// 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.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Host;
 
namespace Microsoft.CodeAnalysis.SemanticModelReuse;
 
/// <summary>
/// Interface only for use by <see cref="ISemanticModelReuseWorkspaceService"/>.  Includes language specific
/// implementations on how to get an appropriate speculated semantic model given an older semantic model and a
/// changed method body.
/// </summary>
internal interface ISemanticModelReuseLanguageService : ILanguageService
{
    /// <summary>
    /// Given a node, returns the parent method-body-esque node that we can get a new speculative semantic model
    /// for.  Returns <see langword="null"/> if not in such a location.
    /// </summary>
    SyntaxNode? TryGetContainingMethodBodyForSpeculation(SyntaxNode node);
 
    /// <summary>
    /// Given a previous semantic model, and a method-eque node in the current tree for that same document, attempts
    /// to create a new speculative semantic model using the top level symbols of <paramref
    /// name="previousSemanticModel"/> but the new body level symbols produced for <paramref
    /// name="currentBodyNode"/>.
    /// <para>
    /// Note: it is critical that no top level changes have occurred between the syntax tree that <paramref
    /// name="previousSemanticModel"/> points at and the syntax tree that <paramref name="currentBodyNode"/> points
    /// at.  In other words, they must be <see cref="SyntaxTree.IsEquivalentTo"/><c>(..., topLevel: true)</c>.  This
    /// function is undefined if they are not.
    /// </para>
    /// </summary>
    Task<SemanticModel?> TryGetSpeculativeSemanticModelAsync(SemanticModel previousSemanticModel, SyntaxNode currentBodyNode, CancellationToken cancellationToken);
}