using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

public static class EnumExtensions
{
	private static void CheckIsEnum<T>(bool withFlags)
	{
		if (!typeof(T).IsEnum)
			throw new ArgumentException(string.Format("Type '{0}' is not an enum", typeof(T).FullName));
		if (withFlags && !Attribute.IsDefined(typeof(T), typeof(FlagsAttribute)))
			throw new ArgumentException(string.Format("Type '{0}' doesn't have the 'Flags' attribute", typeof(T).FullName));
	}

	public static bool HasFlag<T>(this T value, T flag) where T : struct, IConvertible
	{
		CheckIsEnum<T>(true);
		long lValue = Convert.ToInt64(value);
		long lFlag = Convert.ToInt64(flag);

		return (lValue & lFlag) != 0;
	}

	public static IEnumerable<T> GetFlags<T>(this T value) where T : struct, IConvertible
	{
		CheckIsEnum<T>(true);
		foreach(T flag in Enum.GetValues(typeof(T)).Cast<T>())
		{
			if(value.HasFlag(flag))
				yield return flag;
		}
	}

	public static T SetFlags<T>(this T value, T flags, bool on) where T : struct, IConvertible
	{
		CheckIsEnum<T>(true);
		long lValue = Convert.ToInt64(value);
		long lFlag = Convert.ToInt64(flags);
		if (on)
			lValue |= lFlag;
		else
			lValue &= (~lFlag);
		
		return (T)Enum.ToObject(typeof(T), lValue);
	}

	public static T SetFlags<T>(this T value, T flags) where T : struct, IConvertible
	{
		return value.SetFlags(flags, true);
	}

	public static T ClearFlags<T>(this T value, T flags) where T : struct, IConvertible
	{
		return value.SetFlags(flags, false);
	}

	public static T CombineFlags<T>(this IEnumerable<T> flags) where T : struct, IConvertible
	{
		CheckIsEnum<T>(true);
		long lValue = 0;
		foreach (T flag in flags)
		{
			long lFlag = Convert.ToInt64(flag);
			lValue |= lFlag;
		}

		return (T)Enum.ToObject(typeof(T), lValue);
	}
}