#region Copyright & License Information
/*
 * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation. For more information,
 * see COPYING.
 */
#endregion

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

namespace OpenRA.Primitives
{
	static class BitAllocator<T> where T : struct
	{
		static int nextVal = 1;
		static Cache<string, int> bits = new Cache<string, int>(_ => Allocate());

		static int Allocate()
		{
			if (nextVal == 0)
				throw new InvalidOperationException(
					"Too many values in BitAllocator<{0}>".F(typeof(T).Name));

			var val = nextVal;
			nextVal <<= 1;
			return val;
		}

		public static int GetValue(string[] val)
		{
			return val.Select(a => bits[a]).Aggregate(0, (a, b) => a | b);
		}

		public static IEnumerable<string> GetStrings(int val)
		{
			for (var i = 0; i < 32; i++)
			{
				var x = 1 << i;
				if ((val & x) != 0)
					yield return bits.Single(a => a.Value == x).Key;
			}
		}
	}

	public struct Bits<T> : IEquatable<Bits<T>> where T : struct
	{
		public int Value;

		public Bits(string[] val) { Value = BitAllocator<T>.GetValue(val); }
		public Bits(Bits<T> other) { Value = other.Value; }

		public override string ToString()
		{
			return BitAllocator<T>.GetStrings(Value).JoinWith(",");
		}

		public static bool operator ==(Bits<T> me, Bits<T> other) { return me.Value == other.Value; }
		public static bool operator !=(Bits<T> me, Bits<T> other) { return !(me == other); }

		public bool Equals(Bits<T> other) { return other == this; }
		public override bool Equals(object obj) { return obj is Bits<T> && Equals((Bits<T>)obj); }
		public override int GetHashCode() { return Value.GetHashCode(); }
	}
}
