/// <summary>
/// Detects changes not known to the destination and returns a change batch
/// </summary>
/// <param name="destinationKnowledge">Requester Knowledge</param>
/// <param name="batchSize">Maximum number of changes to return</param>
/// <returns>List of changes</returns>
private List <ItemChange> DetectChanges(SyncKnowledge destinationKnowledge, uint batchSize)
{
List <ItemChange> changeBatch = new List <ItemChange>();
if (destinationKnowledge == null)
{
throw new ArgumentNullException("destinationKnowledge");
}
if (batchSize < 0)
{
throw new ArgumentOutOfRangeException("batchSize");
}
if (!localChangedDetected)
{
FindLocalFileChanges(folderPath);
localChangedDetected = true;
}
// Map the destination knowledge
// This maps the knowledge from the remote replica key map (where the destination is replicaKey 0)
// to the local replica key map (where the source is replicaKey)
//
// We do this because our metadata is relative to the local store (and local key map)
// (This is typical of most sync providers)
SyncKnowledge mappedKnowledge = SyncKnowledge.MapRemoteKnowledgeToLocal(destinationKnowledge);
foreach (ItemMetadata item in metadataStore)
{
// Check if the current version of the item is known to the destination
// We simply check if the update version is contained in his knowledge
// If the metadata is for a tombstone, the change is a delete
if (!mappedKnowledge.Contains(ReplicaId, item.ItemId, item.ChangeVersion))
{
ItemChange itemChange = new ItemChange(IdFormats, ReplicaId, item.ItemId, item.IsTombstone ? ChangeKind.Deleted : ChangeKind.Update, item.CreationVersion, item.ChangeVersion);
// Change isn't known to the remote store, so add it to the batch
changeBatch.Add(itemChange);
}
// If the batch is full, break
//
// N.B. Rest of changes will be detected in next batch. Current batch will not be
// reenumerated (except in case destination doesn't successfully apply them) as
// when destination applies the changes in this batch, they will add them to their
// knowledge.
if (changeBatch.Count == batchSize)
{
break;
}
}
return(changeBatch);
}
