/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe 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 General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.frontend.indexbrowser;
  
  import java.io.File;
  import java.io.IOException;
  import java.nio.file.NotDirectoryException;
  import java.text.NumberFormat;
  import java.text.SimpleDateFormat;
  import java.util.ArrayList;
  import java.util.Date;
  import java.util.GregorianCalendar;
  import java.util.List;
  import java.util.Locale;
  import java.util.Objects;
  import java.util.TimeZone;
  import java.util.stream.Collectors;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  import org.apache.solr.client.solrj.SolrQuery;
  import org.apache.solr.client.solrj.SolrServerException;
  import org.apache.solr.client.solrj.response.QueryResponse;
  import org.jdom2.Document;
  import org.jdom2.Element;
  import org.jdom2.Namespace;
  import org.mycore.common.config.MCRConfiguration2;
  import org.mycore.datamodel.common.MCRObjectIDDate;
  import org.mycore.datamodel.ifs2.MCRObjectIDDateImpl;
  import org.mycore.solr.MCRSolrClientFactory;
  
  /**
   * This class implements all common methods to create the sitemap data.
   * <br>
   * used properties:
   * <br>
   * <ul>
   * <li>MCR.baseurl - the application base URL</li>
   * <li>MCR.WebApplication.basedir - the directory where the web application is stored</li>
   * <li>MCR.GoogleSitemap.Directory - the directory where the sitemap should be stored relative to
   *      MCR.WebApplication.basedir (it could be empty)</li>
   * <li>MCR.GoogleSitemap.Types - a list of MCRObject types, they should be included</li>
   * <li>MCR.GoogleSitemap.Freq - the frequency of harvesting, 'monthly' is default<li>
   * <li>MCR.GoogleSitemap.Style - a style extension for the URL in form of ?XSL.Style={style}, default is empty</li>
   * <li>MCR.GoogleSitemap.ObjectPath - the path to get the MCRObject in the sitemap URL, 'receive/' is default</li>
   * <li>MCR.GoogleSitemap.NumberOfURLs - the number of URLs in one sitemap file, 10000 is default</li>
   * </ul>
   *
   * see http://www.sitemaps.org/de/protocol.html
   *
   * @author Frank Lützenkirchen
   * @author Jens Kupferschmidt
   * @author Thomas Scheffler (yagee)
   * @version $Revision$ $Date$
   *
   */
  public final class MCRGoogleSitemapCommon {
  
      /** Zone information **/
      private static final Locale SITEMAP_LOCALE = Locale.ROOT;
  
      private static final TimeZone SITEMAP_TIMEZONE = TimeZone.getTimeZone("UTC");
  
      /** The namespaces */
      private static final Namespace NS = Namespace.getNamespace("http://www.sitemaps.org/schemas/sitemap/0.9");
  
      private static final String XSI_URL = "http://www.w3.org/2001/XMLSchema-instance";
  
      private static final Namespace XSI_NAMESPACE = Namespace.getNamespace("xsi", XSI_URL);
  
      private static final String SITEINDEX_SCHEMA
          = "http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/siteindex.xsd";
  
      private static final String SITEMAP_SCHEMA
          = "http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd";
  
      /** The directory path to store sitemaps relative to MCR.WebApplication.basedir */
      private static final String CDIR = MCRConfiguration2.getString("MCR.GoogleSitemap.Directory").orElse("");
  
      /** The frequence of crawle by Google */
      private static final String FREQ = MCRConfiguration2.getString("MCR.GoogleSitemap.Freq").orElse("monthly");
  
      /** The style for by Google link */
     private static final String STYLE = MCRConfiguration2.getString("MCR.GoogleSitemap.Style").orElse("");
 
     /** The url path for retrieving object metadata */
     private static final String OBJECT_PATH = MCRConfiguration2.getString("MCR.GoogleSitemap.ObjectPath")
         .orElse("receive/");
 
     /** The filter query for selecting objects to present in google sitemap */
     private static final String SOLR_QUERY = MCRConfiguration2.getStringOrThrow("MCR.GoogleSitemap.SolrQuery");
 
     /** The logger */
     private static Logger LOGGER = LogManager.getLogger(MCRGoogleSitemapCommon.class.getName());
 
