// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.IO;
using System.Runtime.InteropServices;
using System.Security;
using Microsoft.Win32;
using Xunit;
using static Interop;

namespace System
{
    public static partial class PlatformDetection
    {
        public static Version OSXVersion => throw new PlatformNotSupportedException();
        public static Version OpenSslVersion => throw new PlatformNotSupportedException();
        public static bool IsSuperUser => throw new PlatformNotSupportedException();
        public static bool IsCentos6 => false;
        public static bool IsOpenSUSE => false;
        public static bool IsUbuntu => false;
        public static bool IsDebian => false;
        public static bool IsAlpine => false;
        public static bool IsDebian8 => false;
        public static bool IsUbuntu1404 => false;
        public static bool IsUbuntu1604 => false;
        public static bool IsUbuntu1704 => false;
        public static bool IsUbuntu1710 => false;
        public static bool IsUbuntu1710OrHigher => false;
        public static bool IsUbuntu1804 => false;
        public static bool IsTizen => false;
        public static bool IsNotFedoraOrRedHatFamily => true;
        public static bool IsFedora => false;
        public static bool IsWindowsNanoServer => (IsNotWindowsIoTCore && GetInstallationType().Equals("Nano Server", StringComparison.OrdinalIgnoreCase));
        public static bool IsWindowsServerCore => GetInstallationType().Equals("Server Core", StringComparison.OrdinalIgnoreCase);
        public static int WindowsVersion => GetWindowsVersion();
        public static bool IsMacOsHighSierraOrHigher { get; }
        public static Version ICUVersion => new Version(0, 0, 0, 0);
        public static bool IsRedHatFamily => false;
        public static bool IsNotRedHatFamily => true;
        public static bool IsRedHatFamily6 => false;
        public static bool IsRedHatFamily7 => false;
        public static bool IsNotRedHatFamily6 => true;

        public static bool IsWindows10Version1607OrGreater =>
            GetWindowsVersion() == 10 && GetWindowsMinorVersion() == 0 && GetWindowsBuildNumber() >= 14393;
        public static bool IsWindows10Version1703OrGreater =>
            GetWindowsVersion() == 10 && GetWindowsMinorVersion() == 0 && GetWindowsBuildNumber() >= 15063;
        public static bool IsWindows10Version1709OrGreater =>
            GetWindowsVersion() == 10 && GetWindowsMinorVersion() == 0 && GetWindowsBuildNumber() >= 16299;
        public static bool IsWindows10Version1803OrGreater =>
            GetWindowsVersion() == 10 && GetWindowsMinorVersion() == 0 && GetWindowsBuildNumber() >= 17134;

        // Windows OneCoreUAP SKU doesn't have httpapi.dll
        public static bool IsNotOneCoreUAP =>
            File.Exists(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Windows), "System32", "httpapi.dll"));

        public static bool IsWindowsIoTCore
        {
            get
            {
                int productType = GetWindowsProductType();
                if ((productType == PRODUCT_IOTUAPCOMMERCIAL) ||
                    (productType == PRODUCT_IOTUAP))
                {
                    return true;
                }

                return false;
            }
        }

        public static bool IsWindowsHomeEdition
        {
            get
            {
                int productType = GetWindowsProductType();
                switch (productType)
                {
                    case PRODUCT_CORE:
                    case PRODUCT_CORE_COUNTRYSPECIFIC:
                    case PRODUCT_CORE_N:
                    case PRODUCT_CORE_SINGLELANGUAGE:
                    case PRODUCT_HOME_BASIC:
                    case PRODUCT_HOME_BASIC_N:
                    case PRODUCT_HOME_PREMIUM:
                    case PRODUCT_HOME_PREMIUM_N:
                        return true;
                    default:
                        return false;
                }
            }
        }

        public static bool IsWindows => true;
        public static bool IsWindows7 => GetWindowsVersion() == 6 && GetWindowsMinorVersion() == 1;
        public static bool IsWindows8x => GetWindowsVersion() == 6 && (GetWindowsMinorVersion() == 2 || GetWindowsMinorVersion() == 3);

        public static string LibcRelease => "glibc_not_found";
        public static string LibcVersion => "glibc_not_found";

        public static string GetDistroVersionString() { return "WindowsProductType=" + GetWindowsProductType() + " WindowsInstallationType=" + GetInstallationType(); }

        private static int s_isInAppContainer = -1;

        public static bool IsInAppContainer
        {
            // This actually checks whether code is running in a modern app.
            // Currently this is the only situation where we run in app container.
            // If we want to distinguish the two cases in future,
            // EnvironmentHelpers.IsAppContainerProcess in desktop code shows how to check for the AC token.
            get
            {
                if (s_isInAppContainer != -1)
                {
                    return s_isInAppContainer == 1;
                }

                if (!IsWindows || IsWindows7)
                {
                    s_isInAppContainer = 0;
                    return false;
                }

