////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code for adherence to a set of rules.
   // Copyright (C) 2001-2019 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.internal.utils;
  
  import java.io.IOException;
  import java.nio.file.DirectoryStream;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.HashSet;
  import java.util.Set;
  
  import javax.xml.parsers.DocumentBuilder;
  import javax.xml.parsers.DocumentBuilderFactory;
  import javax.xml.parsers.ParserConfigurationException;
  
  import org.w3c.dom.Document;
  import org.w3c.dom.Element;
  import org.w3c.dom.Node;
  import org.w3c.dom.NodeList;
  import org.xml.sax.SAXException;
  
  /**
   * XdocUtil.
   * @noinspection ClassOnlyUsedInOnePackage
   */
  public final class XdocUtil {
  
      public static final String DIRECTORY_PATH = "src/xdocs";
  
      private XdocUtil() {
      }
  
      /**
       * Gets xdocs file paths.
       * @return a list of xdocs file paths.
       * @throws IOException if an I/O error occurs.
       */
      public static Set<Path> getXdocsFilePaths() throws IOException {
          final Path directory = Paths.get(DIRECTORY_PATH);
          try (DirectoryStream<Path> stream = Files.newDirectoryStream(directory, "*.xml")) {
              final Set<Path> xdocs = new HashSet<>();
              for (Path entry : stream) {
                  xdocs.add(entry);
              }
              return xdocs;
          }
      }
  
      /**
       * Gets xdocs documentation file paths.
       * @param files list of all xdoc files
       * @return a list of xdocs config file paths.
       */
      public static Set<Path> getXdocsConfigFilePaths(Set<Path> files) {
          final Set<Path> xdocs = new HashSet<>();
          for (Path entry : files) {
              final String fileName = entry.getFileName().toString();
              if (fileName.startsWith("config_")) {
                  xdocs.add(entry);
              }
          }
          return xdocs;
      }
  
      /**
       * Gets xdocs style file paths.
       * @param files list of all xdoc files
       * @return a list of xdocs style file paths.
       */
      public static Set<Path> getXdocsStyleFilePaths(Set<Path> files) {
          final Set<Path> xdocs = new HashSet<>();
          for (Path entry : files) {
              final String fileName = entry.getFileName().toString();
              if (fileName.endsWith("_style.xml")) {
                  xdocs.add(entry);
              }
          }
          return xdocs;
      }
  
      /**
      * Gets names of checkstyle's modules which are documented in xdocs.
      * @return a set of checkstyle's modules which have xdoc documentation.
      * @throws ParserConfigurationException if a DocumentBuilder cannot be created which satisfies
      *              the configuration requested.
      * @throws IOException if any IO errors occur.
      * @throws SAXException if any parse errors occur.
      */
     public static Set<String> getModulesNamesWhichHaveXdoc() throws Exception {
         final DocumentBuilderFactory factory = DocumentBuilderFactory
                 .newInstance();
 
         // Validations of XML file make parsing too slow, that is why we disable
         // all validations.
         factory.setNamespaceAware(false);
         factory.setValidating(false);
         factory.setFeature("http://xml.org/sax/features/namespaces", false);
         factory.setFeature("http://xml.org/sax/features/validation", false);
         factory.setFeature(
                 "http://apache.org/xml/features/nonvalidating/load-dtd-grammar",
                 false);
         factory.setFeature(
                 "http://apache.org/xml/features/nonvalidating/load-external-dtd",
                 false);
 
         final Set<String> modulesNamesWhichHaveXdoc = new HashSet<>();
 
         for (Path path : getXdocsConfigFilePaths(getXdocsFilePaths())) {
             final DocumentBuilder builder = factory.newDocumentBuilder();
             final Document document = builder.parse(path.toFile());
 
             // optional, but recommended
             // FYI:
             // http://stackoverflow.com/questions/13786607/normalization-in-dom-parsing-with-
             // java-how-does-it-work
             document.getDocumentElement().normalize();
 
             final NodeList nodeList = document.getElementsByTagName("section");
 
             for (int i = 0; i < nodeList.getLength(); i++) {
                 final Node currentNode = nodeList.item(i);
                 if (currentNode.getNodeType() == Node.ELEMENT_NODE) {
                     final Element module = (Element) currentNode;
                     final String moduleName = module.getAttribute("name");
                     if (!"Content".equals(moduleName)
                             && !"Overview".equals(moduleName)) {
                         modulesNamesWhichHaveXdoc.add(moduleName);
                     }
                 }
             }
         }
         return modulesNamesWhichHaveXdoc;
     }
 
 }