package nl.dedicon.pipeline.braille.calabash.impl;
   
   import com.xmlcalabash.core.XProcException;
   import com.xmlcalabash.core.XProcRuntime;
   import com.xmlcalabash.core.XProcStep;
   import com.xmlcalabash.library.DefaultStep;
   import com.xmlcalabash.runtime.XAtomicStep;
   import java.io.File;
   import java.io.IOException;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.StandardOpenOption;
  import net.sf.saxon.s9api.QName;
  import net.sf.saxon.s9api.SaxonApiException;
  import org.apache.commons.lang3.StringUtils;
  import org.daisy.common.xproc.calabash.XProcStepProvider;
  import org.osgi.service.component.annotations.Component;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * XProc step for inserting a newline in BRL files
   * 
   * @author Paul Rambags
   */
  public class BrlMustStartWithNewlineStep extends DefaultStep {
  
      private static final Logger logger = LoggerFactory.getLogger(BrlMustStartWithNewlineStep.class);
  
      private static final QName _brl_uri = new QName("brl-uri");
  
      private BrlMustStartWithNewlineStep(XProcRuntime runtime, XAtomicStep step) {
          super(runtime, step);
      }
  
      @Override
      public void reset() {
      }
  
      @Override
      public void run() throws SaxonApiException {
          super.run();
  
          try {
              String brlUri = getOption(_brl_uri, "");
              if (StringUtils.isNotBlank(brlUri)) {
                  
                  try {
  
                      Path path = new File(new URI(brlUri)).toPath();
                      // The path refers to a CP850 encoded file
                      // A CR + LF (hex 0D 0A) is inserted if the file does not already start with it
                      byte[] bytes = Files.readAllBytes(path);
                      if (bytes.length > 1 && bytes[0] != 0xD && bytes[1] != 0xA) {
                          byte[] newLine = new byte[]{ 0xD, 0xA };
                          Files.write(path, newLine);
                          Files.write(path, bytes, StandardOpenOption.APPEND);
                      }
  
                  } catch (URISyntaxException|IOException e) {
                      logger.error(String.format("Failed to insert a newline in file %s due to %s", brlUri, e.getMessage()));
                      throw e;
                  }
              }
          } catch (Exception e) {
              logger.error("dedicon:brl-must-start-with-newline failed", e);
              throw new XProcException(step.getNode(), e);
          }
      }
  
      @Component(
              name = "dedicon:brl-must-start-with-newline",
              service = {XProcStepProvider.class},
              property = {"type:String={http://www.dedicon.nl}brl-must-start-with-newline"}
      )
      public static class Provider implements XProcStepProvider {
  
          @Override
          public XProcStep newStep(XProcRuntime runtime, XAtomicStep step) {
              return new BrlMustStartWithNewlineStep(runtime, step);
          }
      }
  }