using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

public class VideoSeparator
{
    private readonly Regex episodePattern = new Regex(@"E\d{1,3}", RegexOptions.IgnoreCase);

    public async Task<(List<string> seriesFiles, List<string> movieFiles)> SeparateVideosAsync(List<string> videoFiles)
    {
        int coreCount = Environment.ProcessorCount;
        int totalFiles = videoFiles.Count;
        int chunkSize = (int)Math.Ceiling((double)totalFiles / coreCount);

        var seriesBag = new ConcurrentBag<string>();
        var movieBag = new ConcurrentBag<string>();
        var tasks = new List<Task>();

        for (int i = 0; i < coreCount; i++)
        {
            int start = i * chunkSize;
            int end = Math.Min(start + chunkSize, totalFiles);

            tasks.Add(Task.Run(() =>
            {
                for (int j = start; j < end; j++)
                {
                    string path = videoFiles[j];
                    string filename = Path.GetFileNameWithoutExtension(path);

                    if (filename == null)
                        continue;

                    if (episodePattern.IsMatch(filename))
                        seriesBag.Add(path);
                    else
                        movieBag.Add(path);
                }
            }));
        }

        await Task.WhenAll(tasks);

        return (new List<string>(seriesBag), new List<string>(movieBag));
    }
}