// 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;
using System.Collections.Generic;
using System.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CallHierarchy;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.LanguageServer.Protocol;
using LSP = Roslyn.LanguageServer.Protocol;
 
namespace Microsoft.CodeAnalysis.LanguageServer.Handler.CallHierarchy;
 
[ExportCSharpVisualBasicStatelessLspService(typeof(CallHierarchyIncomingCallsHandler)), Shared]
[Method(LSP.Methods.CallHierarchyIncomingCallsName)]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed class CallHierarchyIncomingCallsHandler() : ILspServiceDocumentRequestHandler<LSP.CallHierarchyIncomingCallsParams, LSP.CallHierarchyIncomingCall[]?>
{
    public bool MutatesSolutionState => false;
 
    public bool RequiresLSPSolution => true;
 
    public TextDocumentIdentifier GetTextDocumentIdentifier(LSP.CallHierarchyIncomingCallsParams request)
        => CallHierarchyHelpers.GetResolveData(request.Item).TextDocument;
 
    public async Task<LSP.CallHierarchyIncomingCall[]?> HandleRequestAsync(LSP.CallHierarchyIncomingCallsParams request, RequestContext context, CancellationToken cancellationToken)
    {
        var document = context.GetRequiredDocument();
        var solution = document.Project.Solution;
        var resolveData = CallHierarchyHelpers.GetResolveData(request.Item);
 
        var service = document.GetRequiredLanguageService<ICallHierarchyService>();
        var results = await service.SearchIncomingCallsAsync(
            solution,
            new CallHierarchySearchDescriptor(CallHierarchyRelationshipKind.Callers, resolveData.GetItemId()),
            documents: null,
            cancellationToken).ConfigureAwait(false);
 
        var incomingCalls = new List<LSP.CallHierarchyIncomingCall>();
        foreach (var result in results.Where(result => result.Item != null))
        {
            var locationsByDocumentId = result.ReferenceLocations
                .Where(static location => location.IsInSource)
                .GroupBy(location => solution.GetDocument(location.SourceTree)?.Id);
 
            foreach (var locationGroup in locationsByDocumentId)
            {
                if (locationGroup.Key == null)
                    continue;
 
                var callerDocument = solution.GetDocument(locationGroup.Key);
                if (callerDocument == null)
                    continue;
 
                var fromItem = await CallHierarchyHelpers.CreateItemAsync(result.Item!, solution, locationGroup.Key, cancellationToken).ConfigureAwait(false);
                if (fromItem == null)
                    continue;
 
                var ranges = await CallHierarchyHelpers.ConvertLocationsToRangesAsync([.. locationGroup], callerDocument, cancellationToken).ConfigureAwait(false);
                incomingCalls.Add(new LSP.CallHierarchyIncomingCall
                {
                    From = fromItem,
                    FromRanges = [.. ranges],
                });
            }
        }
 
        return [.. incomingCalls];
    }
}