Zero/ZeroLevel/Services/MemoryPools/Collections/Linq/Union.Enumerable.cs

using System.Collections.Generic;
using MemoryPools.Collections.Specialized;

namespace MemoryPools.Collections.Linq
{
    internal class UnionExprEnumerable<T> : IPoolingEnumerable<T>
    {
        private int _count;
        private PoolingDictionary<T, int> _src;

        public UnionExprEnumerable<T> Init(PoolingDictionary<T, int> src)
        {
            _src = src;
            _count = 0;
            return this;
        }

        public IPoolingEnumerator<T> GetEnumerator()
        {
            _count++;
            return Pool<UnionExprEnumerator>.Get().Init(this, _src.GetEnumerator());
        }

        private void Dispose()
        {
            if(_count == 0) return;
            _count--;
            if (_count == 0)
            {
                _src?.Dispose();
                Pool<PoolingDictionary<T, int>>.Return(_src);
                _src = default;

                Pool<UnionExprEnumerable<T>>.Return(this);
            }
        }
        internal class UnionExprEnumerator : IPoolingEnumerator<T>
        {
            private UnionExprEnumerable<T> _parent;
            private IPoolingEnumerator<KeyValuePair<T, int>> _src;
            
            public UnionExprEnumerator Init(UnionExprEnumerable<T> parent, IPoolingEnumerator<KeyValuePair<T, int>> src)
            {
                _src = src;
                _parent = parent;
                return this;
            }

            public bool MoveNext() => _src.MoveNext();

            public void Reset() => _src.Reset();

            object IPoolingEnumerator.Current => Current;

            public T Current => _src.Current.Key;

            public void Dispose()
            {
                _src?.Dispose();
                _src = null;
                
                _parent?.Dispose();
                _parent = default;
                
                Pool<UnionExprEnumerator>.Return(this);
            }
        }
        IPoolingEnumerator IPoolingEnumerable.GetEnumerator() => GetEnumerator();
    }
}