/**
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.hadoop.hbase.http;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  
  /**
   * This class is responsible for quoting HTML characters.
   */
  public class HtmlQuoting {
    private static final byte[] ampBytes = "&".getBytes();
    private static final byte[] aposBytes = "'".getBytes();
    private static final byte[] gtBytes = ">".getBytes();
    private static final byte[] ltBytes = "<".getBytes();
    private static final byte[] quotBytes = """.getBytes();
  
    /**
     * Does the given string need to be quoted?
     * @param data the string to check
     * @param off the starting position
     * @param len the number of bytes to check
     * @return does the string contain any of the active html characters?
     */
    public static boolean needsQuoting(byte[] data, int off, int len) {
      if (off+len > data.length) {
          throw new IllegalStateException("off+len=" + off+len + " should be lower"
                  + " than data length=" + data.length);
      }
      for(int i=off; i< off+len; ++i) {
        switch(data[i]) {
        case '&':
        case '<':
        case '>':
        case '\'':
        case '"':
          return true;
        default:
          break;
        }
      }
      return false;
    }
  
    /**
     * Does the given string need to be quoted?
     * @param str the string to check
     * @return does the string contain any of the active html characters?
     */
    public static boolean needsQuoting(String str) {
      if (str == null) {
        return false;
      }
      byte[] bytes = str.getBytes();
      return needsQuoting(bytes, 0 , bytes.length);
    }
  
    /**
     * Quote all of the active HTML characters in the given string as they
     * are added to the buffer.
     * @param output the stream to write the output to
     * @param buffer the byte array to take the characters from
     * @param off the index of the first byte to quote
     * @param len the number of bytes to quote
     */
    public static void quoteHtmlChars(OutputStream output, byte[] buffer,
                                      int off, int len) throws IOException {
      for(int i=off; i < off+len; i++) {
        switch (buffer[i]) {
        case '&': output.write(ampBytes); break;
        case '<': output.write(ltBytes); break;
        case '>': output.write(gtBytes); break;
        case '\'': output.write(aposBytes); break;
        case '"': output.write(quotBytes); break;
        default: output.write(buffer, i, 1);
        }
      }
    }
    
    /**
     * Quote the given item to make it html-safe.
     * @param item the string to quote
     * @return the quoted string
    */
   public static String quoteHtmlChars(String item) {
     if (item == null) {
       return null;
     }
     byte[] bytes = item.getBytes();
     if (needsQuoting(bytes, 0, bytes.length)) {
       ByteArrayOutputStream buffer = new ByteArrayOutputStream();
       try {
         quoteHtmlChars(buffer, bytes, 0, bytes.length);
       } catch (IOException ioe) {
         // Won't happen, since it is a bytearrayoutputstream
       }
       return buffer.toString();
     } else {
       return item;
     }
   }
 
   /**
    * Return an output stream that quotes all of the output.
    * @param out the stream to write the quoted output to
    * @return a new stream that the application show write to
    * @throws IOException if the underlying output fails
    */
   public static OutputStream quoteOutputStream(final OutputStream out
                                                ) throws IOException {
     return new OutputStream() {
       private byte[] data = new byte[1];
       @Override
       public void write(byte[] data, int off, int len) throws IOException {
         quoteHtmlChars(out, data, off, len);
       }
       
       @Override
       public void write(int b) throws IOException {
         data[0] = (byte) b;
         quoteHtmlChars(out, data, 0, 1);
       }
       
       @Override
       public void flush() throws IOException {
         out.flush();
       }
       
       @Override
       public void close() throws IOException {
         out.close();
       }
     };
   }
 
   /**
    * Remove HTML quoting from a string.
    * @param item the string to unquote
    * @return the unquoted string
    */
   public static String unquoteHtmlChars(String item) {
     if (item == null) {
       return null;
     }
     int next = item.indexOf('&');
     // nothing was quoted
     if (next == -1) {
       return item;
     }
     int len = item.length();
     int posn = 0;
     StringBuilder buffer = new StringBuilder();
     while (next != -1) {
       buffer.append(item.substring(posn, next));
       if (item.startsWith("&amp;", next)) {
         buffer.append('&');
         next += 5;
       } else if (item.startsWith("&apos;", next)) {
         buffer.append('\'');
         next += 6;        
       } else if (item.startsWith("&gt;", next)) {
         buffer.append('>');
         next += 4;
       } else if (item.startsWith("&lt;", next)) {
         buffer.append('<');
         next += 4;
       } else if (item.startsWith("&quot;", next)) {
         buffer.append('"');
         next += 6;
       } else {
         int end = item.indexOf(';', next)+1;
         if (end == 0) {
           end = len;
         }
         throw new IllegalArgumentException("Bad HTML quoting for " + 
                                            item.substring(next,end));
       }
       posn = next;
       next = item.indexOf('&', posn);
     }
     buffer.append(item.substring(posn, len));
     return buffer.toString();
   }
   
   public static void main(String[] args) throws Exception {
     if (args.length == 0) {
         throw new IllegalArgumentException("Please provide some arguments");
     }
     for(String arg:args) {
       System.out.println("Original: " + arg);
       String quoted = quoteHtmlChars(arg);
       System.out.println("Quoted: "+ quoted);
       String unquoted = unquoteHtmlChars(quoted);
       System.out.println("Unquoted: " + unquoted);
       System.out.println();
     }
   }
 
 }