/* (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 com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import net.sf.json.JSONObject;
import org.apache.commons.codec.Charsets;
import org.apache.commons.lang.StringUtils;
import org.springframework.http.MediaType;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.OutputStreamWriter;
import java.util.Map;
import java.util.concurrent.TimeUnit;

/**
 * Simple endpoint to expose JDBC request metrics.
 * <p>
 *   This class utilizes a cache of request metric values, keyed by request id. The cache
 *   entries are short lived as it is assumed that client code requesting metrics will do 
 *   shortly after the original request. That said the cache expiry time is configurable 
 *   with a default value of 1 minute.
 * </p>
 */
public class RequestMetricsController extends AbstractController {

  static Cache<String,Map<String,Object>> METRICS = CacheBuilder.newBuilder()
      .expireAfterWrite(Long.getLong("jdbc-metrics.cacheExpiry", 1), TimeUnit.MINUTES)
      .maximumSize(Long.getLong("jdbc-metrics.cacheMaxSize", 2000))
      .build();

  @Override
  protected ModelAndView handleRequestInternal(HttpServletRequest req, HttpServletResponse rsp) throws Exception {
    
    String[] split = req.getPathInfo().split("/");
    String reqId = StringUtils.stripEnd(StringUtils.stripStart(split[split.length-1], "/"), "/");
    
    JSONObject obj = new JSONObject();
    obj.put("request", reqId);

    Map<String,Object> m = METRICS.getIfPresent(reqId);
    if (m != null) {
      obj.put("metrics", m);
      rsp.setStatus(HttpServletResponse.SC_OK);
    }
    else {
      rsp.setStatus(HttpServletResponse.SC_NOT_FOUND);
      obj.put("message", "metrics unavailable");
    }

    rsp.setContentType(MediaType.APPLICATION_JSON_VALUE);
    try (OutputStreamWriter w = new OutputStreamWriter(rsp.getOutputStream(), Charsets.UTF_8)) {
      obj.write(w);
      w.flush();
    }
    
    return null;
  }
}