/*
    WebBox - Dein Server.
    Copyright (C) 2020 Ulrich Hilger, http://uhilger.de

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program 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 Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package de.uhilger.wbx.web;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Map;

import static org.asciidoctor.AttributesBuilder.attributes;
import static org.asciidoctor.OptionsBuilder.options;
import static org.asciidoctor.Asciidoctor.Factory.create;
import org.asciidoctor.Asciidoctor;



/**
 * Das AdocServlet wandelt AsciiDoc-Inhalte (*.adoc) 
 * zu HTML-Seiten und PDF-Dokumenten
 * 
 * ?pdf=true im URL fuegt PDF-Ausgabe hinzu
 */
public class AdocServlet extends HttpServlet  {
  
  private static final String DOT = ".";
  private static final String HTMLEXT = ".html";
  private static final String PDFEXT = ".pdf";
  private static final String PDF = "pdf";
  private static final String SERVLET_NAME = "AdocServlet";
  
  /**
   * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
   * methods.
   *
   * @param request servlet request
   * @param response servlet response
   * @throws ServletException if a servlet-specific error occurs
   * @throws IOException if an I/O error occurs
   */
  protected void processRequest(HttpServletRequest request, HttpServletResponse response)
          throws ServletException, IOException 
  {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {

      // Asciidoc-Quelldatei aus HTTP-Request ermitteln
      String vPath = request.getServletPath();
      String absname = getServletContext().getRealPath(vPath);
      File adocfile = new File(absname);
      
      // HTML-Datei ermitteln
      String nameext = adocfile.getName();
      String fname = nameext.substring(0, nameext.lastIndexOf(DOT));
      File htmlfile = new File(adocfile.getParentFile(), fname + HTMLEXT);
      
      /*
        transformieren, wenn die Quelle sich geandert hat oder 
        die HTML-Datei noch nicht existiert
      */
      if(!htmlfile.exists() || adocfile.lastModified() > htmlfile.lastModified()) {
        transform(absname, htmlfile);
      }
   
      String pdf = request.getParameter(PDF);
      if(null != pdf && pdf.length() > 0 && pdf.equalsIgnoreCase(Boolean.TRUE.toString())) {
        File pdffile = new File(adocfile.getParentFile(), fname + PDFEXT);
        if(!pdffile.exists() || adocfile.lastModified() > pdffile.lastModified()) {
          transform(absname, pdffile);
        }
      }
      
      // HTML-Datei ausgeben
      FileInputStream in = new FileInputStream(htmlfile);
      BufferedReader reader = new BufferedReader(new InputStreamReader(in));
      String line;
      while ((line = reader.readLine()) != null) {
        out.println(line);
      }
    }
  }
  
  private void transform(String absoluteFileName, File target) {
    Map<String, Object> options = null;
    Map<String, Object> attributes;
    Asciidoctor asciidoctor = create();    
    String fname = target.getName().toLowerCase();
    
    if(fname.endsWith(HTMLEXT)) {
      attributes = attributes().noFooter(false)
                                .sourceHighlighter("highlightjs")                                        
                                //.tableOfContents(true) 
                                //.sectionNumbers(true)
                                .asMap();
      options = options().inPlace(false)
                                .attributes(attributes) 
                                .asMap();     
    } else if(fname.endsWith(PDFEXT)) {
      attributes = attributes().noFooter(false)
                                .asMap();
      options = options().inPlace(false)
                          .attributes(attributes) 
                          .backend("pdf")
                          .asMap();     
    }
    asciidoctor.convertFile(new File(absoluteFileName), options);    
  }  

  /**
   * Handles the HTTP <code>GET</code> method.
   *
   * @param request servlet request
   * @param response servlet response
   * @throws ServletException if a servlet-specific error occurs
   * @throws IOException if an I/O error occurs
   */
  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response)
          throws ServletException, IOException {
    processRequest(request, response);
  }

  /**
   * Handles the HTTP <code>POST</code> method.
   *
   * @param request servlet request
   * @param response servlet response
   * @throws ServletException if a servlet-specific error occurs
   * @throws IOException if an I/O error occurs
   */
  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response)
          throws ServletException, IOException {
    processRequest(request, response);
  }

  /**
   * Returns a short description of the servlet.
   *
   * @return a String containing servlet description
   */
  @Override
  public String getServletInfo() {
    return SERVLET_NAME;
  }

}