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This is the TeX to PDF converter package of NervalReports (a lightweight report creation library), used to convert a generated report from LaTeX to PDF format.
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/** This file is part of nervalreports.
 *
 * nervalreports 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 3 of the License, or
 * (at your option) any later version.
 *
 * nervalreports 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 nervalreports.  If not, see . */
package net.sf.nervalreports.converters;

import java.io.File;
import java.io.FileInputStream;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.util.concurrent.TimeUnit;

import org.apache.commons.io.FileUtils;

import net.sf.nervalreports.core.ReportGenerator;
import net.sf.nervalreports.core.TextualFileConverter;
import net.sf.nervalreports.core.TextualFileConverterUtils;

/** Converter from TeX files to PDF.

 * 
 
 * Note: This converter needs a 'pdflatex' executable avaiable in the default path. In other
 * words, a full TeX workspace, usually TeXLive (https://www.tug.org/texlive/), although should work
 * with any implementation, as long as it provides all packages needed by the TeX 
 * {@link ReportGenerator} used.
 * @author farrer */
public class TeXToPDFConverter extends TextualFileConverter {

   
   /** Maximun time, in seconds, to wait for each pdflatex command call to finish. */
   private static final int DEFAULT_PDFTEX_TIMEOUT_SECONDS = 60;
   
   /** The singleton instance of this class. */
   private static final TeXToPDFConverter INSTANCE = new TeXToPDFConverter();

   private TeXToPDFConverter() {
   }

   /** @return the single instance {@link TeXToPDFConverter} available. */
   public static final TeXToPDFConverter getInstance() {
      return INSTANCE;
   }

   /** {@inheritDoc} */
   @Override
   public byte[] doConvert(String textualFileAsString, Charset charset) throws Exception {
      
      File tempDir = Files.createTempDirectory("nerval_reports").toFile();
      
      
      /* Save the .tex file temporally, so we can compile it. */
      File texFile = File.createTempFile("report", ".tex", tempDir);
      FileUtils.write(texFile, textualFileAsString, charset);
      
      /* Generate the pdflatex command. Note that '--shel-escape' is needed to 'base64 -d' execution, necessary
       * to insert base64 imagens in the report. Also, '--halt-on-error' is needed to avoid waiting until timeout
       * when some error on the compilation occurs (usually due to bad formed .tex file). */
      ProcessBuilder procesBuilder = new ProcessBuilder().command("pdflatex", "--shell-escape", "--halt-on-error", texFile.getAbsolutePath())
                                                          .directory(tempDir);
      
      /* Do the first compilation. */
      Process execution = procesBuilder.start();
      execution.waitFor(DEFAULT_PDFTEX_TIMEOUT_SECONDS, TimeUnit.SECONDS);
      
      if (execution.exitValue() != 0) {
         /* Note that the default error and warnings from pdflatex is stdout, not stderr.*/
         throw new RuntimeException(TextualFileConverterUtils.getProcessOutputAsString(execution, false));
      }
      
      /* Do the second compilation, needed for number of total pages, for example (but also for other things). */
      execution = procesBuilder.start();
      execution.waitFor(DEFAULT_PDFTEX_TIMEOUT_SECONDS, TimeUnit.SECONDS);
      
      if (execution.exitValue() != 0) {
         throw new RuntimeException(TextualFileConverterUtils.getProcessOutputAsString(execution, false));
      }
      
      
      /* Load the generated pdf file. */
      File pdfFile = new File(texFile.getAbsolutePath().replaceAll("tex", "pdf"));
      
      byte fileContent[];
      
      try (FileInputStream inputStream = new FileInputStream(pdfFile);) {
         fileContent = new byte[(int) pdfFile.length()];
         inputStream.read(fileContent);
      }
      
      /* Delete all created files by deleting the temporary created directory. */
      FileUtils.deleteDirectory(tempDir);
      
      return fileContent;
   }

   /** {@inheritDoc} */
   @Override
   public String getContentType() {
      return "application/pdf";
   }

   /** {@inheritDoc} */
   @Override
   public String getFileExtension() {
      return "pdf";
   }

}