/Utilities/Helpers/RandomHelper.cs

using System;

using System.Collections.Generic;

using System.Security.Cryptography;

using Delta.Utilities.Datatypes;



namespace Delta.Utilities.Helpers

{

	/// <summary>

	/// Random helper, which mostly provides methods to quickly generate random

	/// values for ints, floats, bytes, Vectors, Colors, etc. and some methods

	/// for more complex cases (strings, ids, random values with factors, etc.)

	/// </summary>

	public static class RandomHelper

	{

		#region GetNewRandomGenerator (Static)

		/// <summary>

		/// Get new random generator with help of

		/// Win32Function.GetPerformanceCounter.

		/// </summary>

		/// <returns>Random</returns>

		public static Random GetNewRandomGenerator()

		{

			lastUsedRandomGenerator = new Random((int)DateTime.Now.Ticks);

			//lastUsedRandomGenerator = new Random250Algorithm();

			return lastUsedRandomGenerator;

		}

		#endregion



		#region RandomInt (Static)

		/// <summary>

		/// Gets a random int between '0' and the given (exclusive) maximum.

		/// </summary>

		/// <param name="max">The max. (exclusive) Limit</param>

		/// <returns>Int</returns>

		public static int RandomInt(int max)

		{

			if (max <= 0)

			{

				return 0;

			}



			return lastUsedRandomGenerator.Next(max);

		}



		/// <summary>

		/// Gets a random int between the given minimum and (exclusive) maximum.

		/// </summary>

		/// <param name="min">Min</param>

		/// <param name="max">Max</param>

		/// <returns>Random int</returns>

		public static int RandomInt(int min, int max)

		{

			if (max <= 0 ||

			    min > max)

			{

				return 0;

			}



			return lastUsedRandomGenerator.Next(min, max);

		}

		#endregion



		#region RandomFloat (Static)

		/// <summary>

		/// Get random float between min and max (exclusive max)

		/// </summary>

		/// <param name="rnd">Rnd</param>

		/// <param name="min">Min</param>

		/// <param name="max">Max</param>

		/// <returns>Float</returns>

		public static float RandomFloat(this Random rnd, float min, float max)

		{

			return (float)rnd.NextDouble() * (max - min) + min;

		}



		/// <summary>

		/// Get random float between min and max (exclusive max)

		/// </summary>

		/// <param name="min">Minimum</param>

		/// <param name="max">Maximum</param>

		/// <returns>Float</returns>

		public static float RandomFloat(float min, float max)

		{

			return (float)lastUsedRandomGenerator.NextDouble() * (max - min) + min;

		}

		#endregion



		#region RandomByte (Static)

		/// <summary>

		/// Get random byte between min and max (exclusive max)

		/// </summary>

		/// <param name="rnd">Rnd</param>

		/// <param name="min">Min</param>

		/// <param name="max">Max</param>

		/// <returns>Byte</returns>

		public static byte RandomByte(this Random rnd, byte min, byte max)

		{

			return (byte)(rnd.Next(min, max));

		}

		#endregion



		#region RandomVector (Static)

		/// <summary>

		/// Get random vector between min and max for all components.

		/// </summary>

		/// <param name="min">Minimum</param>

		/// <param name="max">Maximum</param>

		/// <returns>Vector</returns>

		public static Vector RandomVector(float min, float max)

		{

			return new Vector(RandomFloat(min, max), RandomFloat(min, max),

				RandomFloat(min, max));

		}



		/// <summary>

		/// Get random vector between min and max for each component separated.

		/// </summary>

		/// <param name="minX">Minimum X</param>

		/// <param name="maxX">Maximum X</param>

		/// <param name="minY">Minimum Y</param>

		/// <param name="maxY">Maximum Y</param>

		/// <param name="minZ">Minimum Z</param>

		/// <param name="maxZ">Maximum Z</param>

		/// <returns>Vector</returns>

		public static Vector RandomVector(float minX, float maxX,

			float minY, float maxY, float minZ, float maxZ)

		{

			return new Vector(RandomFloat(minX, maxX), RandomFloat(minY, maxY),

				RandomFloat(minZ, maxZ));

		}

		#endregion



		#region CreateRandomBytes (Static)

		/// <summary>

		/// Creates random byte array with given length. Used to generate private

		/// keys and crypto IV values.

		/// </summary>

		/// <param name="length">Length of the byte array we return</param>

		/// <returns>Byte array with random byte data</returns>

		public static byte[] CreateRandomBytes(int length)

		{

			byte[] random = new byte[length];

			RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();

			// The array is now filled with cryptographically strong random bytes.

			rng.GetBytes(random);

			return random;

		}

		#endregion



		#region CreateRandomString (Static)

		/// <summary>

		/// Create random string, helper for GetFreeUnusedSerial()

		/// and RequestActivationKey(), use SerialLength or

		/// ActivationKeyLength as lengths!

		/// </summary>

		public static string CreateRandomString(int length)

		{

			// RNGCryptoServiceProvider is an implementation of a random number

			// generator. It will produce strong random numbers, so this is very

			// useful for us ^^

			byte[] random = new byte[length];

			RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();

			// The array is now filled with cryptographically strong random bytes.

			rng.GetBytes(random);



			string s = "";

			for (int i = 0; i < length; i++)

			{

				// We assume Win32Function.GetPerformanceCounter()

				// will change VERY often, so we never get the same values!

