/*
    * 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
    *
    *     https://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.io.IOException;
  
  import org.xml.sax.Attributes;
  import org.xml.sax.ContentHandler;
  import org.xml.sax.DTDHandler;
  import org.xml.sax.EntityResolver;
  import org.xml.sax.ErrorHandler;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  import org.xml.sax.XMLReader;
  import org.xml.sax.helpers.AttributesImpl;
  
  /**
   * <p>
   * A base class for &quot;faked&quot; {@code XMLReader} classes that transform a configuration object in a set of SAX
   * parsing events.
   * </p>
   * <p>
   * This class provides dummy implementations for most of the methods defined in the {@code XMLReader} interface that are
   * not used for this special purpose. There will be concrete sub classes that process specific configuration classes.
   * </p>
   */
  public abstract class ConfigurationXMLReader implements XMLReader {
  
      /** Constant for the namespace URI. */
      protected static final String NS_URI = "";
  
      /** Constant for the default name of the root element. */
      private static final String DEFAULT_ROOT_NAME = "config";
  
      /** An empty attributes object. */
      private static final Attributes EMPTY_ATTRS = new AttributesImpl();
  
      /** Stores the content handler. */
      private ContentHandler contentHandler;
  
      /** Stores an exception that occurred during parsing. */
      private SAXException exception;
  
      /** Stores the name for the root element. */
      private String rootName;
  
      /**
       * Creates a new instance of {@code ConfigurationXMLReader}.
       */
      protected ConfigurationXMLReader() {
          rootName = DEFAULT_ROOT_NAME;
      }
  
      /**
       * Fires a SAX characters event.
       *
       * @param text the text
       */
      protected void fireCharacters(final String text) {
          if (getException() == null) {
              try {
                  final char[] ch = text.toCharArray();
                  getContentHandler().characters(ch, 0, ch.length);
              } catch (final SAXException ex) {
                  exception = ex;
              }
          }
      }
  
      /**
       * Fires a SAX element end event.
       *
       * @param name the name of the affected element
       */
      protected void fireElementEnd(final String name) {
          if (getException() == null) {
              try {
                  getContentHandler().endElement(NS_URI, name, name);
              } catch (final SAXException ex) {
                  exception = ex;
              }
          }
      }
  
     /**
      * Fires a SAX element start event.
      *
      * @param name the name of the actual element
      * @param attribs the attributes of this element (can be <strong>null</strong>)
      */
     protected void fireElementStart(final String name, final Attributes attribs) {
         if (getException() == null) {
             try {
                 final Attributes at = attribs == null ? EMPTY_ATTRS : attribs;
                 getContentHandler().startElement(NS_URI, name, name, at);
             } catch (final SAXException ex) {
                 exception = ex;
             }
         }
     }
 
     /**
      * Gets the actually set content handler.
      *
      * @return the content handler
      */
     @Override
     public ContentHandler getContentHandler() {
         return contentHandler;
     }
 
     /**
      * Gets the DTD handler. This class does not support DTD handlers, so this method always returns <strong>null</strong>.
      *
      * @return the DTD handler
      */
     @Override
     public DTDHandler getDTDHandler() {
         return null;
     }
 
     /**
      * Gets the entity resolver. This class does not support an entity resolver, so this method always returns
      * <strong>null</strong>.
      *
      * @return the entity resolver
      */
     @Override
     public EntityResolver getEntityResolver() {
         return null;
     }
 
     /**
      * Gets the error handler. This class does not support an error handler, so this method always returns <strong>null</strong>.
      *
      * @return the error handler
      */
     @Override
     public ErrorHandler getErrorHandler() {
         return null;
     }
 
     /**
      * Gets a reference to an exception that occurred during parsing.
      *
      * @return a SAXExcpetion or <strong>null</strong> if none occurred
      */
     public SAXException getException() {
         return exception;
     }
 
