﻿/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace DotPulsar.Internal;

using System.Collections.Generic;

public sealed class IdLookup<T> where T : class
{
    private T?[] _items;

    public IdLookup()
        => _items = new T[1];

    public bool IsEmpty()
    {
        lock (_items)
        {
            for (var i = 0; i < _items.Length; ++i)
            {
                if (_items[i] is not null)
                    return false;
            }

            return true;
        }
    }

    public ulong Add(T item)
    {
        lock (_items)
        {
            for (var i = 0; i < _items.Length; ++i)
            {
                if (_items[i] is not null)
                    continue;

                _items[i] = item;
                return (ulong) i;
            }

            var newArray = new T[_items.Length + 1];
            _items.CopyTo(newArray, 0);
            var id = newArray.Length - 1;
            newArray[id] = item;
            _items = newArray;
            return (ulong) id;
        }
    }

    public T? Remove(ulong id)
    {
        lock (_items)
        {
            var item = _items[(int) id];
            _items[(int) id] = null;
            return item;
        }
    }

    public T[] RemoveAll()
    {
        lock (_items)
        {
            var items = new List<T>();

            for (var i = 0; i < _items.Length; ++i)
            {
                var item = _items[i];

                if (item is not null)
                {
                    items.Add(item);
                    _items[i] = null;
                }
            }

            return items.ToArray();
        }
    }

    public T? this[ulong id]
    {
        get
        {
            lock (_items)
            {
                return _items[(int) id];
            }
        }
    }
}