				Random rnd = new Random(i + (int)DateTime.Now.Ticks);

				int type = (rnd.Next(36 * 7) + random[i]) % (10 + 26);

				char charType = (char)(type < 10

				                       	? '0' + type

				                       	: 'A' + (type - 10));

				// Update 2004-10-21: Don't allow any 0 (Zero) or O (Oh) symbols

				if (charType == '0')

				{

					// Replace 0 with random number from 1 to 9

					charType = (char)('1' + rnd.Next(9));

				}

				else if (charType == 'O')

				{

					// Replace O with random letter from A to A+10

					charType = (char)('A' + rnd.Next(10));

				}

				s += charType;



				// Do some random execution to make next random value more random

				int rndExecutions = rnd.Next(200);

				for (int j = 0; j < rndExecutions; j++)

				{

					type++;

				}

			}

			return s;

		}

		#endregion



		#region CreateRandomStringNoNumbers (Static)

		/// <summary>

		/// Create random string, helper for GetFreeUnusedSerial()

		/// and RequestActivationKey(), use SerialLength or

		/// ActivationKeyLength as lengths!

		/// </summary>

		public static string CreateRandomStringNoNumbers(int length)

		{

			// RNGCryptoServiceProvider is an implementation of a random number

			// generator. It will produce strong random numbers, so this is very

			// useful for us ^^

			byte[] random = new byte[length];

			RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();

			// The array is now filled with cryptographically strong random bytes.

			rng.GetBytes(random);



			string s = "";

			for (int i = 0; i < length; i++)

			{

				// We assume Win32Function.GetPerformanceCounter()

				// will change VERY often, so we never get the same values!

				Random rnd = new Random(i + (int)DateTime.Now.Ticks);

				int type = (rnd.Next(26 * 7) + random[i]) % (26);

				char charType = (char)('A' + type);

				s += charType;



				// Do some random execution to make next random value more random

				int rndExecutions = rnd.Next(200);

				for (int j = 0; j < rndExecutions; j++)

				{

					type++;

				}

			}

			return s;

		}

		#endregion



		#region RandomizeIds (Static)

		/// <summary>

		/// Randomize ids

		/// </summary>

		/// <param name="inputIds">Input ids</param>

		/// <returns>List</returns>

		public static List<int> RandomizeIds(List<int> inputIds)

		{

			// Just go through the whole list and swap entries randomly (good enough

			// approach here, will not be 100% even, but looks pretty random).

			for (int num = inputIds.Count - 1; num > 0; num--)

			{

				int newIndex = RandomInt(num);

				// Swap the values

				int swapId = inputIds[newIndex];

				inputIds[newIndex] = inputIds[num];

				inputIds[num] = swapId;

			}



			// Return the results

			return inputIds;

		}



		/// <summary>

		/// Randomize ids

		/// </summary>

		/// <param name="inputIds">Input ids</param>

		/// <param name="maxCount">Maximum count</param>

		/// <returns>List</returns>

		public static List<int> RandomizeIds(List<int> inputIds,

			int maxCount)

		{

			// Just go through the whole list and swap entries randomly (good enough

			// approach here, will not be 100% even, but looks pretty random).

			for (int num = maxCount - 1; num > 0; num--)

			{

				int newIndex = RandomInt(num);

				// Swap the values

				int swapId = inputIds[newIndex];

				inputIds[newIndex] = inputIds[num];

				inputIds[num] = swapId;

			}



			// Return the results

			return inputIds;

		}

		#endregion



		#region GetRandomValueWithFactors (Static)

		/// <summary>

		/// Very nice function to calc random value with help of

		/// factors, e.g. when calling with { 0.1f, 0.1f, 2.0f }

		/// we will most likly (in >99% of all cases) get 2 as

		/// result and not 0 or 1!

		/// </summary>

		public static int GetRandomValueWithFactors(List<int> factorArray)

		{

			if (factorArray == null ||

			    factorArray.Count == 0)

			{

				return 0;

			}



			// Count all factor values

			int allValuesTogether = 0;

			for (int i = 0; i < factorArray.Count; i++)

			{

				allValuesTogether += factorArray[i];

			}



			// Now calc random value from 0 to allValuesTogehter

			int rndValue = RandomInt(allValuesTogether);



			// Now all we have to do is to check out to which entry

			// the rndValue belongs to

			int currentValue = 0;

			for (int i = 0; i < factorArray.Count; i++)

			{

				if (rndValue >= currentValue &&

				    rndValue < currentValue + factorArray[i])

				{

					return i;

				}

				currentValue += factorArray[i];

			}



			return 0;

		}

		#endregion



		#region RandomizeList (Static)

		/// <summary>

		/// Randomize list

		/// </summary>

		/// <param name="list">List</param>

		/// <param name="maxCount">Maximum count</param>

		/// <returns>List</returns>

		public static List<ListType> RandomizeList<ListType>(

			List<ListType> list, int maxCount)

		{

			List<ListType> ret = new List<ListType>();

			int maximum = 0;

			for (int i = list.Count - 1; i > 0; i--)

			{

				int swapIndex = RandomInt(i + 1);

				if (swapIndex != i)

				{

					ListType tmp = list[swapIndex];

					list[swapIndex] = list[i];

					list[i] = tmp;

				}

			}



			if (maxCount > list.Count)

			{

				maximum = list.Count;

			}

			else

			{

				maximum = maxCount;

			}



			for (int j = 0; j < maximum; j++)

			{

				ret.Add(list[j]);

			}



			return ret;

		}

		#endregion



		#region Private



		#region lastUsedRandomGenerator (Private)

		/// <summary>

		/// Last used random generator

		/// </summary>

		private static Random lastUsedRandomGenerator = GetNewRandomGenerator();

		#endregion



		#endregion

	}

}