using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace IteratorPattern
{
    // 抽象聚合类
    public interface IListCollection
    {
        Iterator GetIterator();
    }

    // 迭代器抽象类
    public interface Iterator
    {
        bool MoveNext();
        Object GetCurrent();
        void Next();
        void Reset();
    }

    // 具体聚合类
    public class ConcreteList : IListCollection
    {
        readonly string[] _collection;
        public ConcreteList()
        {
            _collection = new string[] { "A", "B", "C", "D" };
        }

        public Iterator GetIterator()
        {
            return new ConcreteIterator(this);
        }

        public int Length
        {
            get { return _collection.Length; }
        }

        public string GetElement(int index)
        {
            return _collection[index];
        }
    }

    // 具体迭代器类
    public class ConcreteIterator : Iterator
    {
        // 迭代器要集合对象进行遍历操作，自然就需要引用集合对象
        private ConcreteList _list;
        private int _index;

        public ConcreteIterator(ConcreteList list)
        {
            _list = list;
            _index = 0;
        }

        public bool MoveNext()
        {
            if (_index < _list.Length)
            {
                return true;
            }
            return false;
        }

        public Object GetCurrent()
        {
            return _list.GetElement(_index);
        }

        public void Reset()
        {
            _index = 0;
        }

        public void Next()
        {
            if (_index < _list.Length)
            {
                _index++;
            }

        }
    }
    
}