/// <summary>
/// Creates formatters for RSS 2.0 and Atom 1.0 according to the input content.
/// </summary>
public static class SyndicationFormatterFactory
{
	static XmlReaderSettings settings;

	static SyndicationFormatterFactory()
	{
		// Makes the processing faster for the readers we create.
		settings = new XmlReaderSettings();
		settings.IgnoreComments = true;
		settings.IgnoreProcessingInstructions = true;
		settings.IgnoreWhitespace = true;
		settings.CheckCharacters = true;
		settings.CloseInput = true;
	}

	/// <summary>
	/// Creates a <see cref="SyndicationFeedFormatter"/> according to the 
	/// input format.
	/// </summary>
	/// <param name="uriString">Feed location</param>
	/// <exception cref="NotSupportedException">The input does not contain a valid RSS 2.0 or Atom 1.0 feed.</exception>
	public static SyndicationFeedFormatter CreateFeedFormatter(string uriString)
	{
		using (XmlReader reader = XmlReader.Create(uriString, settings))
			return CreateFeedFormatter(reader);
	}

	/// <summary>
	/// Creates a <see cref="SyndicationFeedFormatter"/> according to the 
	/// input format.
	/// </summary>
	/// <param name="uri">Feed location</param>
	/// <exception cref="NotSupportedException">The input does not contain a valid RSS 2.0 or Atom 1.0 feed.</exception>
	public static SyndicationFeedFormatter CreateFeedFormatter(Uri uri)
	{
		using (XmlReader reader = XmlReader.Create(uri.ToString(), settings))
			return CreateFeedFormatter(reader);
	}

	/// <summary>
	/// Creates a <see cref="SyndicationFeedFormatter"/> according to the 
	/// input format.
	/// </summary>
	/// <param name="reader">Feed source</param>
	/// <exception cref="NotSupportedException">The input does not contain a valid RSS 2.0 or Atom 1.0 feed.</exception>
	public static SyndicationFeedFormatter CreateFeedFormatter(XmlReader reader)
	{
		if (reader.ReadState == ReadState.Initial)
		{
			reader.MoveToContent();
		}

		Rss20FeedFormatter rss = new Rss20FeedFormatter();
		if (rss.CanRead(reader))
		{
			return rss;
		}

		Atom10FeedFormatter atom = new Atom10FeedFormatter();
		if (atom.CanRead(reader))
		{
			return atom;
		}

		throw new NotSupportedException("Invalid feed root element: " + reader.Name);
	}

	/// <summary>
	/// Creates a <see cref="SyndicationItemFormatter"/> according to the 
	/// input format.
	/// </summary>
	/// <param name="uriString">Item location</param>
	/// <exception cref="NotSupportedException">The input does not contain a valid RSS 2.0 or Atom 1.0 item.</exception>
	public static SyndicationItemFormatter CreateItemFormatter(string uriString)
	{
		using (XmlReader reader = XmlReader.Create(uriString, settings))
			return CreateItemFormatter(reader);
	}

	/// <summary>
	/// Creates a <see cref="SyndicationItemFormatter"/> according to the 
	/// input format.
	/// </summary>
	/// <param name="uri">Item location</param>
	/// <exception cref="NotSupportedException">The input does not contain a valid RSS 2.0 or Atom 1.0 item.</exception>
	public static SyndicationItemFormatter CreateItemFormatter(Uri uri)
	{
		using (XmlReader reader = XmlReader.Create(uri.ToString(), settings))
			return CreateItemFormatter(reader);
	}

	/// <summary>
	/// Creates a <see cref="SyndicationItemFormatter"/> according to the 
	/// input format.
	/// </summary>
	/// <param name="reader">Item source</param>
	/// <exception cref="NotSupportedException">The input does not contain a valid RSS 2.0 or Atom 1.0 item.</exception>
	public static SyndicationItemFormatter CreateItemFormatter(XmlReader reader)
	{
		if (reader.ReadState == ReadState.Initial)
		{
			reader.MoveToContent();
		}

		Rss20ItemFormatter rss = new Rss20ItemFormatter();
		if (rss.CanRead(reader))
		{
			return rss;
		}

		Atom10ItemFormatter atom = new Atom10ItemFormatter();
		if (atom.CanRead(reader))
		{
			return atom;
		}

		throw new NotSupportedException("Invalid item element: " + reader.Name);
	}
}