     /**
      * Dummy implementation of the interface method.
      *
      * @param name the name of the feature
      * @return always <strong>false</strong> (no features are supported)
      */
     @Override
     public boolean getFeature(final String name) {
         return false;
     }
 
     /**
      * Gets a reference to the configuration that is parsed by this object.
      *
      * @return the parsed configuration
      */
     public abstract Configuration getParsedConfiguration();
 
     /**
      * Dummy implementation of the interface method. No properties are supported, so this method always returns <strong>null</strong>.
      *
      * @param name the name of the requested property
      * @return the property value
      */
     @Override
     public Object getProperty(final String name) {
         return null;
     }
 
     /**
      * Gets the name to be used for the root element.
      *
      * @return the name for the root element
      */
     public String getRootName() {
         return rootName;
     }
 
     /**
      * Parses the actual configuration object. The passed input source will be ignored.
      *
      * @param input the input source (ignored)
      * @throws IOException if no configuration was specified
      * @throws SAXException if an error occurs during parsing
      */
     @Override
     public void parse(final InputSource input) throws IOException, SAXException {
         parseConfiguration();
     }
 
     /**
      * Parses the current configuration object. The passed system ID will be ignored.
      *
      * @param systemId the system ID (ignored)
      * @throws IOException if no configuration was specified
      * @throws SAXException if an error occurs during parsing
      */
     @Override
     public void parse(final String systemId) throws IOException, SAXException {
         parseConfiguration();
     }
 
     /**
      * Parses the configuration object and generates SAX events. This is the main processing method.
      *
      * @throws IOException if no configuration has been specified
      * @throws SAXException if an error occurs during parsing
      */
     protected void parseConfiguration() throws IOException, SAXException {
         if (getParsedConfiguration() == null) {
             throw new IOException("No configuration specified.");
         }
 
         if (getContentHandler() != null) {
             exception = null;
             getContentHandler().startDocument();
             processKeys();
             if (getException() != null) {
                 throw getException();
             }
             getContentHandler().endDocument();
         }
     }
 
     /**
      * Processes all keys stored in the actual configuration. This method is called by {@code parseConfiguration()} to start
      * the main parsing process. {@code parseConfiguration()} calls the content handler's {@code startDocument()} and
      * {@code endElement()} methods and cares for exception handling. The remaining actions are left to this method that
      * must be implemented in a concrete sub class.
      *
      * @throws IOException if an IO error occurs
      * @throws SAXException if a SAX error occurs
      */
     protected abstract void processKeys() throws IOException, SAXException;
 
     /**
      * Sets the content handler. The object specified here will receive SAX events during parsing.
      *
      * @param handler the content handler
      */
     @Override
     public void setContentHandler(final ContentHandler handler) {
         contentHandler = handler;
     }
 
     /**
      * Sets the DTD handler. The passed value is ignored.
      *
      * @param handler the handler to be set
      */
     @Override
     public void setDTDHandler(final DTDHandler handler) {
     }
 
     /**
      * Sets the entity resolver. The passed value is ignored.
      *
      * @param resolver the entity resolver
      */
     @Override
     public void setEntityResolver(final EntityResolver resolver) {
     }
 
     /**
      * Sets the error handler. The passed value is ignored.
      *
      * @param handler the error handler
      */
     @Override
     public void setErrorHandler(final ErrorHandler handler) {
     }
 
     /**
      * Dummy implementation of the interface method.
      *
      * @param name the name of the feature to be set
      * @param value the value of the feature
      */
     @Override
     public void setFeature(final String name, final boolean value) {
     }
 
     /**
      * Dummy implementation of the interface method. No properties are supported, so a call of this method just has no
      * effect.
      *
      * @param name the property name
      * @param value the property value
      */
     @Override
     public void setProperty(final String name, final Object value) {
     }
 
     /**
      * Sets the name for the root element.
      *
      * @param string the name for the root element.
      */
     public void setRootName(final String string) {
         rootName = string;
     }
 }