/*
    * 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.commons.configuration2;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Set;
  
  import javax.naming.Context;
  import javax.naming.InitialContext;
  import javax.naming.NameClassPair;
  import javax.naming.NameNotFoundException;
  import javax.naming.NamingEnumeration;
  import javax.naming.NamingException;
  import javax.naming.NotContextException;
  
  import org.apache.commons.configuration2.event.ConfigurationErrorEvent;
  import org.apache.commons.configuration2.io.ConfigurationLogger;
  import org.apache.commons.lang3.StringUtils;
  
  /**
   * This Configuration class allows you to interface with a JNDI datasource. A JNDIConfiguration is read-only, write
   * operations will throw an UnsupportedOperationException. The clear operations are supported but the underlying JNDI
   * data source is not changed.
   */
  public class JNDIConfiguration extends AbstractConfiguration {
      /** The prefix of the context. */
      private String prefix;
  
      /** The initial JNDI context. */
      private Context context;
  
      /** The base JNDI context. */
      private Context baseContext;
  
      /** The Set of keys that have been virtually cleared. */
      private final Set<String> clearedProperties = new HashSet<>();
  
      /**
       * Creates a JNDIConfiguration using the default initial context as the root of the properties.
       *
       * @throws NamingException thrown if an error occurs when initializing the default context
       */
      public JNDIConfiguration() throws NamingException {
          this((String) null);
      }
  
      /**
       * Creates a JNDIConfiguration using the specified initial context as the root of the properties.
       *
       * @param context the initial context
       */
      public JNDIConfiguration(final Context context) {
          this(context, null);
      }
  
      /**
       * Creates a JNDIConfiguration using the specified initial context shifted by the specified prefix as the root of the
       * properties.
       *
       * @param context the initial context
       * @param prefix the prefix
       */
      public JNDIConfiguration(final Context context, final String prefix) {
          this.context = context;
          this.prefix = prefix;
          initLogger(new ConfigurationLogger(JNDIConfiguration.class));
          addErrorLogListener();
      }
  
      /**
       * Creates a JNDIConfiguration using the default initial context, shifted with the specified prefix, as the root of the
       * properties.
       *
       * @param prefix the prefix
       *
       * @throws NamingException thrown if an error occurs when initializing the default context
       */
      public JNDIConfiguration(final String prefix) throws NamingException {
          this(new InitialContext(), prefix);
      }
 
     /**
      * <p>
      * <strong>This operation is not supported and will throw an UnsupportedOperationException.</strong>
      * </p>
      *
      * @param key the key
      * @param obj the value
      * @throws UnsupportedOperationException always thrown as this method is not supported
      */
     @Override
     protected void addPropertyDirect(final String key, final Object obj) {
         throw new UnsupportedOperationException("This operation is not supported");
     }
 
     /**
      * Removes the specified property.
      *
      * @param key the key of the property to remove
      */
     @Override
     protected void clearPropertyDirect(final String key) {
         clearedProperties.add(key);
     }
 
     /**
      * Checks whether the specified key is contained in this configuration.
      *
      * @param key the key to check
      * @return a flag whether this key is stored in this configuration
      */
     @Override
     protected boolean containsKeyInternal(String key) {
         if (clearedProperties.contains(key)) {
             return false;
         }
         key = key.replace('.', '/');
         try {
             // throws a NamingException if JNDI doesn't contain the key.
             getBaseContext().lookup(key);
             return true;
         } catch (final NameNotFoundException e) {
             // expected exception, no need to log it
             return false;
         } catch (final NamingException e) {
             fireError(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, key, null, e);
             return false;
         }
     }
 
     /**
      * Tests whether this configuration contains one or more matches to this value. This operation stops at first match
      * but may be more expensive than the containsKey method.
      * @since 2.11.0
      */
     @Override
     protected boolean containsValueInternal(final Object value) {
         return contains(getKeys(), value);
     }
 
     /**
      * Gets the base context with the prefix applied.
      *
      * @return the base context
      * @throws NamingException if an error occurs
      */
     public Context getBaseContext() throws NamingException {
         if (baseContext == null) {
             baseContext = (Context) getContext().lookup(prefix == null ? "" : prefix);
         }
 
         return baseContext;
     }
 
     /**
      * Gets the initial context used by this configuration. This context is independent of the prefix specified.
      *
      * @return the initial context
      */
     public Context getContext() {
         return context;
     }
 
     /**
      * Because JNDI is based on a tree configuration, we need to filter down the tree, till we find the Context specified by
      * the key to start from. Otherwise return null.
      *
      * @param path the path of keys to traverse in order to find the context
      * @param context the context to start from
      * @return The context at that key's location in the JNDI tree, or null if not found
      * @throws NamingException if JNDI has an issue
      */
     private Context getContext(final List<String> path, final Context context) throws NamingException {
         // return the current context if the path is empty
         if (path == null || path.isEmpty()) {
             return context;
         }
 
         final String key = path.get(0);
 
         // search a context matching the key in the context's elements
         NamingEnumeration<NameClassPair> elements = null;
 
         try {
             elements = context.list("");
             while (elements.hasMore()) {
                 final NameClassPair nameClassPair = elements.next();
                 final String name = nameClassPair.getName();
                 final Object object = context.lookup(name);
 
                 if (object instanceof Context && name.equals(key)) {
                     final Context subcontext = (Context) object;
 
