source: src/main/java/geniusweb/runserver/WebSocketProtToPartyConn.java

package geniusweb.runserver;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.logging.Level;

import javax.websocket.ClientEndpoint;
import javax.websocket.CloseReason;
import javax.websocket.ContainerProvider;
import javax.websocket.DeploymentException;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.WebSocketContainer;

import geniusweb.actions.Action;
import geniusweb.actions.PartyId;
import geniusweb.inform.Inform;
import geniusweb.protocol.partyconnection.ProtocolToPartyConn;
import geniusweb.references.Reference;
import tudelft.utilities.listener.DefaultListenable;
import tudelft.utilities.logging.ReportToLogger;
import tudelft.utilities.logging.Reporter;

/**
 * A websocket based {@link ProtocolToPartyConn}. it contains a websocket
 * connection to a party (that will be started using the partyserver
 * start-new-party protocol). Must be public so that it can be accessed as
 * ClientEndpoint by apache tomcat. This is internally used.
 * 
 * <p>
 * The @ClientEndpoint annotation is important, the runserver is creating these
 * sockets programatically, from a received ws: URL.
 */
@ClientEndpoint
public class WebSocketProtToPartyConn extends DefaultListenable<Action>
                implements ProtocolToPartyConn {
        // 20MB seems reasonable limit?
        private static final int MAX_MESSAGE_SIZE = 20 * 1024 * 1024;
        private final Reporter log;

        private final Reference reference;

        private WebSocketContainer container;
        private Session session = null;
        private URI partyuri;
        private Throwable error = null;

        /**
         * Buffers incoming text.
         */
        private StringBuffer buffer = new StringBuffer();

        /**
         * Constructor that uses default {@link Reporter}
         * 
         * @param reference the address to to a http GET to get a websocket to a new
         *                  running party.
         */
        public WebSocketProtToPartyConn(Reference reference) {
                this(reference, new ReportToLogger("runserver"));
        }

        /**
         * 
         * @param reference the address to to a http GET to get a websocket to a new
         *                  running party.
         * @param reporter  the {@link Reporter} used for logging important
         *                  events/issues
         * @throws IOException if the party does not start properly.
         */
        public WebSocketProtToPartyConn(Reference reference, Reporter reporter) {
                this.reference = reference;
                this.log = reporter;

        }

        public WebSocketProtToPartyConn init() throws IOException {
                log.log(Level.INFO, "Trying to start up party " + reference);
                URI partyuri = startParty(reference);

                container = ContainerProvider.getWebSocketContainer();
                // #50 disable: might cause large buffer. And why is this a good limit
                // anyway
                // container.setDefaultMaxTextMessageBufferSize(200000);

                log.log(Level.INFO,
                                "Trying to make websocket connection to running party "
                                                + partyuri);
                try {
                        container.connectToServer(this, partyuri);
                } catch (DeploymentException e) {
                        throw new IOException(
                                        "Failed to connect with running party at " + partyuri, e);
                }
                log.log(Level.INFO, "Created websocket connection at  " + partyuri);
                return this;
        }

        /**
         * 
         * @param reference the address to to a http GET to get a websocket to a new
         *                  running party.
         * @return URI of websocket behind which is a running party
         * @throws IOException if party did not start correctly
         */
        private URI startParty(Reference reference) throws IOException {
                HttpURLConnection conn = (HttpURLConnection) reference.getURI().toURL()
                                .openConnection();
                // if this throws, the IOException seems to contain the "retry later"
                // message already
                conn.setRequestMethod("GET");
                conn.setReadTimeout(20000);
                conn.connect();
                BufferedReader rd;
                try {
                        rd = new BufferedReader(
                                        new InputStreamReader(conn.getInputStream()));
                } catch (IOException e) {
                        if (conn.getErrorStream() == null) {
                                throw new IOException("Failed to connect " + reference
                                                + ", no server error message", e);
                        }
                        // read the detail message from the error stream
                        rd = new BufferedReader(
                                        new InputStreamReader(conn.getErrorStream()));
                        throw new IOException(rd.readLine(), e);
                }
                String partysocketaddress = rd.readLine();
                log.log(Level.INFO, "startparty returned " + partysocketaddress);
                if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
                        throw new IOException(
                                        "Something went wrong connecting to the party:"
                                                        + conn.getResponseCode());
                }
                try {
                        this.partyuri = new URI(partysocketaddress);
                } catch (URISyntaxException e1) {
                        throw new IOException("Failed to start party at " + reference, e1);
                }
                return partyuri;
        }

