// 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.Immutable;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis
{
    internal static class IDocumentTrackingServiceExtensions
    {
        /// <summary>
        /// Gets the active <see cref="Document"/> the user is currently working in. May be null if
        /// there is no active document or the active document is not in this <paramref name="solution"/>.
        /// </summary>
        public static Document? GetActiveDocument(this IDocumentTrackingService service, Solution solution)
        {
            // Note: GetDocument checks that the DocId is contained in the solution, and returns null if not.
            return solution.GetDocument(service.TryGetActiveDocument());
        }
 
        /// <summary>
        /// Get a read only collection of all the unique visible documents in the workspace that are
        /// contained within <paramref name="solution"/>.
        /// </summary>
        public static ImmutableArray<Document> GetVisibleDocuments(this IDocumentTrackingService service, Solution solution)
            => service.GetVisibleDocuments()
                      .Select(solution.GetDocument)
                      .WhereNotNull()
                      .Distinct()
                      .ToImmutableArray();
    }
}