     /** Number of URLs in one sitemap */
     private int numberOfURLs = MCRConfiguration2.getInt("MCR.GoogleSitemap.NumberOfURLs").orElse(10000);
 
     /** number format for parts */
     private static NumberFormat number_format = getNumberFormat();
 
     /** date formatter */
     private static SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd", SITEMAP_LOCALE);
 
     /** The webapps directory path from configuration */
     private final File webappBaseDir;
 
     /** The base URL */
     private String baseurl = MCRConfiguration2.getString("MCR.baseurl").orElse("");
 
     /** local data */
     private List<MCRObjectIDDate> objidlist = null;
 
     /** The constructor 
      * @throws NotDirectoryException */
     public MCRGoogleSitemapCommon(File baseDir) throws NotDirectoryException {
         if (!Objects.requireNonNull(baseDir, "baseDir may not be null.").isDirectory()) {
             throw new NotDirectoryException(baseDir.getAbsolutePath());
         }
         this.webappBaseDir = baseDir;
         LOGGER.info("Using webappbaseDir: {}", baseDir.getAbsolutePath());
         objidlist = new ArrayList<>();
         if ((numberOfURLs < 1) || (numberOfURLs > 50000)) {
             numberOfURLs = 50000;
         }
         if (CDIR.length() != 0) {
             File sitemapDirectory = new File(webappBaseDir, CDIR);
             if (!sitemapDirectory.exists()) {
                 sitemapDirectory.mkdirs();
             }
         }
     }
 
     public MCRGoogleSitemapCommon(String baseURL, File baseDir) throws NotDirectoryException {
         this(baseDir);
         this.baseurl = baseURL;
     }
 
     private static NumberFormat getNumberFormat() {
         NumberFormat nf = NumberFormat.getIntegerInstance(SITEMAP_LOCALE);
         nf.setMinimumFractionDigits(5);
         return nf;
     }
 
     /**
      * The method computes the number of sitemap files. If we have less than
      * <em>numberOfURLs</em> URLs and only one MyCoRe type the sitemap_google.xml
      * contained all URLs. Otherwise it split the sitemap in an sitemap_google.xml
      * index file and a lot of sitemap_google_xxxx.xml URL files.
      *
      * @return the number of files, one for a single sitemap_google.xml file, more than
      *         one for the index and all parts.
      *
      */
     protected int checkSitemapFile() throws IOException {
         int number = 0;
         QueryResponse response;
         SolrQuery query = new SolrQuery();
         query.setQuery(SOLR_QUERY);
         query.setRows(Integer.MAX_VALUE);
         query.setParam("fl", "id,modified");
 
         try {
             response = MCRSolrClientFactory.getMainSolrClient().query(query);
             objidlist = response.getResults().stream().map((document) -> {
                 String id = (String) document.getFieldValue("id");
                 Date modified = (Date) document.getFieldValue("modified");
 
                 return new MCRObjectIDDateImpl(modified, id);
             }).collect(Collectors.toList());
 
         } catch (SolrServerException e) {
             LOGGER.error(e);
         }
         number = objidlist.size() / numberOfURLs;
         if (objidlist.size() % numberOfURLs != 0) {
             number++;
         }
         return number;
     }
 
     /**
      * The method return the path to the sitemap_google.xml file.
      *
      * @param number
      *            number of this file - '1' = sitemap_google.xml - '&gt; 1' sitemap_google_xxx.xml
      * @param withpath
      *            true for the full path, false for the file name
      * @return a path to sitemap_google.xml
      */
     protected String getFileName(int number, boolean withpath) {
         String fn = "sitemap_google.xml";
         if (number > 1) {
             fn = "sitemap_google_" + number_format.format(number - 1) + ".xml";
         }
         String localPath = fn;
         if (CDIR.length() != 0) {
             localPath = CDIR + File.separator + fn;
         }
         if (withpath) {
             return webappBaseDir + File.separator + localPath;
         }
         return localPath;
     }
 
