// 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.
 
#nullable disable
 
using System.Collections.Immutable;
using System.Runtime.InteropServices;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.Interop;
using Microsoft.VisualStudio.LanguageServices.Implementation.Interop;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.Collections;
 
[ComVisible(true)]
[ComDefaultInterface(typeof(ICodeElements))]
public sealed class ExternalNamespaceCollection : AbstractCodeElementCollection
{
    internal static EnvDTE.CodeElements Create(
        CodeModelState state,
        object parent,
        ProjectId projectId,
        INamespaceSymbol namespaceSymbol)
    {
        var collection = new ExternalNamespaceCollection(state, parent, projectId, namespaceSymbol);
        return (EnvDTE.CodeElements)ComAggregate.CreateAggregatedObject(collection);
    }
 
    private readonly ProjectId _projectId;
    private readonly SymbolKey _namespaceSymbolId;
    private ImmutableArray<EnvDTE.CodeElement> _children;
 
    internal ExternalNamespaceCollection(CodeModelState state, object parent, ProjectId projectId, INamespaceSymbol namespaceSymbol)
        : base(state, parent)
    {
        _projectId = projectId;
        _namespaceSymbolId = namespaceSymbol.GetSymbolKey();
    }
 
    private ImmutableArray<EnvDTE.CodeElement> GetChildren()
    {
        if (_children == null)
        {
            _children = [.. ExternalNamespaceEnumerator.ChildrenOfNamespace(this.State, _projectId, _namespaceSymbolId)];
        }
 
        return _children;
    }
 
    protected override bool TryGetItemByIndex(int index, out EnvDTE.CodeElement element)
    {
        var children = GetChildren();
        if (index < children.Length)
        {
            element = children[index];
            return true;
        }
 
        element = null;
        return false;
    }
 
    protected override bool TryGetItemByName(string name, out EnvDTE.CodeElement element)
    {
        var children = GetChildren();
        var index = children.IndexOf(e => e.Name == name);
 
        if (index < children.Length)
        {
            element = children[index];
            return true;
        }
 
        element = null;
        return false;
    }
 
    public override int Count
    {
        get { return GetChildren().Length; }
    }
 
    public override System.Collections.IEnumerator GetEnumerator()
        => ExternalNamespaceEnumerator.Create(this.State, _projectId, _namespaceSymbolId);
}