// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections;
 
namespace System.Windows.Forms.Design;
 
/// <summary>
///  Adapter for bridging between generic and non-generic lists.
///  It implements both the generic <see cref="IList&lt;T&gt;"/> and the non-generic
///  <see cref="IWrapper&lt;IList&gt;"/> interfaces
///  to provide a unified interface for working with IList collections.
/// </summary>
/// <typeparam name="T">The type of elements in the list.</typeparam>
internal sealed class ListAdapter<T> : IList<T>, IWrapper<IList>
{
    private readonly IList _list;
    internal ListAdapter(IList list) => _list = list.OrThrowIfNull();
 
    T IList<T>.this[int index]
    {
        get => (T?)_list[index] ?? throw new InvalidOperationException();
        set => _list[index] = value.OrThrowIfNull();
    }
 
    int ICollection<T>.Count => _list.Count;
 
    bool ICollection<T>.IsReadOnly => _list.IsReadOnly;
 
    void ICollection<T>.Add(T item) => _list.Add(item.OrThrowIfNull());
    void ICollection<T>.Clear() => _list.Clear();
    bool ICollection<T>.Contains(T item) => _list.Contains(item);
    void ICollection<T>.CopyTo(T[] array, int arrayIndex) => _list.CopyTo(array, arrayIndex);
    IEnumerator IEnumerable.GetEnumerator() => _list.GetEnumerator();
    int IList<T>.IndexOf(T item) => _list.IndexOf(item);
    void IList<T>.Insert(int index, T item) => _list.Insert(index, item.OrThrowIfNull());
    void IList<T>.RemoveAt(int index) => _list.RemoveAt(index);
 
    bool ICollection<T>.Remove(T item)
    {
        if (_list.IsReadOnly || !_list.Contains(item))
        {
            return false;
        }
 
        _list.Remove(item);
        return true;
    }
 
    IEnumerator<T> IEnumerable<T>.GetEnumerator() => new Enumerator(_list.GetEnumerator());
 
    private sealed class Enumerator(IEnumerator _enumerator) : IEnumerator<T>
    {
        T IEnumerator<T>.Current => (T)_enumerator.Current;
        object IEnumerator.Current => _enumerator.Current;
 
        void IDisposable.Dispose() { }
        bool IEnumerator.MoveNext() => _enumerator.MoveNext();
        void IEnumerator.Reset() => _enumerator.Reset();
    }
 
    public IList Unwrap() => _list;
}