////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code for adherence to a set of rules.
   // Copyright (C) 2001-2015 the original author or authors.
   //
   // This library is free software; you can redistribute it and/or
   // modify it under the terms of the GNU Lesser General Public
   // License as published by the Free Software Foundation; either
   // version 2.1 of the License, or (at your option) any later version.
   //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ////////////////////////////////////////////////////////////////////////////////
  package com.puppycrawl.tools.checkstyle;
  
  import com.puppycrawl.tools.checkstyle.api.Utils;
  
  import com.google.common.collect.Sets;
  import com.puppycrawl.tools.checkstyle.api.AbstractLoader;
  import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
  import com.puppycrawl.tools.checkstyle.api.FastStack;
  import java.io.BufferedInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import java.util.Enumeration;
  import java.util.Set;
  import javax.xml.parsers.ParserConfigurationException;
  import org.xml.sax.Attributes;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  
  /**
   * Loads a list of package names from a package name XML file.
   * @author Rick Giles
   */
  public final class PackageNamesLoader
      extends AbstractLoader
  {
      /** the public ID for the configuration dtd */
      private static final String DTD_PUBLIC_ID =
          "-//Puppy Crawl//DTD Package Names 1.0//EN";
  
      /** the resource for the configuration dtd */
      private static final String DTD_RESOURCE_NAME =
          "com/puppycrawl/tools/checkstyle/packages_1_0.dtd";
  
      /** Name of default checkstyle package names resource file.
       * The file must be in the classpath.
       */
      private static final String CHECKSTYLE_PACKAGES =
          "checkstyle_packages.xml";
  
      /** The temporary stack of package name parts */
      private final FastStack<String> packageStack = FastStack.newInstance();
  
      /** The fully qualified package names. */
      private final Set<String> packageNames = Sets.newLinkedHashSet();
  
      /**
       * Creates a new <code>PackageNamesLoader</code> instance.
       * @throws ParserConfigurationException if an error occurs
       * @throws SAXException if an error occurs
       */
      private PackageNamesLoader()
          throws ParserConfigurationException, SAXException
      {
          super(DTD_PUBLIC_ID, DTD_RESOURCE_NAME);
      }
  
      /**
       * Returns the set of fully qualified package names this
       * this loader processed.
       * @return the set of package names
       */
      private Set<String> getPackageNames()
      {
          return packageNames;
      }
  
      @Override
      public void startElement(String namespaceURI,
                               String localName,
                               String qName,
                               Attributes atts)
          throws SAXException
      {
          if ("package".equals(qName)) {
              //push package name
              final String name = atts.getValue("name");
              if (name == null) {
                  throw new SAXException("missing package name");
              }
              packageStack.push(name);
         }
     }
 
     /**
      * Creates a full package name from the package names on the stack.
      * @return the full name of the current package.
      */
     private String getPackageName()
     {
         final StringBuilder buf = new StringBuilder();
         for (String subPackage : packageStack) {
             buf.append(subPackage);
             if (!subPackage.endsWith(".")) {
                 buf.append(".");
             }
         }
         return buf.toString();
     }
 
     @Override
     public void endElement(String namespaceURI,
                            String localName,
                            String qName)
     {
         if ("package".equals(qName)) {
 
             packageNames.add(getPackageName());
             packageStack.pop();
         }
     }
 
     /**
      * Returns the set of package names, compiled from all
      * checkstyle_packages.xml files found on the given classloaders
      * classpath.
      * @param classLoader the class loader for loading the
      *          checkstyle_packages.xml files.
      * @return the set of package names.
      * @throws CheckstyleException if an error occurs.
      */
     public static Set<String> getPackageNames(ClassLoader classLoader)
         throws CheckstyleException
     {
 
         Enumeration<URL> packageFiles = null;
         try {
             packageFiles = classLoader.getResources(CHECKSTYLE_PACKAGES);
         }
         catch (IOException e) {
             throw new CheckstyleException(
                     "unable to get package file resources", e);
         }
 
         //create the loader outside the loop to prevent PackageObjectFactory
         //being created anew for each file
         final PackageNamesLoader namesLoader = newPackageNamesLoader();
 
         while (null != packageFiles && packageFiles.hasMoreElements()) {
             final URL packageFile = packageFiles.nextElement();
             InputStream stream = null;
 
             try {
                 stream = new BufferedInputStream(packageFile.openStream());
                 final InputSource source = new InputSource(stream);
                 loadPackageNamesSource(source, "default package names",
                     namesLoader);
             }
             catch (IOException e) {
                 throw new CheckstyleException(
                         "unable to open " + packageFile, e);
             }
             finally {
                 Utils.closeQuietly(stream);
             }
         }
         return namesLoader.getPackageNames();
     }
 
     /**
      * Creates a PackageNamesLoader instance.
      * @return the PackageNamesLoader
      * @throws CheckstyleException if the creation failed
      */
     private static PackageNamesLoader newPackageNamesLoader()
         throws CheckstyleException
     {
         try {
             return new PackageNamesLoader();
         }
         catch (final ParserConfigurationException e) {
             throw new CheckstyleException(
                     "unable to create PackageNamesLoader ", e);
         }
         catch (final SAXException e) {
             throw new CheckstyleException(
                     "unable to create PackageNamesLoader - "
                     + e.getMessage(), e);
         }
     }
 
     /**
      * Returns the list of package names in a specified source.
      * @param source the source for the list.
      * @param sourceName the name of the source.
      * @param nameLoader the PackageNamesLoader instance
      * @throws CheckstyleException if an error occurs.
      */
     private static void loadPackageNamesSource(
             InputSource source, String sourceName,
             PackageNamesLoader nameLoader)
         throws CheckstyleException
     {
         try {
             nameLoader.parseInputSource(source);
         }
         catch (final SAXException e) {
             throw new CheckstyleException("unable to parse "
                     + sourceName + " - " + e.getMessage(), e);
         }
         catch (final IOException e) {
             throw new CheckstyleException("unable to read " + sourceName, e);
         }
     }
 }