/*
Technitium DNS Server
Copyright (C) 2020  Shreyas Zare (shreyas@technitium.com)

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

using DnsServerCore;
using System;
using System.Diagnostics;
using System.Reflection;
using System.Security.Principal;
using System.Threading;
using TechnitiumLibrary.Net.Firewall;

namespace DnsServerApp
{
    class Program
    {
        static void Main(string[] args)
        {
            #region check windows firewall entry

            string appPath = Assembly.GetEntryAssembly().Location;

            if (!WindowsFirewallEntryExists(appPath))
            {
                bool isAdmin = new WindowsPrincipal(WindowsIdentity.GetCurrent()).IsInRole(WindowsBuiltInRole.Administrator);

                if (isAdmin)
                {
                    AddWindowsFirewallEntry(appPath);
                }
                else
                {
                    ProcessStartInfo processInfo = new ProcessStartInfo(appPath, string.Join(" ", args));

                    processInfo.UseShellExecute = true;
                    processInfo.Verb = "runas";

                    try
                    {
                        Process.Start(processInfo);
                        return;
                    }
                    catch
                    { }
                }
            }

            #endregion

            string configFolder = null;

            if (args.Length == 1)
                configFolder = args[0];

            EventWaitHandle waitHandle = new ManualResetEvent(false);
            EventWaitHandle exitHandle = new ManualResetEvent(false);
            WebService service = null;

            try
            {
                service = new WebService(configFolder, new Uri("https://go.technitium.com/?id=20"));
                service.Start();

                Console.CancelKeyPress += delegate (object sender, ConsoleCancelEventArgs e)
                {
                    e.Cancel = true;
                    waitHandle.Set();
                };

                AppDomain.CurrentDomain.ProcessExit += delegate (object sender, EventArgs e)
                {
                    waitHandle.Set();
                    exitHandle.WaitOne();
                };

                Console.WriteLine("Technitium DNS Server was started successfully.");
                Console.WriteLine("Using config folder: " + service.ConfigFolder);
                Console.WriteLine("");
                Console.WriteLine("Note: Open http://" + service.WebServiceHostname + ":" + service.WebServicePort + "/ in web browser to access web console.");
                Console.WriteLine("");
                Console.WriteLine("Press [CTRL + C] to stop...");

                waitHandle.WaitOne();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            finally
            {
                Console.WriteLine("");
                Console.WriteLine("Technitium DNS Server is stopping...");

                if (service != null)
                    service.Dispose();

                Console.WriteLine("Technitium DNS Server was stopped successfully.");
                exitHandle.Set();
            }
        }

        #region private

        private static bool WindowsFirewallEntryExists(string appPath)
        {
            switch (Environment.OSVersion.Platform)
            {
                case PlatformID.Win32NT:
                    if (Environment.OSVersion.Version.Major > 5)
                    {
                        //vista and above
                        try
                        {
                            return WindowsFirewall.RuleExistsVista("", appPath) == RuleStatus.Allowed;
                        }
                        catch
                        {
                            return false;
                        }
                    }
                    else
                    {
                        try
                        {
                            return WindowsFirewall.ApplicationExists(appPath) == RuleStatus.Allowed;
                        }
                        catch
                        {
                            return false;
                        }
                    }

                default:
                    return false;
            }
        }

        private static bool AddWindowsFirewallEntry(string appPath)
        {
            switch (Environment.OSVersion.Platform)
            {
                case PlatformID.Win32NT:
                    if (Environment.OSVersion.Version.Major > 5)
                    {
                        //vista and above
                        try
                        {
                            RuleStatus status = WindowsFirewall.RuleExistsVista("", appPath);

                            switch (status)
                            {
                                case RuleStatus.Blocked:
                                case RuleStatus.Disabled:
                                    WindowsFirewall.RemoveRuleVista("", appPath);
                                    break;

                                case RuleStatus.Allowed:
                                    return true;
                            }

                            WindowsFirewall.AddRuleVista("Technitium DNS Server", "Allow incoming connection request to the DNS server.", FirewallAction.Allow, appPath, Protocol.ANY, null, null, null, null, InterfaceTypeFlags.All, true, Direction.Inbound, true);
                            return true;
                        }
                        catch
                        { }
                    }
                    else
                    {
                        try
                        {
                            RuleStatus status = WindowsFirewall.ApplicationExists(appPath);

                            switch (status)
                            {
                                case RuleStatus.Disabled:
                                    WindowsFirewall.RemoveApplication(appPath);
                                    break;

                                case RuleStatus.Allowed:
                                    return true;
                            }

                            WindowsFirewall.AddApplication("Technitium DNS Server", appPath);
                            return true;
                        }
                        catch
                        { }
                    }

                    break;
            }

            return false;
        }

        #endregion
    }
}