CountdownEvent version #3

class Program
{
    static void Main(string[] args)
    {
        if (args.Length < 2)
        {
            Console.WriteLine("Usage: <path> <minWordLength>");
            return;
        }

        string path = args[0];
        if (!int.TryParse(args[1], out int minWordLength) || minWordLength <= 0)
        {
            Console.WriteLine("Invalid minimum word length.");
            return;
        }

        if (!Directory.Exists(path))
        {
            Console.WriteLine("Directory does not exist.");
            return;
        }

        var files = Directory.GetFiles(path, "*.txt", SearchOption.AllDirectories);
        var countdownEvent = new CountdownEvent(files.Length);
        var localWordCounts = new ConcurrentBag<Dictionary<string, int>>();

        foreach (var filePath in files)
        {
            ThreadPool.QueueUserWorkItem(state =>
            {
                var localCounts = ProcessFile(filePath, minWordLength);
                localWordCounts.Add(localCounts);
                countdownEvent.Signal();
            });
        }

        // Wait for all threads to complete
        countdownEvent.Wait();

        // Aggregate results
        var aggregatedWordCounts = new Dictionary<string, int>();
        foreach (var localCounts in localWordCounts)
        {
            foreach (var kvp in localCounts)
            {
                if (aggregatedWordCounts.ContainsKey(kvp.Key))
                {
                    aggregatedWordCounts[kvp.Key] += kvp.Value;
                }
                else
                {
                    aggregatedWordCounts[kvp.Key] = kvp.Value;
                }
            }
        }

        // Get top-10 most frequent words
        var topWords = aggregatedWordCounts
            .OrderByDescending(kv => kv.Value)
            .Take(10)
            .ToList();

        Console.WriteLine("Top 10 most used words:");
        foreach (var word in topWords)
        {
            Console.WriteLine($"{word.Key}: {word.Value}");
        }
    }

    private static Dictionary<string, int> ProcessFile(string filePath, int minWordLength)
    {
        var wordCounts = new Dictionary<string, int>(100);
        try
        {
            var text = File.ReadAllText(filePath);
            var words = Regex.Matches(text, $"\\w{{{minWordLength},}}", RegexOptions.IgnoreCase);

            foreach (Match word in words)
            {
                if (wordCounts.TryGetValue(word.Value, out int value))
                    wordCounts[word.Value] = ++value;
                else
                    wordCounts[word.Value] = 1;
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error processing file {filePath}: {ex.Message}");
        }
        return wordCounts;
    }
}