#region
/* -----------------------------------------------------------------------
 * <copyright file="BlockExtensions.cs" company="GRNet">
 * 
 * Copyright 2011-2012 GRNET S.A. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 *   1. Redistributions of source code must retain the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer in the documentation and/or other materials
 *      provided with the distribution.
 *
 *
 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and
 * documentation are those of the authors and should not be
 * interpreted as representing official policies, either expressed
 * or implied, of GRNET S.A.
 * </copyright>
 * -----------------------------------------------------------------------
 */
#endregion
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.Contracts;
using System.Linq;
using System.Reflection;
using System.Security.Cryptography;
using System.Text;
using System.IO;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Pithos.Network;
using log4net;

namespace Pithos.Core.Agents
{
    static class BlockExtensions
    {

        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        public static int Read(this FileInfo fileInfo,byte[] buffer,long offset,int count)
        {
            if (offset < 0)
                throw new ArgumentOutOfRangeException("offset", offset, "The file offset can't be negative");
            Contract.EndContractBlock();
            //Open the stream only long enough to read a block
            using (var stream = fileInfo.OpenRead())
            {
                stream.Seek(offset, SeekOrigin.Begin);
                return  stream.Read(buffer, 0, count);                
            }
        }

       public static string CalculateHash(this FileSystemInfo info,int blockSize,string algorithm)
        {
            if (info==null)
                throw new ArgumentNullException("info");
            if (String.IsNullOrWhiteSpace(info.FullName))
                throw new ArgumentException("info");
            if (blockSize<=0)
                throw new ArgumentOutOfRangeException("blockSize",blockSize,"blockSize must be greater than 0");
            if (String.IsNullOrWhiteSpace(algorithm))
                throw new ArgumentNullException("algorithm");
            Contract.EndContractBlock();
           info.Refresh();
           //The hash for directories is an empty string
           if (info is DirectoryInfo)
                return String.Empty;
           //The hash for non-existent files is an empty string
           if (!info.Exists)
               return String.Empty;

           return Signature.CalculateTreeHash(info.FullName, blockSize, algorithm).TopHash.ToHashString();

        }

       /// <summary>
       ///Calculates a simple hash for an entire file
       /// </summary>
       /// <param name="info">The file to hash</param>
       /// <param name="hasher">The hash algorithm to use</param>
       /// <returns>A hash value for the entire file. An empty string if the file does not exist.</returns>
       public static string ComputeShortHash(this FileInfo info, HashAlgorithm hasher,IStatusNotification notification)
       {
           if(info == null)
               throw new ArgumentNullException("info");
           if(hasher== null)
               throw new ArgumentNullException("hasher");
           Contract.EndContractBlock();
           info.Refresh();
           if (!info.Exists)
               return String.Empty;

           if (Log.IsDebugEnabled)
                Log.DebugFormat("Short Hashing [{0}] ",info.FullName);

           var progress = new StatusNotification("");

           using (var stream = new FileStream(info.FullName,FileMode.Open, FileAccess.Read, FileShare.Read,65536))
           {
               var buffer = new byte[65536];
               int counter=0;
               int bytesRead;
               do
               {
                   bytesRead = stream.Read(buffer, 0, 32768);
                   if (bytesRead > 0)
                   {
                       hasher.TransformBlock(buffer, 0, bytesRead, null, 0);
                   }
                   counter++;
                   if (counter % 100 == 0)
                   {
                       progress.Title = String.Format("Hashing {0:p} of {1}", stream.Position*1.0/stream.Length,
                                                      info.Name);
                       notification.Notify(progress);
                   }
               } while (bytesRead > 0);
               hasher.TransformFinalBlock(buffer, 0, 0);
               var hash = hasher.Hash;

               progress.Title = String.Format("Hashed {0} ", info.Name);
               notification.Notify(progress);

               var hashString = hash.ToHashString();

               return hashString;
           }
       }

        public static string ComputeShortHash(this FileInfo info,IStatusNotification notification)
       {
           if(info == null)
               throw new ArgumentNullException("info");
            Contract.EndContractBlock();

           using (var hasher=HashAlgorithm.Create("md5"))
           {               
               return ComputeShortHash(info,hasher,notification);
           }
       }

    }
}