/*
    * SPDX-License-Identifier: Apache-2.0
    * See LICENSE file for details.
    *
    * Copyright 2025-2026 Hazendaz
    * Copyright 2011-2025 Acegi Technology Pty Limited.
    */
   package au.com.acegi.xmlformat;
   
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.UnsupportedEncodingException;
  import java.util.StringTokenizer;
  
  import org.apache.commons.lang3.StringUtils;
  import org.dom4j.Node;
  import org.dom4j.io.XMLWriter;
  
  /**
   * Subclass of {@link XMLWriter} that preserves blank lines in outupt (at most one of them, among two subsequent tags).
   */
  class BlankLinesWriter extends XMLWriter {
  
      BlankLinesWriter(final OutputStream out, final XmlOutputFormat fmt) throws UnsupportedEncodingException {
          super(out, fmt);
      }
  
      @Override
      protected void writeString(final String text) throws IOException {
          if (text == null || text.length() == 0) {
              return;
          }
  
          String input = text;
          if (isEscapeText()) {
              input = escapeElementEntities(text);
          }
  
          if (getOutputFormat().isTrimText()) {
              boolean first = true;
              final StringTokenizer tokenizer = new StringTokenizer(input, " \t\r\f");
  
              final NewLinesHandler newLinesHandler = new NewLinesHandler();
              while (tokenizer.hasMoreTokens()) {
                  final String token = tokenizer.nextToken();
  
                  // Only if more tokens exist, continue
                  if (newLinesHandler.processToken(token, tokenizer.hasMoreTokens())) {
                      continue;
                  }
  
                  if (first) {
                      first = false;
                      if (lastOutputNodeType == Node.TEXT_NODE) {
                          writer.write(" ");
                      }
                  } else {
                      writer.write(" ");
                  }
  
                  writer.write(token.trim());
                  lastOutputNodeType = Node.TEXT_NODE;
              }
              newLinesHandler.finished();
          } else {
              lastOutputNodeType = Node.TEXT_NODE;
              writer.write(input);
          }
      }
  
      private final class NewLinesHandler {
          private int newLinesCount;
  
          /**
           * Processes the token, counting the newlines and producing at most one in output.
           *
           * @param token
           *            The token to be written
           * @param hasMoreTokens
           *            Does more tokens exist
           *
           * @return True if the token needs to be skipped (it's a newline or a set of newlines)
           *
           * @throws IOException
           *             If an I/O error occurs.
           */
          private boolean processToken(final String token, final boolean hasMoreTokens) throws IOException {
              final int tokenNewLines = StringUtils.countMatches(token, '\n');
              if (tokenNewLines > 0) {
                  newLinesCount += tokenNewLines;
                  return hasMoreTokens;
              }
              if (newLinesCount > 1) {
                  writer.write("\n");
                  newLinesCount = 0;
              }
              return false;
          }
  
         /**
          * Marks the end of token streams, allows to emit a last newlines if the last tokens were all newlines.
          *
          * @throws IOException
          *             If an I/O error occurs.
          */
         private void finished() throws IOException {
             if (newLinesCount > 1) {
                 writer.write("\n");
             }
         }
     }
 }