package org.djutils.decoderdumper;
   
   import java.io.IOException;
   
   /**
    * Dump bytes as hexadecimal numbers
    * <p>
    * Copyright (c) 2013-2021 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
    * BSD-style license. See <a href="https://djutils.org/docs/current/djutils/licenses.html">DJUTILS License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jan 3, 2019 <br>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://www.tudelft.nl/staff/p.knoppers/">Peter Knoppers</a>
   */
  public class HexDecoder implements Decoder
  {
      /** Prototype output line. */
      private final String prototypeLine;
  
      /** Number of fields on an output line. */
      private int fieldsPerLine;
  
      /** Insert one extra space every N fields. */
      private final int extraSpaceAfterEvery;
  
      /**
       * Construct a new HexDecoder.
       * @param fieldsPerLine int; maximum number of hex values on one output line this.extraSpaceAfterEvery =
       *            extraSpaceAfterEvery;
       * @param extraSpaceAfterEvery int; insert an extra space after every N fields
       */
      public HexDecoder(final int fieldsPerLine, final int extraSpaceAfterEvery)
      {
          this.fieldsPerLine = fieldsPerLine;
          this.extraSpaceAfterEvery = extraSpaceAfterEvery > 0 ? extraSpaceAfterEvery : Integer.MAX_VALUE;
          String format =
                  String.format("%%%ds", fieldsPerLine * 2 + fieldsPerLine - 1 + (fieldsPerLine - 1) / this.extraSpaceAfterEvery);
          this.prototypeLine = String.format(format, "");
      }
  
      /** String builder for current output line. */
      private StringBuilder buffer = new StringBuilder();
  
      /** {@inheritDoc} */
      @Override
      public String getResult()
      {
          String result = this.buffer.toString();
          this.buffer.setLength(0);
          return result;
      }
  
      /** {@inheritDoc} */
      @Override
      public int getMaximumWidth()
      {
          return this.prototypeLine.length();
      }
  
      /** {@inheritDoc} */
      @Override
      public boolean append(final int address, final byte theByte) throws IOException
      {
          if (this.buffer.length() == 0)
          {
              this.buffer.append(this.prototypeLine);
          }
          int lineByte = address % this.fieldsPerLine;
          int index = lineByte * 3 + lineByte / this.extraSpaceAfterEvery;
          this.buffer.replace(index, index + 2, String.format("%02x", theByte));
          return lineByte == this.fieldsPerLine - 1;
      }
  
      /** {@inheritDoc} */
      @Override
      public boolean ignoreForIdenticalOutputCheck()
      {
          return false;
      }
  
      /** {@inheritDoc} */
      @Override
      public String toString()
      {
          return "HexDecoder [buffer=" + this.buffer + "]";
      }
  
  }