/// <summary>
/// Retrieves an enumerable collection of XMPP extensions that the XMPP
/// entity with the specified JID supports.
/// </summary>
/// <param name="jid">The JID of the XMPP entity to retrieve supported
/// extensions for.</param>
/// <returns>An enumerable collection of XMPP extensions supported by the
/// XMPP entity with the specified JID.</returns>
/// <exception cref="ArgumentNullException">The jid parameter is
/// null.</exception>
/// <exception cref="NotSupportedException">The XMPP entity with
/// the specified JID does not support querying of feature
/// information.</exception>
public IEnumerable <Extension> GetExtensions(Jid jid)
{
jid.ThrowIfNull("jid");
if (hashes.ContainsKey(jid))
{
string hash = hashes[jid];
// If the feature set has already been cached, return it; Otherwise
// request the feature set and subsequently cache it.
// FIXME: Calculate hash of feature set and ensure it equals stored hash.
if (!cachedFeatures.ContainsKey(hash))
{
cachedFeatures.Add(hash, sdisco.GetExtensions(jid));
}
return(cachedFeatures[hash]);
}
// If we don't have a hash for the jid, the XMPP entity probably does not
// support 'caps' so resort to a normal SDisco request.
return(sdisco.GetExtensions(jid));
}
