using System;
using System.Text;
using System.Threading.Tasks;

namespace Multithreading
{
    internal static class Program
    {
        private static readonly object _fileLock = new object();
        
        public static void Main(string[] args)
        {
            Console.WriteLine("Program started");
            
            // int[] numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
            // Task[] tasks = new Task[100];
            // Random random = new Random();
            // for (int i = 0; i < tasks.Length; i++)
            // {
            //     tasks[i] = Task.Run(() =>
            //     {
            //         for (int j = 0; j < numbers.Length; j++)
            //         {
            //             Console.WriteLine($"Before Thread Id: {Thread.CurrentThread.ManagedThreadId}, number({j}): {numbers[j]}");
            //             
            //             Thread.Sleep(random.Next(0, 1000));
            //             
            //             // not thread-safe
            //             // int oldValue = numbers[j];
            //             // int newValue = oldValue * random.Next(10);
            //             // numbers[j] = newValue;
            //             // Thread.Sleep(random.Next(0, 1000));
            //             // Console.WriteLine($"After Thread Id: {Thread.CurrentThread.ManagedThreadId}, number({j}): {numbers[j]} / oldValue: {oldValue} / newValue: {newValue}");
            //
            //             // making this thread-safe
            //             // option 1: lock
            //             lock (numbers)
            //             {
            //                 int oldValue = numbers[j];
            //                 int newValue = oldValue * random.Next(10);
            //                 numbers[j] = newValue;
            //                 Thread.Sleep(random.Next(0, 1000));
            //                 Console.WriteLine($"After Thread Id: {Thread.CurrentThread.ManagedThreadId}, number({j}): {numbers[j]} / oldValue: {oldValue} / newValue: {newValue}");
            //             }
            //             
            //             // option 2: use concurrent collections
            //             // https://learn.microsoft.com/en-us/dotnet/standard/collections/thread-safe/
            //             
            //             // option 3: use chunks to have no overlapping
            //             
            //         }
            //     });
            // }
            
            // Dictionary<int, string> dictionary = new Dictionary<int, string>();
            // Task[] tasks = new Task[1000];
            // Random random = new Random();
            // for (int i = 0; i < tasks.Length; i++)
            // {
            //     tasks[i] = Task.Run(() =>
            //     {
            //         lock (dictionary) // one option, another option is to use ConcurrentDictionary
            //         {
            //             int key = random.Next();
            //             if (!dictionary.ContainsKey(key))
            //             {
            //                 // dictionary[key] = $"Thread Id: {Thread.CurrentThread.ManagedThreadId}, number({key}): {random.Next(10)}";
            //                 dictionary.TryAdd(key, $"Thread Id: {Thread.CurrentThread.ManagedThreadId}, number({key}): {random.Next(10)}");
            //             }
            //         }
            //     });
            // }
            
            Task[] tasks = new Task[100];
            Random random = new Random();
            File.Delete("output.txt");
            for (int i = 0; i < tasks.Length; i++)
            {
                tasks[i] = Task.Run(() =>
                {
                    // not thread-safe
                    // File.AppendAllText("output.txt", $"Thread Id: {Thread.CurrentThread.ManagedThreadId}, number: {random.Next(10)}\n");
                    
                    // FileStream fs = File.OpenWrite("output.txt");
                    // FileStream fs = File.Open("output.txt", FileMode.Append, FileAccess.Write, FileShare.ReadWrite);
                    // string s = $"{Thread.CurrentThread.ManagedThreadId}, number: {random.Next(10)}\n";
                    // byte[] bytes = Encoding.UTF8.GetBytes(s);
                    // fs.Write(bytes, 0, bytes.Length);
                    // fs.Close();
                    // fs.Dispose();
                    
                    // thread-safe
                    lock (_fileLock)
                    {
                        FileStream fs = File.Open("output.txt", FileMode.Append, FileAccess.Write, FileShare.ReadWrite);
                        string s = $"{Thread.CurrentThread.ManagedThreadId}, number: {random.Next(10)}\n";
                        byte[] bytes = Encoding.UTF8.GetBytes(s);
                        fs.Write(bytes, 0, bytes.Length);
                        fs.Close();
                        fs.Dispose();
                    }
                });
            }
            
            Task.WaitAll(tasks);

            Console.WriteLine("Program ended");
        }
    }
}