// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
using Microsoft.CodeAnalysis.Host.Mef;

namespace Microsoft.CodeAnalysis.Host;

internal sealed partial class CodeStyleHostLanguageServices : HostLanguageServices
{
    private static readonly ConditionalWeakTable<HostLanguageServices, CodeStyleHostLanguageServices> s_mappedLanguageServices = new();
    private static readonly ConditionalWeakTable<string, MefHostExportProvider> s_exportProvidersByLanguageCache = new();

    private readonly HostLanguageServices _hostLanguageServices;
    private readonly HostLanguageServices _codeStyleLanguageServices;

    [SuppressMessage("ApiDesign", "RS0030:Do not used banned APIs", Justification = "This is the replacement API")]
    private CodeStyleHostLanguageServices(HostLanguageServices hostLanguageServices)
    {
        _hostLanguageServices = hostLanguageServices;

        var exportProvider = s_exportProvidersByLanguageCache.GetValue(hostLanguageServices.Language, MefHostExportProvider.Create);
        _codeStyleLanguageServices = new MefWorkspaceServices(exportProvider, hostLanguageServices.WorkspaceServices.Workspace)
            .GetLanguageServices(hostLanguageServices.Language);
    }

    public static CodeStyleHostLanguageServices? GetMappedCodeStyleLanguageServices(HostLanguageServices? hostLanguageServices)
        => hostLanguageServices != null ? s_mappedLanguageServices.GetValue(hostLanguageServices, Create) : null;

    public static CodeStyleHostLanguageServices GetRequiredMappedCodeStyleLanguageServices(HostLanguageServices hostLanguageServices)
        => s_mappedLanguageServices.GetValue(hostLanguageServices, Create);

    private static CodeStyleHostLanguageServices Create(HostLanguageServices hostLanguageServices)
        => new(hostLanguageServices);

    public override HostWorkspaceServices WorkspaceServices => _hostLanguageServices.WorkspaceServices;

    public override string Language => _hostLanguageServices.Language;

    public override TLanguageService? GetService<TLanguageService>()
        where TLanguageService : default
        => _codeStyleLanguageServices.GetService<TLanguageService>() ?? _hostLanguageServices.GetService<TLanguageService>();
}