                byte[] buffer = Array.Empty<byte>();
                uint bufferSize = 0;
                try
                {
                    int result = GetCurrentApplicationUserModelId(ref bufferSize, buffer);
                    switch (result)
                    {
                        case 15703: // APPMODEL_ERROR_NO_APPLICATION
                            s_isInAppContainer = 0;
                            break;
                        case 0:     // ERROR_SUCCESS
                        case 122:   // ERROR_INSUFFICIENT_BUFFER
                                    // Success is actually insufficent buffer as we're really only looking for
                                    // not NO_APPLICATION and we're not actually giving a buffer here. The
                                    // API will always return NO_APPLICATION if we're not running under a
                                    // WinRT process, no matter what size the buffer is.
                            s_isInAppContainer = 1;
                            break;
                        default:
                            throw new InvalidOperationException($"Failed to get AppId, result was {result}.");
                    }
                }
                catch (Exception e)
                {
                    // We could catch this here, being friendly with older portable surface area should we
                    // desire to use this method elsewhere.
                    if (e.GetType().FullName.Equals("System.EntryPointNotFoundException", StringComparison.Ordinal))
                    {
                        // API doesn't exist, likely pre Win8
                        s_isInAppContainer = 0;
                    }
                    else
                    {
                        throw;
                    }
                }

                return s_isInAppContainer == 1;
            }
        }

        private static int s_isWindowsElevated = -1;

        public static bool IsWindowsAndElevated
        {
            get
            {
                if (s_isWindowsElevated != -1)
                {
                    return s_isWindowsElevated == 1;
                }

                if (!IsWindows || IsInAppContainer)
                {
                    s_isWindowsElevated = 0;
                    return false;
                }

                Assert.True(OpenProcessToken(Kernel32.GetCurrentProcess(), TOKEN_READ, out IntPtr processToken));

                try
                {
                    Assert.True(GetTokenInformation(
                        processToken, TokenElevation, out uint tokenInfo, sizeof(uint), out uint returnLength));

                    s_isWindowsElevated = tokenInfo == 0 ? 0 : 1;
                }
                finally
                {
                    Kernel32.CloseHandle(processToken);
                }

                return s_isWindowsElevated == 1;
            }
        }

        private static string GetInstallationType()
        {
            string key = @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion";
            string value = string.Empty;

            try
            {
                value = (string)Registry.GetValue(key, "InstallationType", defaultValue: "");
            }
            catch (Exception e) when (e is SecurityException || e is InvalidCastException || e is PlatformNotSupportedException /* UAP */)
            {
            }

            return value;
        }

        private static int GetWindowsProductType()
        {
            Assert.True(GetProductInfo(Environment.OSVersion.Version.Major, Environment.OSVersion.Version.Minor, 0, 0, out int productType));
            return productType;
        }

        private static unsafe int GetWindowsMinorVersion()
        {
            var osvi = new RTL_OSVERSIONINFOEX
            {
                dwOSVersionInfoSize = (uint)sizeof(RTL_OSVERSIONINFOEX)
            };
            Assert.Equal(0, RtlGetVersion(ref osvi));
            return (int)osvi.dwMinorVersion;
        }

        private static unsafe int GetWindowsBuildNumber()
        {
            var osvi = new RTL_OSVERSIONINFOEX
            {
                dwOSVersionInfoSize = (uint)sizeof(RTL_OSVERSIONINFOEX)
            };
            Assert.Equal(0, RtlGetVersion(ref osvi));
            return (int)osvi.dwBuildNumber;
        }

        private const uint TokenElevation = 20;
        private const uint STANDARD_RIGHTS_READ = 0x00020000;
        private const uint TOKEN_QUERY = 0x0008;
        private const uint TOKEN_READ = STANDARD_RIGHTS_READ | TOKEN_QUERY;

        [DllImport("advapi32.dll", SetLastError = true, ExactSpelling = true)]
        private static extern bool GetTokenInformation(
            IntPtr TokenHandle,
            uint TokenInformationClass,
            out uint TokenInformation,
            uint TokenInformationLength,
            out uint ReturnLength);

        private const int PRODUCT_IOTUAP = 0x0000007B;
        private const int PRODUCT_IOTUAPCOMMERCIAL = 0x00000083;
        private const int PRODUCT_CORE = 0x00000065;
        private const int PRODUCT_CORE_COUNTRYSPECIFIC = 0x00000063;
        private const int PRODUCT_CORE_N = 0x00000062;
        private const int PRODUCT_CORE_SINGLELANGUAGE = 0x00000064;
        private const int PRODUCT_HOME_BASIC = 0x00000002;
        private const int PRODUCT_HOME_BASIC_N = 0x00000005;
        private const int PRODUCT_HOME_PREMIUM = 0x00000003;
        private const int PRODUCT_HOME_PREMIUM_N = 0x0000001A;

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

        [DllImport("ntdll.dll", ExactSpelling = true)]
        private static extern int RtlGetVersion(ref RTL_OSVERSIONINFOEX lpVersionInformation);

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        private unsafe struct RTL_OSVERSIONINFOEX
        {
            internal uint dwOSVersionInfoSize;
            internal uint dwMajorVersion;
            internal uint dwMinorVersion;
            internal uint dwBuildNumber;
            internal uint dwPlatformId;
            internal fixed char szCSDVersion[128];
        }

        private static unsafe int GetWindowsVersion()
        {
            var osvi = new RTL_OSVERSIONINFOEX
            {
                dwOSVersionInfoSize = (uint)sizeof(RTL_OSVERSIONINFOEX)
            };
            Assert.Equal(0, RtlGetVersion(ref osvi));
            return (int)osvi.dwMajorVersion;
        }

        [DllImport("kernel32.dll", ExactSpelling = true)]
        private static extern int GetCurrentApplicationUserModelId(ref uint applicationUserModelIdLength, byte[] applicationUserModelId);

        [DllImport("advapi32.dll", SetLastError = true, ExactSpelling = true)]
        private static extern bool OpenProcessToken(IntPtr ProcessHandle, uint DesiredAccess, out IntPtr TokenHandle);
    }
}
