// 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.Composition;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Classification;
using Microsoft.CodeAnalysis.FindUsages;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Options;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
using LSP = Roslyn.LanguageServer.Protocol;
 
namespace Microsoft.CodeAnalysis.LanguageServer.Handler;
 
[ExportCSharpVisualBasicStatelessLspService(typeof(FindImplementationsHandler)), Shared]
[Method(LSP.Methods.TextDocumentImplementationName)]
internal sealed class FindImplementationsHandler : ILspServiceDocumentRequestHandler<LSP.TextDocumentPositionParams, LSP.Location[]>
{
    private readonly IGlobalOptionService _globalOptions;
 
    [ImportingConstructor]
    [System.Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public FindImplementationsHandler(IGlobalOptionService globalOptions)
    {
        _globalOptions = globalOptions;
    }
 
    public bool MutatesSolutionState => false;
    public bool RequiresLSPSolution => true;
 
    public LSP.TextDocumentIdentifier GetTextDocumentIdentifier(LSP.TextDocumentPositionParams request) => request.TextDocument;
 
    public Task<LSP.Location[]> HandleRequestAsync(LSP.TextDocumentPositionParams request, RequestContext context, CancellationToken cancellationToken)
    {
        var document = context.GetRequiredDocument();
        var supportsVisualStudioExtensions = context.GetRequiredClientCapabilities().HasVisualStudioLspCapability();
        var linePosition = ProtocolConversions.PositionToLinePosition(request.Position);
        var classificationOptions = _globalOptions.GetClassificationOptionsProvider();
 
        return FindImplementationsAsync(document, linePosition, classificationOptions, supportsVisualStudioExtensions, cancellationToken);
    }
 
    internal static async Task<LSP.Location[]> FindImplementationsAsync(Document document, LinePosition linePosition, OptionsProvider<ClassificationOptions> classificationOptions, bool supportsVisualStudioExtensions, CancellationToken cancellationToken)
    {
        var locations = ArrayBuilder<LSP.Location>.GetInstance();
 
        var findUsagesService = document.GetRequiredLanguageService<IFindUsagesLSPService>();
        var position = await document.GetPositionFromLinePositionAsync(linePosition, cancellationToken).ConfigureAwait(false);
 
        var findUsagesContext = new SimpleFindUsagesContext();
        await findUsagesService.FindImplementationsAsync(findUsagesContext, document, position, classificationOptions, cancellationToken).ConfigureAwait(false);
 
        foreach (var definition in findUsagesContext.GetDefinitions())
        {
            var text = definition.GetClassifiedText();
            foreach (var sourceSpan in definition.SourceSpans)
            {
                if (supportsVisualStudioExtensions)
                {
                    locations.AddIfNotNull(await ProtocolConversions.DocumentSpanToLocationWithTextAsync(sourceSpan, text, cancellationToken).ConfigureAwait(false));
                }
                else
                {
                    locations.AddIfNotNull(await ProtocolConversions.DocumentSpanToLocationAsync(sourceSpan, cancellationToken).ConfigureAwait(false));
                }
            }
        }
 
        return locations.ToArrayAndFree();
    }
}