/*
    * 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.encoding;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.Bytes;
  
  /**
   * Provide access to all data block encoding algorithms. All of the algorithms
   * are required to have unique id which should <b>NEVER</b> be changed. If you
   * want to add a new algorithm/version, assign it a new id. Announce the new id
   * in the HBase mailing list to prevent collisions.
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public enum DataBlockEncoding {
  
    /** Disable data block encoding. */
    NONE(0, null),
    // id 1 is reserved for the BITSET algorithm to be added later
    PREFIX(2, "org.apache.hadoop.hbase.io.encoding.PrefixKeyDeltaEncoder"),
    DIFF(3, "org.apache.hadoop.hbase.io.encoding.DiffKeyDeltaEncoder"),
    FAST_DIFF(4, "org.apache.hadoop.hbase.io.encoding.FastDiffDeltaEncoder"),
    // id 5 is reserved for the COPY_KEY algorithm for benchmarking
    // COPY_KEY(5, "org.apache.hadoop.hbase.io.encoding.CopyKeyDataBlockEncoder"),
    PREFIX_TREE(6, "org.apache.hadoop.hbase.codec.prefixtree.PrefixTreeCodec");
  
    private final short id;
    private final byte[] idInBytes;
    private DataBlockEncoder encoder;
    private final String encoderCls;
  
    public static final int ID_SIZE = Bytes.SIZEOF_SHORT;
  
    /** Maps data block encoding ids to enum instances. */
    private static Map<Short, DataBlockEncoding> idToEncoding =
        new HashMap<Short, DataBlockEncoding>();
  
    static {
      for (DataBlockEncoding algo : values()) {
        if (idToEncoding.containsKey(algo.id)) {
          throw new RuntimeException(String.format(
              "Two data block encoder algorithms '%s' and '%s' have " +
              "the same id %d",
              idToEncoding.get(algo.id).toString(), algo.toString(),
              (int) algo.id));
        }
        idToEncoding.put(algo.id, algo);
      }
    }
  
    private DataBlockEncoding(int id, String encoderClsName) {
      if (id < Short.MIN_VALUE || id > Short.MAX_VALUE) {
        throw new AssertionError(
            "Data block encoding algorithm id is out of range: " + id);
      }
      this.id = (short) id;
      this.idInBytes = Bytes.toBytes(this.id);
      if (idInBytes.length != ID_SIZE) {
        // White this may seem redundant, if we accidentally serialize
        // the id as e.g. an int instead of a short, all encoders will break.
        throw new RuntimeException("Unexpected length of encoder ID byte " +
            "representation: " + Bytes.toStringBinary(idInBytes));
      }
      this.encoderCls = encoderClsName;
    }
  
    /**
     * @return name converted to bytes.
     */
    public byte[] getNameInBytes() {
      return Bytes.toBytes(toString());
    }
  
    /**
     * @return The id of a data block encoder.
     */
    public short getId() {
      return id;
   }
 
   /**
    * Writes id in bytes.
    * @param stream where the id should be written.
    */
   public void writeIdInBytes(OutputStream stream) throws IOException {
     stream.write(idInBytes);
   }
 
 
   /**
    * Writes id bytes to the given array starting from offset.
    *
    * @param dest output array
    * @param offset starting offset of the output array
    * @throws IOException
    */
   public void writeIdInBytes(byte[] dest, int offset) throws IOException {
     System.arraycopy(idInBytes, 0, dest, offset, ID_SIZE);
   }
 
   /**
    * Return new data block encoder for given algorithm type.
    * @return data block encoder if algorithm is specified, null if none is
    *         selected.
    */
   public DataBlockEncoder getEncoder() {
     if (encoder == null && id != 0) {
       // lazily create the encoder
       encoder = createEncoder(encoderCls);
     }
     return encoder;
   }
 
   /**
    * Find and create data block encoder for given id;
    * @param encoderId id of data block encoder.
    * @return Newly created data block encoder.
    */
   public static DataBlockEncoder getDataBlockEncoderById(short encoderId) {
     if (!idToEncoding.containsKey(encoderId)) {
       throw new IllegalArgumentException(String.format(
           "There is no data block encoder for given id '%d'",
           (int) encoderId));
     }
 
     return idToEncoding.get(encoderId).getEncoder();
   }
 
   /**
    * Find and return the name of data block encoder for the given id.
    * @param encoderId id of data block encoder
    * @return name, same as used in options in column family
    */
   public static String getNameFromId(short encoderId) {
     return idToEncoding.get(encoderId).toString();
   }
 
   /**
    * Check if given encoder has this id.
    * @param encoder encoder which id will be checked
    * @param encoderId id which we except
    * @return true if id is right for given encoder, false otherwise
    * @exception IllegalArgumentException
    *            thrown when there is no matching data block encoder
    */
   public static boolean isCorrectEncoder(DataBlockEncoder encoder,
       short encoderId) {
     if (!idToEncoding.containsKey(encoderId)) {
       throw new IllegalArgumentException(String.format(
           "There is no data block encoder for given id '%d'",
           (int) encoderId));
     }
 
     DataBlockEncoding algorithm = idToEncoding.get(encoderId);
     String encoderCls = encoder.getClass().getName();
     return encoderCls.equals(algorithm.encoderCls);
   }
 
   public static DataBlockEncoding getEncodingById(short dataBlockEncodingId) {
     return idToEncoding.get(dataBlockEncodingId);
   }
 
   protected static DataBlockEncoder createEncoder(String fullyQualifiedClassName){
       try {
         return (DataBlockEncoder)Class.forName(fullyQualifiedClassName).newInstance();
       } catch (InstantiationException e) {
         throw new RuntimeException(e);
       } catch (IllegalAccessException e) {
         throw new RuntimeException(e);
       } catch (ClassNotFoundException e) {
         throw new IllegalArgumentException(e);
       }
   }
 
 }