// -----------------------------------------------------------------------
// <copyright file="FileInfoExtensions.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
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//      disclaimer.
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using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Linq;
using System.Text;
using System.IO;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Pithos.Network;

namespace Pithos.Core.Agents
{
    static class BlockExtensions
    {
        

        public static int Read(this FileInfo fileInfo,byte[] buffer,int offset,int count)
        {            
            //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();

           //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;

           var fileInfo = (FileInfo)info;
           if (fileInfo.Length <= blockSize)
                return Signature.CalculateMD5(info.FullName);
            else
                return Signature.CalculateTreeHash(info.FullName, blockSize, algorithm).TopHash.ToHashString();

        }
    }
}