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

namespace LightlessSync.Utils
{
    public static partial class PtrGuard
    {
        private const ulong _minLikelyPtr = 0x0000_0001_0000_0000UL;
        private const ulong _maxUserPtr = 0x0000_7FFF_FFFF_FFFFUL;
        private const ulong _aligmentPtr = 0x7UL;

        public static bool LooksLikePtr(nint p)
        {
            if (p == 0) return false;
            var u = (ulong)p;
            if (u < _minLikelyPtr) return false;
            if (u > _maxUserPtr) return false;
            if ((u & _aligmentPtr) != 0) 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;
        }
    }
}