// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Diagnostics;
 
namespace System.Runtime.InteropServices
{
    public static partial class NativeLibrary
    {
        private const int LoadWithAlteredSearchPathFlag = 0;
 
        private static IntPtr LoadLibraryHelper(string libraryName, int _ /*flags*/, ref LoadLibErrorTracker errorTracker)
        {
            IntPtr ret = Interop.Sys.LoadLibrary(libraryName);
            if (ret == IntPtr.Zero)
            {
                string? message = Marshal.PtrToStringUTF8(Interop.Sys.GetLoadLibraryError());
                errorTracker.TrackErrorMessage(message ?? string.Empty);
            }
 
            return ret;
        }
 
        private static void FreeLib(IntPtr handle)
        {
            Debug.Assert(handle != IntPtr.Zero);
 
            Interop.Sys.FreeLibrary(handle);
        }
 
        private static unsafe IntPtr GetSymbolOrNull(IntPtr handle, string symbolName)
        {
            return Interop.Sys.GetProcAddress(handle, symbolName);
        }
 
        internal struct LoadLibErrorTracker
        {
            private string? _errorMessage;
 
            public void Throw(string libraryName)
            {
#if TARGET_OSX || TARGET_MACCATALYST || TARGET_IOS || TARGET_TVOS
                throw new DllNotFoundException(SR.Format(SR.DllNotFound_Mac, libraryName, _errorMessage));
#else
                throw new DllNotFoundException(SR.Format(SR.DllNotFound_Linux, libraryName, _errorMessage));
#endif
            }
 
            public void TrackErrorMessage(string message)
            {
                _errorMessage ??= Environment.NewLine;
                if (!_errorMessage.Contains(message))
                {
                    _errorMessage += message + Environment.NewLine;
                }
            }
        }
    }
}