// ARCCheck.cs
// 
// Copyright (C) 2008,2009 Bartek Jasicki
//
// This file is part of Grubng.
//
// Grubng is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
//

/**
 * @file ARCCheck.cs
 * Provide functions for check propriety of .arc file.*/

using System;
using System.Text;

namespace grubupload
{
    
	/// <summary>
	/// Provide function for check propriety of .arc file.
	/// </summary>
    internal static class ARCCheck
    {
        
		/// <summary>
		/// Function check propriety of .arc file. Check sequence of url's, length of each entry in file and type of each url.
		/// </summary>
		/// <param name="arcfile">
		/// A <see cref="System.IO.Stream"/> object which contains arc file content
		/// </param>
		/// <param name="user">
		/// A <see cref="System.String"/> Username from .arc filename
		/// </param>
		/// <param name="filekey">
		/// A <see cref="System.String"/> Key from .arc filename
		/// </param>
		/// <param name="hashpass">
		/// A <see cref="System.String"/> Special secret pharase 
		/// </param>
		/// <returns>
		/// A <see cref="System.String"/> Array of string, element 0 - 'valid' or 'invalid' values - status of
		/// .arc file, element 1 - detailed informations about error in .arc file, element 2 - amount
		/// of links in .arc file.
		/// </returns>
        public static string[] CheckFile(System.IO.Stream arcfile, string user, string filekey, string hashpass)
        {
			byte[] HashValue, PureHash = Encoding.UTF8.GetBytes(hashpass);
			StringBuilder key = new StringBuilder();
			System.Security.Cryptography.SHA1Managed SHhash = new System.Security.Cryptography.SHA1Managed();
			HashValue = SHhash.ComputeHash(PureHash);
			foreach(byte b in HashValue) 
			{
				key.Append(String.Format("{0:x2}", b));
			}
			StringBuilder arc = new StringBuilder();
			string[] arcfields;
			int tmp;
			System.Collections.Generic.List<byte> tmp2 = new System.Collections.Generic.List<byte>();
			string[] parts;
			string path;
			string [] result = new string[3] {"valid", String.Empty, String.Empty};
			int amount = 0;
			arcfile.Position = 131;
			long urllength;
			bool valid;
            while (arcfile.Position < arcfile.Length)
            {
				while (true)
				{
					tmp = arcfile.ReadByte();
					if ((tmp > Char.MaxValue) || (tmp < Char.MinValue))
					{
						result[0] = "invalid";
						break;
					}
					if (tmp == 10)
					{
						break;
					}
					tmp2.Add(Convert.ToByte(tmp));
				}
				//Check for correct data
				if (result[0] == "invalid")
				{
					result[1] = "Invalid data send. Wrong chars in .arc file.";
					break;
				}
				arc.Append(Encoding.UTF8.GetString(tmp2.ToArray(), 0, tmp2.Count));
				tmp2.Clear();
				tmp2.TrimExcess();
				//Check url header
				if (arc.Length == 0)
				{
					result[0] = "invalid";
					result[1] = "Empty record in .arc file. Probably wrong count of chars in .arc file.";
					break;
				}
				arcfields = arc.ToString().Split(' ');
				if (arcfields.Length != 5)
				{
					result[0] = "invalid";
					result[1] = "Invalid amount of informations in url header in .arc file.";
					break;
				}
				if (String.IsNullOrEmpty(arcfields[3]))
				{
					result[0] = "invalid";
					result[1] = "No information about content type in url header in .arc file.";
					break;
				}
				valid = arcfields[0].StartsWith("http://");
				if (!valid)
				{
					result[0] = "invalid";
					result[1] = "Wrong url in .arc file. Probably wrong count of chars in .arc file.";
					break;
				}
				//Check protocol information
				arc.Remove(0, arc.Length);
				while (true)
				{
					tmp = arcfile.ReadByte();
					if (tmp == 10)
					{
						break;
					}
					tmp2.Add(Convert.ToByte(tmp));
				}
				arc.Append(Encoding.UTF8.GetString(tmp2.ToArray(), 0, tmp2.Count));
				parts = arc.ToString().Split(' ');
				if (parts.Length < 2)
				{
					result[0] = "invalid";
					result[1] = "Invalid amount of informations about HTTP protocol";
					break;
				}
				valid = parts[0].StartsWith("HTTP");
				if (!valid)
				{
					result[0] = "invalid";
					result[1] = "Invalid information about HTTP protocol version in .arc file";
					break;
				}
				//TODO: check for HTTP headers
				//TODO: check for content length
				//Move to next record
				valid = long.TryParse(arcfields[4], out urllength);
				if (valid)
				{
					urllength -= Convert.ToInt64(tmp2.Count);
				}
				else
				{
					result[0] = "invalid";
					result[1] = "Wrong record length in .arc file.";
					break;
				}
				tmp2.Clear();
				tmp2.TrimExcess();
				arcfile.Position += urllength;
				arc.Remove(0, arc.Length);
				parts = arcfields[0].Split('/');
				path = "/" + String.Join("/", parts, 3, (parts.Length - 3));
				PureHash = Encoding.UTF8.GetBytes(key.ToString() + " " + parts[2] + " " + path);
				key.Remove(0, key.Length);
				HashValue = SHhash.ComputeHash(PureHash);
				foreach(byte b in HashValue) 
				{
					key.Append(String.Format("{0:x2}", b));
				}
				amount ++;
				GC.Collect();
				GC.WaitForPendingFinalizers();
            }
			if (result[0] == "valid")
			{
				PureHash = Encoding.UTF8.GetBytes(key.ToString() + " " + user);
				key.Remove(0, key.Length);
				HashValue = SHhash.ComputeHash(PureHash);
				foreach(byte b in HashValue) 
				{
					key.Append(String.Format("{0:x2}", b));
				}
				if (key.ToString() != filekey)
				{
					result[0] = "invalid";
					result[1] = "Invalid .arc file key.";
				}
			}
			SHhash = null;
			HashValue = null;
			key = null;
			result[2] = amount.ToString();
            return result;
        }
    }
}