/**
    * 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 org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.Bytes;
  
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  /**
   * Namespace POJO class. Used to represent and define namespaces.
   *
   * Descriptors will be persisted in an hbase table.
   * This works since namespaces are essentially metadata of a group of tables
   * as opposed to a more tangible container.
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public class NamespaceDescriptor {
  
    /** System namespace name. */
    public static final byte [] SYSTEM_NAMESPACE_NAME = Bytes.toBytes("hbase");
    public static final String SYSTEM_NAMESPACE_NAME_STR =
        Bytes.toString(SYSTEM_NAMESPACE_NAME);
    /** Default namespace name. */
    public static final byte [] DEFAULT_NAMESPACE_NAME = Bytes.toBytes("default");
    public static final String DEFAULT_NAMESPACE_NAME_STR =
        Bytes.toString(DEFAULT_NAMESPACE_NAME);
  
    public static final NamespaceDescriptor DEFAULT_NAMESPACE = NamespaceDescriptor.create(
      DEFAULT_NAMESPACE_NAME_STR).build();
    public static final NamespaceDescriptor SYSTEM_NAMESPACE = NamespaceDescriptor.create(
      SYSTEM_NAMESPACE_NAME_STR).build();
  
    public final static Set<String> RESERVED_NAMESPACES;
    static {
      Set<String> set = new HashSet<String>();
      set.add(NamespaceDescriptor.DEFAULT_NAMESPACE_NAME_STR);
      set.add(NamespaceDescriptor.SYSTEM_NAMESPACE_NAME_STR);
      RESERVED_NAMESPACES = Collections.unmodifiableSet(set);
    }
    public final static Set<byte[]> RESERVED_NAMESPACES_BYTES;
    static {
      Set<byte[]> set = new TreeSet<byte[]>(Bytes.BYTES_RAWCOMPARATOR);
      for(String name: RESERVED_NAMESPACES) {
        set.add(Bytes.toBytes(name));
      }
      RESERVED_NAMESPACES_BYTES = Collections.unmodifiableSet(set);
    }
  
    private String name;
    private Map<String, String> configuration;
  
    public static final Comparator<NamespaceDescriptor> NAMESPACE_DESCRIPTOR_COMPARATOR =
        new Comparator<NamespaceDescriptor>() {
      @Override
      public int compare(NamespaceDescriptor namespaceDescriptor,
          NamespaceDescriptor namespaceDescriptor2) {
        return namespaceDescriptor.getName().compareTo(namespaceDescriptor2.getName());
      }
    };
  
    private NamespaceDescriptor() {
    }
  
    private NamespaceDescriptor(String name) {
      this.name = name;
    }
  
    public String getName() {
      return name;
    }
  
    /**
     * Getter for accessing the configuration value by key
     */
   public String getConfigurationValue(String key) {
     return configuration.get(key);
   }
 
   /**
    * Getter for fetching an unmodifiable {@link #configuration} map.
    */
   public Map<String, String> getConfiguration() {
     // shallow pointer copy
     return Collections.unmodifiableMap(configuration);
   }
 
   /**
    * Setter for storing a configuration setting in {@link #configuration} map.
    * @param key Config key. Same as XML config key e.g. hbase.something.or.other.
    * @param value String value. If null, removes the setting.
    */
   public void setConfiguration(String key, String value) {
     if (value == null) {
       removeConfiguration(key);
     } else {
       configuration.put(key, value);
     }
   }
 
   /**
    * Remove a config setting represented by the key from the {@link #configuration} map
    */
   public void removeConfiguration(final String key) {
     configuration.remove(key);
   }
 
   @Override
   public String toString() {
     StringBuilder s = new StringBuilder();
     s.append('{');
     s.append(HConstants.NAME);
     s.append(" => '");
     s.append(name);
     s.append("'");
     for (Map.Entry<String, String> e : configuration.entrySet()) {
       String key = e.getKey();
       String value = e.getValue();
       if (key == null) {
         continue;
       }
       s.append(", ");
       s.append(key);
       s.append(" => '");
       s.append(value);
       s.append("'");
     }
     s.append('}');
     return s.toString();
   }
 
   public static Builder create(String name) {
     return new Builder(name);
   }
 
   public static Builder create(NamespaceDescriptor ns) {
     return new Builder(ns);
   }
 
   @InterfaceAudience.Public
   @InterfaceStability.Evolving
   public static class Builder {
     private String bName;
     private Map<String, String> bConfiguration = new TreeMap<String, String>();
 
     private Builder(NamespaceDescriptor ns) {
       this.bName = ns.name;
       this.bConfiguration = ns.configuration;
     }
 
     private Builder(String name) {
       this.bName = name;
     }
 
     public Builder addConfiguration(Map<String, String> configuration) {
       this.bConfiguration.putAll(configuration);
       return this;
     }
 
     public Builder addConfiguration(String key, String value) {
       this.bConfiguration.put(key, value);
       return this;
     }
 
     public Builder removeConfiguration(String key) {
       this.bConfiguration.remove(key);
       return this;
     }
 
     public NamespaceDescriptor build() {
       if (this.bName == null){
          throw new IllegalArgumentException("A name has to be specified in a namespace.");
       }
 
       NamespaceDescriptor desc = new NamespaceDescriptor(this.bName);
       desc.configuration = this.bConfiguration;
       return desc;
     }
   }
 }