using System.ComponentModel;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Runtime.InteropServices;
using System.Security.Cryptography.X509Certificates;
using Microsoft.Win32;

namespace DeskCoreSetup;

/// <summary>Prüft und installiert die von DeskCore benötigte "Microsoft .NET 9 Desktop Runtime".</summary>
public static class Runtime
{
    public const string DisplayName = "Microsoft .NET 9 Desktop Runtime";
    public const int Major = 9;
    public const string DownloadPage = "https://dotnet.microsoft.com/de-de/download/dotnet/9.0";
    // offizieller Microsoft-Kurzlink auf die jeweils aktuelle 9.0-Version
    private const string InstallerUrl = "https://aka.ms/dotnet/9.0/windowsdesktop-runtime-win-x64.exe";

    public static bool Is64BitWindows => Environment.Is64BitOperatingSystem;

    public static bool IsInstalled
    {
        get
        {
            try
            {
                var dir = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles),
                    "dotnet", "shared", "Microsoft.WindowsDesktop.App");
                if (Directory.Exists(dir) && Directory.GetDirectories(dir).Any(d => Path.GetFileName(d).StartsWith($"{Major}.")))
                    return true;
            }
            catch { }
            try
            {
                using var hklm = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry32);
                using var k = hklm.OpenSubKey(@"SOFTWARE\dotnet\Setup\InstalledVersions\x64\sharedfx\Microsoft.WindowsDesktop.App");
                if (k?.GetValueNames().Any(n => n.StartsWith($"{Major}.")) == true) return true;
            }
            catch { }
            return false;
        }
    }

    /// <summary>Lädt die Laufzeit von Microsoft und installiert sie (Windows fragt einmal nach Administratorrechten).</summary>
    public static void Install(Action<double, string> progress)
    {
        ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls12;
        var file = Path.Combine(Path.GetTempPath(), $"windowsdesktop-runtime-{Major}-win-x64.exe");

        using (var http = new HttpClient { Timeout = TimeSpan.FromMinutes(20) })
        {
            http.DefaultRequestHeaders.UserAgent.ParseAdd("DeskCore-Setup");
            using var resp = http.GetAsync(InstallerUrl, HttpCompletionOption.ResponseHeadersRead).GetAwaiter().GetResult();
            resp.EnsureSuccessStatusCode();
            long total = resp.Content.Headers.ContentLength ?? 0;
            using var input = resp.Content.ReadAsStreamAsync().GetAwaiter().GetResult();
            using var output = File.Create(file);
            var buffer = new byte[81920];
            long done = 0;
            int read;
            while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
            {
                output.Write(buffer, 0, read);
                done += read;
                progress(total > 0 ? (double)done / total : 0,
                    total > 0 ? $"{DisplayName} wird heruntergeladen … {done / 1048576} von {total / 1048576} MB"
                              : $"{DisplayName} wird heruntergeladen … {done / 1048576} MB");
            }
        }

        // Sicherheit: nur ausführen, wenn die Datei gültig von Microsoft signiert ist
        if (!IsSignedByMicrosoft(file))
        {
            try { File.Delete(file); } catch { }
            throw new InvalidOperationException("Die heruntergeladene Datei ist nicht gültig von Microsoft signiert und wurde nicht ausgeführt.");
        }

        progress(1, $"{DisplayName} wird installiert – bitte die Windows-Abfrage bestätigen …");
        Process p;
        try
        {
            p = Process.Start(new ProcessStartInfo(file, "/install /quiet /norestart") { UseShellExecute = true, Verb = "runas" })!;
        }
        catch (Win32Exception ex) when (ex.NativeErrorCode == 1223)
        {
            throw new InvalidOperationException($"Die Installation von {DisplayName} wurde abgebrochen.");
        }
        p.WaitForExit();
        try { File.Delete(file); } catch { }
        // 0 = ok, 3010/1641 = ok, Neustart empfohlen
        if (p.ExitCode is not (0 or 3010 or 1641) || !IsInstalled)
            throw new InvalidOperationException($"{DisplayName} konnte nicht installiert werden (Code {p.ExitCode}).");
    }

    // ---------- Signaturprüfung (WinVerifyTrust) ----------

    private static bool IsSignedByMicrosoft(string file)
    {
        try
        {
            var subject = X509Certificate.CreateFromSignedFile(file).Subject;
            if (subject.IndexOf("O=Microsoft Corporation", StringComparison.OrdinalIgnoreCase) < 0) return false;
        }
        catch { return false; }
        return VerifyTrust(file);
    }

    private static bool VerifyTrust(string file)
    {
        var fileInfo = new WINTRUST_FILE_INFO
        {
            cbStruct = (uint)Marshal.SizeOf<WINTRUST_FILE_INFO>(),
            pcwszFilePath = file,
        };
        var pFile = Marshal.AllocHGlobal(Marshal.SizeOf<WINTRUST_FILE_INFO>());
        try
        {
            Marshal.StructureToPtr(fileInfo, pFile, false);
            var data = new WINTRUST_DATA
            {
                cbStruct = (uint)Marshal.SizeOf<WINTRUST_DATA>(),
                dwUIChoice = 2,            // WTD_UI_NONE
                fdwRevocationChecks = 0,   // WTD_REVOKE_NONE
                dwUnionChoice = 1,         // WTD_CHOICE_FILE
                pFile = pFile,
                dwStateAction = 0,
                dwProvFlags = 0x40,        // WTD_SAFER_FLAG
            };
            var action = new Guid("00AAC56B-CD44-11d0-8CC2-00C04FC295EE"); // WINTRUST_ACTION_GENERIC_VERIFY_V2
            return WinVerifyTrust(IntPtr.Zero, ref action, ref data) == 0;
        }
        finally
        {
            Marshal.FreeHGlobal(pFile);
        }
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct WINTRUST_FILE_INFO
    {
        public uint cbStruct;
        public string pcwszFilePath;
        public IntPtr hFile;
        public IntPtr pgKnownSubject;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct WINTRUST_DATA
    {
        public uint cbStruct;
        public IntPtr pPolicyCallbackData;
        public IntPtr pSIPClientData;
        public uint dwUIChoice;
        public uint fdwRevocationChecks;
        public uint dwUnionChoice;
        public IntPtr pFile;
        public uint dwStateAction;
        public IntPtr hWVTStateData;
        public IntPtr pwszURLReference;
        public uint dwProvFlags;
        public uint dwUIContext;
        public IntPtr pSignatureSettings;
    }

    [DllImport("wintrust.dll", ExactSpelling = true, SetLastError = false, CharSet = CharSet.Unicode)]
    private static extern int WinVerifyTrust(IntPtr hwnd, ref Guid pgActionID, ref WINTRUST_DATA pWVTData);
}