/*
    * Licensed under the GPL License. You may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *   https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
    *
    * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
    * WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
    * PURPOSE.
   */
  package psiprobe.model.stats;
  
  import com.thoughtworks.xstream.XStream;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.file.Files;
  import java.nio.file.Paths;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  import java.util.TreeMap;
  
  import javax.inject.Inject;
  
  import org.jfree.data.xy.XYDataItem;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.factory.DisposableBean;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.beans.factory.annotation.Value;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ApplicationContextAware;
  import org.springframework.web.context.WebApplicationContext;
  
  import psiprobe.tools.UpdateCommitLock;
  
  /**
   * The Class StatsCollection.
   */
  public class StatsCollection implements InitializingBean, DisposableBean, ApplicationContextAware {
  
    /** The Constant logger. */
    private static final Logger logger = LoggerFactory.getLogger(StatsCollection.class);
  
    /** The stats data. */
    private Map<String, List<XYDataItem>> statsData = new TreeMap<>();
  
    /** The xstream. */
    @Inject
    private XStream xstream;
  
    /** The swap file name. */
    private String swapFileName;
  
    /** The storage path. */
    private String storagePath;
  
    /** The context temp dir. */
    private File contextTempDir;
  
    /** The max files. */
    private int maxFiles = 2;
  
    /** The lock. */
    private final UpdateCommitLock lock = new UpdateCommitLock();
  
    /**
     * Gets the swap file name.
     *
     * @return the swap file name
     */
    public String getSwapFileName() {
      return swapFileName;
    }
  
    /**
     * Sets the swap file name.
     *
     * @param swapFileName the new swap file name
     */
    @Value("stats.xml")
    public void setSwapFileName(String swapFileName) {
      this.swapFileName = swapFileName;
    }
  
    /**
     * Gets the storage path.
     *
     * @return the storage path
     */
    public String getStoragePath() {
      return storagePath;
    }
 
   /**
    * Sets the storage path. The default location for the stat files is
    * $CALALINA_BASE/work/&lt;hostname&gt;/&lt;context_name&gt;. Use this property to override it.
    *
    * @param storagePath the new storage path
    */
   // TODO We should make this configurable
   public void setStoragePath(String storagePath) {
     this.storagePath = storagePath;
   }
 
   /**
    * Checks if is collected.
    *
    * @param statsName the stats name
    *
    * @return true, if is collected
    */
   public synchronized boolean isCollected(String statsName) {
     return statsData.get(statsName) != null;
   }
 
   /**
    * Gets the max files.
    *
    * @return the max files
    */
   public int getMaxFiles() {
     return maxFiles;
   }
 
   /**
    * Sets the max files.
    *
    * @param maxFiles the new max files
    */
   public void setMaxFiles(int maxFiles) {
     this.maxFiles = maxFiles > 0 ? maxFiles : 2;
   }
 
   /**
    * New stats.
    *
    * @param name the name
    * @param maxElements the max elements
    *
    * @return the list
    */
   public synchronized List<XYDataItem> newStats(String name, int maxElements) {
     List<XYDataItem> stats = Collections.synchronizedList(new ArrayList<>(maxElements));
     statsData.put(name, stats);
     return stats;
   }
 
   /**
    * Reset stats.
    *
    * @param name the name
    */
   public synchronized void resetStats(String name) {
     List<XYDataItem> stats = getStats(name);
     if (stats != null) {
       stats.clear();
     }
   }
 
   /**
    * Gets the stats.
    *
    * @param name the name
    *
    * @return the stats
    */
   public synchronized List<XYDataItem> getStats(String name) {
     return statsData.get(name);
   }
 
   /**
    * Gets the last value for stat.
    *
    * @param statName the stat name
    *
    * @return the last value for stat
    */
   public long getLastValueForStat(String statName) {
     long statValue = 0;
 
     List<XYDataItem> stats = getStats(statName);
     if (stats != null && !stats.isEmpty()) {
       XYDataItem xy = stats.get(stats.size() - 1);
       if (xy != null && xy.getY() != null) {
         statValue = xy.getY().longValue();
       }
     }
 
     return statValue;
   }
 
   /**
    * Returns series if stat name starts with the prefix.
    *
    * @param statNamePrefix they key under which the stats are stored
    *
    * @return a Map of matching stats. Map keys are stat names and map values are corresponding
    *         series.
    */
   public synchronized Map<String, List<XYDataItem>> getStatsByPrefix(String statNamePrefix) {
     Map<String, List<XYDataItem>> map = new HashMap<>();
     for (Map.Entry<String, List<XYDataItem>> en : statsData.entrySet()) {
       if (en.getKey().startsWith(statNamePrefix)) {
         map.put(en.getKey(), en.getValue());
       }
     }
     return map;
   }
 
   /**
    * Make file.
    *
    * @return the file
    */
   private File makeFile() {
     return storagePath == null ? new File(contextTempDir, swapFileName)
         : new File(storagePath, swapFileName);
   }
 
