// 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.
 
#nullable disable
 
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.FindSymbols;
using Microsoft.VisualStudio.GraphModel;
using Microsoft.VisualStudio.GraphModel.Schemas;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.Progression;
 
internal sealed class InheritedByGraphQuery : IGraphQuery
{
    public async Task<GraphBuilder> GetGraphAsync(Solution solution, IGraphContext context, CancellationToken cancellationToken)
    {
        var graphBuilder = await GraphBuilder.CreateForInputNodesAsync(solution, context.InputNodes, cancellationToken).ConfigureAwait(false);
 
        foreach (var node in context.InputNodes)
        {
            var symbol = graphBuilder.GetSymbol(node, cancellationToken);
            if (symbol is not INamedTypeSymbol namedType)
                continue;
 
            if (namedType.TypeKind == TypeKind.Class)
            {
                var derivedTypes = await SymbolFinder.FindDerivedClassesArrayAsync(
                    namedType, solution, transitive: false, cancellationToken: cancellationToken).ConfigureAwait(false);
                foreach (var derivedType in derivedTypes)
                {
                    var symbolNode = await graphBuilder.AddNodeAsync(
                        derivedType, relatedNode: node, cancellationToken).ConfigureAwait(false);
                    graphBuilder.AddLink(symbolNode, CodeLinkCategories.InheritsFrom, node, cancellationToken);
                }
            }
            else if (namedType.TypeKind == TypeKind.Interface)
            {
                var implementingClassesAndStructs = await SymbolFinder.FindImplementationsArrayAsync(
                    namedType, solution, transitive: false, cancellationToken: cancellationToken).ConfigureAwait(false);
                var derivedInterfaces = await SymbolFinder.FindDerivedInterfacesArrayAsync(
                    namedType, solution, transitive: false, cancellationToken: cancellationToken).ConfigureAwait(false);
                foreach (var derivedType in implementingClassesAndStructs.Concat(derivedInterfaces))
                {
                    var symbolNode = await graphBuilder.AddNodeAsync(
                        derivedType, relatedNode: node, cancellationToken).ConfigureAwait(false);
                    graphBuilder.AddLink(symbolNode, CodeLinkCategories.InheritsFrom, node, cancellationToken);
                }
            }
        }
 
        return graphBuilder;
    }
}