// 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.Collections.Generic;
using Microsoft.CodeAnalysis.FindSymbols;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Completion.Providers;
 
internal readonly struct ExtensionMethodImportCompletionCacheEntry
{
    public Checksum Checksum { get; }
    public string Language { get; }
 
    /// <summary>
    /// Mapping from the name of receiver type to extension method symbol infos.
    /// </summary>
    public readonly MultiDictionary<string, DeclaredSymbolInfo> ReceiverTypeNameToExtensionMethodMap { get; }
 
    public bool ContainsExtensionMethod => !ReceiverTypeNameToExtensionMethodMap.IsEmpty;
 
    private ExtensionMethodImportCompletionCacheEntry(
        Checksum checksum,
        string language,
        MultiDictionary<string, DeclaredSymbolInfo> receiverTypeNameToExtensionMethodMap)
    {
        Checksum = checksum;
        Language = language;
        ReceiverTypeNameToExtensionMethodMap = receiverTypeNameToExtensionMethodMap;
    }
 
    public class Builder(Checksum checksum, string langauge, IEqualityComparer<string> comparer)
    {
        private readonly Checksum _checksum = checksum;
        private readonly string _language = langauge;
 
        private readonly MultiDictionary<string, DeclaredSymbolInfo> _mapBuilder = new MultiDictionary<string, DeclaredSymbolInfo>(comparer);
 
        public ExtensionMethodImportCompletionCacheEntry ToCacheEntry()
        {
            return new ExtensionMethodImportCompletionCacheEntry(
                _checksum,
                _language,
                _mapBuilder);
        }
 
        public void AddItem(TopLevelSyntaxTreeIndex syntaxIndex)
        {
            foreach (var (receiverType, symbolInfoIndices) in syntaxIndex.ReceiverTypeNameToExtensionMethodMap)
            {
                foreach (var index in symbolInfoIndices)
                {
                    _mapBuilder.Add(receiverType, syntaxIndex.DeclaredSymbolInfos[index]);
                }
            }
        }
    }
}