/// <summary>
/// Generates a dictionary of all album IDs in the gallery and, for each one, a flattened list of all album IDs contained in it,
/// recursively including all child IDs, not just those of its immediate children. The key is the album ID and the value is a list
/// of all child album IDs contained in the album.
/// </summary>
/// <param name="albumRelationships">The album relationships for the current gallery.</param>
/// <returns>ConcurrentDictionary<System.Int32, List<System.Int32>>.</returns>
private static ConcurrentDictionary <int, List <int> > GenerateFlattenedAlbums(AlbumTuple[] albumRelationships)
{
var flatIds = new ConcurrentDictionary <int, List <int> >();
var albumLookup = albumRelationships.ToLookup(a => a.AlbumParentId, v => v);
int?rootAlbumParentId = null;
// Get a reference to the root album
AlbumTuple rootAlbum = albumLookup[rootAlbumParentId].FirstOrDefault();
if (rootAlbum != null)
{
// Add the root album to our flat list and set up the child list
flatIds.TryAdd(rootAlbum.AlbumId, new List <int> {
rootAlbum.AlbumId
});
// Now add the children of the root album
foreach (AlbumTuple albumTuple in albumLookup[rootAlbum.AlbumId])
{
FlattenAlbum(albumTuple, albumLookup, flatIds, new List <int> {
rootAlbum.AlbumId
});
}
}
return(flatIds);
}
/// <summary>
/// Flatten the gallery into a dictionary of album IDs (key) and the flattened list of all albums each album
/// contains (value).
/// </summary>
/// <param name="galleryId">The gallery ID.</param>
/// <returns>An instance of Dictionary<int, List<int>>.</returns>
private static Dictionary <int, List <int> > FlattenGallery(int galleryId)
{
Dictionary <int, List <int> > flatIds = new Dictionary <int, List <int> >();
List <AlbumTuple> rawAlbums = new List <AlbumTuple>();
using (IDataReader dr = Album.GetCommandAlbumSelectAll(galleryId).ExecuteReader(CommandBehavior.CloseConnection))
{
while (dr.Read())
{
// SQL:
//SELECT AlbumId, AlbumParentId
//FROM dbo.[gs_Album]
//WHERE FKGalleryId = @GalleryId
rawAlbums.Add(new AlbumTuple
{
AlbumId = dr.GetInt32(0),
AlbumParentId = dr.GetInt32(1)
});
}
}
// To get the ILookup, we have to call ToLookup() on something that implements IEnumerable, so that's why
// we converted the DataReader into a List of AlbumTuples first.
ILookup <int, AlbumTuple> albums = rawAlbums.ToLookup(a => a.AlbumParentId, v => v);
const int rootAlbumParentId = 0;
// Get a reference to the root album
AlbumTuple rootAlbum = albums[rootAlbumParentId].First();
// Add the root album to our flat list and set up the child list
flatIds.Add(rootAlbum.AlbumId, new List <int> {
rootAlbum.AlbumId
});
// Now add the children of the root album
foreach (AlbumTuple albumTuple in albums[rootAlbum.AlbumId])
{
FlattenAlbum(albumTuple, albums, flatIds, new List <int> {
rootAlbum.AlbumId
});
}
return(flatIds);
}
/// <summary>
/// Add the <paramref name="album" /> to all albums in <paramref name="flatIds" /> where it is a child. Recursively
/// process the album's children. The end result is a dictionary of album IDs (key) and the flattened list of all albums
/// each album contains (value).
/// </summary>
/// <param name="album">The album to flatten. This object is not modified.</param>
/// <param name="hierarchicalIds">A lookup list where all albums (value) with a particular parent ID (key) can be quickly
/// found. This object is not modified.</param>
/// <param name="flatIds">The flattened list of albums and their child albums. The <paramref name="album" /> and its
/// children are added to this list.</param>
/// <param name="currentAlbumFlatIds">The current hierarchy of album IDs we are processing. The function uses this to
/// know which items in <paramref name="flatIds" /> to update for each album.</param>
private static void FlattenAlbum(AlbumTuple album, ILookup <int?, AlbumTuple> hierarchicalIds, ConcurrentDictionary <int, List <int> > flatIds, List <int> currentAlbumFlatIds)
{
// First time we get here, ID=2, ParentId=1
flatIds.TryAdd(album.AlbumId, new List <int> {
album.AlbumId
});
// For each album in the current hierarchy, find its match in flatIds and add the album to its list.
foreach (int currentAlbumFlatId in currentAlbumFlatIds)
{
flatIds[currentAlbumFlatId].Add(album.AlbumId);
}
// Now add this album to the list so it will get updated when any children are processed.
currentAlbumFlatIds.Add(album.AlbumId);
foreach (AlbumTuple albumTuple in hierarchicalIds[album.AlbumId])
{
FlattenAlbum(albumTuple, hierarchicalIds, flatIds, new List <int>(currentAlbumFlatIds));
}
}
/// <summary>
/// Add the <paramref name="album" /> to all albums in <paramref name="flatIds" /> where it is a child. Recursively
/// process the album's children. The end result is a dictionary of album IDs (key) and the flattened list of all albums
/// each album contains (value).
/// </summary>
/// <param name="album">The album to flatten. This object is not modified.</param>
/// <param name="hierarchicalIds">A lookup list where all albums (value) with a particular parent ID (key) can be quickly
/// found. This object is not modified.</param>
/// <param name="flatIds">The flattened list of albums and their child albums. The <paramref name="album" /> and its
/// children are added to this list.</param>
/// <param name="currentAlbumFlatIds">The current hierarchy of album IDs we are processing. The function uses this to
/// know which items in <paramref name="flatIds" /> to update for each album.</param>
private static void FlattenAlbum(AlbumTuple album, ILookup<int, AlbumTuple> hierarchicalIds, Dictionary<int, List<int>> flatIds, List<int> currentAlbumFlatIds)
{
// First time we get here, ID=2, ParentId=1
flatIds.Add(album.AlbumId, new List<int> { album.AlbumId });
// For each album in the current hierarchy, find its match in flatIds and add the album to its list.
foreach (int currentAlbumFlatId in currentAlbumFlatIds)
{
flatIds[currentAlbumFlatId].Add(album.AlbumId);
}
// Now add this album to the list so it will get updated when any children are processed.
currentAlbumFlatIds.Add(album.AlbumId);
foreach (AlbumTuple albumTuple in hierarchicalIds[album.AlbumId])
{
FlattenAlbum(albumTuple, hierarchicalIds, flatIds, new List<int>(currentAlbumFlatIds));
}
}
