// 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;
using System.Collections.Generic;
using System.Composition;
 
namespace Microsoft.CodeAnalysis.Host.Mef;
 
/// <summary>
/// Use this attribute to declare a <see cref="ILanguageServiceFactory"/> implementation for inclusion in a MEF-based workspace.
/// </summary>
/// <remarks>
/// Declares a <see cref="ILanguageServiceFactory"/> implementation for inclusion in a MEF-based workspace.
/// </remarks>
/// <param name="type">The type that will be used to retrieve the service from a <see cref="HostLanguageServices"/>.</param>
/// <param name="language">The language that the service is target for; <see cref="LanguageNames.CSharp"/>, etc.</param>
/// <param name="layer">The layer that the service is specified for; <see cref="ServiceLayer.Default"/>, etc.</param>
[MetadataAttribute]
[AttributeUsage(AttributeTargets.Class)]
public class ExportLanguageServiceFactoryAttribute(Type type, string language, string layer = ServiceLayer.Default) : ExportAttribute(typeof(ILanguageServiceFactory))
{
    /// <summary>
    /// The assembly qualified name of the service's type.
    /// </summary>
    public string ServiceType { get; } = LayeredServiceUtilities.GetAssemblyQualifiedServiceTypeName(type, nameof(type));
 
    /// <summary>
    /// The language that the service is target for. Specify a value from <see cref="LanguageNames"/>, or other language name.
    /// </summary>
    public string Language { get; } = language ?? throw new ArgumentNullException(nameof(language));
 
    /// <summary>
    /// The layer that the service is specified for. Specify a value from <see cref="ServiceLayer"/>.
    /// </summary>
    public string Layer { get; } = layer ?? throw new ArgumentNullException(nameof(layer));
 
    /// <summary>
    /// <see cref="WorkspaceKind"/>s that the service is specified for.
    /// If non-empty the service is only exported for the listed workspace kinds and <see cref="Layer"/> is not applied,
    /// unless <see cref="Layer"/> is <see cref="ServiceLayer.Test"/> in which case the export overrides all other exports.
    /// </summary>
    internal IReadOnlyList<string> WorkspaceKinds { get; } = [];
 
    internal ExportLanguageServiceFactoryAttribute(Type type, string language, string[] workspaceKinds)
        : this(type, language)
    {
        WorkspaceKinds = workspaceKinds;
    }
}