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/*
 * This file is part of the DITA Open Toolkit project.
 *
 * Copyright 2005 IBM Corporation
 *
 * See the accompanying LICENSE file for applicable license.

 */
package org.dita.dost.writer;

import static javax.xml.transform.OutputKeys.*;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;
import javax.xml.transform.Transformer;
import org.dita.dost.exception.DITAOTException;
import org.dita.dost.index.IndexTerm;
import org.dita.dost.index.IndexTermTarget;
import org.dita.dost.util.XMLSerializer;
import org.xml.sax.SAXException;

/**
 * This class extends AbstractWriter, used to output IndexTerm list to CHM index
 * file.
 *
 * @version 1.0 2005-05-11
 *
 * @author Anders Svensson (based on modifications of the CHMIndexWriter class by Wu, Zhi Qiang)
 * The class outputs an index for html, including alphabetical headings. (Thanks to pre-existing functionality in DITA OT,
 * these will be sorted based on locale as long as the xml:lang attribute is used.)
 *
 */
@SuppressWarnings("ForLoopReplaceableByForEach")
public final class HTMLIndexWriter extends AbstractExtendDitaWriter {

  @Override
  public void write(final File filename) throws DITAOTException {
    OutputStream out = null;
    try {
      out = new FileOutputStream(filename);
      final XMLSerializer serializer = XMLSerializer.newInstance(out);
      final Transformer transformer = serializer.getTransformerHandler().getTransformer();
      transformer.setOutputProperty(DOCTYPE_PUBLIC, "-//IETF//DTD HTML//EN");
      transformer.setOutputProperty(METHOD, "html");
      transformer.setOutputProperty(ENCODING, "UTF-8");

      serializer.writeStartDocument();
      serializer.writeStartElement("html");
      serializer.writeStartElement("head");
      serializer.writeComment("Sitemap 1.0");
      serializer.writeEndElement(); // head
      serializer.writeStartElement("body");
      serializer.writeStartElement("ul");
      // Initializing the variable for the alphabetical headings.
      String printLetter = "A";
      final int termNum = termList.size();
      for (int i = 0; i < termNum; i++) {
        final IndexTerm term = termList.get(i);
        //Add alphabetical headings:
        if (i == 0) {
          printLetter = term.getTermFullName().substring(0, 1);
          serializer.writeCharacters(printLetter);
        }
        final String firstLetter = term.getTermFullName().substring(0, 1);
        if (!firstLetter.equals(printLetter)) {
          printLetter = firstLetter;
          serializer.writeCharacters(printLetter);
        }
        //End alphabetical heading.
        outputIndexTerm(term, serializer);
      }
      serializer.writeEndElement(); // ul
      serializer.writeEndElement(); // body
      serializer.writeEndElement(); // html
      serializer.writeEndDocument();
    } catch (final Exception e) {
      throw new DITAOTException(e);
    } finally {
      if (out != null) {
        try {
          out.close();
        } catch (final IOException e) {
          logger.error(e.getMessage(), e);
        }
      }
    }
  }

  /**
   * Output the given indexterm into the XML writer.
   *
   * @param term term to serializer
   * @param serializer XML output to write to
   */
  private void outputIndexTerm(final IndexTerm term, final XMLSerializer serializer) throws SAXException {
    List targets = term.getTargetList();
    final List subTerms = term.getSubTerms();

    serializer.writeStartElement("li");

    //if term doesn't have target to link to, it won't appear in the index tab
    //we need to create links for such terms
    if (targets.isEmpty()) {
      findTargets(term);
      targets = term.getTargetList();
    }

    if (targets.isEmpty()) {
      serializer.writeCharacters(term.getTermFullName());
    } else {
      final IndexTermTarget target = targets.get(0);
      serializer.writeStartElement("a");
      serializer.writeAttribute("href", target.getTargetURI());
      serializer.writeCharacters(term.getTermFullName());
      serializer.writeEndElement(); // a
    }
    if (subTerms.size() > 0) {
      serializer.writeStartElement("ul");
      for (final IndexTerm subTerm : subTerms) {
        outputIndexTerm(subTerm, serializer);
      }
      serializer.writeEndElement(); // ul
    }
    serializer.writeEndElement(); // li
  }

  /**
   * Find the targets in its subterms when the current term doesn't have any target
   *
   * @param term current IndexTerm instance
   */
  private void findTargets(final IndexTerm term) {
    final List subTerms = term.getSubTerms();
    List subTargets;
    if (subTerms != null && !subTerms.isEmpty()) {
      for (final IndexTerm subTerm : subTerms) {
        subTargets = subTerm.getTargetList();
        if (subTargets != null && !subTargets.isEmpty()) {
          findTargets(subTerm);
        }
        term.addTargets(subTerm.getTargetList());
      }
    }
  }

  /**
   * Get index file name.
   * @param outputFileRoot root
   * @return index file name
   */
  @Override
  public String getIndexFileName(final String outputFileRoot) {
    return outputFileRoot + ".hhk";
  }
}