/// <summary>
/// Gets the description of the given URL in a background thread.
/// </summary>
/// <param name="url">URL to grab.</param>
/// <returns>The description from the website's meta tag.</returns>
public Task <UrlResponse> AsyncGetDescription(string url)
{
return(Task.Run(
async delegate
{
UrlResponse response = new UrlResponse();
try
{
long totalBytes;
// Get the length of the file we are going to download.
// Ignore if its going to be too big.
//
// The HEAD method is the same thing as a GET request... the only
// difference being the content does not get returned.
//
// Check the content length first so we don't download a massive file.
{
HttpRequestMessage headRequest = new HttpRequestMessage(HttpMethod.Head, url);
HttpResponseMessage headResponse = await this.httpClient.SendAsync(headRequest);
// Set to max value if there is no content length. We'll assume the file is too big
// if its trying to hide this.
totalBytes = headResponse.Content.Headers.ContentLength ?? long.MaxValue;
}
// If th length is too big, ignore.
if (totalBytes <= maxFileSize)
{
HttpResponseMessage getResponse = await this.httpClient.GetAsync(url);
string webResponse = await getResponse.Content.ReadAsStringAsync();
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(webResponse);
HtmlNode node = doc.DocumentNode.SelectSingleNode("//title");
if (node != null)
{
// Issue #15: Ensure we decode characters such as < and >
response.Title = WebUtility.HtmlDecode(node.InnerText);
}
}
else
{
this.logger.WriteLine("Ignoring URL '{0}' whose file size is {1}", url, totalBytes);
}
}
catch (Exception e)
{
this.logger.ErrorWriteLine("Error when getting response from {0}{1}{2}", url, Environment.NewLine, e.ToString());
}
return response;
}
));
}
/// <summary>
/// Handles a message from the channel.
/// </summary>
private async void HandleMessage(MessageHandlerArgs args)
{
string url;
if (UrlReader.TryParseUrl(args.Message, out url))
{
UrlResponse urlResponse = await this.urlReader.AsyncGetDescription(url);
if (urlResponse.IsValid)
{
args.Writer.SendMessage(
string.Format("Title: {0}", urlResponse.TitleShortened),
args.Channel
);
}
}
}