        /************* implements {@link ConnectionWithParty} ***************/
        @Override
        public void send(Inform info) throws IOException {
                if (session == null)
                        return;
                session.getBasicRemote()
                                .sendText(Jackson.instance().writeValueAsString(info));
        }

        @Override
        public Reference getReference() {
                return this.reference;
        }

        @Override
        public PartyId getParty() {
                String name = partyuri.getPath();
                return new PartyId(name.substring(name.lastIndexOf('/') + 1));
        }

        @Override
        public void close() {
                log.log(Level.INFO, "Party close called");
                // a close event is not necessarily a bug?
                // setError(new SocketException("socket is closed"));
                try {
                        session.close();
                        this.session = null;
                } catch (IOException e) {
                        log.log(Level.SEVERE, "failed to close websocket", e);
                }
        }

        /************* implements ClientEndpoint ***************/

        @OnOpen
        public void onOpen(Session session) {
                log.log(Level.INFO, "Party is being connected: " + session);
// #50 we now buffer partial messages
//              session.setMaxTextMessageBufferSize(MAX_MESSAGE_SIZE);
//              session.setMaxBinaryMessageBufferSize(MAX_MESSAGE_SIZE);
                this.session = session;
        }

        @OnClose
        public void onClose(Session userSession, CloseReason reason) {
                log.log(Level.INFO, "closing websocket " + reference + ":" + reason);
                if (reason.getReasonPhrase() != null
                                && !reason.getReasonPhrase().isEmpty()) {
                        setError(new RemoteException("Session " + reference
                                        + " closed abnormally (see party server for more details) "
                                        + reason.getReasonPhrase()));
                }
                // seems NOT an error. Unless the party deliberately and silently
                // closes its connection.
                // Setting error will cause a print of stacktrace that is disturbing.
                // It seems we can not check at this point if session was finished.
                // setError(new SocketException("socket has been closed"));
        }

        @OnMessage
        public void processMessage(String message, boolean islast) {
                // #50 avoid fixed (large) buffers
                buffer.append(message);
                if (islast) {
                        String msg = buffer.toString();
                        buffer = new StringBuffer();
                        try {
                                Action act = Jackson.instance().readValue(msg, Action.class);
                                notifyListeners(act);
                        } catch (IOException e) {
                                log.log(Level.WARNING,
                                                "received bad message from client " + reference, e);
                                setError(e);
                                close();
                        }
                }
        }

        @OnError
        public void processError(Throwable t) {
                log.log(Level.SEVERE, "Something went wrong internally!", t);
                setError(t);
        }

        @Override
        public URI getRemoteURI() {
                return partyuri;
        }

        @Override
        public Throwable getError() {
                return error;
        }

        /**
         * Sets the connection to final error state and report null to listeners.
         * Only the first error is reported, the rest is ignored.
         * 
         * @param err the error that occurred.
         */
        private void setError(Throwable err) {
                boolean isSet = false;
                synchronized (this) {
                        if (this.error == null) {
                                this.error = err;
                                isSet = true;
                        }
                }
                if (isSet) {
                        // special event that tells protocol that we're probably in error
                        // state.
                        notifyListeners(null);
                }
        }

}

/**
 * Indicates an exceeption occured on a remote machine. The remote machine did
 * not pass a stacktrace (because it does not fit into a websocket close call).
 *
 */
class RemoteException extends Exception {
        public RemoteException(String message) {
                super(message, null, false, false);

        }
}