ReferralUrlBlacklist.cs :  » Bloggers » dasBlog » newtelligence » DasBlog » Web » Core » C# / CSharp Open Source

using System;
using System.Text.RegularExpressions;

namespace newtelligence.DasBlog.Web.Core{
  /// <summary>
  /// Summary description for ContentReferralBlacklist.
  /// </summary>
  public class ReferralUrlBlacklist : IBlackList
  {
    private static bool loaded = false;
    private static Regex blackListRegex = null;
    private static string blacklist = null;
    private static object blackListLock = new object();

    public void Initialize(string newBlackList)
    {
      lock(blackListLock)
      {
        if (blacklist == null || blacklist != newBlackList)
        {
          if (newBlackList != null && newBlackList.Length > 0)
          {
            blacklist = newBlackList;
            blacklist = blacklist.Replace(";","|");
            blacklist = blacklist.Replace("+","\\+");
            blacklist = blacklist.Replace("*","\\*");
            blackListRegex = new Regex(blacklist,RegexOptions.Compiled|RegexOptions.IgnoreCase|RegexOptions.IgnorePatternWhitespace);
          }
          else
          {
            throw new NullReferenceException("blacklist string is empty");
          }
        }
      }

      loaded = true;
    }

    public Match IsBlacklisted(string url)
    {
      if (!loaded)
      {
        return null;
      }

      try
      {
        Match match = null;
        Uri urlReferrer = new Uri(url);

        // we want to remove the Query from the url as it may contain keywords that easily match
        // the black list. 
        // However, we CHECK against the stripped referrer and log the COMPLETE referral!
        string strippedReferrer = (urlReferrer != null) ? urlReferrer.Scheme + "://" + urlReferrer.Authority + urlReferrer.AbsolutePath : String.Empty;

        lock (blackListLock)
        {
          match = blackListRegex.Match(strippedReferrer);
        }

        return match;
      }
      catch (Exception ex)
      {
        throw new Exception(String.Format("An error occured trying to determine if {0} is blacklisted", url), ex.InnerException);
      }
    }

    public BlacklistUpdateState UpdateBlacklist()
    {
      return BlacklistUpdateState.None;
    }
  }
}