/**

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     licenses@blazegraph.com

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
/*
 * Created on Apr 12, 2011
 */

package com.bigdata.rdf.sail.webapp;

import java.io.IOException;
import java.io.OutputStreamWriter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

import com.bigdata.counters.CounterSet;
import com.bigdata.counters.ICounterSetAccess;
import com.bigdata.counters.format.CounterSetFormat;
import com.bigdata.counters.query.CounterSetSelector;
import com.bigdata.counters.query.URLQueryModel;
import com.bigdata.counters.render.IRenderer;
import com.bigdata.counters.render.RendererFactory;
import com.bigdata.journal.IIndexManager;
import com.bigdata.service.IBigdataFederation;
import com.bigdata.service.IEventReceivingService;
import com.bigdata.service.IService;

/**
 * Servlet for exposing performance counters.
 * 
 * @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
 * 
 *          TODO The SPARQL layer needs to be separated from the core bigdata
 *          layer, with the BigdataContext moving into a servlet package in the
 *          bigdata module and the CountersServlet moving into a servlet package
 *          in the com.bigdata.counters package namespace.
 *          <p>
 *          The flot resources need to be retrievable.
 *          <p>
 *          The event reporting needs to be hooked via
 *          {@link IEventReceivingService}, at least for scale-out.
 */
public class CountersServlet extends BigdataServlet {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    
    static private final transient Logger log = Logger.getLogger(CountersServlet.class); 

    /**
     * 
     */
    public CountersServlet() {
    }

    /**
     * Performance counters
     * <pre>
     * GET /counters
     * </pre>
     */
    @Override
    protected void doGet(final HttpServletRequest req,
            final HttpServletResponse resp) throws IOException {

        try {
        
        // TODO Hook this how? (NSS does not define an IService right now)
        final IService service = null;
        
        final IIndexManager indexManager = getIndexManager();

        if (indexManager instanceof IBigdataFederation) {

            ((IBigdataFederation<?>) indexManager).reattachDynamicCounters();

        }

        final CounterSet counterSet = ((ICounterSetAccess) indexManager)
                .getCounters();

        final CounterSetSelector counterSelector = new CounterSetSelector(
                counterSet);

        /*
         * Obtain a renderer.
         * 
         * @todo if controller state error then send HTTP_BAD_REQUEST
         * 
         * @todo Write XSL and stylesheet for interactive browsing of the
         * CounterSet XML?
         */

        // Do conneg.
        final String acceptStr = req.getHeader("Accept");

        final ConnegUtil util = new ConnegUtil(acceptStr);

        final CounterSetFormat format = util
                .getCounterSetFormat(CounterSetFormat.HTML/* fallback */);

//         final String mimeType = MIME_TEXT_HTML;
        final String mimeType = format.getDefaultMIMEType();

        if (log.isDebugEnabled())
            log.debug("\nAccept=" + acceptStr + ",\nformat=" + format
                    + ", mimeType=" + mimeType);

        final IRenderer renderer;
        {

            // build model of the controller state.
            final URLQueryModel model = URLQueryModel.getInstance(service,
                    req, resp);

            if (log.isDebugEnabled())
                log.debug("\nmodel=" + model);

            renderer = RendererFactory.get(model, counterSelector, mimeType);

            if (log.isDebugEnabled())
                log.debug("\nrenderer=" + renderer);

        }

        resp.setStatus(HTTP_OK);

        resp.setContentType(mimeType);

        if (format.hasCharset()) {

            // Note: Binary encodings do not specify charset.
            resp.setCharacterEncoding(format.getCharset().name());

        }

        /*
         * Sets the cache behavior -- the data should be good for up to 60
         * seconds unless you change the query parameters. These cache control
         * parameters SHOULD indicate that the response is valid for 60 seconds,
         * that the client must revalidate, and that the response is cachable
         * even if the client was authenticated.
         */
        resp.addHeader("Cache-Control", "max-age=60, must-revalidate, public");
        // to disable caching.
        // r.addHeader("Cache-Control", "no-cache");

        /*
         * Render the counters as specified by the query for the negotiated MIME
         * type.
         */
        {

            final OutputStreamWriter w = new OutputStreamWriter(
                    resp.getOutputStream(), charset);

            // render the view.
            renderer.render(w);

            w.flush();

        }

        if (log.isTraceEnabled())
            log.trace("done");
        
        } catch (Throwable t) {
            
            BigdataRDFServlet.launderThrowable(t, resp, "");
            
        }

    }
    
}