Synchronizer.java

package co.mwater.clientapp.dbsync;

public class Synchronizer {
	SyncClient client;
	SyncServer server;

	public Synchronizer(SyncClient client, SyncServer server) {
		this.client = client;
		this.server = server;
	}

	public void synchronize(DataSlice dataSlice) throws SyncServerException {
		// First upload
		upload();

		boolean repeatDownload; // Set when upload was done after changes gotten
		do {
			// Download change set
			long until = client.getUntil(dataSlice);
			ChangeSet downloadSet = server.downloadChangeSet(dataSlice, until);
			if (downloadSet == null)
				return;
			try {

				// Only repeat if another upload is needed
				repeatDownload = false;

				// Apply, trying until uploads are no longer required
				boolean uploadNeeded;
				do {
					try {
						client.applyChangeSet(downloadSet, dataSlice);
						uploadNeeded = false;
					} catch (PendingChangesException pce) {
						// Perform upload and try again
						uploadNeeded = true;
						repeatDownload = true;
						upload();
					}
				} while (uploadNeeded);
			} finally {
				downloadSet.close();
			}
		} while (repeatDownload);
	}

	private void upload() throws SyncServerException {
		ChangeSet uploadSet = client.getChangeSet();
		if (uploadSet == null)
			return;
		try {
			server.uploadChangeSet(uploadSet);
			client.markChangeSetSent(uploadSet.getUntil());
		} finally {
			uploadSet.close();
		}
	}

	public void cancel() {
		server.cancel();
	}
}