using System.Runtime.InteropServices;

namespace CursorLang.Core.Interop;

/// <summary>
/// Answers whether the application runs from an MSIX package.
/// </summary>
/// <remarks>
/// The same application runs both installed from the Store and simply unpacked
/// into a folder. Some Windows features — startup through <c>StartupTask</c>, for
/// instance — are available only to a package, and reaching for them without a
/// check is not allowed: outside a package they throw.
/// </remarks>
internal static class PackageIdentityNative
{
    /// <summary>APPMODEL_ERROR_NO_PACKAGE — the process runs outside a package.</summary>
    private const int NoPackage = 15700;

    /// <summary>
    /// The application runs from an MSIX package.
    /// </summary>
    /// <remarks>
    /// The value is computed once: it cannot change during the lifetime of
    /// the process.
    /// </remarks>
    internal static bool IsPackaged { get; } = DetectPackage();

    private static bool DetectPackage()
    {
        // The answer comes from the return code rather than from the name itself, so
        // no buffer is needed: with zero length a package replies complaining about space
        uint length = 0;
        return GetCurrentPackageFullName(ref length, IntPtr.Zero) != NoPackage;
    }

    [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
    private static extern int GetCurrentPackageFullName(ref uint packageFullNameLength, IntPtr packageFullName);
}