using System;
using System.Runtime.InteropServices;
using System.Threading;

namespace Server
{
    public static class NativeReader
    {
        private static readonly INativeReader m_NativeReader;

        static NativeReader()
        {
            if (Core.Unix)
            {
                m_NativeReader = new NativeReaderUnix();
            }
            else
            {
                m_NativeReader = new NativeReaderWin32();
            }
        }

        public static unsafe void Read(IntPtr p, void* buffer, int length)
        {
            m_NativeReader.Read(p, buffer, length);
        }
    }

    public interface INativeReader
    {
        unsafe void Read(IntPtr p, void* buffer, int length);
    }

    public sealed class NativeReaderWin32 : INativeReader
    {
        public unsafe void Read(IntPtr p, void* buffer, int length)
        {
            uint lpNumberOfBytesRead = 0;
            UnsafeNativeMethods.ReadFile(p, buffer, (uint)length, ref lpNumberOfBytesRead, null);
        }

        internal static class UnsafeNativeMethods
        {
            /*[DllImport("kernel32")]
            internal unsafe static extern int _lread(IntPtr hFile, void* lpBuffer, int wBytes);*/

            [DllImport("kernel32")]
            internal static extern unsafe bool ReadFile(
                IntPtr hFile, void* lpBuffer, uint nNumberOfBytesToRead,
                ref uint lpNumberOfBytesRead, NativeOverlapped* lpOverlapped
            );
        }
    }

    public sealed class NativeReaderUnix : INativeReader
    {
        public unsafe void Read(IntPtr p, void* buffer, int length)
        {
            _ = UnsafeNativeMethods.read(p, buffer, length);
        }

        internal static class UnsafeNativeMethods
        {
            [DllImport("libc")]
            internal static extern unsafe int read(IntPtr p, void* buffer, int length);
        }
    }
}