// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
 
namespace MS.Internal.Text.TextInterface
{
    internal static unsafe class DWriteLoader
    {
        private static IntPtr _dwrite;
        private static delegate* unmanaged<int, void*, void*, int> _dwriteCreateFactory;
 
        internal static void LoadDWrite()
        {
            // We load dwrite here because it's cleanup logic is different from the other native dlls
            // and don't want to abstract that
            _dwrite = LoadDWriteLibraryAndGetProcAddress(out delegate* unmanaged<int, void*, void*, int> dwriteCreateFactory);
 
            if (_dwrite == IntPtr.Zero)
                throw new DllNotFoundException("dwrite.dll", new Win32Exception());
 
            if (dwriteCreateFactory == null)
                throw new InvalidOperationException();
 
            _dwriteCreateFactory = dwriteCreateFactory;
        }
 
        internal static void UnloadDWrite()
        {
            ClearDWriteCreateFactoryFunctionPointer();
        
            if (_dwrite != IntPtr.Zero)
            {
                NativeLibrary.Free(_dwrite);
 
                _dwrite = IntPtr.Zero;
            }
        }
 
        internal static delegate* unmanaged<int, void*, void*, int> GetDWriteCreateFactoryFunctionPointer()
        {
            return _dwriteCreateFactory;
        }
 
        private static void ClearDWriteCreateFactoryFunctionPointer()
        {
            _dwriteCreateFactory = null;
        }
 
        private static IntPtr LoadDWriteLibraryAndGetProcAddress(out delegate* unmanaged<int, void*, void*, int> DWriteCreateFactory)
        {
            IntPtr hDWriteLibrary = NativeLibrary.Load("dwrite.dll", typeof(DWriteLoader).Assembly, DllImportSearchPath.System32);
 
            if (hDWriteLibrary != IntPtr.Zero)
            {
                DWriteCreateFactory = (delegate* unmanaged<int, void*, void*, int>)NativeLibrary.GetExport(hDWriteLibrary, "DWriteCreateFactory");
            }
            else
            {
                DWriteCreateFactory = null;
            }
 
            return hDWriteLibrary;
        }
    }
}