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

namespace file_finder__test;

public class FileClassifier
{
    //returns 2 seperat lists music and vidio
    public async Task<(List<string> musicFiles, List<string> videoFiles, List<string> photoFiles)> ClassifyFilesAsync(
        //3 lists. all file paths and a list for vidio and music ext
        List<string> allFiles,
        List<string> musicExtensions,
        List<string> videoExtensions,
        List<string>  photoExtensions)
    {
        //limit the max paralel tasks and split the total amount of files by the limit set
        int coreCount = Environment.ProcessorCount/2;
        int totalFiles = allFiles.Count;
        int chunkSize = (int)Math.Ceiling((double)totalFiles / coreCount);
        //concurrent bag instead of lists due to multi tasks 
        var musicBag = new ConcurrentBag<string>();
        var videoBag = new ConcurrentBag<string>();
        var photoBag = new ConcurrentBag<string>();
        //a list of tasks. needed to check if all are done
        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 file = allFiles[j];
                    string ext = Path.GetExtension(file)?.ToLowerInvariant();

                    if (ext == null)
                        continue;

                    if (musicExtensions.Contains(ext))
                        musicBag.Add(file);
                    else if (videoExtensions.Contains(ext))
                        videoBag.Add(file);
                    else if (photoExtensions.Contains(ext))
                    {
                        photoBag.Add(file);
                    }
                }
            }));
        }
        //wait till all tasks are done and return 2 lists
        await Task.WhenAll(tasks);
        return (new List<string>(musicBag), new List<string>(videoBag), new List<string>(photoBag));
    }
}