/*
    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 java.util.HashMap;
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.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 HTML = "html";
  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 
  {

    // 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 + DOT + HTML);
    File outfile = htmlfile; // Standardmaessig wird HTML zurueckgegeben
    response.setContentType("text/html;charset=UTF-8");

    /*
      nach HTML transformieren, wenn die Quelle sich geandert hat oder 
      die HTML-Datei noch nicht existiert
    */
    if(!htmlfile.exists() || adocfile.lastModified() > htmlfile.lastModified()) {
      transform(absname);
    }

    /*
      nach PDF transformieren, wenn der Parameter pdf=true existiert und 
      wenn die Quelle sich geandert hat oder 
      die PDF-Datei noch nicht existiert
    */
    String pdf = request.getParameter(PDF);
    if(null != pdf && pdf.equalsIgnoreCase(Boolean.TRUE.toString())) {
      File pdffile = new File(adocfile.getParentFile(), fname + DOT + PDF);
      outfile = pdffile; // PDF soll zurueckgegeben werden
      response.setContentType("application/pdf;charset=UTF-8");
      if(!pdffile.exists() || adocfile.lastModified() > pdffile.lastModified()) {
        transform(absname, PDF);
      }
    }
      
    try (PrintWriter out = response.getWriter()) {
      // abhaengig vom Parameter pdf HTML- oder PDF-Datei ausgeben
      FileInputStream in = new FileInputStream(outfile);
      BufferedReader reader = new BufferedReader(new InputStreamReader(in));
      String line;
      while ((line = reader.readLine()) != null) {
        out.println(line);
      }
    }
  }
  
  private void transform(String fileName) {
    transform(fileName, null);
  }  
  
  private void transform(String fileName, String backend) {    
    Map<String, Object> attributes = new HashMap<>();
    attributes.put("no_footer", false);
    attributes.put("source_highlighter", "highlightjs");

    Map<String, Object> options = new HashMap<>();
    options.put("attributes", attributes); 
    options.put("in_place", false); 
    if(null != backend) {
      options.put("backend", backend);
    }
    
    Asciidoctor asciidoctor = create();    
    asciidoctor.convertFile(new File(fileName), 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;
  }

}