package emissary.util.web;
   
   import java.io.ByteArrayOutputStream;
   import java.io.IOException;
   
   /**
    * Methods for dealing with escaped HTML as bytes and strings
    */
   public class HtmlEscaper {
  
      private static final byte[] LT_BYTES = "<".getBytes();
      private static final byte[] GT_BYTES = ">".getBytes();
      private static final byte[] AMPERSAND_BYTES = "&".getBytes();
  
      /**
       * encode greater than, less than, and ampersand characters in a byte arroy.
       * 
       * @param theData input bytes
       * @return a copy of the input byte array with specific characters encoded.
       */
      public static byte[] escapeHtml(final byte[] theData) {
          byte[] escaped = null;
  
          try (ByteArrayOutputStream output = new ByteArrayOutputStream(theData.length)) {
              for (int i = 0; i < theData.length; i++) {
                  if (theData[i] == '<') {
                      output.write(LT_BYTES);
                  } else if (theData[i] == '>') {
                      output.write(GT_BYTES);
                  } else if (theData[i] == '&') {
                      output.write(AMPERSAND_BYTES);
                  } else {
                      output.write(theData[i]);
                  }
              }
              escaped = output.toByteArray();
  
          } catch (IOException ignored) {
              /* dont care */
          }
  
          return escaped;
      }
  
      /**
       * Escape html string
       * 
       * @param s the input string
       * @return the escaped string
       */
      public static String escapeHtml(final String s) {
          return new String(escapeHtml(s.getBytes()));
      }
  
      /** This class is not meant to be instantiated. */
      private HtmlEscaper() {}
  }