// See https://aka.ms/new-console-template for more information

using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;

class TcpServer
{
    private static TcpListener server;
    private static bool isRunning = true;
    private static List<TcpClient> connectedClients = new List<TcpClient>();

    static void Main(string[] args)
    {
        server = new TcpListener(IPAddress.Any, 5000);
        server.Start();
        Console.WriteLine("Server started on port 5000.");

        while (isRunning)
        {
            var client = server.AcceptTcpClient();
            Console.WriteLine("Client connected!");

            lock (connectedClients)
            {
                connectedClients.Add(client); // Add new client to the list
            }

            // Handle each client connection in a new thread
            Thread clientThread = new Thread(HandleClient);
            clientThread.Start(client);
        }
    }

    private static void HandleClient(object obj)
    {
        TcpClient client = (TcpClient)obj;
        NetworkStream stream = client.GetStream();
        byte[] buffer = new byte[4096];
        int bytesRead;

        try
        {
            while ((bytesRead = stream.Read(buffer, 0, buffer.Length)) != 0)
            {
                string receivedData = Encoding.ASCII.GetString(buffer, 0, bytesRead);
                Console.WriteLine("Received: " + receivedData);

                // Split the message into command and data
                string[] messageParts = receivedData.Split(new char[] { ':' }, 2);
                if (messageParts.Length < 2) continue; // Ignore malformed messages

                string command = messageParts[0];
                string message = messageParts[1];

                switch (command)
                {
                    case "PUBKEY":
                        Console.WriteLine("Received RSA Public Key: " + message);
                        // Broadcast the message to all connected clients (excluding the sender)
                        BroadcastMessageToClients(client, $"{command}:{message}");
                        break;
                    case "AESKEY":
                        Console.WriteLine("Received Encrypted AES Key: " + message);
                        // Broadcast the message to all connected clients (excluding the sender)
                        BroadcastMessageToClients(client, $"{command}:{message}");
                        break;
                    case "MSG":
                        Console.WriteLine("Received AES Encrypted Message: " + message);
                        // Broadcast the message to all connected clients (excluding the sender)
                        BroadcastMessageToClients(client, $"{command}:{message}");
                        break;
                    case "EXIT":
                        Console.WriteLine("Client is disconnecting...");
                        client.Close();
                        lock (connectedClients)
                        {
                            connectedClients.Remove(client); // Remove client from the list
                        }
                        return;
                    default:
                        Console.WriteLine("Unknown command received: " + command);
                        break;
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Client disconnected with error: " + ex.Message);
        }
        finally
        {
            client.Close();
            lock (connectedClients)
            {
                connectedClients.Remove(client);
            }
            Console.WriteLine("Client disconnected.");
        }
    }

    private static void BroadcastMessageToClients(TcpClient senderClient, string message)
    {
        byte[] data = Encoding.ASCII.GetBytes("Broadcast: " + message);

        lock (connectedClients)
        {
            foreach (var client in connectedClients)
            {
                // Send to all clients except the sender
                if (client != senderClient)
                {
                    try
                    {
                        NetworkStream stream = client.GetStream();
                        stream.Write(data, 0, data.Length);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine("Error sending to client: " + ex.Message);
                    }
                }
            }
        }
    }
}