/* (c) 2017 Open Source Geospatial Foundation - all rights reserved
 * 
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geoserver.jdbc.metrics;

import org.geoserver.GeoServerNodeData;
import org.geoserver.filters.GeoServerFilter;
import org.geoserver.ows.util.ResponseUtils;

import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicLong;

/**
 * Servlet filter that adds headers providing access to jdbc request metrics.
 * <p>
 *   Since headers need to be written before the start of the response body 
 *   we need to store the metric values into a cache to be later retrieved. See
 *   {@link RequestMetricsController} for details.
 * </p>
 */
public class RequestMetricsFilter implements GeoServerFilter {

  AtomicLong requestId = new AtomicLong(System.currentTimeMillis());

  GeoServerNodeData nodeData = GeoServerNodeData.createFromEnvironment();

  @Override
  public void init(FilterConfig config) throws ServletException {
  }

  @Override
  public void doFilter(ServletRequest req, ServletResponse rsp, FilterChain filterChain) throws IOException, ServletException {
    HttpServletRequest httpReq = (HttpServletRequest) req;
    HttpServletResponse httpRsp = (HttpServletResponse) rsp;

    // set a header that represents the request id
    String reqId = String.valueOf(requestId.getAndIncrement());
    httpRsp.setHeader("x-geoserver-request", reqId);
    httpRsp.setHeader("x-geoserver-jdbc-metrics", ResponseUtils.baseURL(httpReq)+"jdbc-metrics/"+reqId);
    httpRsp.setHeader("x-geoserver-node-info", nodeData.getId());

    // do the request
    filterChain.doFilter(req, rsp);

    // write the metrics out to the cache
    Optional.ofNullable(RequestMetricsCallback.metrics.get()).ifPresent(map -> {
      RequestMetricsController.METRICS.put(reqId, map);
      RequestMetricsCallback.metrics.remove();
    });
  }

  @Override
  public void destroy() {

  }
}