using System;

using System.Linq;

using System.Numerics;

​

public class Program

{

    public static void Main()

    {

        //var permission = new Permission<Policy>();

        var permission = (Permission<Policy>)0;

        Console.WriteLine("所有權限: {0}", permission.AllValue);

        Console.WriteLine("當前權限: {0} ({1})", permission, permission.Value);

        Console.WriteLine("加入權限 {0}...", Policy.Create);

        permission.Add(Policy.Create);

        Console.WriteLine("當前權限: {0} ({1})", permission, (BigInteger)permission);

        Console.WriteLine("加入權限 {0}...", Policy.Read);

        permission.Add(Policy.Read);

        Console.WriteLine("當前權限: {0} ({1})", permission, permission.Value);

        Console.WriteLine("是否含權限 {0}: {1}", Policy.Read, permission.Contains(Policy.Read));

        Console.WriteLine("移除權限 {0}...", Policy.Read);

        permission.Remove(Policy.Read);

        Console.WriteLine("當前權限: {0} ({1})", permission, permission.Value);

        Console.WriteLine("是否含權限 {0}: {1}", Policy.Read, permission.Contains(Policy.Read));

        Console.WriteLine();

        var permissionA = new Permission<Policy>(Policy.Create);

        var permissionB = new Permission<Policy>(Policy.Read);

        var permissionC = permissionA + permissionB;

        var permissionD = permissionC - permissionB;

        Console.WriteLine("permissionC: {0} ({1})", permissionC, permissionC.Value);

        Console.WriteLine("permissionD: {0} ({1})", permissionD, permissionD.Value);

    }

}

​

enum Policy

{

    Create,

    Read

}

​

public class Permission<T>

    where T : Enum

{

    public BigInteger AllValue

    {

        get;

        private set;

    }

​

    public BigInteger Value

    {

        get;

        private set;

    }

​

    public T[] Policies

    {

        get

        {

            return Enum.GetValues(typeof(T)).OfType<T>().Where(Contains).ToArray();

        }

    }

​

    public Permission(): this(0)

    {

    }

​

    public Permission(params T[] policies): this(ConvertToValue(policies))

    {

    }

​

    public Permission(int value): this((BigInteger)value)

    {

    }

​

    public Permission(BigInteger value)

    {

        Init(value);

    }

​

    private static BigInteger ConvertToValue(params T[] policies)

    {

        return policies.Aggregate((BigInteger)0, (total, next) => total | (BigInteger)Math.Pow(2, (int)Enum.Parse(typeof(T), next.ToString())));

    }

​

    public void Init(BigInteger value)

    {

        this.Value = value;

        this.AllValue = ConvertToValue(Enum.GetValues(typeof(T)).OfType<T>().ToArray());

    }

​

    public void Add(T policy)

    {

        this.Value = this.Value | ConvertToValue(policy);

    }

    public void Add(Permission<T> permission)

    {

        this.Value = (this + permission).Value;

    }

​

    public void Remove(T policy)

    {

        this.Value &= this.AllValue ^ ConvertToValue(policy);

    }

    public void Remove(Permission<T> permission)

    {

        this.Value = (this - permission).Value;

    }

​

    public bool Contains(T policy)

    {

        var value = ConvertToValue(policy);

        return (this.Value & value) == value;

    }

​

    public static implicit operator BigInteger(Permission<T> permission)

    {

        return permission.Value;

    }

​

    public static implicit operator Permission<T>(BigInteger value)

    {

        return new Permission<T>(value);

    }

​

    public static implicit operator int (Permission<T> permission)

    {

        return (int)permission.Value;

    }

​

    public static implicit operator Permission<T>(int value)

    {

        return new Permission<T>(value);

    }

​

    public static Permission<T> operator +(Permission<T> permissionA, Permission<T> permissionB)

    {

        return permissionA.Value | permissionB.Value;

    }

​

    public static Permission<T> operator -(Permission<T> permissionA, Permission<T> permissionB)

    {

        return permissionA.Value & permissionA.AllValue ^ permissionB.Value;

    }

​

    public override string ToString()

    {

        return string.Join(',', this.Policies);

    }

}