/**
    * 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;
  
  import java.io.IOException;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.io.util.HeapMemorySizeUtil;
  import org.apache.hadoop.hbase.util.VersionInfo;
  import org.apache.hadoop.hbase.zookeeper.ZKConfig;
  
  /**
   * Adds HBase configuration files to a Configuration
   */
  @InterfaceAudience.Public
  @InterfaceStability.Stable
  public class HBaseConfiguration extends Configuration {
    private static final Log LOG = LogFactory.getLog(HBaseConfiguration.class);
  
    /**
     * Instantiating HBaseConfiguration() is deprecated. Please use
     * HBaseConfiguration#create() to construct a plain Configuration
     */
    @Deprecated
    public HBaseConfiguration() {
      //TODO:replace with private constructor, HBaseConfiguration should not extend Configuration
      super();
      addHbaseResources(this);
      LOG.warn("instantiating HBaseConfiguration() is deprecated. Please use"
          + " HBaseConfiguration#create() to construct a plain Configuration");
    }
  
    /**
     * Instantiating HBaseConfiguration() is deprecated. Please use
     * HBaseConfiguration#create(conf) to construct a plain Configuration
     */
    @Deprecated
    public HBaseConfiguration(final Configuration c) {
      //TODO:replace with private constructor
      this();
      merge(this, c);
    }
  
    private static void checkDefaultsVersion(Configuration conf) {
      if (conf.getBoolean("hbase.defaults.for.version.skip", Boolean.FALSE)) return;
      String defaultsVersion = conf.get("hbase.defaults.for.version");
      String thisVersion = VersionInfo.getVersion();
      if (!thisVersion.equals(defaultsVersion)) {
        throw new RuntimeException(
          "hbase-default.xml file seems to be for an older version of HBase (" +
          defaultsVersion + "), this version is " + thisVersion);
      }
    }
  
    public static Configuration addHbaseResources(Configuration conf) {
      conf.addResource("hbase-default.xml");
      conf.addResource("hbase-site.xml");
  
      checkDefaultsVersion(conf);
      HeapMemorySizeUtil.checkForClusterFreeMemoryLimit(conf);
      return conf;
    }
  
    /**
     * Creates a Configuration with HBase resources
     * @return a Configuration with HBase resources
     */
    public static Configuration create() {
      Configuration conf = new Configuration();
      // In case HBaseConfiguration is loaded from a different classloader than
      // Configuration, conf needs to be set with appropriate class loader to resolve
      // HBase resources.
      conf.setClassLoader(HBaseConfiguration.class.getClassLoader());
      return addHbaseResources(conf);
    }
  
    /**
    * @param that Configuration to clone.
    * @return a Configuration created with the hbase-*.xml files plus
    * the given configuration.
    */
   public static Configuration create(final Configuration that) {
     Configuration conf = create();
     merge(conf, that);
     return conf;
   }
 
   /**
    * Merge two configurations.
    * @param destConf the configuration that will be overwritten with items
    *                 from the srcConf
    * @param srcConf the source configuration
    **/
   public static void merge(Configuration destConf, Configuration srcConf) {
     for (Map.Entry<String, String> e : srcConf) {
       destConf.set(e.getKey(), e.getValue());
     }
   }
 
   /**
    * Returns a subset of the configuration properties, matching the given key prefix.
    * The prefix is stripped from the return keys, ie. when calling with a prefix of "myprefix",
    * the entry "myprefix.key1 = value1" would be returned as "key1 = value1".  If an entry's
    * key matches the prefix exactly ("myprefix = value2"), it will <strong>not</strong> be
    * included in the results, since it would show up as an entry with an empty key.
    */
   public static Configuration subset(Configuration srcConf, String prefix) {
     Configuration newConf = new Configuration(false);
     for (Map.Entry<String, String> entry : srcConf) {
       if (entry.getKey().startsWith(prefix)) {
         String newKey = entry.getKey().substring(prefix.length());
         // avoid entries that would produce an empty key
         if (!newKey.isEmpty()) {
           newConf.set(newKey, entry.getValue());
         }
       }
     }
     return newConf;
   }
 
   /**
    * Sets all the entries in the provided {@code Map<String, String>} as properties in the
    * given {@code Configuration}.  Each property will have the specified prefix prepended,
    * so that the configuration entries are keyed by {@code prefix + entry.getKey()}.
    */
   public static void setWithPrefix(Configuration conf, String prefix,
                                    Iterable<Map.Entry<String, String>> properties) {
     for (Map.Entry<String, String> entry : properties) {
       conf.set(prefix + entry.getKey(), entry.getValue());
     }
   }
 
   /**
    * @return whether to show HBase Configuration in servlet
    */
   public static boolean isShowConfInServlet() {
     boolean isShowConf = false;
     try {
       if (Class.forName("org.apache.hadoop.conf.ConfServlet") != null) {
         isShowConf = true;
       }
     } catch (LinkageError e) {
        // should we handle it more aggressively in addition to log the error?
        LOG.warn("Error thrown: ", e);
     } catch (ClassNotFoundException ce) {
       LOG.debug("ClassNotFound: ConfServlet");
       // ignore
     }
     return isShowConf;
   }
 
