using System.Diagnostics;
using System.Reflection;
using System.Security.Cryptography;
using System.Security.Principal;
using System.Windows.Forms;

namespace MsPrivate.Launcher;

internal static class Program
{
    private const string PayloadResource = "MsPrivate.Payload.zip";

    [STAThread]
    private static int Main()
    {
        Application.SetHighDpiMode(HighDpiMode.PerMonitorV2);
        Application.EnableVisualStyles();
        using var mutex = new Mutex(initiallyOwned: true, @"Local\ms-private-launcher", out var ownsMutex);
        if (!ownsMutex)
        {
            MessageBox.Show("ms-private is already running.", "ms-private", MessageBoxButtons.OK, MessageBoxIcon.Information);
            return 2;
        }
        try
        {
            if (!OperatingSystem.IsWindows() || !Environment.Is64BitOperatingSystem) throw new PlatformNotSupportedException("ms-private requires 64-bit Windows.");
            using var identity = WindowsIdentity.GetCurrent();
            if (!new WindowsPrincipal(identity).IsInRole(WindowsBuiltInRole.Administrator)) throw new UnauthorizedAccessException("Administrator rights are required.");

            var bytes = ReadPayload();
            var payloadHash = Convert.ToHexString(SHA256.HashData(bytes)).ToLowerInvariant();
            var version = Assembly.GetExecutingAssembly().GetName().Version ?? throw new InvalidDataException("The launcher version is missing.");
            var productVersion = $"{version.Major}.{version.Minor}.{version.Build}";
            var runtimeRoot = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), "ms-private", "runtime");
            var runtimeName = productVersion + "-" + payloadHash[..12];
            var runtimeDirectory = Path.Combine(runtimeRoot, runtimeName);
            PayloadInstaller.EnsureInstalled(bytes, runtimeDirectory);
            RemoveOlderRuntimes(runtimeRoot, runtimeDirectory);

            var entryPoint = Path.Combine(runtimeDirectory, "ms-private-GUI.ps1");
            var powershell = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "WindowsPowerShell", "v1.0", "powershell.exe");
            if (!File.Exists(powershell)) throw new FileNotFoundException("Windows PowerShell 5.1 was not found.", powershell);
            var start = new ProcessStartInfo
            {
                FileName = powershell,
                WorkingDirectory = runtimeDirectory,
                UseShellExecute = false,
                CreateNoWindow = true
            };
            foreach (var argument in new[] { "-NoLogo", "-NoProfile", "-ExecutionPolicy", "RemoteSigned", "-File", entryPoint }) start.ArgumentList.Add(argument);
            using var process = Process.Start(start) ?? throw new InvalidOperationException("Windows PowerShell could not be started.");
            process.WaitForExit();
            if (process.ExitCode != 0) throw new InvalidOperationException($"The ms-private interface exited with code {process.ExitCode}.");
            return 0;
        }
        catch (Exception exception)
        {
            MessageBox.Show(exception.Message, "ms-private could not start", MessageBoxButtons.OK, MessageBoxIcon.Error);
            return 1;
        }
        finally
        {
            mutex.ReleaseMutex();
        }
    }

    private static byte[] ReadPayload()
    {
        using var stream = Assembly.GetExecutingAssembly().GetManifestResourceStream(PayloadResource)
            ?? throw new InvalidDataException("The embedded ms-private payload is missing.");
        using var memory = new MemoryStream();
        stream.CopyTo(memory);
        return memory.ToArray();
    }

    private static void RemoveOlderRuntimes(string runtimeRoot, string currentDirectory)
    {
        if (!Directory.Exists(runtimeRoot) || PayloadInstaller.IsReparsePoint(runtimeRoot)) return;
        foreach (var directory in Directory.GetDirectories(runtimeRoot))
        {
            if (Path.GetFullPath(directory).Equals(Path.GetFullPath(currentDirectory), StringComparison.OrdinalIgnoreCase)) continue;
            if (PayloadInstaller.IsReparsePoint(directory)) continue;
            try { PayloadInstaller.DeleteOrdinaryDirectory(directory); } catch { }
        }
    }
}