/**
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.hadoop.hbase.io.hfile;
  
  import java.io.IOException;
  import java.util.NavigableMap;
  import java.util.NavigableSet;
  import java.util.concurrent.ConcurrentSkipListMap;
  import java.util.concurrent.ConcurrentSkipListSet;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.codehaus.jackson.JsonGenerationException;
  import org.codehaus.jackson.annotate.JsonIgnoreProperties;
  import org.codehaus.jackson.map.JsonMappingException;
  import org.codehaus.jackson.map.ObjectMapper;
  import org.codehaus.jackson.map.SerializationConfig;
  
  import com.yammer.metrics.core.Histogram;
  import com.yammer.metrics.core.MetricsRegistry;
  import com.yammer.metrics.stats.Snapshot;
  
  /**
   * Utilty for aggregating counts in CachedBlocks and toString/toJSON CachedBlocks and BlockCaches.
   * No attempt has been made at making this thread safe.
   */
  @InterfaceAudience.Private
  public class BlockCacheUtil {
    /**
     * Needed making histograms.
     */
    private static final MetricsRegistry METRICS = new MetricsRegistry();
  
    /**
     * Needed generating JSON.
     */
    private static final ObjectMapper MAPPER = new ObjectMapper();
    static {
      MAPPER.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);
      MAPPER.configure(SerializationConfig.Feature.FLUSH_AFTER_WRITE_VALUE, true);
      MAPPER.configure(SerializationConfig.Feature.INDENT_OUTPUT, true);
    }
  
    /**
     * @param cb
     * @return The block content as String.
     */
    public static String toString(final CachedBlock cb, final long now) {
      return "filename=" + cb.getFilename() + ", " + toStringMinusFileName(cb, now);
    }
  
    /**
     * Little data structure to hold counts for a file.
     * Used doing a toJSON.
     */
    static class CachedBlockCountsPerFile {
      private int count = 0;
      private long size = 0;
      private int countData = 0;
      private long sizeData = 0;
      private final String filename;
  
      CachedBlockCountsPerFile(final String filename) {
        this.filename = filename;
      }
  
      public int getCount() {
        return count;
      }
  
      public long getSize() {
        return size;
      }
  
      public int getCountData() {
        return countData;
      }
  
      public long getSizeData() {
        return sizeData;
      }
  
      public String getFilename() {
        return filename;
     }
   }
 
   /**
    * @param filename
    * @param blocks
    * @return A JSON String of <code>filename</code> and counts of <code>blocks</code>
    * @throws JsonGenerationException
    * @throws JsonMappingException
    * @throws IOException
    */
   public static String toJSON(final String filename, final NavigableSet<CachedBlock> blocks)
   throws JsonGenerationException, JsonMappingException, IOException {
     CachedBlockCountsPerFile counts = new CachedBlockCountsPerFile(filename);
     for (CachedBlock cb: blocks) {
       counts.count++;
       counts.size += cb.getSize();
       BlockType bt = cb.getBlockType();
       if (bt != null && bt.isData()) {
         counts.countData++;
         counts.sizeData += cb.getSize();
       }
     }
     return MAPPER.writeValueAsString(counts);
   }
 
   /**
    * @param cbsbf
    * @return JSON string of <code>cbsf</code> aggregated
    * @throws JsonGenerationException
    * @throws JsonMappingException
    * @throws IOException
    */
   public static String toJSON(final CachedBlocksByFile cbsbf)
   throws JsonGenerationException, JsonMappingException, IOException {
     return MAPPER.writeValueAsString(cbsbf);
   }
 
   /**
    * @param bc
    * @return JSON string of <code>bc</code> content.
    * @throws JsonGenerationException
    * @throws JsonMappingException
    * @throws IOException
    */
   public static String toJSON(final BlockCache bc)
   throws JsonGenerationException, JsonMappingException, IOException {
     return MAPPER.writeValueAsString(bc);
   }
 
   /**
    * @param cb
    * @return The block content of <code>bc</code> as a String minus the filename.
    */
   public static String toStringMinusFileName(final CachedBlock cb, final long now) {
     return "offset=" + cb.getOffset() +
       ", size=" + cb.getSize() +
       ", age=" + (now - cb.getCachedTime()) +
       ", type=" + cb.getBlockType() +
       ", priority=" + cb.getBlockPriority();
   }
 