   /**
    * Get the value of the <code>name</code> property as an <code>int</code>, possibly
    * referring to the deprecated name of the configuration property.
    * If no such property exists, the provided default value is returned,
    * or if the specified value is not a valid <code>int</code>,
    * then an error is thrown.
    *
    * @param name property name.
    * @param deprecatedName a deprecatedName for the property to use
    * if non-deprecated name is not used
    * @param defaultValue default value.
    * @throws NumberFormatException when the value is invalid
    * @return property value as an <code>int</code>,
    *         or <code>defaultValue</code>.
    */
   // TODO: developer note: This duplicates the functionality of deprecated
   // property support in Configuration in Hadoop 2. But since Hadoop-1 does not
   // contain these changes, we will do our own as usual. Replace these when H2 is default.
   public static int getInt(Configuration conf, String name,
       String deprecatedName, int defaultValue) {
     if (conf.get(deprecatedName) != null) {
       LOG.warn(String.format("Config option \"%s\" is deprecated. Instead, use \"%s\""
         , deprecatedName, name));
       return conf.getInt(deprecatedName, defaultValue);
     } else {
       return conf.getInt(name, defaultValue);
     }
   }
 
   /**
    * Get the password from the Configuration instance using the
    * getPassword method if it exists. If not, then fall back to the
    * general get method for configuration elements.
    * @param conf configuration instance for accessing the passwords
    * @param alias the name of the password element
    * @param defPass the default password
    * @return String password or default password
    * @throws IOException
    */
   public static String getPassword(Configuration conf, String alias,
       String defPass) throws IOException {
     String passwd = null;
     try {
       Method m = Configuration.class.getMethod("getPassword", String.class);
       char[] p = (char[]) m.invoke(conf, alias);
       if (p != null) {
         LOG.debug(String.format("Config option \"%s\" was found through" +
             " the Configuration getPassword method.", alias));
         passwd = new String(p);
       }
       else {
         LOG.debug(String.format(
             "Config option \"%s\" was not found. Using provided default value",
             alias));
         passwd = defPass;
       }
     } catch (NoSuchMethodException e) {
       // this is a version of Hadoop where the credential
       //provider API doesn't exist yet
       LOG.debug(String.format(
           "Credential.getPassword method is not available." +
           " Falling back to configuration."));
       passwd = conf.get(alias, defPass);
     } catch (SecurityException e) {
       throw new IOException(e.getMessage(), e);
     } catch (IllegalAccessException e) {
       throw new IOException(e.getMessage(), e);
     } catch (IllegalArgumentException e) {
       throw new IOException(e.getMessage(), e);
     } catch (InvocationTargetException e) {
       throw new IOException(e.getMessage(), e);
     }
     return passwd;
   }
 
   /**
    * Generates a {@link Configuration} instance by applying the ZooKeeper cluster key
    * to the base Configuration.  Note that additional configuration properties may be needed
    * for a remote cluster, so it is preferable to use
    * {@link #createClusterConf(Configuration, String, String)}.
    *
    * @param baseConf the base configuration to use, containing prefixed override properties
    * @param clusterKey the ZooKeeper quorum cluster key to apply, or {@code null} if none
    *
    * @return the merged configuration with override properties and cluster key applied
    *
    * @see #createClusterConf(Configuration, String, String)
    */
   public static Configuration createClusterConf(Configuration baseConf, String clusterKey)
       throws IOException {
     return createClusterConf(baseConf, clusterKey, null);
   }
 
   /**
    * Generates a {@link Configuration} instance by applying property overrides prefixed by
    * a cluster profile key to the base Configuration.  Override properties are extracted by
    * the {@link #subset(Configuration, String)} method, then the merged on top of the base
    * Configuration and returned.
    *
    * @param baseConf the base configuration to use, containing prefixed override properties
    * @param clusterKey the ZooKeeper quorum cluster key to apply, or {@code null} if none
    * @param overridePrefix the property key prefix to match for override properties,
    *     or {@code null} if none
    * @return the merged configuration with override properties and cluster key applied
    */
   public static Configuration createClusterConf(Configuration baseConf, String clusterKey,
                                                 String overridePrefix) throws IOException {
     Configuration clusterConf = HBaseConfiguration.create(baseConf);
     if (clusterKey != null && !clusterKey.isEmpty()) {
       applyClusterKeyToConf(clusterConf, clusterKey);
     }
 
     if (overridePrefix != null && !overridePrefix.isEmpty()) {
       Configuration clusterSubset = HBaseConfiguration.subset(clusterConf, overridePrefix);
       HBaseConfiguration.merge(clusterConf, clusterSubset);
     }
     return clusterConf;
   }
 
   /**
    * Apply the settings in the given key to the given configuration, this is
    * used to communicate with distant clusters
    * @param conf configuration object to configure
    * @param key string that contains the 3 required configuratins
    * @throws IOException
    */
   private static void applyClusterKeyToConf(Configuration conf, String key)
       throws IOException{
     ZKConfig.ZKClusterKey zkClusterKey = ZKConfig.transformClusterKey(key);
     conf.set(HConstants.ZOOKEEPER_QUORUM, zkClusterKey.getQuorumString());
     conf.setInt(HConstants.ZOOKEEPER_CLIENT_PORT, zkClusterKey.getClientPort());
     conf.set(HConstants.ZOOKEEPER_ZNODE_PARENT, zkClusterKey.getZnodeParent());
   }
 
   /**
    * For debugging.  Dump configurations to system output as xml format.
    * Master and RS configurations can also be dumped using
    * http services. e.g. "curl http://master:16010/dump"
    */
   public static void main(String[] args) throws Exception {
     HBaseConfiguration.create().writeXml(System.out);
   }
 }