/*
    * Copyright (c) 2002-2025 Gargoyle Software Inc.
    *
    * Licensed 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
    * https://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.htmlunit.util;
  
  import java.nio.ByteBuffer;
  import java.nio.CharBuffer;
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetDecoder;
  import java.nio.charset.CharsetEncoder;
  import java.nio.charset.CoderResult;
  import java.nio.charset.StandardCharsets;
  
  /**
   * Simple implementation of the 'x-user-defined' {@link Charset}.
   * @author Ronald Brill
   *
   */
  public final class XUserDefinedCharset extends Charset {
  
      /** The single instance. */
      public static final String NAME = "x-user-defined";
  
      /** The single instance. */
      public static final XUserDefinedCharset INSTANCE = new XUserDefinedCharset();
  
      private XUserDefinedCharset() {
          super(NAME, new String[0]);
      }
  
      @Override
      public boolean contains(final Charset charset) {
          return StandardCharsets.US_ASCII.equals(charset);
      }
  
      @Override
      public CharsetDecoder newDecoder() {
          return new XUserDefinedDecoder();
      }
  
      @Override
      public CharsetEncoder newEncoder() {
          // not implemented for now
          return null;
      }
  
      private static final class XUserDefinedDecoder extends CharsetDecoder {
          XUserDefinedDecoder() {
              super(XUserDefinedCharset.INSTANCE, 1, 1);
          }
  
          @Override
          protected CoderResult decodeLoop(final ByteBuffer in, final CharBuffer out) {
              while (true) {
                  if (!in.hasRemaining()) {
                      return CoderResult.UNDERFLOW;
                  }
                  if (!out.hasRemaining()) {
                      return CoderResult.OVERFLOW;
                  }
                  final byte b = in.get();
                  if (b >= 0) {
                      out.append((char) b);
                  }
                  else {
                      out.append((char) (0xF700 + (b & 0xFF)));
                  }
              }
          }
      }
  }