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

public class FileScanner
{
    //all extensions and cuncurrent bag as a list wich works threw out multiple threads
    private readonly string[] _extensions;
    private readonly ConcurrentBag<string> _foundFiles = new ConcurrentBag<string>();

    public FileScanner(string[] extensions)
    {
        _extensions = extensions.Select(e => e.ToLower()).ToArray();
    }
    //return a list of all coneckted drives
    public async Task<List<string>> ScanAllDrivesAsync()
    {
        var drives = new List<string>();

        foreach (var drive in DriveInfo.GetDrives())
        {
            if (!drive.IsReady) continue;

            Console.WriteLine($"Scanning {drive.Name} ...");

            string root = drive.RootDirectory.FullName;
            drives.Add(root);
        }

        return drives.ToList();
    }
    //scan teh designated drive or folder 
    public async Task<List<string>> ScanDriveParallel(string rootPath)
    {
        //all sub direcktorys will be also added to this bag
        var folderQueue = new ConcurrentQueue<string>();
        folderQueue.Enqueue(rootPath);
        //all aktive skanners are placed here
        var folderWorkers = new List<Task>();
        //keep max tasks at half teh amounts of cores
        int maxWorkers = Environment.ProcessorCount/2;

        for (int i = 0; i < maxWorkers; i++)
        {
            folderWorkers.Add(Task.Run(() =>
            {
                while (folderQueue.TryDequeue(out string currentPath))
                {
                    try
                    {
                        // Check files
                        foreach (var file in Directory.GetFiles(currentPath))
                        {
                            if (_extensions.Any(ext => file.EndsWith(ext, StringComparison.OrdinalIgnoreCase)))
                            {
                                //Console.WriteLine(file);
                                _foundFiles.Add(file);
                            }
                        }

                        // Enqueue subdirectories
                        foreach (var dir in Directory.GetDirectories(currentPath))
                        {
                            folderQueue.Enqueue(dir);
                        }
                    }
                    catch
                    {
                        // Skip inaccessible folders silently
                    }
                }
            }));
        }
        //wait till all tasks are done
        Task.WaitAll(folderWorkers.ToArray());
        //return the found paths as string
        return _foundFiles.ToList();
    }
}