   /**
    * Shift files.
    *
    * @param index the index
    */
   private void shiftFiles(int index) {
     if (index >= maxFiles - 1) {
       try {
         if (Files.exists(Paths.get(makeFile().getAbsolutePath() + "." + index))) {
           Files.delete(Paths.get(makeFile().getAbsolutePath() + "." + index));
         }
       } catch (IOException e) {
         logger.error("Could not delete file {}",
             new File(makeFile().getAbsolutePath() + "." + index).getName());
       }
     } else {
       shiftFiles(index + 1);
       File srcFile = index == 0 ? makeFile() : new File(makeFile().getAbsolutePath() + "." + index);
       if (Files.exists(srcFile.toPath())) {
         File destFile = new File(makeFile().getAbsolutePath() + "." + (index + 1));
         if (!srcFile.renameTo(destFile)) {
           logger.error("Could not rename file {} to {}", srcFile.getName(), destFile.getName());
         }
       }
     }
   }
 
   /**
    * Writes stats data to file on disk.
    *
    * @throws InterruptedException if a lock cannot be obtained
    */
   public synchronized void serialize() throws InterruptedException {
     lock.lockForCommit();
     long start = System.currentTimeMillis();
     try {
       shiftFiles(0);
       try (OutputStream os = Files.newOutputStream(makeFile().toPath())) {
         xstream.toXML(statsData, os);
       }
     } catch (Exception e) {
       logger.error("Could not write stats data to '{}'", makeFile().getAbsolutePath(), e);
     } finally {
       lock.releaseCommitLock();
       logger.debug("stats serialized in {}ms", System.currentTimeMillis() - start);
     }
   }
 
   /**
    * Deserialize.
    *
    * @param file the file
    *
    * @return the map
    */
   @SuppressWarnings("unchecked")
   private Map<String, List<XYDataItem>> deserialize(File file) {
     Map<String, List<XYDataItem>> stats = null;
     if (file.exists() && file.canRead()) {
       long start = System.currentTimeMillis();
       try {
         try (InputStream fis = Files.newInputStream(file.toPath())) {
           stats = (Map<String, List<XYDataItem>>) xstream.fromXML(fis);
 
           if (stats != null) {
             // adjust stats data so that charts look realistic.
             // we do that by ending the previous stats group with 0 value
             // and starting the current stats group also with 0
             // thus giving the chart nice plunge to zero indicating downtime
             // and lets not bother about rotating stats;
             // regular stats collection cycle will do it
 
             for (Entry<String, List<XYDataItem>> set : stats.entrySet()) {
               List<XYDataItem> list = set.getValue();
               if (!list.isEmpty()) {
                 XYDataItem xy = list.get(list.size() - 1);
                 list.add(new XYDataItem(xy.getX().longValue() + 1, 0));
                 list.add(new XYDataItem(System.currentTimeMillis(), 0));
               }
             }
           }
         }
         logger.debug("stats data read in {}ms", System.currentTimeMillis() - start);
       } catch (ExceptionInInitializerError e) {
         if (e.getCause() != null && e.getCause().getMessage() != null && e.getCause().getMessage()
             .contains("does not \"opens java.util\" to unnamed module")) {
           logger.error(
               "Stats deserialization disabled, use '--add-opens java.base/java.util=ALL-UNNAMED' to start Tomcat to enable again");
         } else {
           logger.error("Could not read stats data from '{}' during initialization",
               file.getAbsolutePath(), e);
         }
       } catch (Exception e) {
         logger.error("Could not read stats data from '{}'", file.getAbsolutePath(), e);
       }
     }
 
     return stats;
   }
 
   /**
    * Lock for update.
    *
    * @throws InterruptedException the interrupted exception
    */
   public void lockForUpdate() throws InterruptedException {
     lock.lockForUpdate();
   }
 
   /**
    * Release lock.
    */
   public void releaseLock() {
     lock.releaseUpdateLock();
   }
 
   /**
    * Reads stats data from file on disk.
    */
   @Override
   public synchronized void afterPropertiesSet() {
     int index = 0;
     Map<String, List<XYDataItem>> stats;
 
     while (true) {
       File file = index == 0 ? makeFile() : new File(makeFile().getAbsolutePath() + "." + index);
       stats = deserialize(file);
       index += 1;
       if (stats != null || index >= maxFiles - 1) {
         break;
       }
     }
 
     if (stats != null) {
       statsData = stats;
     } else {
       logger.debug("Stats data file not found. Empty file assumed.");
     }
 
   }
 
   @Override
   public void destroy() throws Exception {
     serialize();
   }
 
   @Override
   public void setApplicationContext(ApplicationContext applicationContext) {
     WebApplicationContext wac = (WebApplicationContext) applicationContext;
     contextTempDir = (File) wac.getServletContext().getAttribute("javax.servlet.context.tempdir");
   }
 
 }