using System.Runtime.InteropServices;
using static LightlessSync.Utils.PtrGuardMemory;

namespace LightlessSync.Utils
{
    public static partial class PtrGuard
    {
        private const ulong _aligmentPtr = 0x7UL;
        private static readonly nuint _minAppAddr = (nuint)GetMinAppAddr();
        private static readonly nuint _maxAppAddr = (nuint)GetMaxAppAddr();

        private static nint GetMinAppAddr()
        {
            GetSystemInfo(out var si);
            return si.lpMinimumApplicationAddress;
        }

        private static nint GetMaxAppAddr()
        {
            GetSystemInfo(out var si);
            return si.lpMaximumApplicationAddress;
        }

            public static bool LooksLikePtr(nint p)
            {
                if (p == 0) return false;
                nuint u = (nuint)p;

                if (u < _minAppAddr) return false;
                if (u > _maxAppAddr) return false;
                if ((u & _aligmentPtr) != 0) return false;
                if ((uint)u == 0x12345679u) return false;

                return true;
            }

        public static bool TryReadIntPtr(nint addr, out nint value)
        {
            value = 0;
            
            if (!LooksLikePtr(addr))
                return false;

            return ReadProcessMemory(GetCurrentProcess(), addr, out value, (nuint)IntPtr.Size, out nuint bytesRead)
                   && bytesRead == (nuint)IntPtr.Size;
        }

        public static bool IsReadable(nint addr, nuint size)
        {
            if (addr == 0 || size == 0) return false;

            if (VirtualQuery(addr, out var mbi, (nuint)Marshal.SizeOf<MEMORY_BASIC_INFORMATION>()) == 0)
                return false;

            const uint Commit = 0x1000;
            const uint NoAccess = 0x01;
            const uint PageGuard = 0x100;

            if (mbi.State != Commit) return false;
            if ((mbi.Protect & PageGuard) != 0) return false;
            if (mbi.Protect == NoAccess) return false;

            ulong start = (ulong)addr;
            ulong end = start + size - 1;
            ulong r0 = (ulong)mbi.BaseAddress;
            ulong r1 = r0 + mbi.RegionSize - 1;

            return start >= r0 && end <= r1;
        }
    }
}