using System.Collections.Generic;

namespace GFGGame
{
    public class ListUtil
    {
        /// <summary>
        /// 用来做泛型数据切换,上一条,下一条...
        /// </summary>
        /// <param name="list"></param>
        /// <param name="type"></param>
        /// <param name="currentIndex">当前处于的索引</param>
        /// <param name="newIndex">操作数据之后返回的数据的索引，也就是最新的索引</param>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static T Navigate<T>(List<T> list, NavigateType type, int currentIndex, out int newIndex) where T : new()
        {
            if (type == NavigateType.Previous)
            {
                //如果已经是最前面的一条数据,则切换到最后一条数据,形成一个切换循环
                if (currentIndex <= 0)
                {
                    currentIndex = list.Count - 1;
                    newIndex = currentIndex;
                    return list[currentIndex];
                }
            }
            else if (type == NavigateType.Next)
            {
                //如果已经是最后一条数据,则切换到第一条数据,形成一个切换循环
                if (currentIndex >= list.Count - 1)
                {
                    currentIndex = 0;
                    newIndex = currentIndex;
                    return list[currentIndex];
                }
            }
            else
            {
                newIndex = currentIndex;
                return list[currentIndex];
            }

            int previousIndex = currentIndex - 1;
            int nextIndex = currentIndex + 1;

            if (previousIndex < 0 && nextIndex >= list.Count)
            {
                newIndex = currentIndex;
                return list[currentIndex];
            }

            if (type == NavigateType.Previous && previousIndex >= 0)
            {
                newIndex = previousIndex;
                return list[previousIndex];
            }

            if (type == NavigateType.Next && nextIndex < list.Count)
            {
                newIndex = nextIndex;
                return list[nextIndex];
            }

            newIndex = currentIndex;
            return list[currentIndex];
        }

        /// <summary>
        /// 动作枚举
        /// </summary>
        public enum NavigateType
        {
            /// <summary>
            /// 不作切换动作，返回当前索引的数据
            /// </summary>
            None = 0,

            /// <summary>
            /// 上一条
            /// </summary>
            Previous = 1,

            /// <summary>
            /// 下一条
            /// </summary>
            Next = 2
        }
    }
}