using System;
using System.Text;
using System.Threading.Tasks;
using System.Net.Sockets;
using System.Net;

namespace Server
{
    internal class Program
    {
        // Attributes
        // Port Number of the server.
        public const int PORT_NUMBER = 19000;
        // Define the buffer size.
        public const int BUFFER_SIZE = 100;
        // Server host name.
        public const string HOST_NAME = "localhost";

        /// <summary>
        /// Setting up and establishing the server code.
        /// </summary>
        /// <param name="args"(unused)></param>

        static void Main(string[] args)
        {
            // Determines the IP via the .GetHostAddresses
            IPAddress myIP = Dns.GetHostAddresses(HOST_NAME)[0];
            TcpListener listener = new TcpListener(myIP, PORT_NUMBER);
            listener.Start();
            // To test whether or not the server is able to start correctly, if there is an issue, this is caught in the catch block.
            try
            {
                // Start a listener which is used to catch socket exceptions.
                // This is where TCP will be used. 
                Socket Listener = new Socket(SocketType.Stream, ProtocolType.Tcp);
                // The socket should be bound to the IP end point.
                // This is done for a maximum of 10 incomming connections. 
                // if it is sucessful then report to the console that it was successfully started.
                listener.Start();
                Console.ForegroundColor = ConsoleColor.Blue;
                Console.WriteLine("The Server has Sucessfully Started.");
                Console.ForegroundColor= ConsoleColor.Blue;
                Console.WriteLine("Host Name: " + HOST_NAME + " | Hosting on Port: " + PORT_NUMBER);
                Console.ForegroundColor = ConsoleColor.Blue;
                Console.WriteLine("Server is now being hosted on the IP of: " + myIP);
                Console.ForegroundColor = ConsoleColor.Blue;
                Console.WriteLine("---------------------------------------------------------------------");
            }

            // This is used to notify that the server was unable to start successfully. 
            // Errors messages are used via Exception e, which are outputted to the console for the user to read.
            catch (Exception e)
            {
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine("The Server is unable to start sucessfully");
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine("Type of error: " + e.GetType() + "Exception: " + (e.Message));
                Console.ReadKey();
            }

            /// <summary>
            /// Main Method of code which is used to carry out the game process.
            /// </summary>
            /// <param name="args"(unused)></param>

            while (true)
            {
                // Waits for a client to join the server. 
                TcpClient client = listener.AcceptTcpClient();
                // Console writes a new line to show that the client has connected.
                Console.WriteLine($"Client has connected to the server.");

                // When the client joins the server, the guess a number task starts.
                Task.Run(() =>
                {
                    try
                    {
                        // Generates a random number from 1 to 50.
                        Random rand = new Random();
                        int RandomNumber = rand.Next(1, 51);
                        // Output to the console the number that has been generated. 
                        Console.WriteLine("The number that has been generated for the client to guess is: " + RandomNumber);
                        
                        // Guess the number message has been generated and is sent to the client. 
                        byte[] buffer = Encoding.ASCII.GetBytes("Guess the number between 1 and 50.");
                        NetworkStream stream = client.GetStream();
                        stream.Write(buffer, 0, buffer.Length);

                        while (true)
                        {
                            // Recieves the clients guess of the number that is between 1 and 50.
                            // Message is buffered. 
                            buffer = new byte[BUFFER_SIZE];
                            int bytesRead = stream.Read(buffer, 0, buffer.Length);
                            string ClientGuess = Encoding.ASCII.GetString(buffer, 0, bytesRead);
                            // Logs the clients guess of the number and is stored into a string.
                            Console.WriteLine("Received guess: " + ClientGuess);
                            // Declare the string that is the clients number.   
                            int ClientGuessNumber;
                            if (int.TryParse(ClientGuess, out ClientGuessNumber))
                            {
                                // If the client guesses the number which is the same as the number that was generated between 1 and 50.
                                if (ClientGuessNumber == RandomNumber)
                                {
                                    // Send a message to the client that they were correct and that they have won the game.
                                    buffer = Encoding.ASCII.GetBytes("Correct! You win!");
                                    stream.Write(buffer, 0, buffer.Length);
                                    break;
                                }
                                // If the number that the client has provided is lower than the number that was generated. 
                                else if (ClientGuessNumber < RandomNumber)
                                {
                                    // Send a message to the client to highlight that the guess was too low, they will need to guess again. 
                                    buffer = Encoding.ASCII.GetBytes("Too low. Guess again.");
                                    stream.Write(buffer, 0, buffer.Length);
                                }
                                // If the number that the client has provided is higher than the number that was generated. 
                                else
                                {
                                    // Send a message to the client to highlight that the guess was too high, they will need to guess again. 
                                    buffer = Encoding.ASCII.GetBytes("Too high. Guess again.");
                                    stream.Write(buffer, 0, buffer.Length);
                                }
                            }
                            // If the user does not provide a relative number.
                            else
                            {
                                // Send a message to the client that their input is incorrect/invalid.
                                buffer = Encoding.ASCII.GetBytes("Invalid input. Please enter a number.");
                                stream.Write(buffer, 0, buffer.Length);
                            }
                        }
                    }
                    // If an error is experienced in this section, display to the console that there is an error.
                    // Exception ex, is used to provide an error message of the problem. 
                    catch (Exception ex)
                    {
                        Console.WriteLine("Error: " + ex.Message);
                    }
                });
            }
        }
    }
}