using System.Runtime.InteropServices;

namespace SpdUp.Core;

/// <summary>
/// P/Invoke declarations used across the application.
/// </summary>
public static class NativeMethods
{
    // ── Memory management ──────────────────────────────────────────────
    [DllImport("psapi.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool EmptyWorkingSet(IntPtr hProcess);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern IntPtr OpenProcess(uint dwDesiredAccess, bool bInheritHandle, int dwProcessId);

    [DllImport("kernel32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool CloseHandle(IntPtr hObject);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern bool SetProcessWorkingSetSizeEx(
        IntPtr hProcess, IntPtr dwMinimumWorkingSetSize, IntPtr dwMaximumWorkingSetSize, uint flags);

    // ── Timer resolution ───────────────────────────────────────────────
    [DllImport("ntdll.dll", SetLastError = true)]
    public static extern int NtSetTimerResolution(uint DesiredResolution, bool SetResolution, out uint CurrentResolution);

    [DllImport("ntdll.dll", SetLastError = true)]
    public static extern int NtQueryTimerResolution(out uint MinimumResolution, out uint MaximumResolution, out uint CurrentResolution);

    // ── System memory info ─────────────────────────────────────────────
    [StructLayout(LayoutKind.Sequential)]
    public struct MEMORYSTATUSEX
    {
        public uint dwLength;
        public uint dwMemoryLoad;
        public ulong ullTotalPhys;
        public ulong ullAvailPhys;
        public ulong ullTotalPageFile;
        public ulong ullAvailPageFile;
        public ulong ullTotalVirtual;
        public ulong ullAvailVirtual;
        public ulong ullAvailExtendedVirtual;
    }

    [DllImport("kernel32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool GlobalMemoryStatusEx(ref MEMORYSTATUSEX lpBuffer);

    // ── System cache / standby list purge ──────────────────────────────
    public enum SYSTEM_MEMORY_LIST_COMMAND
    {
        MemoryCaptureAccessedBits = 0,
        MemoryCaptureAndResetAccessedBits = 1,
        MemoryEmptyWorkingSets = 2,
        MemoryFlushModifiedList = 3,
        MemoryPurgeStandbyList = 4,
        MemoryPurgeLowPriorityStandbyList = 5,
        MemoryCommandMax = 6
    }

    [DllImport("ntdll.dll")]
    public static extern int NtSetSystemInformation(
        int SystemInformationClass, ref int SystemInformation, int SystemInformationLength);

    // SystemMemoryListInformation = 0x0050
    public const int SystemMemoryListInformation = 0x0050;

    // ── Privilege ──────────────────────────────────────────────────────
    [DllImport("advapi32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool OpenProcessToken(IntPtr ProcessHandle, uint DesiredAccess, out IntPtr TokenHandle);

    [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool LookupPrivilegeValue(string? lpSystemName, string lpName, out LUID lpLuid);

    [DllImport("advapi32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool AdjustTokenPrivileges(
        IntPtr TokenHandle, bool DisableAllPrivileges,
        ref TOKEN_PRIVILEGES NewState, uint BufferLength,
        IntPtr PreviousState, IntPtr ReturnLength);

    [StructLayout(LayoutKind.Sequential)]
    public struct LUID
    {
        public uint LowPart;
        public int HighPart;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct LUID_AND_ATTRIBUTES
    {
        public LUID Luid;
        public uint Attributes;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct TOKEN_PRIVILEGES
    {
        public uint PrivilegeCount;
        public LUID_AND_ATTRIBUTES Privileges;
    }

    public const uint TOKEN_ADJUST_PRIVILEGES = 0x0020;
    public const uint TOKEN_QUERY = 0x0008;
    public const uint SE_PRIVILEGE_ENABLED = 0x00000002;
    public const string SE_DEBUG_NAME = "SeDebugPrivilege";
    public const string SE_PROF_SINGLE_PROCESS_NAME = "SeProfileSingleProcessPrivilege";
    public const string SE_INC_BASE_PRIORITY_NAME = "SeIncreaseBasePriorityPrivilege";

    public const uint PROCESS_ALL_ACCESS = 0x001F0FFF;
    public const uint PROCESS_SET_INFORMATION = 0x0200;
    public const uint PROCESS_QUERY_INFORMATION = 0x0400;

    /// <summary>
    /// Enable a privilege on the current process token.
    /// </summary>
    public static bool EnablePrivilege(string privilege)
    {
        try
        {
            if (!OpenProcessToken(System.Diagnostics.Process.GetCurrentProcess().Handle,
                TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, out var tokenHandle))
                return false;

            try
            {
                if (!LookupPrivilegeValue(null, privilege, out var luid))
                    return false;

                var tp = new TOKEN_PRIVILEGES
                {
                    PrivilegeCount = 1,
                    Privileges = new LUID_AND_ATTRIBUTES { Luid = luid, Attributes = SE_PRIVILEGE_ENABLED }
                };

                return AdjustTokenPrivileges(tokenHandle, false, ref tp, 0, IntPtr.Zero, IntPtr.Zero);
            }
            finally
            {
                CloseHandle(tokenHandle);
            }
        }
        catch
        {
            return false;
        }
    }
}