   /**
    * Get a {@link CachedBlocksByFile} instance and load it up by iterating content in
    * {@link BlockCache}.
    * @param conf Used to read configurations
    * @param bc Block Cache to iterate.
    * @return Laoded up instance of CachedBlocksByFile
    */
   public static CachedBlocksByFile getLoadedCachedBlocksByFile(final Configuration conf,
       final BlockCache bc) {
     CachedBlocksByFile cbsbf = new CachedBlocksByFile(conf);
     for (CachedBlock cb: bc) {
       if (cbsbf.update(cb)) break;
     }
     return cbsbf;
   }
 
   /**
    * Use one of these to keep a running account of cached blocks by file.  Throw it away when done.
    * This is different than metrics in that it is stats on current state of a cache.
    * See getLoadedCachedBlocksByFile
    */
   @JsonIgnoreProperties({"cachedBlockStatsByFile"})
   public static class CachedBlocksByFile {
     private int count;
     private int dataBlockCount;
     private long size;
     private long dataSize;
     private final long now = System.nanoTime();
     private final int max;
     public static final int DEFAULT_MAX = 100000;
  
     CachedBlocksByFile() {
       this(null);
     }
 
     CachedBlocksByFile(final Configuration c) {
       this.max = c == null? DEFAULT_MAX:
         c.getInt("hbase.ui.blockcache.by.file.max", DEFAULT_MAX);
     }
 
     /**
      * Map by filename. use concurent utils because we want our Map and contained blocks sorted.
      */
     private NavigableMap<String, NavigableSet<CachedBlock>> cachedBlockByFile =
       new ConcurrentSkipListMap<String, NavigableSet<CachedBlock>>();
     Histogram age = METRICS.newHistogram(CachedBlocksByFile.class, "age");
 
     /**
      * @param cb
      * @return True if full.... if we won't be adding any more.
      */
     public boolean update(final CachedBlock cb) {
       if (isFull()) return true;
       NavigableSet<CachedBlock> set = this.cachedBlockByFile.get(cb.getFilename());
       if (set == null) {
         set = new ConcurrentSkipListSet<CachedBlock>();
         this.cachedBlockByFile.put(cb.getFilename(), set);
       }
       set.add(cb);
       this.size += cb.getSize();
       this.count++;
       BlockType bt = cb.getBlockType();
       if (bt != null && bt.isData()) {
         this.dataBlockCount++;
         this.dataSize += cb.getSize();
       }
       long age = this.now - cb.getCachedTime();
       this.age.update(age);
       return false;
     }
 
     /**
      * @return True if full; i.e. there are more items in the cache but we only loaded up
      * the maximum set in configuration <code>hbase.ui.blockcache.by.file.max</code>
      * (Default: DEFAULT_MAX).
      */
     public boolean isFull() {
       return this.count >= this.max;
     }
  
     public NavigableMap<String, NavigableSet<CachedBlock>> getCachedBlockStatsByFile() {
       return this.cachedBlockByFile;
     }
 
     /**
      * @return count of blocks in the cache
      */
     public int getCount() {
       return count;
     }
 
     public int getDataCount() {
       return dataBlockCount;
     }
 
     /**
      * @return size of blocks in the cache
      */
     public long getSize() {
       return size;
     }
 
     /**
      * @return Size of data.
      */
     public long getDataSize() {
       return dataSize;
     }
 
     public AgeSnapshot getAgeInCacheSnapshot() {
       return new AgeSnapshot(this.age);
     }
 
     @Override
     public String toString() {
       Snapshot snapshot = this.age.getSnapshot();
       return "count=" + count + ", dataBlockCount=" + this.dataBlockCount + ", size=" + size +
           ", dataSize=" + getDataSize() +
           ", mean age=" + this.age.mean() + ", stddev age=" + this.age.stdDev() +
           ", min age=" + this.age.min() + ", max age=" + this.age.max() +
           ", 95th percentile age=" + snapshot.get95thPercentile() +
           ", 99th percentile age=" + snapshot.get99thPercentile();
     }
   }
 }