private Opml DownloadOpmlFeed(Uri uri)
{
// look for disk cache first
Opml opmlFeed = TryLoadFromDisk(uri);
if (opmlFeed != null)
{
return(opmlFeed);
}
// May fail under partial trust
try
{
byte[] feed = new WebClient().DownloadData(uri.AbsoluteUri);
var opmlDoc = new XmlDocument();
opmlDoc.Load(new MemoryStream(feed));
opmlFeed = Opml.LoadFromXml(opmlDoc);
opmlFeed.UtcExpiry = DateTime.UtcNow.AddMinutes(_defaultTtlMinutes);
// save to disk
TrySaveToDisk(opmlDoc, uri, opmlFeed.UtcExpiry);
}
catch
{
return(new Opml());
}
return(opmlFeed);
}
private Opml TryLoadFromDisk(Uri uri)
{
if (_directoryOnDisk == null)
{
return(null); // no place to cache
}
// look for all files matching the prefix
// looking for the one matching url that is not expired
// removing expired (or invalid) ones
string pattern = GetTempFileNamePrefixFromUrl(uri) + "_*.opml.resources";
string[] files = Directory.GetFiles(_directoryOnDisk, pattern, SearchOption.TopDirectoryOnly);
foreach (string opmlFilename in files)
{
XmlDocument opmlDoc = null;
bool isOpmlFileValid = false;
DateTime utcExpiryFromOpmlFile = DateTime.MinValue;
string urlFromOpmlFile = null;
try
{
opmlDoc = new XmlDocument();
opmlDoc.Load(opmlFilename);
// look for special XML comment (before the root tag)'
// containing expiration and url
var comment = opmlDoc.DocumentElement.PreviousSibling as XmlComment;
if (comment != null)
{
string c = comment.Value;
int i = c.IndexOf('@');
long expiry;
if (long.TryParse(c.Substring(0, i), out expiry))
{
utcExpiryFromOpmlFile = DateTime.FromBinary(expiry);
urlFromOpmlFile = c.Substring(i + 1);
isOpmlFileValid = true;
}
}
}
catch
{
// error processing one file shouldn't stop processing other files
}
// remove invalid or expired file
if (!isOpmlFileValid || utcExpiryFromOpmlFile < DateTime.UtcNow)
{
try
{
File.Delete(opmlFilename);
}
catch (Exception ex)
{
Logger.Error(ex);
}
// try next file
continue;
}
// match url
if (urlFromOpmlFile.ToLower() == uri.AbsoluteUri.ToLower())
{
// found a good one - create DOM and set expiry (as found on disk)
Opml opmlFeed = Opml.LoadFromXml(opmlDoc);
opmlFeed.UtcExpiry = utcExpiryFromOpmlFile;
return(opmlFeed);
}
}
// not found
return(null);
}