using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Reflection;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Threading;

/// <summary>The EnumExtensions class</summary>
/// <created author="laurentiu.macovei" date="Thu, 10 Mar 2011 01:08:46 GMT"/>
public static class EnumExtensions
{

	/// <summary>The EnumStorage class</summary>
	/// <created author="laurentiu.macovei" date="Thu, 10 Mar 2011 01:08:46 GMT"/>
	private class EnumStorage<T>
	{
		public static readonly Dictionary<int, Dictionary<T, string>> Description = new Dictionary<int, Dictionary<T, string>>();
	}
	/// <summary>
	/// Returns the localized value of the DisplayAttribute or DescriptionAttribute or the enum.ToString() 
	/// </summary>
	/// <param name="enum">The enum for which to return </param>
	/// <remarks>
	/// You need to decorate your enum with attributes like these:
	/// [Display(Description = "MyResourceName", ResourceType = typeof(MyResourceTypeName))]
	/// or
	/// [Description("My custom description text - not localizable")]
	/// 
	/// Please NOTE that the value is cached per culture info and enum value for faster subsequent access.
	/// </remarks>
	/// <created author="laurentiu.macovei" date="Thu, 10 Mar 2011 01:08:46 GMT"/>
	[DebuggerStepThrough]
	public static string AsString<T>(this T @enum) //ext method
		where T : struct, IComparable, IFormattable, IConvertible
	{
		string result;
		Dictionary<T, string> dic;
		var cultureHash = Thread.CurrentThread.CurrentUICulture.GetHashCode();
		if (!EnumStorage<T>.Description.TryGetValue(cultureHash, out dic))
		{
			dic = new Dictionary<T, string>();
			EnumStorage<T>.Description[cultureHash] = dic;
		}
		if (dic.TryGetValue(@enum, out result))
			return result;
		if (@enum is int)
			return @enum.ToString();
		var type = @enum.GetType();
		MemberInfo[] memInfo = type.GetMember(@enum.ToString());

		if (memInfo != null && memInfo.Length > 0)
		{

			object[] attrs = memInfo[0].GetCustomAttributes(typeof(DisplayAttribute), false);
			if (attrs != null && attrs.Length > 0)
				result = ((DisplayAttribute)attrs[0]).GetDescription();
			else
			{
				attrs = memInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);

				if (attrs != null && attrs.Length > 0)
					result = ((DescriptionAttribute)attrs[0]).Description;

			}
		}
		if (result == null)
			result = @enum.ToString();
		dic[@enum] = result;
		return result;
	}
}