public async Task <ArtistWorkReport> AggregateDataAsync(Guid artistId)
{
// Get artist albums/works
var artist = await _artistService.GetArtistAsync(artistId);
artist.Works = await _artistService.GetArtistWorksAsync(artistId);
var report = new ArtistWorkReport
{
ArtistId = artistId,
Name = artist.Name
};
if (artist.Works == null || !artist.Works.Any())
{
return(report);
}
int sum = 0, validValuesCount = 0;
ArtistWork minWorkInfo = null, maxWorkInfo = null;
var syncLock = new object();
_cacheService.InitializeArtistWorks(artistId);
await artist.Works.ParallelForEachAsync(async (work) =>
{
// retrieve lyrics
work.Lyrics = await _lyricsService.SearchAsync(artist.Name, work.Title);
// calculate number of words
work.WordCount = _wordCounterService.Count(work.Lyrics);
// keep a copy so we can do further operations on the data without interogating the APIs
_cacheService.AddArtistWork(artistId, work);
// skip from the report songs that we couldn't find lyrics for
if (work.WordCount == 0)
{
return;
}
lock (syncLock)
{
// keep the sum and number of values to calculate the average
sum += work.WordCount;
validValuesCount++;
// keep info about the song with shortest number of words
if (minWorkInfo == null || work.WordCount < minWorkInfo.WordCount)
{
minWorkInfo = work;
}
// keep info about the song with maximum number of words
if (maxWorkInfo == null || work.WordCount > maxWorkInfo.WordCount)
{
maxWorkInfo = work;
}
}
});
if (validValuesCount > 0)
{
report.AverageWords = sum / validValuesCount;
report.TotalSongs = artist.Works.Count;
report.SongsConsidered = validValuesCount;
report.MinWords = minWorkInfo;
report.MaxWords = maxWorkInfo;
// using https://www.mathsisfun.com/data/standard-deviation-formulas.html
var stdDevSum = artist.Works
.Where(x => x.WordCount > 0)
.Sum(x => Math.Pow(x.WordCount - report.AverageWords, 2));
report.Variance = Math.Round(stdDevSum / validValuesCount, 2);
report.StandardDeviation = Math.Round(Math.Sqrt(report.Variance), 2);
}
return(report);
}