// 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.Collections.Immutable;
using System.Reflection;
using Microsoft.AspNetCore.Razor;
using Microsoft.CodeAnalysis.Host;
 
namespace Microsoft.CodeAnalysis.Razor.Workspaces;
 
internal sealed class AdhocServices : HostServices
{
    private readonly ImmutableArray<IWorkspaceService> _workspaceServices;
    private readonly ImmutableArray<ILanguageService> _languageServices;
    private readonly HostServices _fallbackHostServices;
    private readonly MethodInfo _createWorkspaceServicesMethod;
 
    private AdhocServices(
        ImmutableArray<IWorkspaceService> workspaceServices,
        ImmutableArray<ILanguageService> languageServices,
        HostServices fallbackHostServices)
    {
        _workspaceServices = workspaceServices;
        _languageServices = languageServices;
        _fallbackHostServices = fallbackHostServices;
 
        // We need to create workspace services from the provided fallback host services. To do that we need to invoke into Roslyn's
        // CreateWorkspaceServices method. Ultimately the reason behind this is to ensure that any services created by this class are
        // truly isolated from the passed in fallback services host workspace.
        _createWorkspaceServicesMethod = typeof(HostServices)
            .GetMethod(nameof(CreateWorkspaceServices), BindingFlags.Instance | BindingFlags.NonPublic)
            .AssumeNotNull();
    }
 
    protected override HostWorkspaceServices CreateWorkspaceServices(Workspace workspace)
    {
        if (workspace is null)
        {
            throw new ArgumentNullException(nameof(workspace));
        }
 
        var fallbackServices = CreateFallbackWorkspaceServices(workspace);
        return new AdhocWorkspaceServices(this, _workspaceServices, _languageServices, workspace, fallbackServices);
    }
 
    public static HostServices Create(
        ImmutableArray<IWorkspaceService> workspaceServices,
        ImmutableArray<ILanguageService> languageServices,
        HostServices fallbackServices)
        => new AdhocServices(workspaceServices, languageServices, fallbackServices);
 
    private HostWorkspaceServices CreateFallbackWorkspaceServices(Workspace workspace)
    {
        var result = _createWorkspaceServicesMethod.Invoke(_fallbackHostServices, new[] { workspace }) as HostWorkspaceServices;
 
        return result.AssumeNotNull();
    }
}