#pragma warning disable IDE1006 // Naming Styles (interface for native functions)
using System;
using System.Runtime.InteropServices;

namespace Python.Runtime.Platform
{
 interface ILibDL
 {
 IntPtr dlopen(string? fileName, int flags);
 IntPtr dlsym(IntPtr handle, string symbol);
 int dlclose(IntPtr handle);
 IntPtr dlerror();

 int RTLD_NOW { get; }
 int RTLD_GLOBAL { get; }
 IntPtr RTLD_DEFAULT { get; }
 }

 class LinuxLibDL : ILibDL
 {
 private const string NativeDll = "libdl.so";

 public int RTLD_NOW => 0x2;
 public int RTLD_GLOBAL => 0x100;
 public IntPtr RTLD_DEFAULT => IntPtr.Zero;

 public static ILibDL GetInstance()
 {
 try
 {
 ILibDL libdl2 = new LinuxLibDL2();
 // call dlerror to ensure library is resolved
 libdl2.dlerror();
 return libdl2;
 } catch (DllNotFoundException)
 {
 return new LinuxLibDL();
 }
 }

 IntPtr ILibDL.dlopen(string? fileName, int flags) => dlopen(fileName, flags);
 IntPtr ILibDL.dlsym(IntPtr handle, string symbol) => dlsym(handle, symbol);
 int ILibDL.dlclose(IntPtr handle) => dlclose(handle);
 IntPtr ILibDL.dlerror() => dlerror();

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
 private static extern IntPtr dlopen(string? fileName, int flags);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
 private static extern IntPtr dlsym(IntPtr handle, string symbol);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
 private static extern int dlclose(IntPtr handle);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
 private static extern IntPtr dlerror();
 }

 class LinuxLibDL2 : ILibDL
 {
 private const string NativeDll = "libdl.so.2";

 public int RTLD_NOW => 0x2;
 public int RTLD_GLOBAL => 0x100;
 public IntPtr RTLD_DEFAULT => IntPtr.Zero;

 IntPtr ILibDL.dlopen(string? fileName, int flags) => dlopen(fileName, flags);
 IntPtr ILibDL.dlsym(IntPtr handle, string symbol) => dlsym(handle, symbol);
 int ILibDL.dlclose(IntPtr handle) => dlclose(handle);
 IntPtr ILibDL.dlerror() => dlerror();

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
 private static extern IntPtr dlopen(string? fileName, int flags);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
 private static extern IntPtr dlsym(IntPtr handle, string symbol);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
 private static extern int dlclose(IntPtr handle);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
 private static extern IntPtr dlerror();
 }

 class MacLibDL : ILibDL
 {
 public int RTLD_NOW => 0x2;
 public int RTLD_GLOBAL => 0x8;
 const string NativeDll = "/usr/lib/libSystem.dylib";
 public IntPtr RTLD_DEFAULT => new(-2);

 IntPtr ILibDL.dlopen(string? fileName, int flags) => dlopen(fileName, flags);
 IntPtr ILibDL.dlsym(IntPtr handle, string symbol) => dlsym(handle, symbol);
 int ILibDL.dlclose(IntPtr handle) => dlclose(handle);
 IntPtr ILibDL.dlerror() => dlerror();

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
 private static extern IntPtr dlopen(string? fileName, int flags);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
 private static extern IntPtr dlsym(IntPtr handle, string symbol);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
 private static extern int dlclose(IntPtr handle);

 [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
 private static extern IntPtr dlerror();
 }
}