#region Using
using System;
using System.IO;
using System.Web;
using System.Net;
using System.Xml;
using System.Text.RegularExpressions;
using System.ComponentModel;
using BlogEngine.Core;
#endregion
namespace BlogEngine.Core.Web.HttpHandlers{
/// <summary>
/// Summary description for TrackbackHandler
/// </summary>
public class TrackbackHandler : IHttpHandler
{
#region Private fields
private static readonly Regex REGEX_HTML = new Regex(@"</?\w+((\s+\w+(\s*=\s*(?:"".*?""|'.*?'|[^'"">\s]+))?)+\s*|\s*)/?>", RegexOptions.Singleline | RegexOptions.Compiled);
private bool _SourceHasLink;
#endregion
/// <summary>
/// Enables processing of HTTP Web requests by a custom HttpHandler that
/// implements the <see cref="T:System.Web.IHttpHandler"></see> interface.
/// </summary>
/// <param name="context">An <see cref="T:System.Web.HttpContext"></see>
/// object that provides references to the intrinsic server objects
/// (for example, Request, Response, Session, and Server) used to service HTTP requests.
/// </param>
public void ProcessRequest(HttpContext context)
{
if (!BlogSettings.Instance.IsCommentsEnabled || !BlogSettings.Instance.EnableTrackBackReceive)
{
context.Response.StatusCode = 404;
context.Response.End();
}
CancelEventArgs e = new CancelEventArgs();
OnReceived(e);
if (e.Cancel)
return;
string postId = context.Request.Params["id"]; ;
string title = context.Request.Params["title"];
string excerpt = context.Request.Params["excerpt"];
string blog_name = context.Request.Params["blog_name"];
string url = string.Empty;
if (context.Request.Params["url"] != null)
url = context.Request.Params["url"].Split(',')[0];
Post post = null;
if (!string.IsNullOrEmpty(title) && !string.IsNullOrEmpty(postId) && !string.IsNullOrEmpty(blog_name) && postId.Length == 36)
{
post = Post.GetPost(new Guid(postId));
ExamineSourcePage(url, post.AbsoluteLink.ToString());
bool containsHtml = !string.IsNullOrEmpty(excerpt) && (REGEX_HTML.IsMatch(excerpt) || REGEX_HTML.IsMatch(title) || REGEX_HTML.IsMatch(blog_name));
if (post != null && IsFirstPingBack(post, url) && _SourceHasLink && !containsHtml)
{
AddComment(url, post, blog_name, title, excerpt);
OnAccepted(url);
context.Response.Write("<?xml version=\"1.0\" encoding=\"iso-8859-1\"?><response><error>0</error></response>");
context.Response.End();
}
else if (!IsFirstPingBack(post, url))
{
OnRejected(url);
context.Response.Write("<?xml version=\"1.0\" encoding=\"iso-8859-1\"?><response><error>Trackback already registered</error></response>");
context.Response.End();
}
else if (!_SourceHasLink || containsHtml)
{
OnSpammed(url);
context.Response.Write("<?xml version=\"1.0\" encoding=\"iso-8859-1\"?><response><error>The source page does not link</error></response>");
context.Response.End();
}
}
else if (post != null)
{
context.Response.Redirect(post.RelativeLink.ToString());
}
else
{
context.Response.Redirect(Utils.RelativeWebRoot);
}
}
/// <summary>
/// Insert the pingback as a comment on the post.
/// </summary>
private static void AddComment(string sourceUrl, Post post, string blogName, string title, string excerpt)
{
Comment comment = new Comment();
comment.Id = Guid.NewGuid();
comment.Author = blogName;
comment.Website = new Uri(sourceUrl);
comment.Content = title + Environment.NewLine + Environment.NewLine + excerpt;
comment.Email = "trackback";
comment.Parent = post;
comment.DateCreated = DateTime.Now;
comment.IP = HttpContext.Current.Request.UserHostAddress;
comment.IsApproved = true; //NOTE: Trackback comments are approved by default
post.AddComment(comment);
}
/// <summary>
/// Parse the HTML of the source page.
/// </summary>
private void ExamineSourcePage(string sourceUrl, string targetUrl)
{
try
{
using (WebClient client = new WebClient())
{
client.Credentials = CredentialCache.DefaultNetworkCredentials;
string html = client.DownloadString(sourceUrl);
_SourceHasLink = html.ToUpperInvariant().Contains(targetUrl.ToUpperInvariant());
}
}
catch (WebException)
{
_SourceHasLink = false;
//throw new ArgumentException("Trackback sender does not exists: " + sourceUrl, ex);
}
}
/// <summary>
/// Checks to see if the source has already pinged the target.
/// If it has, there is no reason to add it again.
/// </summary>
private static bool IsFirstPingBack(Post post, string sourceUrl)
{
foreach (Comment comment in post.Comments)
{
if (comment.Website != null && comment.Website.ToString().Equals(sourceUrl, StringComparison.OrdinalIgnoreCase))
return false;
if (comment.IP != null && comment.IP == HttpContext.Current.Request.UserHostAddress)
return false;
}
return true;
}
/// <summary>
/// Gets a value indicating whether another request can use the <see cref="T:System.Web.IHttpHandler"></see> instance.
/// </summary>
/// <value></value>
/// <returns>true if the <see cref="T:System.Web.IHttpHandler"></see> instance is reusable; otherwise, false.</returns>
public bool IsReusable
{
get { return true; }
}
#region Events
/// <summary>
/// Occurs when a hit is made to the trackback.axd handler.
/// </summary>
public static event EventHandler<CancelEventArgs> Received;
/// <summary>
/// Raises the event in a safe way
/// </summary>
protected virtual void OnReceived(CancelEventArgs e)
{
if (Received != null)
{
Received(null, e);
}
}
/// <summary>
/// Occurs when a trackback is accepted as valid and added as a comment.
/// </summary>
public static event EventHandler<EventArgs> Accepted;
/// <summary>
/// Raises the event in a safe way
/// </summary>
protected virtual void OnAccepted(string url)
{
if (Accepted != null)
{
Accepted(url, EventArgs.Empty);
}
}
/// <summary>
/// Occurs when a trackback request is rejected because the sending
/// website already made a trackback or pingback to the specific page.
/// </summary>
public static event EventHandler<EventArgs> Rejected;
/// <summary>
/// Raises the event in a safe way
/// </summary>
protected virtual void OnRejected(string url)
{
if (Rejected != null)
{
Rejected(url, EventArgs.Empty);
}
}
/// <summary>
/// Occurs when the request comes from a spammer.
/// </summary>
public static event EventHandler<EventArgs> Spammed;
/// <summary>
/// Raises the event in a safe way
/// </summary>
public static void OnSpammed(string url)
{
if (Spammed != null)
{
Spammed(url, EventArgs.Empty);
}
}
#endregion
}
}
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