// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;
using System.Globalization;
using System.Security;
using Microsoft.Win32;

namespace Microsoft.DotNet.Cli.Telemetry;

// Some properties we need for telemetry, that don't yet have suitable
// public API
internal static class ExternalTelemetryProperties
{
    /// <summary>
    /// For Windows, returns the OS installation type, eg. "Nano Server", "Server Core", "Server", or "Client".
    /// For Unix, or on error, currently returns empty string.
    /// </summary>
    internal static string? GetInstallationType()
    {
        if (!OperatingSystem.IsWindows())
        {
            return "";
        }

        const string Key = @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion";
        const string ValueName = @"InstallationType";

        try
        {
            return (string?)Registry.GetValue(Key, ValueName, defaultValue: "");
        }
        // Catch everything: this is for telemetry only.
        catch (Exception e)
        {
            Debug.Assert(e is ArgumentException | e is SecurityException | e is InvalidCastException);
            return "";
        }
    }

    [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = false)]
    private static extern bool GetProductInfo(uint dwOSMajorVersion, uint dwOSMinorVersion, uint dwSpMajorVersion, uint dwSpMinorVersion, out uint pdwReturnedProductType);

    /// <summary>
    /// For Windows, returns the product type, loosely the SKU, as encoded by GetProductInfo().
    /// For example, Enterprise is "4" (0x4) and Professional is "48" (0x30)
    /// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms724358(v=vs.85).aspx for the full list.
    /// We're not attempting to decode the value on the client side as new Windows releases may add new values.
    /// For Unix, or on error, returns an empty string.
    /// </summary>
    internal static string? GetProductType()
    {
        if (!OperatingSystem.IsWindows())
        {
            return "";
        }

        try
        {
            if (GetProductInfo((uint)Environment.OSVersion.Version.Major, (uint)Environment.OSVersion.Version.Minor, 0, 0, out uint productType))
            {
                return productType.ToString("D", CultureInfo.InvariantCulture);
            }
        }
        // Catch everything: this is for telemetry only
        catch (Exception e)
        {
            Debug.Assert(false, $"Unexpected exception from GetProductInfo: ${e.GetType().Name}: ${e.Message}");
        }

        return "";
    }

    [DllImport("libc", ExactSpelling = true, CallingConvention = CallingConvention.Cdecl)]
    private static extern IntPtr gnu_get_libc_release();

    [DllImport("libc", ExactSpelling = true, CallingConvention = CallingConvention.Cdecl)]
    private static extern IntPtr gnu_get_libc_version();

    /// <summary>
    /// If gnulibc is available, returns the release, such as "stable".
    /// If the libc is musl, currently returns empty string.
    /// Otherwise returns empty string.
    /// </summary>
    internal static string? GetLibcRelease()
    {
        if (OperatingSystem.IsWindows())
        {
            return "";
        }

        try
        {
            return Marshal.PtrToStringUTF8(gnu_get_libc_release());
        }
        // Catch everything: this is for telemetry only
        catch (Exception e)
        {
            Debug.Assert(e is DllNotFoundException || e is EntryPointNotFoundException);
            return "";
        }
    }

    /// <summary>
    /// If gnulibc is available, returns the version, such as "2.22".
    /// If the libc is musl, currently returns empty string. (In future could run "ldd -version".)
    /// Otherwise returns empty string.
    /// </summary>
    internal static string? GetLibcVersion()
    {
        if (OperatingSystem.IsWindows())
        {
            return "";
        }

        try
        {
            return Marshal.PtrToStringUTF8(gnu_get_libc_version());
        }
        // Catch everything: this is for telemetry only
        catch (Exception e)
        {
            Debug.Assert(e is DllNotFoundException || e is EntryPointNotFoundException);
            return "";
        }
    }
}