//
// Author:
//   Jb Evain (jbevain@gmail.com)
//
// Copyright (c) 2008 - 2015 Jb Evain
// Copyright (c) 2008 - 2011 Novell, Inc.
//
// Licensed under the MIT/X11 license.
//

using System;
using System.Collections;
using System.Collections.Generic;
using System.Threading;

namespace MonoFN.Collections.Generic
{
    public sealed class ReadOnlyCollection<T> : Collection<T>, ICollection<T>, IList
    {
        private static ReadOnlyCollection<T> empty;
        public static ReadOnlyCollection<T> Empty
        {
            get
            {
                if (empty != null)
                    return empty;

                Interlocked.CompareExchange(ref empty, new(), null);
                return empty;
            }
        }
        bool ICollection<T>.IsReadOnly
        {
            get { return true; }
        }
        bool IList.IsFixedSize
        {
            get { return true; }
        }
        bool IList.IsReadOnly
        {
            get { return true; }
        }
        private ReadOnlyCollection() { }

        public ReadOnlyCollection(T[] array)
        {
            if (array == null)
                throw new ArgumentNullException();

            Initialize(array, array.Length);
        }

        public ReadOnlyCollection(Collection<T> collection)
        {
            if (collection == null)
                throw new ArgumentNullException();

            Initialize(collection.items, collection.size);
        }

        private void Initialize(T[] items, int size)
        {
            this.items = new T [size];
            Array.Copy(items, 0, this.items, 0, size);
            this.size = size;
        }

        internal override void Grow(int desired)
        {
            throw new InvalidOperationException();
        }

        protected override void OnAdd(T item, int index)
        {
            throw new InvalidOperationException();
        }

        protected override void OnClear()
        {
            throw new InvalidOperationException();
        }

        protected override void OnInsert(T item, int index)
        {
            throw new InvalidOperationException();
        }

        protected override void OnRemove(T item, int index)
        {
            throw new InvalidOperationException();
        }

        protected override void OnSet(T item, int index)
        {
            throw new InvalidOperationException();
        }
    }
}