﻿// 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 Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Tagging;

namespace Microsoft.CodeAnalysis.Editor.Tagging
{
    internal abstract partial class AbstractAsynchronousTaggerProvider<TTag>
    {
        private partial class TagSource : IEqualityComparer<ITagSpan<TTag>>
        {
            public bool Equals(ITagSpan<TTag>? x, ITagSpan<TTag>? y)
                => x != null && y != null && x.Span == y.Span && _dataSource.TagEquals(x.Tag, y.Tag);

            /// <summary>
            /// For the purposes of hashing, just hash spans.  This will prevent most collisions.  And the rare
            /// collision of two tag spans with the same span will be handled by checking if their tags are the same
            /// through <see cref="Equals(ITagSpan{TTag}, ITagSpan{TTag})"/>.  This prevents us from having to
            /// define a suitable hashing strategy for all our tags.
            /// </summary>
            public int GetHashCode(ITagSpan<TTag> obj)
                => obj.Span.Span.GetHashCode();
        }
    }
}
