// MIT license
// Copyright 2005-2008 Ken Egozi
// 
// 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;
using System.Collections.Generic;
using System.Text;
using System.Security.Cryptography;
using System.Collections;

namespace KenEgozi.CryptographicServices
{
	public static class Hashing
	{
		private static Hashtable hashAlgorithms = Hashtable.Synchronized(new Hashtable());
		
		/// <summary>
		/// Hashing a given string with SHA2.
		/// </summary>
		/// <param name="data">Data to hash</param>
		/// <returns>Hashed data</returns>
		public static string HashData(string data)
		{
			return HashData(data, HashType.SHA256);
		}
		
		/// <summary>
		/// Hashing a given string with any of the supported hash algorithms.
		/// </summary>
		/// <param name="data">Data to hash</param>
		/// <param name="hashType">Hashing algorithm to use</param>
		/// <returns>Hashed data</returns>
		public static string HashData(string data, HashType hashType)
		{
			HashAlgorithm hash = GetHash(hashType);
			byte[] bytes = (new UnicodeEncoding()).GetBytes(data);
			byte[] hashed = hash.ComputeHash(bytes);
			StringBuilder sb = new StringBuilder(64);
			foreach (byte b in hashed)
				sb.AppendFormat("{0:x2}", b);
			return sb.ToString();
		}

		private static HashAlgorithm GetHash(HashType hashType)
		{
			if (!hashAlgorithms.ContainsKey(hashType))
				hashAlgorithms.Add(hashType, CreateaHashAlgorithm(hashType));
			return hashAlgorithms[hashType] as HashAlgorithm;
		}

		private static HashAlgorithm CreateaHashAlgorithm(HashType hashType)
		{
			switch (hashType)
			{
				case HashType.MD5:
					return new MD5CryptoServiceProvider();
				case HashType.SHA1:
					return new SHA1Managed();
				case HashType.SHA256:
					return new SHA256Managed();
				case HashType.SHA384:
					return new SHA384Managed();
				case HashType.SHA512:
					return new SHA512Managed();
				default:
					throw new NotImplementedException();
			}
		}

	}

	public enum HashType
	{
		MD5,
		SHA1,
		SHA256,
		SHA384,
		SHA512
	}

}