// 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.Runtime.Serialization;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis;

/// <summary>
/// Lightweight analog to <see cref="DocumentSpan"/> that should be used in features that care about
/// pointing at a particular location in a <see cref="Document"/> but do not want to root a potentially
/// very stale <see cref="Solution"/> snapshot that may keep around a lot of memory in a host.
/// </summary>
[DataContract]
internal readonly record struct DocumentIdSpan(DocumentId documentId, TextSpan sourceSpan)
{
    [DataMember(Order = 0)]
    public readonly DocumentId DocumentId = documentId;
    [DataMember(Order = 1)]
    public readonly TextSpan SourceSpan = sourceSpan;

    public static implicit operator DocumentIdSpan(DocumentSpan documentSpan)
        => new(documentSpan.Document.Id, documentSpan.SourceSpan);

    public async Task<DocumentSpan?> TryRehydrateAsync(Solution solution, CancellationToken cancellationToken)
    {
        var document = await solution.GetDocumentAsync(this.DocumentId, includeSourceGenerated: true, cancellationToken).ConfigureAwait(false);
        return document == null ? null : new DocumentSpan(document, this.SourceSpan);
    }
}