// 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.Immutable;
using System.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Completion;
using Microsoft.CodeAnalysis.CSharp.Completion.Providers.DeclarationName;
using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.ExternalAccess.Pythia.Api;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.PooledObjects;
 
namespace Microsoft.CodeAnalysis.CSharp.ExternalAccess.Pythia
{
    [ExportDeclarationNameRecommender(nameof(PythiaDeclarationNameRecommender)), Shared]
    [ExtensionOrder(Before = nameof(DeclarationNameRecommender))]
    internal sealed class PythiaDeclarationNameRecommender : IDeclarationNameRecommender
    {
        private readonly Lazy<IPythiaDeclarationNameRecommenderImplementation>? _lazyImplementation;
 
        [ImportingConstructor]
        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
        public PythiaDeclarationNameRecommender([Import(AllowDefault = true)] Lazy<IPythiaDeclarationNameRecommenderImplementation>? implementation)
            => _lazyImplementation = implementation;
 
        public async Task<ImmutableArray<(string name, Glyph glyph)>> ProvideRecommendedNamesAsync(
            CompletionContext completionContext,
            Document document,
            CSharpSyntaxContext syntaxContext,
            NameDeclarationInfo nameInfo,
            CancellationToken cancellationToken)
        {
            if (_lazyImplementation is null || nameInfo.PossibleSymbolKinds.IsEmpty)
                return ImmutableArray<(string, Glyph)>.Empty;
 
            var context = new PythiaDeclarationNameContext(syntaxContext);
            var result = await _lazyImplementation.Value.ProvideRecommendationsAsync(context, cancellationToken).ConfigureAwait(false);
 
            // We just pick the first possible symbol kind for glyph.
            return result.SelectAsArray(
                name => (name, NameDeclarationInfo.GetGlyph(NameDeclarationInfo.GetSymbolKind(nameInfo.PossibleSymbolKinds[0]), nameInfo.DeclaredAccessibility)));
        }
    }
}