using System;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;

namespace MelonVPNCore
{
    public static class DaemonSocketServer
    {
        private static Process currentVpnProcess;
        private static bool shouldBeRunning;
        private static bool isRestarting;
        private const int startingTime = 3000;
        private const int restartDelay = 250;
        private static DaemonConfig config;
        public const string daemonConfigPath = "/etc/melon-vpn/daemon.cfg";

        private static void SaveConfig()
        {
            File.WriteAllText(daemonConfigPath, config.ToJson());
        }

        public static void StartServer()
        {
            if (File.Exists(daemonConfigPath)) config = DaemonConfig.FromJson(File.ReadAllText(daemonConfigPath));
            else config = new DaemonConfig();

            IPHostEntry host = Dns.GetHostEntry("localhost");
            IPAddress ipAddress = host.AddressList[0];
            IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 22035);

            try
            {
                Socket listener = new Socket(ipAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
                listener.Bind(localEndPoint);
                listener.Listen(32);

                string lastClientUpdate = Messages.EOF;

                while (true)
                {
                    Socket handler = listener.Accept();

                    string data = null;
                    byte[] bytes = null;

                    while (true)
                    {
                        bytes = new byte[1024];
                        int bytesRec = handler.Receive(bytes);
                        data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
                        if (data.IndexOf(Messages.EOF, StringComparison.CurrentCulture) > -1) break;
                    }

                    if (data.StartsWith(Messages.ClientListStartMsg, StringComparison.CurrentCulture) && shouldBeRunning)
                    {
                        lastClientUpdate = data;
                        Client.SendCustomMessage(lastClientUpdate, true);
                    }
                    else if (data == Messages.RestartOnMsg)
                    {
                        Console.WriteLine("Updated shouldRestart to true");
                        config.ShouldRestart = true;
                        SaveConfig();
                        Client.SendDataMessage(DataMessage.RestartOn, true);
                    }
                    else if (data == Messages.RestartOffMsg)
                    {
                        Console.WriteLine("Updated shouldRestart to false");
                        config.ShouldRestart = false;
                        SaveConfig();
                        Client.SendDataMessage(DataMessage.RestartOff, true);
                    }
                    else if (data == Messages.StatusMsg)
                    {
                        Console.WriteLine("Status requested");
                        if (IsProcessOnline(currentVpnProcess) || shouldBeRunning)
                        {
                            if (isRestarting)
                            {
                                Console.WriteLine("Sending response: restarting");
                                Client.SendDataMessage(DataMessage.Restarting, true);
                                Client.SendCustomMessage(lastClientUpdate, true);
                            }
                            else
                            {
                                Console.WriteLine("Sending response: online");
                                Client.SendDataMessage(DataMessage.Online, true);
                                Client.SendCustomMessage(lastClientUpdate, true);
                            }
                        }
                        else
                        {
                            Console.WriteLine("Sending response: offline");
                            Client.SendDataMessage(DataMessage.Offline, true);
                            Client.SendCustomMessage(Messages.ClientListEmptyMsg, true);
                        }
                        Client.SendDataMessage(config.ShouldRestart ? DataMessage.RestartOn : DataMessage.RestartOff);
                    }
                    else if (data == Messages.StartMsg)
                    {
                        if (! IsProcessOnline(currentVpnProcess))
                        {
                            shouldBeRunning = true;
                            Console.WriteLine("Starting VPN");
                            try
                            {
                                Console.WriteLine("Starting embedded process");
                                Console.WriteLine("Sending starting reply");
                                Client.SendDataMessage(DataMessage.Starting, true);
                                if (StartEProcess(true))
                                {
                                    Console.WriteLine("Sending online reply");
                                    Client.SendDataMessage(DataMessage.Online, true);
                                    currentVpnProcess.EnableRaisingEvents = true;
                                }
                                else { throw new InvalidOperationException("Client crashed!"); }
                            }
                            catch (Exception e)
                            {
                                shouldBeRunning = false;
                                Console.WriteLine("There was an error. But I fixed it.");
                                Console.WriteLine("It looked like this: " + e);
                                currentVpnProcess.Dispose();
                                currentVpnProcess = null;
                                Client.SendDataMessage(DataMessage.Error, true);
                                Client.SendCustomMessage(Messages.ClientListEmptyMsg, true);
                            }
                        }
                        else
                        {
                            Console.WriteLine("VPN already started");
                        }
                    }
                    else if (data == Messages.StopMsg)
                    {
                        shouldBeRunning = false;
                        bool haderr = false;
                        if (IsProcessOnline(currentVpnProcess))
                        {
                            Console.WriteLine("Stopping VPN");
                            try
                            {
                                currentVpnProcess.EnableRaisingEvents = false;
                                Console.WriteLine("Stopping embedded process");
                                currentVpnProcess.Kill();
                                currentVpnProcess = null;
                            }
                            catch (Exception e)
                            {
                                Console.WriteLine("There was an error. But I fixed it.");
                                Console.WriteLine("It looked like this: " + e);
                                currentVpnProcess = null;
                                Client.SendDataMessage(DataMessage.Error, true);
                                Client.SendCustomMessage(Messages.ClientListEmptyMsg, true);
                                haderr = true;
                            }
                        }
                        else
                        {
                            Console.WriteLine("VPN already stopped");
                        }
                        if (!haderr)
                        {
                            Console.WriteLine("Sending offline reply");
                            Client.SendDataMessage(DataMessage.Offline, true);
                            Client.SendCustomMessage(Messages.ClientListEmptyMsg, true);
                        }
                    }

