// 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;
using System.Diagnostics;
using Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.Interop;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.Collections;
 
public abstract class AbstractCodeElementCollection : AbstractCodeModelObject, ICodeElements
{
    private readonly ParentHandle<object> _parentHandle;
 
    internal AbstractCodeElementCollection(
        CodeModelState state,
        object parent)
        : base(state)
    {
        Debug.Assert(parent != null);
 
        _parentHandle = new ParentHandle<object>(parent);
    }
 
    internal virtual Snapshot CreateSnapshot()
        => new CodeElementSnapshot(this);
 
    protected abstract bool TryGetItemByName(string name, out EnvDTE.CodeElement element);
    protected abstract bool TryGetItemByIndex(int index, out EnvDTE.CodeElement element);
 
    protected bool MatchesNameOrIndex(string name, int index, string specifiedName, int specifiedIndex)
    {
        return (specifiedName != null && specifiedName == name)
            || (specifiedIndex != -1 && specifiedIndex == index);
    }
 
    public abstract int Count { get; }
 
    public int Item(object index, out EnvDTE.CodeElement element)
    {
        if (index is string elementName)
        {
            if (TryGetItemByName(elementName, out element))
            {
                return VSConstants.S_OK;
            }
        }
        else if (index is int i)
        {
            var elementIndex = i - 1;
            if (elementIndex >= 0 && TryGetItemByIndex(elementIndex, out element))
            {
                return VSConstants.S_OK;
            }
        }
 
        element = null;
        return VSConstants.E_INVALIDARG;
    }
 
    public object Parent
    {
        get
        {
            return _parentHandle.Value;
        }
    }
 
    public bool CreateUniqueID(string prefix, ref string newName)
        => throw new NotImplementedException();
 
    public void Reserved1(object element)
        => throw new NotImplementedException();
 
    public virtual System.Collections.IEnumerator GetEnumerator()
        => Enumerator.Create(CreateSnapshot());
}