// 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.Collections.Generic;
using System.Collections.Immutable;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Notification;
using Microsoft.CodeAnalysis.Shared.Utilities;

namespace Microsoft.CodeAnalysis.FindUsages;

internal abstract partial class AbstractFindUsagesService
{
    /// <summary>
    /// Forwards <see cref="IFindUsagesContext"/> notifications to an underlying <see cref="IFindUsagesContext"/>
    /// while also keeping track of the <see cref="DefinitionItem"/> definitions reported.
    /// 
    /// These can then be used by <see cref="GetThirdPartyDefinitionsAsync"/> to report the
    /// definitions found to third parties in case they want to add any additional definitions
    /// to the results we present.
    /// </summary>
    private sealed class DefinitionTrackingContext(IFindUsagesContext underlyingContext) : IFindUsagesContext
    {
        private readonly IFindUsagesContext _underlyingContext = underlyingContext;
        private readonly object _gate = new();
        private readonly List<DefinitionItem> _definitions = [];

        public IStreamingProgressTracker ProgressTracker
            => _underlyingContext.ProgressTracker;

        public ValueTask ReportNoResultsAsync(string message, CancellationToken cancellationToken)
            => _underlyingContext.ReportNoResultsAsync(message, cancellationToken);

        public ValueTask ReportMessageAsync(string message, NotificationSeverity severity, CancellationToken cancellationToken)
            => _underlyingContext.ReportMessageAsync(message, severity, cancellationToken);

        public ValueTask SetSearchTitleAsync(string title, CancellationToken cancellationToken)
            => _underlyingContext.SetSearchTitleAsync(title, cancellationToken);

        public ValueTask OnReferencesFoundAsync(IAsyncEnumerable<SourceReferenceItem> references, CancellationToken cancellationToken)
            => _underlyingContext.OnReferencesFoundAsync(references, cancellationToken);

        public ValueTask OnDefinitionFoundAsync(DefinitionItem definition, CancellationToken cancellationToken)
        {
            lock (_gate)
            {
                _definitions.Add(definition);
            }

            return _underlyingContext.OnDefinitionFoundAsync(definition, cancellationToken);
        }

        public ImmutableArray<DefinitionItem> GetDefinitions()
        {
            lock (_gate)
            {
                return [.. _definitions];
            }
        }
    }
}