                    Client.SendDataMessage(DataMessage.Blank, true);

                    handler.Shutdown(SocketShutdown.Both);
                    handler.Close();
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
        }

        public static bool IsProcessOnline(Process p)
        {
            if (p == null) return false;
            return !p.HasExited;
        }

        static void CurrentVpnProcess_Exited(object sender, EventArgs e)
        {
            Console.WriteLine("Restarting embedded process");
            currentVpnProcess.Dispose();
            currentVpnProcess = null;
            Thread.Sleep(restartDelay);
            bool imonline = false;
            isRestarting = true;
            while (config.ShouldRestart && shouldBeRunning)
            {
                Console.WriteLine("Sending restarting reply");
                Client.SendDataMessage(DataMessage.Restarting, true);
                if (StartEProcess(false))
                {
                    Console.WriteLine("Sending online reply");
                    Client.SendDataMessage(DataMessage.Online, true);
                    currentVpnProcess.EnableRaisingEvents = true;
                    imonline = true;
                    break;
                }
                else
                {
                    currentVpnProcess.Dispose();
                    currentVpnProcess = null;
                    Thread.Sleep(restartDelay);
                }
            }
            isRestarting = false;
            if (! imonline)
            {
                shouldBeRunning = false;
                Console.WriteLine("Sending offline reply");
                Client.SendDataMessage(DataMessage.Offline, true);
                Client.SendCustomMessage(Messages.ClientListEmptyMsg, true);
            }
        }

        static bool StartEProcess(bool reraisee)
        {
            if (shouldBeRunning)
            {
                try
                {
                    currentVpnProcess = new Process
                    {
                        StartInfo = new ProcessStartInfo("simple-vpn", "client /etc/melon-vpn/client.cfg"),
                        EnableRaisingEvents = false
                    };
                    currentVpnProcess.Exited += CurrentVpnProcess_Exited;
                    currentVpnProcess.Start();
                    Thread.Sleep(startingTime);
                    return !currentVpnProcess.HasExited;
                }
                catch (Exception e)
                {
                    //Not really fixed is it?
                    Console.WriteLine("There was an error. But I fixed it.");
                    Console.WriteLine("It looked like this: " + e);
                    if (reraisee) { throw e; }
                }
            }
            return false;
        }
    }
}