IEnumerable<ISongValidator> _songValidators;

    private readonly ILogger logger;

    public SongResolver()
    {
        using ILoggerFactory factory = LoggerFactory.Create(builder => builder.AddConsole().SetMinimumLevel(LogLevel.Information));
        this.logger = factory.CreateLogger("SongResolver");
        
        this._songValidators = new List<ISongValidator>();

        foreach (Type mytype in System.Reflection.Assembly.GetExecutingAssembly().GetTypes()
                 .Where(mytype => mytype.GetInterfaces().Contains(typeof(ISongValidator)) && !(mytype.Name.EndsWith("Base")))) {
            if (Activator.CreateInstance(mytype) is ISongValidator validator)
            {
                logger.LogDebug("Registering song validator: {ValidatorType}", mytype.Name);
                this._songValidators = this._songValidators.Append(validator);
            }
        }
    }

    public async Task<Song> ResolveSongAsync(Uri songUri)
    {
        foreach (var validator in _songValidators)
        {
            if (validator.CanValidateUri(songUri))
            {
                if (!await validator.CanExtractSongMetadataAsync(songUri))
                {
                    this.logger.LogWarning("Cannot extract metadata for song URI: {SongUri}", songUri);
                    return new Song {
                                    Artist = "Unknown Artist",
                                    Name = "Unknown Title",
                                    Url = songUri.ToString(),
                                    Provider = SongProvider.PlainHttp,
                                };
                }
                return await validator.ValidateAsync(songUri);
            }
        }

        return new Song {
                        Artist = "Unknown Artist",
                        Name = "Unknown Title",
                        Url = songUri.ToString(),
                        Provider = SongProvider.PlainHttp,
                    };
    }

    public bool CanValidate(Uri songUri)
    {
        foreach (var validator in _songValidators)
        {
            if (validator.CanValidateUri(songUri))
            {
                return true;
            }
        }

        return false;
    }
}