using IPClab._4.Models;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace IPClab._4.Services;

public class TcpServerService
{
    private TcpListener? _listener;
    private CancellationTokenSource? _cts;
    private long _totalBytesReceived;
    private long _totalBytesSent;

    public bool IsListening { get; private set; }

    public async Task StartAsync(string ipAddress, int port, IProgress<NetworkEvent> progress)
    {
        if (IsListening) return;

        _totalBytesReceived = 0;
        _totalBytesSent = 0;
        _cts = new CancellationTokenSource();

        try
        {
            IPAddress localAddr = IPAddress.Parse(ipAddress);
            _listener = new TcpListener(localAddr, port);
            _listener.Start();
            IsListening = true;

            progress.Report(new NetworkEvent { StatusText = "Listening", Message = $"Server started on {ipAddress}:{port}" });

            // Run the acceptance loop on a background thread task
            _ = Task.Run(() => AcceptClientsAsync(_cts.Token, progress), _cts.Token);
        }
        catch (Exception ex)
        {
            IsListening = false;
            progress.Report(new NetworkEvent { StatusText = "Faulted", Message = $"Failed to start server: {ex.Message}", IsError = true });
            throw;
        }
    }

    private async Task AcceptClientsAsync(CancellationToken token, IProgress<NetworkEvent> progress)
    {
        while (!token.IsCancellationRequested)
        {
            try
            {
                // Accept incoming connection
                TcpClient client = await _listener!.AcceptTcpClientAsync(token).ConfigureAwait(false);
                progress.Report(new NetworkEvent { StatusText = "Connected", Message = "Client connected to server." });

                // Handle this client session
                await HandleClientSessionAsync(client, token, progress).ConfigureAwait(false);
            }
            catch (OperationCanceledException) when (token.IsCancellationRequested)
            {
                break;
            }
            catch (Exception ex)
            {
                progress.Report(new NetworkEvent { StatusText = "Listening", Message = $"Error accepting client: {ex.Message}", IsError = true });
            }
        }
    }

    private async Task HandleClientSessionAsync(TcpClient client, CancellationToken token, IProgress<NetworkEvent> progress)
    {
        using (client)
        using (NetworkStream stream = client.GetStream())
        {
            // Quality Control Step: Enforce timeout boundaries
            stream.ReadTimeout = 5000;
            stream.WriteTimeout = 5000;

            using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
            {
                while (!token.IsCancellationRequested && client.Connected)
                {
                    try
                    {
                        // Delimiter-based Framing: Read line until '\n' boundary
                        string? receivedLine = await reader.ReadLineAsync(token).ConfigureAwait(false);

                        // TCP Disconnect Signal: stream returns null/0 bytes
                        if (receivedLine == null) break;

                        long messageBytes = Encoding.UTF8.GetByteCount(receivedLine) + Environment.NewLine.Length;
                        _totalBytesReceived += messageBytes;

                        progress.Report(new NetworkEvent
                        {
                            StatusText = "Data Received",
                            Message = receivedLine,
                            BytesTransferred = _totalBytesReceived
                        });

                        // Lab 6 Echo/Response confirmation logic
                        byte[] responseBytes = Encoding.UTF8.GetBytes($"ACK: {receivedLine}\n");
                        await stream.WriteAsync(responseBytes, 0, responseBytes.Length, token).ConfigureAwait(false);
                        _totalBytesSent += responseBytes.Length;
                    }
                    catch (Exception ex)
                    {
                        progress.Report(new NetworkEvent { StatusText = "Disconnected", Message = $"Session terminated: {ex.Message}", IsError = true });
                        break;
                    }
                }
            }
        }
        progress.Report(new NetworkEvent { StatusText = "Listening", Message = "Client disconnected clean." });
    }

    public void Stop()
    {
        _cts?.Cancel();
        _listener?.Stop();
        IsListening = false;
    }
}