using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Reflection;
using System.Web.Mvc;

namespace Common
{
    public class EnumHelper
    {
        /// <summary>
        ///  把枚举的描述和值绑定到DropDownList
        /// </summary>
        /// <param name="enumType"></param>
        /// <returns></returns>
        public static List<SelectListItem> GetCategorySelectList(Type enumType, bool addAll = true, object value = null)
        {
            List<SelectListItem> selectList = new List<SelectListItem>();
            if (addAll)
            {
                selectList.Add(value == null
                    ? new SelectListItem { Text = "--请选择--", Value = "", Selected = true }
                    : new SelectListItem { Text = "--请选择--", Value = "" });
            }

            foreach (object e in System.Enum.GetValues(enumType))
            {
                if (value != null && ((int)e) == (decimal)value)
                {
                    selectList.Add(new SelectListItem
                    {
                        Text = GetEnumDescription(e),
                        Value = ((int)e).ToString(),
                        Selected = true
                    });
                }
                else
                {
                    selectList.Add(new SelectListItem { Text = GetEnumDescription(e), Value = ((int)e).ToString() });
                }
            }

            return selectList;
        }

        /// <summary>
        ///  把枚举的描述和字面值绑定到DropDownList
        /// </summary>
        /// <param name="enumType"></param>
        /// <returns></returns>
        public static List<SelectListItem> GetCategorySelectTextList(Type enumType, bool addAll = true, object value = null)
        {
            List<SelectListItem> selectList = new List<SelectListItem>();
            if (addAll)
            {
                selectList.Add(value == null
                    ? new SelectListItem { Text = "--请选择--", Value = "", Selected = true }
                    : new SelectListItem { Text = "--请选择--", Value = "" });
            }

            foreach (object e in Enum.GetValues(enumType))
            {
                if (value != null && e.ToString() == value.ToString())
                {
                    selectList.Add(new SelectListItem
                    {
                        Text = GetEnumDescription(e),
                        Value = e.ToString(),
                        Selected = true
                    });
                }
                else
                {
                    selectList.Add(new SelectListItem { Text = GetEnumDescription(e), Value = e.ToString() });
                }
            }

            return selectList;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="strValue"></param>
        /// <returns></returns>
        public static string ConvertToE<T>(string strValue) where T : struct, IConvertible
        {
            if (!string.IsNullOrEmpty(strValue))
            {
                T t;
                return System.Enum.TryParse(strValue, true, out t) ? t.ToString() : "";
            }
            return string.Empty;
        }

        /// <summary>
        /// 将字符串转换为枚举类型
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="strValue"></param>
        /// <returns></returns>
        public static T? ConvertToEnum<T>(string strValue) where T : struct, IConvertible
        {
            T t;
            if (System.Enum.TryParse(strValue, true, out t))
            {
                return t;
            }
            return null;
        }

        /// <summary>
        /// 根据枚举字面值返回描述文件
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="strValue"></param>
        /// <returns></returns>
        public static string GetDesc<T>(object e) where T : struct, IConvertible
        {
            if (e == null)
            {
                return "";
            }
            return GetEnumDescription(e);
        }


        /// <summary>
        /// 获取枚举的描述文本
        /// </summary>
        /// <param name="e">枚举成员</param>
        /// <returns></returns>
        public static string GetEnumDescription(object e)
        {
            //获取字段信息
            System.Reflection.FieldInfo[] ms = e.GetType().GetFields();

            //Type t = e.GetType();
            foreach (System.Reflection.FieldInfo f in ms)
            {
                //判断名称是否相等
                if (f.Name != e.ToString()) continue;

                //反射出自定义属性
                foreach (Attribute attr in f.GetCustomAttributes(true))
                {
                    //类型转换找到一个Description，用Description作为成员名称
                    System.ComponentModel.DescriptionAttribute dscript = attr as System.ComponentModel.DescriptionAttribute;
                    if (dscript != null)
                        return dscript.Description;
                }
            }
            //如果没有检测到合适的注释，则用默认名称
            return e.ToString();
        }
        public static string GetEnumDesc(Enum en)
        {
            Type type = en.GetType();
            MemberInfo[] memInfo = type.GetMember(en.ToString()); if (memInfo != null && memInfo.Length > 0)
            {
                object[] attrs = memInfo[0].GetCustomAttributes(typeof(System.ComponentModel.DataAnnotations.DisplayAttribute), false); if (attrs != null && attrs.Length > 0) return ((System.ComponentModel.DataAnnotations.DisplayAttribute)attrs[0]).Name;
            }
            return en.ToString();
        }

        public static List<EnumSelectItem> GetSelectItems<T>() where T : struct
        {
            var pairs = new List<EnumSelectItem>();
            var ttype = typeof(T);
            if (!ttype.IsEnum)
            {
                throw new Exception("需传入枚举类型");
            }

            var fs = ttype.GetFields();
            var arr = Enum.GetValues(ttype);
            for (var i = 0; i < arr.Length; i++)
            {
                var obj = arr.GetValue(i);
                var val = (int)arr.GetValue(i);
                var description = GetDescription(fs, obj, val);
                pairs.Add(new EnumSelectItem
                {
                    Key = obj.ToString(),
                    Value = val,
                    Description = description
                });
            }

            return pairs.Where(w => w.Key != "None").ToList();
        }

        private static string GetDescription(FieldInfo[] fs, object obj, int val)
        {
            foreach (var tf in fs)
            {
                if (tf.FieldType == typeof(int))
                {
                    continue;
                }

                if ((int)tf.GetValue(obj) != val)
                {
                    continue;
                }

                var attr = tf.GetCustomAttribute<DescriptionAttribute>();
                if (attr != null)
                {
                    return attr.Description;
                }
                else
                {
                    return obj.ToString();
                }
            }

            return "";
        }
    }

    public class EnumSelectItem
    {
        public string Key { get; set; }

        public int Value { get; set; }

        public string Description { get; set; }
    }
}