/// <summary>
/// This <c>GetAlbumInfoAsync</c> method is responsible for calling the
/// LastFM album.getInfo method for the supplied search criteria. It then
/// maps the results to an instance of the <see cref="Core.Services.LastFMAlbumInfo"/>
/// class.
/// <para>
/// It uses the XElement.Load method of Linq to XML to call the service, and then
/// uses Linq-To-Xml to interrogate the result. Xml is used in preference to
/// JSon, as the JSon didn't deserialise properly with NewtonSoft.Json. Rather
/// than attempt to write a JSon deserialised, Linq-To-Xml was used instead.
/// This had been used in a previous project so was a quicker option in this case.
/// </para>
/// </summary>
/// <param name="albumName">The album to search for.</param>
/// <param name="artistName">The artist to search for.</param>
/// <returns>A populated instance of LastFMAlbumInfo class.</returns>
/// <remarks>
/// This methods contains no asynchronous call, and is therefore the bottleneck
/// in the asynchronous nature of the application. This is due to XElement not
/// providing an asynchronous method to call it.
/// However, by making this method itself callabe in an asynchronous way, allows
/// the UI to remain unblocked.
/// Using XElement to call the LastFM XML restful service rather than the Json version
/// because the Json deserialiser in currently not providing a fully working model,
/// it currently contain some invalid names properties. Tried using NewtonSoft.Json
/// which is a .Net implementation of a Json deserialiser, but it does not fully
/// retrieve the model as yet.
/// Don't want to spend too long learning how to configure this deserialiser just
/// now as there's not much time for this project. However, if it can be configured
/// to retrieve the full model, then it would be possible to make the call to the
/// LastFM service asynchronously, which ultimately would be the best way.
/// </remarks>
public async Task<LastFMAlbumInfo> GetAlbumInfoAsync(string albumName, string artistName)
{
var info = new LastFMAlbumInfo(); // This should created using a Factory!!!
// Encode the parameters before including in the url
// Do NOT encode the full url as this causes problems and corrupts the url.
string encodedAlbumName = WebUtility.UrlEncode(albumName);
string encodedArtistName = WebUtility.UrlEncode(artistName);
// create the Url for the Google Elevation Api
string url = string.Format("http://ws.audioscrobbler.com/2.0/?method=album.getinfo&api_key=883f78cd9f3317abb2e2a88008dc0e99&artist={0}&album={1}", encodedArtistName, encodedAlbumName);
//string url = string.Format("http://ws.audioscrobbler.com/2.0/?method=album.getinfo&api_key=883f78cd9f3317abb2e2a88008dc0e99&artist={0}&album={1}&format=json");
// Create the result by streaming the return from the load(url). This has
// the effect of submitting an HttpWebRequest as the "file" is a url which
// returns XML serialised data.
// We could also have the results returned in JSON format, but we would need
// a different parsers. C# is easiest with XML at this level.
try
{
var result = XElement.Load(url);
// Get the statues returned and check it was successful
var status = (string)result.Attribute("status");
if (status == "ok")
{
// Deserialize the result
var album = LastFMHelper.Deserialise(result);
// et the Status
album.Status.code = status;
return album;
}
else
{
// Get the message from the returned string
var error = new LastFMAlbumInfo();
var errorElement = result.Element("error");
error.Status.code = (string)errorElement.Attribute("code");
error.Status.message = (string)errorElement;
return error;
}
}
catch (Exception ex)
{
// Error encountered from http server
var error = new LastFMAlbumInfo();
error.Status.code = "Unknown error";
error.Status.message = ex.Message;
return error;
}
}
/// <summary>
/// Retrieves the basic album information from the supplied XML Xelement
/// are returns an instance of the LastFMAlbumInfo class
/// </summary>
/// <param name="albumElement">The Album XElement</param>
/// <returns>A LastFMAlbumInfo class</returns>
private static LastFMAlbumInfo LoadAlbumInfo(XElement albumElement)
{
LastFMAlbumInfo album = new LastFMAlbumInfo();
album.name = (string)albumElement.Element("name");
album.id = (string)albumElement.Element("id");
album.mbid = (string)albumElement.Element("mbid");
album.url = (string)albumElement.Element("url");
album.releasedDate = (string)albumElement.Element("releasedate");
// Artist stuff. Only name here, tracks hold url etc.
album.artist = new LastFMArtist();
album.artist.name = (string)albumElement.Element("artist");
album.listeners = (string)albumElement.Element("listeners");
album.playcount = (string)albumElement.Element("playcount");
return album;
}
