/// <summary>
/// Add a contact if possible, based on the algorithm described
/// in sections 2.2, 2.4 and 4.2
/// </summary>
public void AddContact(Contact contact)
{
Validate.IsFalse<OurNodeCannotBeAContactException>(ourID == contact.ID, "Cannot add ourselves as a contact!");
contact.Touch(); // Update the LastSeen to now.
lock (this)
{
KBucket kbucket = GetKBucket(contact.ID);
if (kbucket.Contains(contact.ID))
{
// Replace the existing contact, updating the network info and LastSeen timestamp.
kbucket.UpdateContactInfo(contact);
}
else if (kbucket.IsBucketFull)
{
if (CanSplit(kbucket))
{
// Split the bucket and try again.
(KBucket k1, KBucket k2) = kbucket.Split();
int idx = GetKBucketIndex(contact.ID);
buckets[idx] = k1;
buckets.Insert(idx + 1, k2);
buckets[idx].Touch();
buckets[idx + 1].Touch();
AddContact(contact);
}
else
{
Contact lastSeenContact = kbucket.Contacts.OrderBy(c => c.LastSeen).First();
RpcError error = lastSeenContact.Protocol.Ping(ourContact);
if (error.HasError)
{
// Null continuation is used because unit tests may not initialize a DHT.
dht?.DelayEviction(lastSeenContact, contact);
}
else
{
// Still can't add the contact, so put it into the pending list.
dht?.AddToPending(contact);
}
}
}
else
{
// Bucket isn't full, so just add the contact.
kbucket.AddContact(contact);
dht?.ContactAddedToBucket(kbucket, contact);
}
}
}