                     // recursive search in the sub context
                     return getContext(path.subList(1, path.size()), subcontext);
                 }
             }
         } finally {
             if (elements != null) {
                 elements.close();
             }
         }
 
         return null;
     }
 
     /**
      * Gets an iterator with all property keys stored in this configuration.
      *
      * @return an iterator with all keys
      */
     @Override
     protected Iterator<String> getKeysInternal() {
         return getKeysInternal("");
     }
 
     /**
      * Gets an iterator with all property keys starting with the given prefix.
      *
      * @param prefix the prefix
      * @return an iterator with the selected keys
      */
     @Override
     protected Iterator<String> getKeysInternal(final String prefix) {
         // build the path
         final String[] splitPath = StringUtils.split(prefix, ".");
 
         final List<String> path = Arrays.asList(splitPath);
 
         try {
             // find the context matching the specified path
             final Context context = getContext(path, getBaseContext());
 
             // return all the keys under the context found
             final Set<String> keys = new HashSet<>();
             if (context != null) {
                 recursiveGetKeys(keys, context, prefix, new HashSet<>());
             } else if (containsKey(prefix)) {
                 // add the prefix if it matches exactly a property key
                 keys.add(prefix);
             }
 
             return keys.iterator();
         } catch (final NameNotFoundException e) {
             // expected exception, no need to log it
             return new ArrayList<String>().iterator();
         } catch (final NamingException e) {
             fireError(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, null, null, e);
             return new ArrayList<String>().iterator();
         }
     }
 
     /**
      * Gets the prefix.
      *
      * @return the prefix
      */
     public String getPrefix() {
         return prefix;
     }
 
     /**
      * Gets the value of the specified property.
      *
      * @param key the key of the property
      * @return the value of this property
      */
     @Override
     protected Object getPropertyInternal(String key) {
         if (clearedProperties.contains(key)) {
             return null;
         }
 
         try {
             key = key.replace('.', '/');
             return getBaseContext().lookup(key);
         } catch (final NameNotFoundException | NotContextException nctxex) {
             // expected exception, no need to log it
             return null;
         } catch (final NamingException e) {
             fireError(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, key, null, e);
             return null;
         }
     }
 
     /**
      * Returns a flag whether this configuration is empty.
      *
      * @return the empty flag
      */
     @Override
     protected boolean isEmptyInternal() {
         try {
             NamingEnumeration<NameClassPair> enumeration = null;
 
             try {
                 enumeration = getBaseContext().list("");
                 return !enumeration.hasMore();
             } finally {
                 // close the enumeration
                 if (enumeration != null) {
                     enumeration.close();
                 }
             }
         } catch (final NamingException e) {
             fireError(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, null, null, e);
             return true;
         }
     }
 
     /**
      * This method recursive traverse the JNDI tree, looking for Context objects. When it finds them, it traverses them as
      * well. Otherwise it just adds the values to the list of keys found.
      *
      * @param keys All the keys that have been found.
      * @param context The parent context
      * @param prefix What prefix we are building on.
      * @param processedCtx a set with the so far processed objects
      * @throws NamingException If JNDI has an issue.
      */
     private void recursiveGetKeys(final Set<String> keys, final Context context, final String prefix, final Set<Context> processedCtx) throws NamingException {
         processedCtx.add(context);
         NamingEnumeration<NameClassPair> elements = null;
 
         try {
             elements = context.list("");
 
             // iterates through the context's elements
             while (elements.hasMore()) {
                 final NameClassPair nameClassPair = elements.next();
                 final String name = nameClassPair.getName();
                 final Object object = context.lookup(name);
 
                 // build the key
                 final StringBuilder keyBuilder = new StringBuilder();
                 keyBuilder.append(prefix);
                 if (keyBuilder.length() > 0) {
                     keyBuilder.append(".");
                 }
                 keyBuilder.append(name);
 
                 if (object instanceof Context) {
                     // add the keys of the sub context
                     final Context subcontext = (Context) object;
                     if (!processedCtx.contains(subcontext)) {
                         recursiveGetKeys(keys, subcontext, keyBuilder.toString(), processedCtx);
                     }
                 } else {
                     // add the key
                     keys.add(keyBuilder.toString());
                 }
             }
         } finally {
             // close the enumeration
             if (elements != null) {
                 elements.close();
             }
         }
     }
 
     /**
      * Sets the initial context of the configuration.
      *
      * @param context the context
      */
     public void setContext(final Context context) {
         // forget the removed properties
         clearedProperties.clear();
 
         // change the context
         this.context = context;
     }
 
     /**
      * Sets the prefix.
      *
      * @param prefix The prefix to set
      */
     public void setPrefix(final String prefix) {
         this.prefix = prefix;
 
         // clear the previous baseContext
         baseContext = null;
     }
 
     /**
      * <p>
      * <strong>This operation is not supported and will throw an UnsupportedOperationException.</strong>
      * </p>
      *
      * @param key the key
      * @param value the value
      * @throws UnsupportedOperationException always thrown as this method is not supported
      */
     @Override
     protected void setPropertyInternal(final String key, final Object value) {
         throw new UnsupportedOperationException("This operation is not supported");
     }
 }