using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Net.NetworkInformation;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Threading;
using System.Threading.Tasks;

namespace StreamPlayer.Desktop.Services;

public sealed class WindowsDnsService
{
    private static readonly string[] PreferredDns = { "8.8.8.8", "8.8.4.4" };
    private bool _attempted;

    public async Task<DnsSetupResult> EnsureGoogleDnsAsync(CancellationToken cancellationToken)
    {
        if (!OperatingSystem.IsWindows())
        {
            return DnsSetupResult.CreateSuccess();
        }

        if (_attempted)
        {
            return DnsSetupResult.CreateSuccess();
        }

        _attempted = true;

        bool needsElevation = !IsRunningAsAdministrator();
        if (needsElevation)
        {
            var consent = PromptForElevation();
            if (!consent)
            {
                return DnsSetupResult.CreateFailure("Se canceló la solicitud de permisos. Ejecuta la app como administrador o configura los DNS manualmente (8.8.8.8 y 8.8.4.4).");
            }
        }

        var interfaces = GetEligibleInterfaces().ToList();
        if (interfaces.Count == 0)
        {
            return DnsSetupResult.CreateSuccess("No se detectaron adaptadores de red activos para forzar DNS.");
        }

        foreach (var adapter in interfaces)
        {
            bool primary = await RunNetshAsync(
                $"interface ipv4 set dns name=\"{adapter}\" static {PreferredDns[0]} primary",
                cancellationToken,
                needsElevation);
            bool secondary = await RunNetshAsync(
                $"interface ipv4 add dns name=\"{adapter}\" {PreferredDns[1]} index=2",
                cancellationToken,
                needsElevation);
            if (!primary || !secondary)
            {
                return DnsSetupResult.CreateFailure($"No se pudo configurar DNS para el adaptador \"{adapter}\". Verifica permisos de administrador o configura manualmente los DNS de Google.");
            }
        }

        return DnsSetupResult.CreateSuccess("DNS de Google aplicados correctamente a los adaptadores de red activos.");
    }

    private static bool IsRunningAsAdministrator()
    {
        if (!OperatingSystem.IsWindows())
        {
            return false;
        }

        try
        {
            using var identity = WindowsIdentity.GetCurrent();
            var principal = new WindowsPrincipal(identity);
            return principal.IsInRole(WindowsBuiltInRole.Administrator);
        }
        catch
        {
            return false;
        }
    }

    private static IEnumerable<string> GetEligibleInterfaces()
    {
        return NetworkInterface.GetAllNetworkInterfaces()
            .Where(ni =>
                ni.OperationalStatus == OperationalStatus.Up &&
                ni.NetworkInterfaceType != NetworkInterfaceType.Loopback &&
                ni.NetworkInterfaceType != NetworkInterfaceType.Tunnel &&
                ni.Supports(NetworkInterfaceComponent.IPv4))
            .Select(ni => ni.Name);
    }

    private static bool PromptForElevation()
    {
        try
        {
            var psi = new ProcessStartInfo
            {
                FileName = "netsh",
                Arguments = "advfirewall show currentprofile",
                UseShellExecute = true,
                Verb = "runas",
                CreateNoWindow = true
            };
            using var process = Process.Start(psi);
            if (process == null)
            {
                return false;
            }
            process.WaitForExit();
            return process.ExitCode == 0;
        }
        catch (System.ComponentModel.Win32Exception ex) when (ex.NativeErrorCode == 1223)
        {
            // User cancelled UAC prompt.
            return false;
        }
        catch
        {
            return false;
        }
    }

    private static async Task<bool> RunNetshAsync(string arguments, CancellationToken cancellationToken, bool elevate)
    {
        try
        {
            var psi = new ProcessStartInfo
            {
                FileName = "netsh",
                Arguments = arguments,
                UseShellExecute = elevate,
                RedirectStandardOutput = !elevate,
                RedirectStandardError = !elevate,
                CreateNoWindow = true
            };
            if (elevate)
            {
                psi.Verb = "runas";
            }

            using var process = Process.Start(psi);
            if (process == null)
            {
                return false;
            }
            await process.WaitForExitAsync(cancellationToken);
            return process.ExitCode == 0;
        }
        catch (System.ComponentModel.Win32Exception ex) when (ex.NativeErrorCode == 1223)
        {
            return false;
        }
        catch
        {
            return false;
        }
    }
}

public sealed record DnsSetupResult(bool Success, string Message)
{
    public static DnsSetupResult CreateSuccess(string message = "") => new(true, message);
    public static DnsSetupResult CreateFailure(string message) => new(false, message);
}