package emissary.output.io;
   
   import emissary.directory.EmissaryNode;
   import emissary.util.TimeUtil;
   import emissary.util.io.FileNameGenerator;
   
   import org.apache.commons.lang3.StringUtils;
   
   import java.time.Instant;
  import java.time.format.DateTimeFormatter;
  
  /**
   * Create a filename generator that uses a datestamp as the name
   */
  public class DateStampFilenameGenerator implements FileNameGenerator {
  
      // the date/time pattern
      protected final DateTimeFormatter formatter;
  
      // unique identifier to add to the file
      protected final String identifier;
  
      // file suffix/extension
      protected final String fileSuffix;
  
      // track last file name
      protected String lastFileName = "";
  
      // add a sequence number to the file
      protected int seq = 0;
  
      public DateStampFilenameGenerator() {
          this("");
      }
  
      public DateStampFilenameGenerator(String fileSuffix) {
          this(fileSuffix, System.getProperty(EmissaryNode.NODE_NAME_PROPERTY));
      }
  
      public DateStampFilenameGenerator(String fileSuffix, String identifier) {
          this(fileSuffix, identifier, "yyyyMMddHHmm");
      }
  
      public DateStampFilenameGenerator(String fileSuffix, String identifier, String datePattern) {
          this.fileSuffix = fileSuffix;
          this.identifier = identifier;
          this.formatter = DateTimeFormatter.ofPattern(datePattern).withZone(TimeUtil.getTimezone());
      }
  
      @Override
      public String nextFileName() {
          String dateFileName = formatter.format(Instant.now());
          seq = StringUtils.startsWith(lastFileName, dateFileName) ? seq + 1 : 0;
          lastFileName = dateFileName;
          return dateFileName + String.format("%03d", seq) + identifier + fileSuffix;
      }
  }