/* Copyright © 2013 Matthew Champion

 All rights reserved.

 Redistribution and use in source and binary forms, with or without

 modification, are permitted provided that the following conditions are met:

  * Redistributions of source code must retain the above copyright

       notice, this list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above copyright

       notice, this list of conditions and the following disclaimer in the

       documentation and/or other materials provided with the distribution.

  * Neither the name of mattunderscore.com nor the

       names of its contributors may be used to endorse or promote products

       derived from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 DISCLAIMED. IN NO EVENT SHALL MATTHEW CHAMPION BE LIABLE FOR ANY

 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */

 package com.mattunderscore.filter.contentnegotiation.variantsource;

 import java.io.ByteArrayInputStream;

 import java.io.FileInputStream;

 import java.io.FileNotFoundException;

 import java.util.Enumeration;

 import java.util.HashMap;

 import java.util.List;

 import java.util.Map;

 import javax.servlet.FilterConfig;

 import javax.servlet.ServletContext;

 import com.mattunderscore.filter.contentnegotiation.parser.Variant;

 /**

  * A variant source that parses XML for variants and is configured from a filter. It is intended to

  * be called from filters and is configured with a filter config. Any configuration this needs

  * should be set in the filter init-params of the web.xml. The {@link VariantSAXHandler} that is

  * used to parse the XML as be configured.

  * <P>

  * It uses the {@link BaseVariantXMLSource} and enhances it by supporting configuration from a

  * {@link FilterConfig} object.

  * 

  * @author Matt Champion

  * @since 0.2.0

  */

 public class FilterVariantXMLSource implements VariantSourceForFilter

 {

     /**

      * Name of the parameter that identifies the SAX hander to use.

      */

     public static final String SAX_HANDLER = "saxHandlerClass";

     public static final String XML_INPUT_FILE = "xmlInputFile";

     public static final String XML_INPUT_STRING = "xmlInputString";

     /**

      * Name of parameter that identifies a resource that can be retrieved as a stream from the

      * servlet context.

      */

     public static final String XML_INPUT_RESOURCE = "xmlInputResource";

     private final Map<String, String> parameterMap = new HashMap<String, String>();

     private final BaseVariantXMLSource source = new BaseVariantXMLSource();

     public FilterVariantXMLSource()

     {

     }

     @Override

     public void configureSource(FilterConfig config) throws VariantSourceConfigurationException

     {

         final ServletContext context = config.getServletContext();

         @SuppressWarnings("unchecked")

         final Enumeration<String> parameterNames = config.getInitParameterNames();

         while (parameterNames.hasMoreElements())

         {

             final String parameterName = parameterNames.nextElement();

             final String parameterValue = config.getInitParameter(parameterName);

             parameterMap.put(parameterName, parameterValue);

         }

         if (parameterMap.containsKey(SAX_HANDLER))

         {

             try

             {

                 final Class<?> handlerClass = Class.forName(parameterMap.get(SAX_HANDLER));

                 final Object handlerObject = handlerClass.newInstance();

                 source.setHandler((VariantSAXHandler) handlerObject);

             }

             catch (final InstantiationException ex)

             {

                 throw new VariantSourceConfigurationException("Unable to construct SAX handler",

                         ex);

             }

             catch (final IllegalAccessException ex)

             {

                 throw new VariantSourceConfigurationException("Unable to construct SAX handler",

                         ex);

             }

             catch (final ClassNotFoundException ex)

             {

                 throw new VariantSourceConfigurationException("Unable to construct SAX handler",

                         ex);

             }

         }

         if (parameterMap.containsKey(XML_INPUT_RESOURCE))

         {

             source.setInputStream(context.getResourceAsStream(

                     parameterMap.get(XML_INPUT_RESOURCE)));

         }

         else if (parameterMap.containsKey(XML_INPUT_FILE))

         {

             try

             {

                 source.setInputStream(new FileInputStream(parameterMap.get(XML_INPUT_FILE)));

             }

             catch (final FileNotFoundException exception)

             {

                 throw new VariantSourceConfigurationException("Unable get XML file", exception);

             }

         }

         else if (parameterMap.containsKey(XML_INPUT_STRING))

         {

             source.setInputStream(new ByteArrayInputStream(parameterMap.get(XML_INPUT_STRING)

                     .getBytes()));

         }

         else

         {

             throw new VariantSourceConfigurationException("Input stream not set");

         }

     }

     @Override

     public List<Variant> getVariants() throws VariantSourceException

     {

         return source.getVariants();

     }

 }