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/*
* Copyright 2013 Jeanfrancois Arcand
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
/*
 * Copyright 2009 Richard Zschech.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package org.atmosphere.gwt.client.impl;

import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;
import com.google.gwt.user.client.rpc.SerializationException;
import com.google.gwt.user.client.rpc.StatusCodeException;
import org.atmosphere.gwt.client.AtmosphereClient;
import org.atmosphere.gwt.client.AtmosphereClientException;
import org.atmosphere.gwt.client.AtmosphereListener;

import java.util.Collections;

/**
 * This class uses Opera's event-source element to stream events.

 * http://my.opera.com/WebApplications/blog/show.dml/438711
 * 
 * The main issue with Opera's implementation is that we can't detect connection events. To support this three event
 * listeners are setup: one "s" for string messages, one "o" for the GWT serialized object messages, and the other "c"
 * for connection events. The server sends the event "c" as soon as the connection is established and "d"
 * when the connection is terminated. A connection timer is setup to detect initial connection errors. To detect
 * subsequent connection failure it also sends a heart beat events "h" when no messages have been sent for a specified
 * heart beat interval.
 *
 * @author Richard Zschech
 */
public class OperaEventSourceCometTransport extends BaseCometTransport {

    private Element eventSource;
    private boolean connected;

    @Override
    public void initiate(AtmosphereClient client, AtmosphereListener listener) {
        super.initiate(client, listener);
        eventSource = createEventSource(this);
    }

    @Override
    public void connect(int connectionCount) {
        DOM.setElementAttribute(eventSource, "src", getUrl(connectionCount));
    }

    @Override
    public void disconnect() {
        DOM.setElementAttribute(eventSource, "src", "");
        super.disconnect();
        if (connected) {
            connected = false;
            listener.onDisconnected();
        }
    }

    private static native Element createEventSource(OperaEventSourceCometTransport client) /*-{
        var eventSource = document.createElement("event-source");

        var stringMessageHandler = $entry(function(event) {
            client.@org.atmosphere.gwt.client.impl.OperaEventSourceCometTransport::onString(Ljava/lang/String;)(event.data);
        });

        eventSource.addEventListener("s", stringMessageHandler, false);

        var objectMessageHandler = $entry(function(event) {
            client.@org.atmosphere.gwt.client.impl.OperaEventSourceCometTransport::onObject(Ljava/lang/String;)(event.data);
        });

        eventSource.addEventListener("o", objectMessageHandler, false);

        var connectionHandler = $entry(function(event) {
            client.@org.atmosphere.gwt.client.impl.OperaEventSourceCometTransport::onConnection(Ljava/lang/String;)(event.data);
        });

        eventSource.addEventListener("c", connectionHandler, false);

        return eventSource;
    }-*/;

    @SuppressWarnings("unused")
    private void onString(String message) {
        listener.onMessage(Collections.singletonList(HTTPRequestCometTransport.unescape(message)));
    }

    @SuppressWarnings("unused")
    private void onObject(String message) {
        try {
            listener.onMessage(Collections.singletonList(parse(message)));
        } catch (SerializationException e) {
            listener.onError(e, true);
        }
    }

    @SuppressWarnings("unused")
    private void onConnection(String message) {
        if (message.startsWith("c")) {
            connected = true;
            String initParameters = message.substring(1);
            try {
                String[] params = initParameters.split(":");
                connectionId = Integer.parseInt(params[1]);
                listener.onConnected(Integer.parseInt(params[0]), connectionId);
            } catch (NumberFormatException e) {
                listener.onError(new AtmosphereClientException("Unexpected init parameters: " + initParameters), true);
            }
        } else if (message.startsWith("e")) {
            disconnect();
            String status = message.substring(1);
            try {
                int statusCode;
                String statusMessage;
                int index = status.indexOf(' ');
                if (index == -1) {
                    statusCode = Integer.parseInt(status);
                    statusMessage = null;
                } else {
                    statusCode = Integer.parseInt(status.substring(0, index));
                    statusMessage = HTTPRequestCometTransport.unescape(status.substring(index + 1));
                }
                listener.onError(new StatusCodeException(statusCode, statusMessage), false);
            } catch (NumberFormatException e) {
                listener.onError(new AtmosphereClientException("Unexpected status code: " + status), false);
            }
        } else if (message.equals("d")) {
            connected = false;
            disconnect();
            listener.onDisconnected();
        } else if (message.equals("h")) {
            listener.onHeartbeat();
        } else {
            listener.onError(new AtmosphereClientException("Unexpected connection status: " + message), true);
        }
    }
}