     /**
      * The method build the sitemap_google.xml JDOM document over all items.
      *
      * @return The sitemap_google.xml as JDOM document
      */
     protected Document buildSingleSitemap() throws Exception {
         LOGGER.debug("Build Google URL sitemap_google.xml for whole items.");
         // build document frame
         Element urlset = new Element("urlset", NS);
         urlset.addNamespaceDeclaration(XSI_NAMESPACE);
         urlset.setAttribute("noNamespaceSchemaLocation", SITEMAP_SCHEMA, XSI_NAMESPACE);
         Document jdom = new Document(urlset);
         // build over all types
         for (MCRObjectIDDate objectIDDate : objidlist) {
             urlset.addContent(buildURLElement(objectIDDate));
         }
         return jdom;
     }
 
     /**
      * The method call the database and build the sitemap_google.xml JDOM document.
      *
      * @param number
      *            number of this file - '1' = sitemap_google.xml - '&gt; 1' sitemap_google_xxx.xml
      * @return The sitemap.xml as JDOM document
      */
     protected Document buildPartSitemap(int number) throws Exception {
         LOGGER.debug("Build Google URL sitemap list number {}", Integer.toString(number));
         // build document frame
         Element urlset = new Element("urlset", NS);
         urlset.addNamespaceDeclaration(XSI_NAMESPACE);
         urlset.setAttribute("schemaLocation", SITEMAP_SCHEMA, XSI_NAMESPACE);
         Document jdom = new Document(urlset);
 
         // build over all types
         int start = numberOfURLs * (number);
         int stop = numberOfURLs * (number + 1);
         if (stop > objidlist.size()) {
             stop = objidlist.size();
         }
         LOGGER.debug("Build Google URL in range from {} to {}.", Integer.toString(start), Integer.toString(stop - 1));
         for (int i = start; i < stop; i++) {
             MCRObjectIDDate objectIDDate = objidlist.get(i);
             urlset.addContent(buildURLElement(objectIDDate));
 
         }
         return jdom;
     }
 
     private Element buildURLElement(MCRObjectIDDate objectIDDate) {
         String mcrID = objectIDDate.getId();
         StringBuilder sb = new StringBuilder(1024);
         sb.append(baseurl).append(OBJECT_PATH).append(mcrID);
         if ((STYLE != null) && (STYLE.trim().length() > 0)) {
             sb.append("?XSL.Style=").append(STYLE);
         }
         // build entry
         Element url = new Element("url", NS);
         url.addContent(new Element("loc", NS).addContent(sb.toString()));
         String datestr = formatter.format(objectIDDate.getLastModified());
         url.addContent(new Element("lastmod", NS).addContent(datestr));
         url.addContent(new Element("changefreq", NS).addContent(FREQ));
         return url;
     }
 
     /**
      * The method build the index sitemap_google.xml JDOM document.
      *
      * @param number
      *            number of indexed files (must greater than 1
      * @return The index sitemap_google.xml as JDOM document
      */
     protected Document buildSitemapIndex(int number) {
         LOGGER.debug("Build Google sitemap number {}", Integer.toString(number));
         // build document frame
         Element index = new Element("sitemapindex", NS);
         index.addNamespaceDeclaration(XSI_NAMESPACE);
         index.setAttribute("schemaLocation", SITEINDEX_SCHEMA, XSI_NAMESPACE);
         Document jdom = new Document(index);
         // build over all files
         for (int i = 0; i < number; i++) {
             Element sitemap = new Element("sitemap", NS);
             index.addContent(sitemap);
             sitemap.addContent(new Element("loc", NS).addContent((baseurl + getFileName(i + 2, false)).trim()));
             String datestr = formatter.format((new GregorianCalendar(SITEMAP_TIMEZONE, SITEMAP_LOCALE)).getTime());
             sitemap.addContent(new Element("lastmod", NS).addContent(datestr.trim()));
         }
         return jdom;
     }
 
     /**
      * This method remove all sitemap files from the webapps directory.
      */
     protected void removeSitemapFiles() {
         File dir = new File(webappBaseDir, CDIR);
         File[] li = dir.listFiles();
         if (li != null) {
             for (File fi : li) {
                 if (fi.getName().startsWith("sitemap_google")) {
                     LOGGER.debug("Remove file {}", fi.getName());
                     fi.delete();
                 }
             }
         }
     }
 }