// 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.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis;
using Microsoft.VisualStudio.GraphModel;
using Microsoft.VisualStudio.GraphModel.Schemas;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.Progression;
 
internal sealed class InheritsGraphQuery : IGraphQuery
{
    public async Task<GraphBuilder> GetGraphAsync(Solution solution, IGraphContext context, CancellationToken cancellationToken)
    {
        var graphBuilder = await GraphBuilder.CreateForInputNodesAsync(solution, context.InputNodes, cancellationToken).ConfigureAwait(false);
        var nodesToProcess = context.InputNodes;
 
        for (var depth = 0; depth < context.LinkDepth; depth++)
        {
            // This is the list of nodes we created and will process
            var newNodes = new HashSet<GraphNode>();
 
            foreach (var node in nodesToProcess)
            {
                var symbol = graphBuilder.GetSymbol(node, cancellationToken);
                if (symbol is INamedTypeSymbol namedType)
                {
                    if (namedType.BaseType != null)
                    {
                        var baseTypeNode = await graphBuilder.AddNodeAsync(
                            namedType.BaseType, relatedNode: node, cancellationToken).ConfigureAwait(false);
                        newNodes.Add(baseTypeNode);
                        graphBuilder.AddLink(node, CodeLinkCategories.InheritsFrom, baseTypeNode, cancellationToken);
                    }
                    else if (namedType.TypeKind == TypeKind.Interface && !namedType.OriginalDefinition.AllInterfaces.IsEmpty)
                    {
                        foreach (var baseNode in namedType.OriginalDefinition.AllInterfaces.Distinct())
                        {
                            var baseTypeNode = await graphBuilder.AddNodeAsync(
                                baseNode, relatedNode: node, cancellationToken).ConfigureAwait(false);
                            newNodes.Add(baseTypeNode);
                            graphBuilder.AddLink(node, CodeLinkCategories.InheritsFrom, baseTypeNode, cancellationToken);
                        }
                    }
                }
            }
 
            nodesToProcess = newNodes;
        }
 
        return graphBuilder;
    }
}