using System;

namespace Funique
{
    /// <summary>
    /// Enum cycle utility class <br />
    /// This can only use for default int enum type <br />
    /// ------------------------------------------------ <br />
    /// 列舉循環功能類 <br />
    /// 這只能用於預設正整數 Key 的列舉
    /// </summary>
    /// <typeparam name="T">Enum Type</typeparam>
    public class EnumCycle<T> where T : Enum
    {
        /// <summary>
        /// Next enum value <br />
        /// ------------------------------------------------ <br />
        /// 下一個列舉值
        /// </summary>
        /// <param name="v"></param>
        /// <returns></returns>
        public int Next(int v)
        {
            v++;
            if (v >= Enum.GetNames(typeof(T)).Length) v = 0;
            return v;
        }
        /// <summary>
        /// <inheritdoc cref="Next"/>
        /// </summary>
        public T Next(T v)
        {
            return (T)Enum.ToObject(typeof(T), Next((int)(object)v));
        }
        /// <summary>
        /// Last enum value <br />
        /// ------------------------------------------------ <br />
        /// 上一個列舉值
        /// </summary>
        /// <param name="v"></param>
        /// <returns></returns>
        public int Last(int v)
        {
            v--;
            if (v <= -1) v = Enum.GetNames(typeof(T)).Length - 1;
            return v;
        }
        /// <summary>
        /// <inheritdoc cref="Last"/>
        /// </summary>
        public T Last(T v)
        {
            return (T)Enum.ToObject(typeof(T), Last((int)(object)v));
        }
    }
}