//
// System.Random.cs
//
// Authors:
//   Bob Smith (bob@thestuff.net)
//   Ben Maurer (bmaurer@users.sourceforge.net)
//
// (C) 2001 Bob Smith.  http://www.thestuff.net
// (C) 2003 Ben Maurer
//

//
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System.Runtime.InteropServices;

namespace System
{
	[Serializable]
#if NET_2_0
	[ComVisible (true)]
#endif
	public class Random
	{
		const int MBIG = int.MaxValue;
		const int MSEED = 161803398;
		const int MZ = 0;

		int inext, inextp;
		int [] SeedArray = new int [56];
		
		public Random ()
			: this (Environment.TickCount)
		{
		}

		public Random (int Seed)
		{
			int ii;
			int mj, mk;

			// Numerical Recipes in C online @ http://www.library.cornell.edu/nr/bookcpdf/c7-1.pdf
			mj = MSEED - Math.Abs (Seed);
			SeedArray [55] = mj;
			mk = 1;
			for (int i = 1; i < 55; i++) {  //  [1, 55] is special (Knuth)
				ii = (21 * i) % 55;
				SeedArray [ii] = mk;
				mk = mj - mk;
				if (mk < 0)
					mk += MBIG;
				mj = SeedArray [ii];
			}
			for (int k = 1; k < 5; k++) {
				for (int i = 1; i < 56; i++) {
					SeedArray [i] -= SeedArray [1 + (i + 30) % 55];
					if (SeedArray [i] < 0)
						SeedArray [i] += MBIG;
				}
			}
			inext = 0;
			inextp = 31;
		}

		protected virtual double Sample ()
		{
			int retVal;

			if (++inext  >= 56) inext  = 1;
			if (++inextp >= 56) inextp = 1;

			retVal = SeedArray [inext] - SeedArray [inextp];

			if (retVal < 0)
				retVal += MBIG;

			SeedArray [inext] = retVal;

			return retVal * (1.0 / MBIG);
		}

		public virtual int Next ()
		{
			return (int)(Sample () * int.MaxValue);
		}

		public virtual int Next (int maxValue)
		{
			if (maxValue < 0)
				throw new ArgumentOutOfRangeException(Locale.GetText (
					"Max value is less than min value."));

			return (int)(Sample () * maxValue);
		}

		public virtual int Next (int minValue, int maxValue)
		{
			if (minValue > maxValue)
				throw new ArgumentOutOfRangeException (Locale.GetText (
					"Min value is greater than max value."));

			// special case: a difference of one (or less) will always return the minimum
			// e.g. -1,-1 or -1,0 will always return -1
			uint diff = (uint) (maxValue - minValue);
			if (diff <= 1)
				return minValue;

			return (int)(Sample () * diff) + minValue;
		}

		public virtual void NextBytes (byte [] buffer)
		{
			if (buffer == null)
				throw new ArgumentNullException ("buffer");

			for (int i = 0; i < buffer.Length; i++) {
				buffer [i] = (byte)(Sample () * (byte.MaxValue + 1)); 
			}
		}

		public virtual double NextDouble ()
		{
			return this.Sample ();
		}
	}
}