public static void AddOrUpdateLink(Person follower, Person leader)
{
using (var db = new CloutContext())
{
db.Following.AddOrUpdate(new Following { PersonId = follower.Id, FollowingId = leader.Id });
db.SaveChanges();
}
}
public static IEnumerable<Person> GetFollowers(Person leader)
{
using (var db = new CloutContext())
{
return (from follower in db.Following
join person in db.Person on follower.PersonId equals person.Id
where follower.FollowingId == leader.Id
select person).ToList();
}
}
/// <summary>
/// Gets the clout of person
/// This is a recursive function which traverses the tree up to it's roots
/// </summary>
/// <param name="leader">The current person's name for which clout is being calculated</param>
/// <param name="processed">
/// A list containing the persons for which clout has been processed
/// This is needed in order to escape loops in the graph
/// Example: A follows B, B follows A - the recursion will continue infinitely.
/// By keeping track of which nodes we already processed we avoid the loop and potential double processing
/// </param>
/// <returns>The number of followers for the users</returns>
private static int GetClout(Person leader, ConcurrentBag<Person> processed = null)
{
if (processed == null) processed = new ConcurrentBag<Person>(); // Not created yet? Create it
if (processed.Contains(leader)) return 0; // Already processed? break the recursion without affecting the calculation
processed.Add(leader);
var followers = DataAccess.GetFollowers(leader);
// For each follower return the sum of 1 (for the node) and the clout of thier followers
return followers.Sum(follower => 1 + GetClout(follower, processed));
}