// 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="IWorkspaceService"/> implementation for inclusion in a MEF-based workspace.
/// </summary>
/// <remarks>
/// Declares a <see cref="IWorkspaceService"/> implementation for inclusion in a MEF-based workspace.
/// </remarks>
/// <param name="serviceType">The type that will be used to retrieve the service from a <see cref="HostWorkspaceServices"/>.</param>
/// <param name="layer">The layer that the service is specified for; <see cref="ServiceLayer.Default" />, etc.</param>
[MetadataAttribute]
[AttributeUsage(AttributeTargets.Class)]
public class ExportWorkspaceServiceAttribute(Type serviceType, string layer = ServiceLayer.Default) : ExportAttribute(typeof(IWorkspaceService))
{
    /// <summary>
    /// The assembly qualified name of the service's type.
    /// </summary>
    public string ServiceType { get; } = LayeredServiceUtilities.GetAssemblyQualifiedServiceTypeName(serviceType, nameof(serviceType));

    /// <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 ExportWorkspaceServiceAttribute(Type serviceType, string[] workspaceKinds)
        : this(serviceType)
    {
        WorkspaceKinds = workspaceKinds;
    }
}