using System;
using System.Runtime.InteropServices;

namespace BepInEx
{
    /// <summary>
    /// Provides information about system memory status
    /// </summary>
    internal static class MemoryInfo
    {
        /// <summary>
        /// Can return null if the call fails for whatever reason
        /// </summary>
        public static MEMORYSTATUSEX GetCurrentStatus()
        {
            try
            {
                var msex = new MEMORYSTATUSEX();
                if (GlobalMemoryStatusEx(msex))
                    return msex;
                return null;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
                return null;
            }
        }

        /// <summary>
        /// contains information about the current state of both physical and virtual memory, including extended memory
        /// </summary>
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        public class MEMORYSTATUSEX
        {
            /// <summary>
            /// Size of the structure, in bytes. You must set this member before calling GlobalMemoryStatusEx.
            /// </summary>
            public uint dwLength;

            /// <summary>
            /// Number between 0 and 100 that specifies the approximate percentage of physical memory that is in use (0 indicates no memory use and 100 indicates full memory use).
            /// </summary>
            public uint dwMemoryLoad;

            /// <summary>
            /// Total size of physical memory, in bytes.
            /// </summary>
            public ulong ullTotalPhys;

            /// <summary>
            /// Size of physical memory available, in bytes.
            /// </summary>
            public ulong ullAvailPhys;

            /// <summary>
            /// Size of the committed memory limit, in bytes. This is physical memory plus the size of the page file, minus a small overhead.
            /// </summary>
            public ulong ullTotalPageFile;

            /// <summary>
            /// Size of available memory to commit, in bytes. The limit is ullTotalPageFile.
            /// </summary>
            public ulong ullAvailPageFile;

            /// <summary>
            /// Total size of the user mode portion of the virtual address space of the calling process, in bytes.
            /// </summary>
            public ulong ullTotalVirtual;

            /// <summary>
            /// Size of unreserved and uncommitted memory in the user mode portion of the virtual address space of the calling process, in bytes.
            /// </summary>
            public ulong ullAvailVirtual;

            /// <summary>
            /// Size of unreserved and uncommitted memory in the extended portion of the virtual address space of the calling process, in bytes.
            /// </summary>
            public ulong ullAvailExtendedVirtual;

            /// <summary>
            /// Initializes a new instance of the <see cref="T:MEMORYSTATUSEX"/> class.
            /// </summary>
            public MEMORYSTATUSEX()
            {
                dwLength = (uint)Marshal.SizeOf(typeof(MEMORYSTATUSEX));
            }
        }

        [return: MarshalAs(UnmanagedType.Bool)]
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern bool GlobalMemoryStatusEx([In, Out] MEMORYSTATUSEX lpBuffer);
    }
}
