source: src/main/java/geniusweb/partiesserver/websocket/RunningListSocket.java

package geniusweb.partiesserver.websocket;

import java.io.IOException;
import java.util.List;
import java.util.logging.Level;
import java.util.stream.Collectors;

import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

import geniusweb.actions.PartyId;
import geniusweb.partiesserver.Constants;
import geniusweb.partiesserver.repository.RunningPartiesRepo;
import geniusweb.partiesserver.repository.RunningPartyInfo;
import tudelft.utilities.listener.Listener;
import tudelft.utilities.logging.ReportToLogger;
import tudelft.utilities.logging.Reporter;

/**
 * Returns a websocket that communicates the list of currently available
 * (runnable) parties. Every time something changes, a new list of parties is
 * sent.
 */
@ServerEndpoint("/running")
public class RunningListSocket {

        private Listener<PartyId> changeListener; // final, but only initialized in
                                                                                                // startSession.
        private Session session;
        private RunningPartiesRepo repo;
        private SendBuffer outstream;
        private final Reporter log;

        public RunningListSocket() {
                this(new ReportToLogger("partiesserver"));
        }

        public RunningListSocket(Reporter reporter) {
                this.log = reporter;
        }

        @OnOpen
        public void start(Session session) throws IOException {
                this.session = session;
                this.outstream = new SendBuffer(session.getBasicRemote(), log);

                repo = getRepo();
                changeListener = new Listener<PartyId>() {
                        @Override
                        public void notifyChange(PartyId data) {
                                sendUpdatedParties();
                        }
                };
                repo.addListener(changeListener);

                sendUpdatedParties();
        }

        /**
         * Send the currently running parties to the client.
         */
        private void sendUpdatedParties() {
                List<RunningPartyInfo> list = repo.list().stream()
                                .map(party -> new RunningPartyInfo(party))
                                .collect(Collectors.toList());
                log.log(Level.FINE, "sending updated running parties list " + list);
                try {
                        outstream.send(Constants.getJackson().writeValueAsString(repo.list()));
                } catch (IOException e) {
                        log.log(Level.SEVERE, "Internal problem converting json", e);
                }
        }

        @OnMessage
        public void onMessage(String message, Session session) {
                log.log(Level.WARNING,
                                "runninglistsocket does not handle incoming messages ("
                                                + message + ")");
        }

        @OnClose
        public void onClose() {
                try {
                        outstream.stop();
                        session.close();
                } catch (IOException e) {
                        log.log(Level.SEVERE, "Failed to close websocket", e);
                }
                repo.removeListener(changeListener);
        }

        @OnError
        public void onError(Throwable t) throws Throwable {
                log.log(Level.SEVERE, "Internal problem converting json", t);
        }

        /**
         * FactoryMethod for testing
         * 
         * @return RunningPartiesRepo
         */
        protected RunningPartiesRepo getRepo() {
                return RunningPartiesRepo.instance();
        }

}