// 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.Collections.Immutable;
using System.Linq;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.PooledObjects;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Shared.Extensions
{
    internal static class ILanguageMetadataExtensions
    {
        public static TInterface? ToSpecificLanguage<TInterface, TMetadata>(this IEnumerable<Lazy<TInterface, TMetadata>> services, string languageName)
            where TMetadata : ILanguageMetadata
        {
            return services.Where(s => s.Metadata.Language == languageName).Select(s => s.Value).FirstOrDefault();
        }
 
        public static IEnumerable<TInterface> FilterToSpecificLanguage<TInterface, TMetadata>(this IEnumerable<Lazy<TInterface, TMetadata>> services, string languageName)
            where TMetadata : ILanguageMetadata
        {
            return services.Where(s => s.Metadata.Language == languageName).Select(s => s.Value);
        }
 
        public static ImmutableDictionary<string, ImmutableArray<Lazy<TInterface, TMetadata>>> ToPerLanguageMap<TInterface, TMetadata>(this IEnumerable<Lazy<TInterface, TMetadata>> services)
            where TMetadata : ILanguageMetadata
        {
            var builder = ImmutableDictionary.CreateBuilder<string, ArrayBuilder<Lazy<TInterface, TMetadata>>>();
 
            foreach (var service in services)
            {
                var language = service.Metadata?.Language ?? string.Empty;
                var list = builder.GetOrAdd(language, _ => ArrayBuilder<Lazy<TInterface, TMetadata>>.GetInstance());
                list.Add(service);
            }
 
            return builder.Select(kvp => new KeyValuePair<string, ImmutableArray<Lazy<TInterface, TMetadata>>>(kvp.Key, kvp.Value.ToImmutableAndFree())).ToImmutableDictionary();
        }
 
        public static ImmutableDictionary<string, ImmutableArray<Lazy<TInterface, TMetadata>>> ToPerLanguageMapWithMultipleLanguages<TInterface, TMetadata>(this IEnumerable<Lazy<TInterface, TMetadata>> services)
            where TMetadata : ILanguagesMetadata
        {
            using var _ = PooledDictionary<string, ArrayBuilder<Lazy<TInterface, TMetadata>>>.GetInstance(out var map);
 
            foreach (var service in services)
            {
                foreach (var language in service.Metadata.Languages.Distinct())
                {
                    if (!string.IsNullOrEmpty(language))
                    {
                        var list = map.GetOrAdd(language, _ => ArrayBuilder<Lazy<TInterface, TMetadata>>.GetInstance());
                        list.Add(service);
                    }
                }
            }
 
            return map.ToImmutableDictionary(kvp => kvp.Key, kvp => kvp.Value.ToImmutableAndFree());
        }
    }
}