/*

  * 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.pipeline.config;

 import java.io.File;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.URL;

 import java.util.ArrayList;

 import java.util.Iterator;

 import java.util.List;

 import org.apache.commons.digester.Digester;

 import org.apache.commons.digester.RuleSet;

 import org.apache.commons.pipeline.PipelineCreationException;

 import org.apache.commons.pipeline.Pipeline;

 import org.xml.sax.SAXException;

 /**

  * This factory is designed to simplify creating a pipeline using Digester.

  * @see  PipelineRuleSet for additional information on the format of the

  * XML configuration file.

  */

 public class DigesterPipelineFactory implements org.apache.commons.pipeline.PipelineFactory {

     /** Digester rule sets used to configure the Digester instance. */

     private List<RuleSet> ruleSets = new ArrayList<RuleSet>();

     /**

      * Factory will create a pipeline from the specified Digester configuration file

      * if this filename is not null.

      */

     private URL confURL;

     /**

      * A factory created by this constructor will create a pipeline from the specified

      * XML configuration file.

      * @param configFile the XML file containing pipeline configuration information

      */

     public DigesterPipelineFactory(URL confURL) {

         if (confURL == null) throw new IllegalArgumentException("Configuration file URL may not be null.");

         this.confURL = confURL;

         //PipelineRuleSet needs a reference to {@link org.apache.commons.digester.RuleSet RuleSet}s

         //used to parse the configuration file in case configuration is split up between multiple

         //files.

         ruleSets.add(new PipelineRuleSet(ruleSets));        

     }

     /**

      * Creates a new pipeline based upon the configuration of this factory instance.

      * @throws org.apache.commons.pipeline.PipelineCreationException Thrown if an error is encountered parsing the configuration file.

      * @return The newly created pipeline instance

      */

     public Pipeline createPipeline() throws PipelineCreationException {

         try {

                 Digester digester = new Digester();

                 this.initDigester(digester);

             InputStream in = confURL.openStream();

             try {

                 return (Pipeline) digester.parse(in);

             } finally {

                 in.close();

             }

         } catch (IOException e) {

             throw new PipelineCreationException("An IOException occurred reading the configuration file: " + e.getMessage(), e);

         } catch (SAXException e) {

             throw new PipelineCreationException("A formatting error exists in the configuration file: " + e.getMessage(), e);

         }

     }

     /**

      * Initialize a Digester instance with the rule sets provided to this factory.

      * @param digester The digester instance to be initialized

      */

     public void initDigester(Digester digester) {

         for (Iterator iter = ruleSets.iterator(); iter.hasNext();) {

             digester.addRuleSet((RuleSet) iter.next());

         }

     }

     /**

      * Adds a RuleSet to the list of rules available to Digester for parsing

      * the configuration file.

      * @param ruleSet The rule set to be added to the Digester

      */

     public void addRuleSet(RuleSet ruleSet) {

         this.ruleSets.add(ruleSet);

     }

     /**

      * The simplest possible main method that creates a pipeline from a configuration file,

      * then runs the pipeline processing from start to finish.

      *

      * When run from the command line, the only argument to this method should be

      * the path to the configuration file.

      *

      * @param argv the command line arguments

      */

     public static void main(String[] argv) {

         try {

             File configFile = new File(argv[0]);

             DigesterPipelineFactory factory = new DigesterPipelineFactory(configFile.toURL());

             Pipeline pipeline = factory.createPipeline();

             for (int i = 1; i < argv.length; i++) {

                 pipeline.getSourceFeeder().feed(argv[i]);

             }

             System.out.println("Pipeline created, about to begin processing...");

             pipeline.start();

             pipeline.finish();

             System.out.println("Pipeline successfully finished processing. See logs for details.");

         } catch (Exception e) {

             e.printStackTrace(System.err);

         }

     }

 }