using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;

namespace Transmission.SDK
{
    public class EnumHelper
    {
        /// <summary>
        /// 获取变量名称
        /// </summary>
        /// <param name="exp">变量</param>
        /// <returns></returns>
        public static string GetVarName(Expression<Func<string, string>> exp)
        {
            return ((MemberExpression)exp.Body).Member.Name;
        }

        /// <summary>        
        /// 获取枚举项描述信息 例如GetEnumDesc(Days.Sunday)
        /// </summary>        
        /// <param name="en">枚举项 如Days.Sunday</param>        
        /// <returns></returns>        
        public static string GetEnumDesc(System.Enum en)
        {
            Type type = en.GetType();
            MemberInfo[] memInfo = type.GetMember(en.ToString());
            if (memInfo != null && memInfo.Length > 0)
            {
                object[] attrs = memInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);
                if (attrs != null && attrs.Length > 0)
                    return ((DescriptionAttribute)attrs[0]).Description;
            }
            return en.ToString();
        }

        ///<summary>
        /// EnumToNameValueCollection
        ///</summary>
        ///<param name="enumType">Type,该参数的格式为typeof(需要读的枚举类型)</param>
        ///<returns>键值对</returns>
        public static NameValueCollection EnumToNVC(Type enumType)
        {
            NameValueCollection nvc = new NameValueCollection();
            Type typeDescription = typeof(DescriptionAttribute);
            FieldInfo[] fields = enumType.GetFields();
            string strText = string.Empty;
            string strValue = string.Empty;
            foreach (FieldInfo field in fields)
            {
                if (field.FieldType.IsEnum)
                {
                    strValue = ((int)enumType.InvokeMember(field.Name, BindingFlags.GetField, null, null, null)).ToString();
                    object[] arr = field.GetCustomAttributes(typeDescription, true);
                    if (arr.Length > 0)
                    {
                        DescriptionAttribute aa = (DescriptionAttribute)arr[0];
                        strText = aa.Description;
                    }
                    else
                    {
                        strText = field.Name;
                    }
                    nvc.Add(strValue, strText);
                }
            }
            return nvc;
        }

        ///<summary>
        /// EnumToDictionary
        ///</summary>
        ///<param name="enumType"></param>
        ///<returns>Dictionary枚举项，描述</returns>
        public static Dictionary<string, string> EnumToDictionary(Type enumType)
        {
            Dictionary<string, string> dic = new Dictionary<string, string>();
            FieldInfo[] fieldinfos = enumType.GetFields();
            foreach (FieldInfo field in fieldinfos)
            {
                if (field.FieldType.IsEnum)
                {
                    Object[] objs = field.GetCustomAttributes(typeof(DescriptionAttribute), false);
                    dic.Add(field.Name, ((DescriptionAttribute)objs[0]).Description);
                }
            }
            return dic;
        }
    }
}